Antigen fragments for the diagnosis of Toxoplasma gondii

Abstract

The invention described herein relates to a method for identifying antigen fragments of Toxoplasma gondii proteins, and their use as diagnostic and immunogenic agents. Said method is implemented by means of selection of DNA fragments libraries of the parasite with sera of subjects who have been infected, using the phage display technique, and is characterised in that it uses the expression/exposure vector .lamda.KM4. The method allows also to identify antigen fragments related to the time of the infection.

Description

[0001] This application is a divisional of Ser. No. 10/508,622, filed Dec. 10, 2004, which is a U.S. national phase of international application PCT/IT03/00162, filed Mar. 18, 2003, which designated the U.S. and claims benefit of IT Application No. RM02A000159, filed Mar. 21, 2002 and IT Application No. RM02A000568, filed Nov. 13, 2002, the entire contents of each of which is incorporated herein by reference.

[0002] The invention described herein relates to a method for identifying antigen fragments of Toxoplasma gondii proteins, and their use as diagnostic and immunogenic agents. Said method is implemented by means of selection of cDNA libraries of the parasite or of DNA fragments of specific genes of the parasite with sera of subjects who have been infected by the parasite, using the phage display technique, and is characterised in that it uses the vector .lamda.KM4.

[0003] The invention described herein also relates to the technical field of the preparation of diagnostic means not applied directly to the animal or human body and furnishes compounds, methods for their preparation, methods for their use and compositions containing them which are suitable for industrial application in the pharmaceutical and diagnostic field, particularly for the detection and diagnosis of Toxoplasma gondii infections, as well as for the treatment and prevention of said infections.

BACKGROUND TO THE INVENTION

[0004] Early diagnosis is a priority and highly desirable objective in all fields of medicament, particularly because it allows an appreciable improvement in the patient's life and a concomitant saving on the part of health care systems or on the part of the actual patients. In the particular case of the invention described herein, early diagnosis is that of potential or existing Toxoplasma gondii infection in pregnant women, with particular concern for the health of the foetus, and in infected subjects, particularly those with impaired immunity.

[0005] Toxoplasma gondii is an obligate intracellular parasite that infects all mammalian cells, including those of human subjects (McCabe and Remington, N. Engl. J. Med. 1988, 318-313-5), and other animal genera, e.g. birds. The life cycle of the parasite is complex and one may distinguish between three stages of infection: tachyzoite (asexual), bradyzoite (in tissue cysts, asexual) and sporozoite (in oocysts, sexual reproduction). Transmission typically occurs through ingestion of undercooked meat harbouring tissue cysts or vegetables contaminated with oocysts shed by cats. Human infection is generally asymptomatic and self-limiting in immunocompetent hosts. In contrast, in subjects with impaired immunity (particularly those affected by AIDS), toxoplasmosis is a severe opportunist infection, which may give rise to encephalitis with very serious outcomes (Luft, B. J., Remington J. S., 1992, Clin. Infect. Dis. 15, 211-22). Moreover, contracting primary infection during pregnancy may lead to miscarriages or to severe foetal disease in mammals.

[0006] For an extensive overview of the problem of toxoplasmosis the reader is referred to the specialistic medical literature.

[0007] Diagnosis of T. gondii infection is established by isolating the micro-organism in the blood or body fluids, identifying the parasite in tissues, detecting specific nucleotide sequences with PCR, or by detecting specific anti-T. gondii immunoglobulins produced by the host in response to the infection (Beaman et al., 1995 Principles and Practice of Infectious Diseases 4th Ed., Churchill Livingstone Inc., New York, 2455-75; Remington J S et al. 1995, Infectious Diseases of the Fetus and Newborn Infant, W.B. Saunders, Philadelphia, Pa., 140-267).

[0008] One of the main problems in diagnosing T. gondii infections has to do with pregnant women. To implement suitable therapies in good time and avoid possible damage to the foetus it is very important to establish if parasitic infection occurred before or after conception. This is generally done by attempting to detect the presence of the various classes of anti-Toxoplasma immunoglobulins (IgG, IgM, IgA, avidity of IgG). For this reason, the availability of specific, sensitive diagnostic agents is desirable.

[0009] T. gondii antigens have long been known and available, first of all as antigen mixtures obtained in various ways (FR 2,226,468, Merieux; SU 533376, Veterinary Research Institute; JP 54044016, Nihon Toketsu Kanso), then as subsequent isolations of pure antigens (EP 0 082 745, Merieux; EP 0 301 961, INSERM, Pasteur; WO 89/5658, Transgene) and their characterisation both as proteins, and of their respective genes (WO 89/08700, U. Leland, Dartmouth Coll.; U.S. Pat. No. 4,877,726, Res. Inst. Palo Alto; WO 89/12683, INSERM, Pasteur; EP 0 391 319, Mochida Pharm.; IT 1,196,817, CNR; EP 0 431 541, Behringwerke; WO 92/01067, CNRS; WO 92/02624, U. Flinders; WO 92/11366, Innogenetics, Smithkline Beecham; U.S. Pat. No. 5,215,917, Res. Inst. Palo Alto; WO 92/25689, FR 2702491, INSERM, Pasteur; WO 96/02654, bioMerieux, Transgene; EP 0 710 724 Akzo; EP 0 724 016, bioMerieux; EP 0 751 147, Behringwerke; U.S. Pat. No. 5,633,139, Res. Inst. Palo Alto; WO 97/27300, Innogenetics; U.S. Pat. No. 5,665,542, U.S. Pat. No. 5,686,575, Res. Inst. Palo Alto; WO 99/32633, Heska; JP 11225783, Yano; WO 99/61906, Abbott; WO 99/66043, Smithkline Beecham; JP 2000300278, Yano; WO 00/164243, Virsol).

[0010] Numerous studies have found various different antigenic proteins of T. gondii and the gene sequences of these have also been determined.

[0011] Among the most interesting proteins both for diagnostic and therapeutic purposes, in the form of vaccines, we should mention: the surface antigens SAG1 (or P30) (WO 89/08700, Stanford University; WO 89/12683 Pasteur, INSERM; WO 94/17813, WO 96/02654, Transgene, bioMerieux; EP 0 724 016, WO 99/61906, U.S. Pat. No. 5,962,654, Harning et al., Clinical and Diagnostic Laboratory Immunology, May 1996, 355-357); SAG2 (or P22) (Parmley et al., 1992, J. Clin. Microbiol. 30, 1127-33); the dense granule proteins GRA1 (or P24) (EP 0 301 961, Pasteur, INSERM; WO 89/05658, Transgene, Cesbron-Delauw, et al., 1989 P.N.A.S. USA 86, 7537-41); GRA2 (or P28) (WO 93/25689, INSERM, Pasteur; U.S. Pat. No. 5,633,139, U.S. Pat. No. 5,665,542, U.S. Pat. No. 5,686,575, Res. Inst. Palo Alto; Prince et al., Mol. Biochem. Parasitol., 34 3-14); GRA4 (Mevelec et al., Mol. Biochem. Parasitol. 56, 227-38); GRA6 (or P32) (FR 2,702,491, INSERM, Pasteur; Lecordier al., Mol. Biochem. Parasitol. 70, 85-94); GRA7 (WO 99/61906, Abbott; Jacobs et al., Mol. Biochem. Parasitol. 91, 237-49); GRA3 (Robben et al. 2002, J. Biol. Chem. 277, 17544-47): the rhoptry antigens ROP1 (or P66) (U.S. Pat. No. 5,976,553, U. Leland; EP 0 431 541, Innogenetics); ROP2 (or P54) (Sharma et al., J. Immunol., 131, 377-83).

[0012] As described in the above-mentioned references, the antigens were obtained with well-known recombinant cDNA techniques in expression vectors. For example, for the antigen SAG1, WO 98/08700 uses known expression vectors in phage .lamda.gt11. WO 98/12683 uses the same phage and transfects E. coli with a proprietary plasmid, or by preparing a special expression cassette, as in WO 96/02654. EP 0 724 016 obtains mimotypes, using combinatorial expression libraries of peptides. EP 0 301 961 describes how to obtain excretion-secretion antigens with molecular weights ranging from 20 kDa to 185 kDa. WO 89/05658 describes a protein containing the epitopes of the 24 kDa protein recognised by the antibodies produced against Toxoplasma excretion-secretion antigens; this protein is obtained by transfection of cells by means of expression vectors. The antigen P28 (GRA2) is described in U.S. Pat. No. 5,633,139 and the method of obtaining it is again implemented through expression in phage .lamda.gt11. The antigen P32 (GRA6) is described in patent FR 2,702,491, the antigen ROP1 (P66) in U.S. Pat. No. 5,976,553, P35 (or GRA8) in EP 0 431 541, WO 99/57295 and WO 99/61906, and lastly P68 in EP 0 431 541.

[0013] It should be stressed that all these antigens are obtained by means of molecular biology techniques that use the expression of proteins in bacterial cells. None of the documents cited describe the technique of expression/exposure of libraries of cDNA deriving from Toxoplasma gondii in the lambda phage (phage display) to obtain fragments of antigens of the pathogen.

[0014] The invention described herein uses a new vector of DNA expression and protein exposure as molecular fusion with the amino-terminal part of protein D of the lambda bacteriophage capsid (pD) (.lamda.KM4).

[0015] The expression/exposure vector was described for the first time in patent application PCT/IT01/00405, filed on Jul. 26, 2001, the most important part of which is incorporated herein. This vector, called .lamda.KM4, differs from that used in expression only experiments (.lamda.gt11) in that the recombinant protein coded for by the DNA fragment is expressed as fusion with a protein of the bacteriophage itself and then exposed on the capsid. According to the vector project, the phage exposes the protein fragment on the surface only if its open reading frame (ORF) coincides with pD. The size of the fragments of DNA cloned in our libraries was selected in order to represent a population of medium size ranging from 300 to 1000 nucleotide base pairs (bp), and, for statistical reasons, most of the out-of-frame sequences contain stop codons which do not permit their translation and consequently exposure on the surface of the phage.

SUMMARY OF THE INVENTION

[0016] It has now been found that the combination of the affinity selection and phage display techniques, together with the use of the vector .lamda.KM4, provides a method for the identification of specific antigen fragments of Toxoplasma gondii by means of the selection of display libraries of DNA fragments with sera of infected individuals. DNA fragments are obtained either from cDNA of whole parasite or from DNA encoding for known specific gene products. With this method it proves possible to identify antigen fragments from very large libraries (i.e. expressing a large number of different sequences). The antigen fragments thus identified enable specific ligands to be obtained, which in turn can be used as diagnostic and therapeutic means.

[0017] Therefore, one object of the invention described herein is a method for the identification of antigen fragments of Toxoplasma gondii proteins, by means of the selection of libraries of DNA fragments with sera of subjects who have been infected by the parasite, using the phage display technique, characterised in that it uses the vector .lamda.KM4.

[0018] Another object of the present invention are antigen fragments obtainable with the above-mentioned method, both isolated and characterised, and as sets of antigen fragments called "collections". The invention described herein also extends to the antigen portions of said fragments (epitopes).

[0019] The use of said antigen fragments as diagnostic agents and the related diagnostic aids containing them, for example in the form of kits or other supports, constitute a further object of the present invention.

[0020] The use of said antigen fragments as active agents, particularly with an immunogenic action, for the preparation of medicaments for the prevention and therapy of Toxoplasma gondii infection, constitute a further object of the present invention.

[0021] Another object of the present invention are the gene sequences coding for the above-mentioned antigen fragments, their use as medicaments, particularly for the prevention and therapy of Toxoplasma gondii infection, e.g. as gene therapy. The present invention also extends to the gene sequences that hybridise with the sequences of the above-mentioned fragments in stringent hybridisation conditions.

[0022] Another object of the present invention are anti-epitope antibodies and their use in the preparation of diagnostic, preventive and therapeutic means, e.g. as conjugates with active ingredients such as chemo-therapy agents. Antibodies can be generated also against collections of said epitopes.

[0023] The method provided by the present invention makes it possible to confirm the use of the Toxoplasma gondii antigens described above as such as diagnostic agents and also to identify in known antigens the epitopes that trigger an immune response in human subjects; this portion is a further object of the present invention; but it also makes it possible to identify the antigenic function of proteins of Toxoplasma gondii, or of portions thereof, which, though their structure and possibly their physiological function may be known, are unknown as regards their antigenic function, and such function comes within the framework of the present invention; lastly, the method according to the present invention also provides new antigen fragments of Toxoplasma gondii proteins, that constitute yet another object of the present invention.

[0024] Another object of the present invention is the use of the antigen fragments thus identified for the preparation of means of diagnosing the infection, as well as the actual diagnostic means containing them. The use realtes also to the diagnosis of the time of the infection, in particular by the IgG avidity assay.

[0025] Another object of the present invention is the use of the antigen fragments thus identified as medicaments, particularly for the preparation of formulations, and particularly in the form of vaccines, which are useful for the prevention and cure of the infection. The vaccines according to the present invention are suitable for use in humans and other animals (particularly pigs, cats, sheeps).

[0026] Another object of the present invention are ligands generated from the above-mentioned antigen fragments and the related collections and the use of such ligands for the preparation of diagnostic means for the detection of the infection, with particular reference to the time of infection, as well as therapeutic means for the prevention and treatment of the infection itself.

[0027] Another object of the present invention is a method for the diagnosis of Toxoplasma gondii infection, comprising the selection of sera of subjects affected or suspected of being affected by said infection with the above mentioned antigen fragments and/or their collection and/or at least one ligand and/or antibody.

[0028] These and other objects will be illustrated here below in detail, also by means of examples and figures, where FIG. 1 represents the map of the vector .lamda.KM4.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention comprises the construction of expression/exposure libraries of DNA fragments prepared from Toxoplasma gondii cells, the selection of such libraries with the sera of patients who have been infected by Toxoplasma gondii, the characterisation of the antigen fragments, and the use of said fragments for developing selective diagnostic means.

[0030] Optionally, the present invention may entail the generation of specific ligands for said antigen fragments (e.g. human recombinant antibodies or humanised murine recombinant antibodies) and the construction of selective diagnostic means that incorporate the ligands generated.

[0031] Antibodies and ligands of the present invention can be obtained according according to the general common knowledge and conventional methods.

[0032] The method according to the present invention advantageously combines affinity selection and the power of phage display.

[0033] What is meant by phage display, as understood by the person of ordinary skill in the art, is a strategy based on the selection of expression/exposure libraries in which small protein domains are exposed on the surface of bacteriophages containing the corresponding genetic information.

[0034] The method implemented according to the present invention for the first time provides new and advantageous analysis possibilities: [0035] the use of small amounts of serum to identify antigen fragments of the infectious agent, [0036] the possibility of selecting only the domains responsible for the interaction with the antibodies, without having to express the entire gene, the product of which may be insoluble or toxic; lastly, the possibility of effecting successive cycles of selection using sera from different patients or mixtures of sera facilitates the identification of cross-reactive antigens which represent one of the main objectives of the present invention.

[0037] For the above-mentioned reasons, for each library, messenger RNA was purified from an adequate number of cells (e.g. 10.sup.6 cells), using common commercially available means, from which the corresponding cDNA was generated. The latter was fragmented (by means of the bacterial enzyme DNaseI) and then cloned in the expression/exposure vector .lamda.KM4 (see example).

[0038] In the other embodiment, relating to specific T. gondii gene, each specific T. gondii gene, was amplified from the DNA of the parasite (either cDNA or genomic DNA, both prepared by using common commercially available kits) by means of PCR with specific synthetic oligonucleotides. DNA of single genes was then fragmented randomly by means of the bacterial enzyme DNaseI and then cloned as a pool in the expression/exposure vector .lamda.KM4.

[0039] The amplification of the libraries was done by means of normal techniques with which the expert in the field is familiar, e.g. by plating, growth, elution, purification and concentration (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY). The libraries were then used to develop the selection conditions, screening and characterisation of the sequences identified. Lastly, the phage clones identified were characterised by immunoenzymatic assays.

[0040] A library of the phage display type, constructed using cDNA deriving from cells of pathogenic organisms, makes it possible to exploit affinity selection, which is based on incubation of specific sera (reactive with the pathogen) with collections of bacteriophages that express portions of proteins of the pathogen on their capside and that contain the corresponding genetic information. The bacteriophages that specifically bind the antibodies present in the serum are easily recovered, remaining bound (by the antibodies themselves) to a solid support (e.g. magnetic beads); the non-specific ones, by contrast, are washed away. Direct screening, i.e. the analysis of the ability of single phage clones to bind the antibodies of a given serum, is done only at a later stage, when the complexity of the library (i.e. the different number of sequences) is substantially reduced, precisely as a result of the selection.

[0041] The use of selection strategies allows faster analysis of a large number of different protein sequences for the purposes of identifying those that respond to a particular characteristic, e.g. interacting specifically with antibodies present in the serum of patients who have been infected by the pathogen. What is more, the combination of affinity selection and phage display makes it possible to use a smaller amount of serum for each analysis. The direct screening of a classic cDNA library, in fact, entails the use of large amounts of serum, which are not always easy to obtain. For example, to analyse a library of approximately 10.sup.6 independent clones it would be necessary to incubate along with the preselected serum the numerous filters containing a total of approximately 10.sup.7 phage plaques transferred from the different culture plates with the infected bacteria (e.g. a serum volume of 1-10 ml). The use of a display-type library, on the other hand, permits affinity selection in small volumes (0.1-1 ml) prior to direct screening, and from limited amounts of serum, such as, for example, 10 .mu.l.

[0042] Lastly, given that a very large number of bacteriophages can be contained in small volumes (e.g. 10.sup.11 phage particles are normally contained in a volume of 0.1 ml), and affinity selection is done in small volumes (0.1-1 ml), a further advantage of the use of display-type libraries consists in analysing a number of independent clones (particles of recombinant phages exposing different cDNA sequences on their surfaces) 10-100 times greater (e.g. 10.sup.8 different bacteriohages) than expression-alone libraries where, as a result of technical problems, not more than 10.sup.6 independent clones are normally analysed.

[0043] As regards industrial applicability, one possible realisation of the present invention is in the form of diagnostic kits containing the antigen fragments and/or ligands and/or antibodies described above.

[0044] The diagnostic kits which are the object of the present invention are known to the expert in the field and do not require any particular description. By way of an example, the reader is referred to the patent literature cited above, to which may be added U.S. Pat. No. 6,265,176 and WO 01/63283 as further references.

[0045] Similar considerations hold good for the therapeutic application, where the preparation of medicaments or vaccines comes within the framework of general knowledge; for further reference purposes the reader is again referred to the patent literature cited in the present description.

[0046] The invention will now be illustrated in greater detail by means of examples and figures, where FIG. 1 presents the map of the vector .lamda.KM4.

EXAMPLE 1

Construction of the Vector .lamda.KM4

[0047] This technique is described in international patent application N.sup.o PCT/IT01/00405, filed on Jul. 26, 2001 and incorporated herein for reference purposes, explicitly mentioning the references cited therein. FIG. 1 represents the map of the vector .lamda.KM4. The plasmid pNS3785 (Sternberg and Hoess, 1995, Proc. Natl. Acad. Sci. USA., 92:1609-1613) was amplified by inverse PCR using the synthetic oligonucleotides 5'-TTTATCTAGACCCAGCCCTAGGAAGCTTCTCCTGAGTAGGACAAATCC-3' (SEQ ID No 1) bearing the sites XbaI and AvrII (underlined) for the subsequent cloning of the lambda phage, and 5'-GGGTCTAGATAAAACGAAAGGCCCAGTCTTTC-3' (SEQ ID No 2) bearing the site XbaI. In inverse PCR a mixture of Taq DNA polymerase and Pfu DNA polymerase was used to increase the fidelity of the DNA synthesis. Twenty-five amplification cycles were performed (95.degree. C.--30 sec, 55.degree. C.--30 sec, 72.degree. C.--20 min). The autoligation of the PCR product, previously digested with XbaI endonuclease gave rise to the plasmid pKM3. The lambda gene pD was amplified with PCR from the plasmid pNS3785 using the primers 5'-CCGCCTTCCATGGGTACTAGTTTTAAATGCGGCCGCACGAGCAAAGAAACCTTTAC-3' (SEQ ID No 3) e 5'-AGCTTCCTAGGGCTGGGTCTAG-3' (SEQ ID No 4) containing the restriction sites NcoI, SpeI, NotI and EcoRI, respectively, (underlined). The PCR product was then purified, digested with NcoI and EcoRI endonuclease and recloned in sites NcoI and EcoRI of pKM3, resulting in the plasmid pKM4 bearing only the restriction sites SpeI and NotI at the 5' end of the protein gpD. The plasmid was then digested with XbaI endonuclease and cloned in the XbaI site of the lambda phage Dam15imm21nin5 (Sternberg and Hoess, 1995, Proc. Natl. Acad. Sci. USA., 92:1609-1613).

Construction of cDNA Library from Tachyzoites of Toxoplasma gondii

[0048] Tachyzoites of the protozoon Toxoplasma gondii (RH strain) were grown in vitro in monkey kidney cells ("VERO" African green monkey cells) using DMEM culture medium containing 10% foetal bovine serum, 2 mM glutamine and 0.05 mg/ml gentamicin (Gibco BRL, Canada). The parasites were collected after complete lysis of the host cells and purified by filtration (filter porosity 3 .mu.m) followed by centrifuging. 4 .mu.g of mRNA were isolated from 10.sup.7 tachyzoites using the "QuickPrep Micro mRNA Purification Kit" (Amersham Pharmacia Biotech, Sweden) and following the manufacturer's instructions. The double-helix cDNA was synthesised from 200 ng of poly(A).sup.+ RNA using the "SMART cDNA Library Construction Kit" (Clontech, CA, USA) and following the manufacturer's instructions. 10 .mu.g of total cDNA were then fragmented randomly using 0.5 ng of the endonuclease DNaseI (Sigma-Aldrich, USA). The mixture of cDNA and DNaseI was incubated for 20 minutes at 15.degree. C. and the cDNA fragments were purified with extraction in phenol/chloroform and subsequent purification by means of the "QIAquick PCR Purification Kit" (Qiagen, CA, USA), following the manufacturer's instructions. The 3 .mu.g ends of the cDNA fragments were "flattened" by incubating the DNA with 9 units of the enzyme T4 DNA polymerase (New England Biolabs, MA, USA) for 60 minutes at 15.degree. C. The fragments were then purified by means of extraction in phenol/chloroform and subsequent precipitation in ethanol. 500 ng of the resulting DNA were bound with a 20-fold molar excess of "synthetic adaptors" for the purposes of adding the restriction sites SpeI and NotI to the ends of the fragments. Six adaptors were used, obtained by hybridisation of the following pairs of oligonucleotides: K185 5'-CTAGTCGTGCTGGCCAGC-3' (SEQ ID No 5) and K186 5'-GCTGGCCAGCACGA-3' (SEQ ID No 6); K187 5'-CTAGTCGTGCTGGCCAGCT-3' (SEQ ID No 7) and K188 5'-AGCTGGCCAGCACGA-3' (SEQ ID No 8); K189 5'-CTAGTCGTGCTGGCCAGCTG-3' (SEQ ID No 9) and K190 5'-CAGCTGGCCAGCACGA-3' (SEQ ID No 10); K191 5'-TCTGGTGGCGGTAGC-3' (SEQ ID No 11) and K192 5'-GGCCGCTACCGCCACCAGA-3' (SEQ ID No 12); K193 5'-TTCTGGTGGCGGTAGC-3' (SEQ ID No 13) and K194 5'-GGCCGCTACCGCCACCAGAA-3' (SEQ ID No 14); K195 5'-TTTCTGGTGGCGGTAGC-3' (SEQ ID No 15) and K196 5'-GGCCGCTACCGCCACCAGAAA-3' (SEQ ID No 16). The excess of unligated adaptors was removed from the ligation mixture by electrophoresis on 2% agarose gel and the cDNA fragments with molecular weights ranging from 300 bp to 1000 bp were excised from the gel and purified by means of the "Qiaquick gel extraction kit" (Qiagen, CA, USA) following the manufacturer's instructions. The vector .lamda.KM4 was digested with SpeI/NotI and for the construction of the library 6 ligation mixtures were performed, each containing 0.4 .mu.g of vector and approximately 7 ng of insert. After overnight incubation at 4.degree. C. the ligation mixtures were packaged in vitro with the "Ready-To-Go lambda packaging kit" (Amersham Pharmacia Biotech, Sweden) and plated for infection of BB4 cells (bacterial cells of E. coli strain BB4; Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY). After overnight incubation at 37.degree. C. the phage was eluted from the plates with SM buffer (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY), purified, concentrated and stored at -80.degree. C. in SM buffer containing 7% dimethylsulphoxide. The complexity of the library calculated as the number of total independent clones with inserts was 10.sup.7 clones.

Affinity Selection

[0049] Two distinct methods were used for selecting the phage library with human sera. In the first method 100 .mu.l of magnetic beads coated with Protein G (Dynabeads Protein-G, Dynal, Norway) were incubated with 10 .mu.l of human serum for 30 minutes at room temperature. The beads were then incubated for 1 hour at 37.degree. C. with blocking solution consisting of: 5% skimmed milk powder in PBS (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY), 0.05% Tween 20, and MgSO.sub.4 10 mM. Approximately 10.sup.10 phage particles of the library were added to the beads and diluted in 1 ml of blocking solution for a further 4-hour incubation at room temperature with weak stirring. In the second method 40 .mu.l of "M280-Tosyl activated" magnetic beads (Dynal, Norway) were coated with human anti-IgM antibodies (Sigma-Aldrich, USA) following the manufacturer's instructions. The beads were then washed with PBS/TritonX-100 1% and incubated with 10 .mu.l of human serum in 300 .mu.l of blocking solution for 2 hours at room temperature. After washing the beads three times with washing solution (PBS, 1% TritonX100, 10 mM MgSO.sub.4), 10.sup.10 phage particles of the library were added to the beads and diluted in 200 .mu.l of blocking solution for a further 3-hour incubation at room temperature with weak stirring.

[0050] With both selection methods, the beads were washed 10 times with 1 ml of washing solution (PBS, 1% TritonX100, 10 mM MgSO.sub.4). The bound bacteriophages were amplified for infection of BB4 cells added directly to the beads (1.2 ml per selection) and subsequent 30-minute incubation at room temperature. 12 ml of NZY-Top Agar (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY) were added to the mixture of beads and cells and immediately poured onto NZY plates (2 15-cm Petri capsules for selection). The plates were incubated for 12-16 hours at 37.degree. C. The next day the phages were collected from the plates by means of the addition of 15 ml of SM buffer per plate and stirring for 4 hours at room temperature. The phages were purified by precipitation in PEG/NaCl (20% polyethylene glycol, NaCl 1M) and finally resuspended in 5 ml of SM and stored at +4.degree. C.

Selection of the Library with Human Sera

[0051] To identify the specific antigens of T. gondii an affinity selection procedure was used consisting of two "panning" cycles with one or more positive sera (that is to say sera deriving from a patient who tested positive for the presence of antibodies directed against the parasite), followed by an immunological screening procedure carried out with the same sera or, alternatively, by analysis of single clones taken at random from the mixture of selected phages. Preferably, the library was selected with 10 positive sera (T1, T2, T3, T4, T5, T6, T7, T8, T9 and T10), generating, after a single selection cycle, the corresponding mixtures p1.sup.I, p2.sup.I, p3.sup.I, p4.sup.I, p5.sup.I, p6.sup.I, p7.sup.I, p8.sup.I, p9.sup.I and p10.sup.I. Each mixture was then subjected to a second affinity selection cycle with the same serum, according to the first strategy mentioned above, giving rise to a second series of mixtures (called p1.sup.II, p2.sup.II, p3.sup.II, p4.sup.II, p5.sup.II, p6.sup.II, p7.sup.II, p8.sup.II, p9.sup.II and p10.sup.II). The initial characterisation by means of an enzyme-linked immunosorbent assay (Phage-ELISA) showed that some of the mixtures were more reactive with the corresponding serum used for the selection, thus confirming the efficacy of the library and the affinity selection procedure. Various positive clones were identified by means of immunoplate screening per plaque of reactive mixtures.

Phage-ELISA

[0052] Multi-well plates (Immunoplate Maxisorb, Nunc, Denmark) were coated, incubating 100 .mu.l/well of anti-lambda polyclonal antibodies overnight at 4.degree. C. with a concentration of 0.7 .mu.g/ml in NaHCO.sub.3 50 mM, pH 9.6. After eliminating the coating solution, the plates were incubated with 250 .mu.l of blocking solution (5% skimmed milk powder in PBS, 0.05% Tween-20). The plates were then washed twice with washing buffer (PBS, 0.05% Tween-20). A mixture of 100 .mu.l of blocking solution containing phage lysate (diluted 1:1) was added to each well and incubated for 60 minutes at 37.degree. C. 1 .mu.l of human serum was preincubated for 30 minutes at room temperature with 10.sup.9 wild-type phage particles, 1 .mu.l of rabbit serum, 1 .mu.l of bacterial extract of BB4 cells, 1 .mu.l of foetal bovine serum in 100 .mu.l of blocking solution. The plates were washed 5 times after incubation with the phage lysate and then incubated with the serum solution for 60 minutes at 37.degree. C. The plates were then washed 5 times and incubated in blocking solution containing human anti-immunoglobulin antibodies conjugated with the enzyme peroxidase (Sigma-Aldrich, USA) diluted 1:10000 and rabbit serum diluted 1:40. After 30 minutes' incubation the plates were washed 5 times and the peroxidase activity was measured with 100 .mu.l of TMB liquid substrate (Sigma-Aldrich, USA). After 15 minutes' development, the reaction was stopped by adding 25 .mu.l of H.sub.2SO.sub.4 2M. Lastly, the plates were analysed using an automatic ELISA reader (Multiskan, Labsystem, Finland) and the results were expressed as OD=OD.sub.450nm-OD.sub.620nm. The ELISA data were assessed as mean values of two independent assays.

Immunoscreening

[0053] Phage plaques were transferred from the bacterial medium to nitrocellulose filters (Schleicher & Schuell, Germany) by means of incubation at room temperature for 60 minutes. The filters were blocked for 60 minutes at room temperature in blocking solution (5% skimmed milk powder in PBS, 0.05% Tween-20). 40 .mu.l of human serum were preincubated with 40 .mu.l of bacterial extract of BB4 cells, 10.sup.9 wild-type lambda phage particles in 4 ml of blocking solution. After eliminating the blocking solution, the filters were incubated with the serum for 3 hours at room temperature under stirring. The filters were then washed 5 times with washing buffer (PBS, 0.05% Tween-20) and then incubated for 60 minutes at room temperature, alternatively with human anti-IgG antibodies conjugated with alkaline phosphatase (Sigma-Aldrich, USA), or with human anti-IgM antibodies conjugated with alkaline phosphatase (Sigma-Aldrich, USA), both diluted 1:7500 in blocking solution. After washing the filters 5 times, 5 ml of development solution (substrates BCIP and NBT, Sigma-Aldrich, USA) were added and the development was interrupted by washing the filters in water.

Preparation of the Lambda Phase from Lysogenic Cells

[0054] Phage clones that proved positive at immunoscreening (direct screening) were isolated from the respective phage plaques and then amplified for subsequent characterisation. The bacterial BB4 cells were grown under stirring at 37.degree. C. up to an optical density OD.sub.600=1.0 in LB culture medium (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY) containing 0.2% maltose and 10 mM MgSO.sub.4, recuperated by centrifuging and resuspended in SM buffer at optical density OD.sub.600=0.2. 100 .mu.l of cells were infected with recombinant bacteriophages recovered from single plaques, incubated for 20 minutes at room temperature, plated on LB medium with ampicillin (100 .mu.g/ml) and then incubated for 18-20 hours at 32.degree. C. A single bacterial colony was then grown in 10 ml of LB/ampicillin overnight at 32.degree. C. under stirring. 500 ml of LB/ampicillin and MgSO.sub.4 10 mM were added to 5 ml of the overnight culture and incubated at 32.degree. C. up to an optical density OD.sub.600=0.6 under vigorous stirring. The culture was then incubated for 15 minutes in a water bath at 45.degree. C. and then at 37.degree. C. for a further 3 hours. After this, the bacteriophages were purified of the bacterial culture according to standard procedures (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY) and stored at +4.degree. C.

[0055] Lastly, the phage clones were analysed by means of phage-ELISA with a substantial panel of positive and negative sera. Clones whose ELISA value exceeded the background value, as obtained from the sum of the mean of the measurements of the negative sera and three times the standard deviation, were judged to be positive.

[0056] The following table 1 gives, by way of examples, the reactivity of a number of the recombinant bacteriophages selected. TABLE-US-00001 TABLE 1 Reactivity of phage Reactivity of phage clone clone with positive with negative sera Name of clone sera (positive/total pos.) (negative/total neg.) Tx-4.11 13/21 0/10 TxM-17.2 4/8 1/8 Tx-15.11 11/21 0/10 Tx-1.11 19/21 0/10 Tx-8.0 6/21 0/10 Tx-1.16 20/21 0/10 Tx-9.18 9/21 0/8 Tx-7.11 21/21 0/10

Characterisation of Positive Clones

[0057] The clones which showed multiple reactivity with the Toxoplasma gondii positive sera and which presented no reactivity to the negative sera were subsequently sequenced and compared with various databases of sequences currently available (Non-Redundant Genbank CDS, Non-Redundant Database of Genbank Est Division, Non-Redundant Genbank+EMBL+DDBJ+PDB Sequences).

[0058] The sequences obtained can be classified in four groups: [0059] sequences that code for known T. gondii antigen fragments; [0060] sequences that code for known proteins which, however, are not known to be involved in the human antibody response; [0061] sequences that code for unknown proteins (e.g. EST); [0062] new sequences, not yet figuring in the databases.

[0063] The following table 2 gives, by way of examples, the sequences of some of the clones selected: TABLE-US-00002 TABLE 2 Name of clone Sequence Identification Classification Tx-4.11 AGTGGAGGGACAGGGC GRA 1 Dense granul (SEQ ID No 17) AGGGATTAGGAATCGG known protein AGAATCTGTAGATTTG T. gondii GAGATGATGGGGAACA antigen CGTATCGTGTGGAGAG ACCCACAGGCAACCCG GACTTGCTCAAGATCG CCATTAAAGCTTCAGA TGGATCGTACAGCGAA GTCGGCAATGTTAACG TGGAGGAGGTGATTGA TACTATGAAAAGCATG CAGAGGGACGAGGACA TTTCCTTCGTGCGTTG AACAAAGGCGAAACAG TAGAGGAAGCGATCGA AGACGTGGCTCAAGCA GAAGGGCTTAATTCGG AGCAAACCCTGCAACT GGAAGATGCAGTGAGC GCGGTGGCGTCTGTTG TTCAAGACGAG TxM-17.2 TACTCTTCACCACGAA GRA2 Dense granul (SEQ ID No 18) TAGTTGTTTTGATTAG known protein ATATTGCTTCTTCTCC T. gondii ACATATCGCCTCACAA antigen TGTTCGCCGTAAAACA TTGTTTGCTGGTTGTT GCCGTTGGCGCCCTGG TCAACGTCTCGGTGAG GGCTGCCGAGTTTTCC GGAGTTGATTAACCAG GGACCT Tx.15.11 GCTGCCTTGGGAGGCC GRA 3 Dense granul (SEQ ID No 19) TTGCGGCGGATCAGCC protein- TGAAAATCATCAGGCT unknown CTTGCAGAACCAGTTA as antigen i CGGGTGTGGGGGAAGC human AGGAGTGTCCCCCGTC response AACGAAGCTGGTGAGT CATACAGTTCTGCAAC TTCGGGTGTCCAAGAA GCTACCGCCCCAGGTG CAGTGCTCCTGGACGC AATCGATGCCGAGTCG GATAAGGTGGACAATC AGGCGGAGGGAGGTGA GCGTATGAAGAAGGTC GAAGAGGAGTTGTCGT TATTGAGGCGGGAATT ATATGATCGCACAGAT CGCCCTGGT Tx-1.11 CAGTTCGCTACCGCGG GRA 7 Dense granul (SEQ ID No 20) CCACCGCGTCAGATGA known protein CGAACTGATGAGTCGA T. gondii ATCCGAAATTCTGACT antigen TTTTCGATGGTCAAGC ACCCGTTGACAGTCTC AGACCGACGAACGCCG GTGTCGACTCGAAAGG GACCGACGATCACCTC ACCACCAGCATGGATA AGGCATCTGTAGAGAG TCAGCTTCCGAGAAGA GAGCCATTGGAGACGG AGCCAGATGAACAAGA AGAAGTTCAT Tx-8.0 GAGAACCCGGTGAGAC GRA8 Dense granul (SEQ ID No 21) CGCCTCCTCCCGGTTT known protein CCATCCAAGCGTTATT T. gondii CCCAATCCCCCGTACC antigen CGCTGGGCACTCCAGC GGGCATGCCACAGCCA GAGGTTCC Tx-1.16 AGGAGGACTGGATGTC MIC 3 Microneme (SEQ ID No 22) ATGCCTTCAGGGAGAA protein- CTGCAGCCCTGGTAGA unknown a TGTATTGATGACGCCT antigen i CGCATGAGAATGGCTA human CACCTGCGAGTGCCCC response ACAGGGTACTCACGTG AGGTGACTTCCAAGGC GGAGGAGTCGTGTGTG GAAGGAGTCGAAGTCA CGCTGGCTGAGAAATG CGAGAAGGAATTCGGC ATCAGCGCGTCATCCT GCAAATGCGAT Tx-9.18 GCACCCACTCAATCTG MIC 5 Microneme (SEQ ID No 23) AAATGAAAGAATTCCA known protein AGAGGAAATCAAAGAA T. gondii GGGGTGGAGGAAACAA antigen AGCATGAAGACGATCC TGAGATGACGCGGCTC ATGGTGACCGAGAAGC AGGAGAGCAAAAATTT CAGCAAGATGGCGAAA TCCCAGAGTTTAGCAC GCGAATCGAAGAGCTC GGGGGATCCATTTCGT TTCTAACTGAAACGGG GGTCACAATGATCGAG TTGCCCAAAACTGTCA GTGAACATGACATGGA CCAACTACTCCAC Tx-7.11 GTTATGGCATCGGATC SAG 1 Surface (SEQ ID No 24) CCCCTCTTGTTGCCAA known protein TCAAGTTGTCACCTGC T. gondii CCAGATAAAAAATCGA antigen CAGCCGCGGTCATTCT CACACCGACGGAGAAC CACTTCACTCTCAAGT GCCCTAAAACAGCGCT CACAGAGCCTCCCACT CTTGCGTACTCACCCA ACAGGCAAATCTGCCC AGCGGGTACTACAAGT AGCTGTACATCAAAGG CTGTAACATTGAGCTC CTTGATTCCTGAAGCA GAAGATAGCTGGTGGA CGGGGGATTCTGCTAG TCTCGACACGGCAGGC ATCAAACTCACAGTTC CAATCGAGAAGTTCCC CGTGACAACGCAGACG TTTGTGGTCGGTTGCA TCAAGGGAGACGACGC ACAGAGTTGTATGGTC ACGGTGACAGTACAAG CCAGAGCCTCATCGGT CGTCAATAATGTCGCA AGGTGCTCCTATGGTG CGGACAGC Tx-4.18 CCATCGGTCGTCAATA SAG 1 Surface (SEQ ID No 25) ATGTCGCAAGGTGCTC known protein CTACGGTGCAGACAGC T. gondii ACTCTTGGTCCTGTCA antigen AGTTGTCTGCGGAAGG ACCCACTACAATGACC CTCGTGTGCGGGAAAG ATGGAGTCAAAGTTCC TCAAGACAACAATCAG TACTGTTCCGGGACGA CGCTGACTGGTTGCAA CGAGAAATCGTTCAAA GATATTTTGCCAAAAT TAACTGAGAACCCGTG GCAGGGTAACGCTTCG AGTGATAAGGGTGCCA CGCTAACGATCAAGAA GGAAGCATTTCCAGCC GAGTCAAAAAGCGTCA TTATTGGATGCACAGG GGGATCGCCTGAGAAG CATCACTGTACCGTGA AACTGGAGTTTGCCGG GGCTGCAGGGTCAGCA AAATCGGCT

[0064] The clone Tx-4.11 constitutes a fragment of the antigen GRA1 (Cesbron-Delauw et al., 1989, Proc. Natl. Acad. Sci. USA 86:7537-7541) but has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 26) SGGTGQGLGIGESVDLEMMGNTYRVERPTGNPDLLKIAIKASDGSYSEVGNVNVEEVIDTMKS- MQRDEDIFLR ALNKGETVEEAIEDVAQAEGLNSEQTLQLEDAVSAVASVVQDE and its use as a fragment containing an epitope is covered by the present invention.

[0065] The clone TxM-17.2 constitutes a fragment of the antigen GRA2 (Prince et al., 1989, Mol. Biochem. Parasitol., 34: 3-14) but has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 27) YSSPRIVVLIRYCFFSTYRLTMFAVKHCLLVVAVGALVNVSVRAAEFSGVVNQGP and its use a fragment containing an epitope is covered by the present invention.

[0066] The clone Tx-15.11 constitutes a fragment of the gene GRA3 (Bermudes et al., 1994, Mol. Biochem. Parasitol., 68: 247-257) and has never been identified as an antigen in the human antibody response. Said clone has the amino acid sequence (SEQ ID No 28) AALGGLAADQPENHQALAEPVTGVGEAGVSPVNEAGESYSSATSG VQEATAPGAVLLDAIDAESDKVDNQAEGGERMKKVEEELSLLRRE LYDRTDRPG and its use as a fragment containing an epitope is covered by the present invention.

[0067] The clone Tx-1.11 constitutes a fragment of the antigen GRA7 (Bonhomme et al., 1998, J. Histochem. Cytochem. 46, 1411-1421) and has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 29) FATAATASDDELMSRIRNSDFFDGQAPVDSLRPTNAGVDSKGTDDHLTTSMDKASVESQLPRREPLETE- PDEQEEVHF and its use as a fragment containing an epitope is covered by the present invention.

[0068] The clone Tx-8.0 constitutes a fragment of the antigen GRA8 (Kimberly et al., 2000, Mol. Biochem. Parasitol., 105: 25-37) and has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 30) ENPVRPPPPGFHPSVIPNPPYPLGTPAGMPQPEVP and its use as a fragment containing an epitope is covered by the present invention.

[0069] The clone Tx-1.16 constitutes a fragment of the gene MIC3 (Garcia-Reguet et al., 2000, Cellular Microbiol., 2: 353-364) and has never been identified as an antigen in the human antibody response. Said clone has the amino acid sequence (SEQ ID No 31) RRTGCHAFRENCSPGRCIDDASHENGYTCECPTGYSREVTSKAEESCVEGVEVTLAEKCEKE FGISASSCKCD and its use as a fragment containing an epitope is covered by the present invention.

[0070] The clone Tx-9.18 constitutes a fragment of the antigen MIC5 (Brydges et al., 2000, Mol. Biochem. Parasitol., 111: 51-66) but has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 32) APTQSEMKEFQEEIKEGVEETKHEDDPEMTRLMVTEKQESKNFSKMAKSQSFSTRIEELGGSISFLTET- GVTMIELPKTVSEHDMDQLL H and its use as a fragment containing an epitope is covered by the present invention.

[0071] The clone Tx-7.11 constitutes a fragment of the antigen SAG1 (Burg et al., 1988, J. Immunol., 141:3584-3591) but has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 33) VMASDPPLVANQVVTCPDKKSTAAVILTPTENHFTLKCPKTALTEPPTLAYSPNR QICPAGTTSSCTSKAVTLSSLIPEAEDSWWTGDSASLDTAGIKLTVPI EKFPVTTQTFVVGCIKGDDAQSCMVTVTVQARASSVVNNVARCSYG ADS and its use a fragment containing an epitope is covered by the present invention.

[0072] The clone Tx-4.18 constitutes a fragment of the antigen SAG1 (Burg et al., 1988, J. Immunol., 141:3584-3591) but has never been identified as an "antigen fragment" of the protein in the human humoral response. Said clone has the amino acid sequence (SEQ ID No 34) PSVVNNVARCSYGADSTLGPVKLSAEGPTTMTLVCGKDGVKVPQDNNQYCSGTT LTGCNEKSFKDILPKLTENPWQGNASSDKGATLTIKEAFPAESKS VIIGCTGGSPEKHHCTVLLEFAGAAGSAKSA and its use as a fragment containing an epitope is covered by the present invention.

Expression of cDNA Fragments Selected from the Library as Fusion Products with GST

[0073] The plasmid pGEX-SN was constructed by cloning the DNA fragment deriving from the hybridisation of the synthetic oligo-nucleotides K108 5'-GATCCTTACTAGTTTTAGTAGCGGCCGCGGG-3' (SEQ ID No 35) and K109 5'-AATTCCCGCGGCCGCTACTAAAACTAGTAAG-3' (SEQ ID No 36) in the BamHI and EcoRI sites of plasmid pGEX-3X (Smith and Johnson, 1988, Gene, 67, 31-40).

[0074] The phage clones for which specific reactivity with sera of patients testing positive for Toxoplasma gondii was demonstrated, were amplified and then analysed with a substantial panel of positive and negative sera. After this ELISA study, DNA inserts of clones that showed multiple reactivity with Toxoplasma gondii-positive sera and presented no reactivity with the negative sera were cloned as fusion products with the protein Glutathione Sulphur Transferase (GST) and expressed in the cytoplasma of bacterial cells, for the purposes of determining their specificity and selectivity. To produce the fusion proteins each clone was amplified from a single phage plaque by PCR, using the following oligonucleotides: K47 5'-GGGCACTCGACCGGAATTATCG-3' (SEQ ID No 37) and K85 5'-GGGTAAAGGTTTCTTTGCTCG-3' (SEQ ID No 38). The resulting fragment was then purified by means of the "Qiagen Purification Kit" (Qiagen, CA, USA), digested with the restriction enzymes SpeI and NotI and cloned in the vector pGEX-SN to generate the fusion with GST. The corresponding recombinant proteins were then expressed in E. coli and purified by affinity using Glutathione-Sepharose resin (Amersham Pharmacia Biotech, Sweden) and following standard protocols (Sambrook et al., 1989, Molecular Cloning, Cold Spring Harbor Laboratory Press, Cold Spring Harbor).

[0075] The following table 3, by way of examples, presents the reactivity with negative and positive sera of a number of the clones selected, assayed in the form of fusion proteins: TABLE-US-00003 TABLE 3 Reactivity of GST fusion Reactivity of GST fusion protein Name of protein with positive sera with negative sera clone (pos./total neg.) (neg./total neg.) Tx-4.11 32/40 1/28 Tx-15.11 22/40 0/28 Tx-1.11 27/40 0/28 Tx-8.0 13/40 0/28 Tx-1.16 31/40 0/28 Tx-9.18 3/40 1/28 Tx-7.11 39/40 3/28 Tx-4.18 21/40 1/28

IgG Avidity for Determining the Time of Infection

[0076] Measurement of the binding force between immunoglobulin G (IgG) and the T. gondii-specific antigens (IgG avidity) is a diagnostic method used to establish the time of infection: IgG avidity is lower during the acute phase of the infection and then tends to increase in the course of time (Hedman et al. 1989 J. Infect. Dis. 159, 736-740). Evaluation of IgG avidity is based on an enzyme-linked immunosorbent assay (ELISA) in which the immunoglobulins are "detached" from the antigen by washing with a urea denaturing solution. A mathematical calculation based on the reactivity before and after the denaturing washing makes it possible to estimate serum IgG avidity (Jenum et al., 1997. J. Clin. Microbiol. 35, 1972-1977). To evaluate the antigenic properties of the protein fragments described in the present invention, an IgG avidity test based on recombinant antigen fragments was developed and the results obtained were compared with the assay performed with a commercial kit (Toxo-IgG avidity kit, bioMerieux, France) that employs the whole parasite extract as antigen.

[0077] For the avidity analysis 27 sera coming from women who contracted primary Toxoplasmosis during pregnancy and collected at different times after infection were used. The infection was diagnosed by seroconversion during gestation, taking into consideration last negative and first positive samples. For each sample the specific IgG and IgM levels for T. gondii and the IgG avidity were determined by means of the use of commercial kits (LDBIO Diagnostic, France; bioMerieux, France). Multi-well plates (Nunc, Denmark) were incubated overnight at 4.degree. C. with a solution of NaHCO.sub.3 50 mM, pH 9.6 containing the antigen fragments expressed as GST fusion proteins at a final concentration of 5 .mu.g/ml. The plates were blocked with 200 .mu.l of blocking solution (5% skimmed milk powder in PBS, 0.05% Tween-20) and then washed 5 times with washing buffer (PBS, 0.05% tween-20). Serial dilutions of serum (1:50, 1:200, 1:800, 1:3200) in 100 .mu.l of blocking solution were incubated on plates for 60 minutes at 37.degree. C. The plates were then incubated with a denaturing solution of urea 6M in PBS/0.02% Tween-20 for 30 minutes at 37.degree. C. In parallel, for every sample, the same dilutions of serum were effected and the wells concerned were incubated with normal washing buffer. 100 .mu.l of blocking solution containing human anti-IgG antibodies conjugated with the enzyme alkaline phosphatase (diluted 1:10000) were added to the plates. After 30 minutes' incubation at 37.degree. C. the plates were washed and the enzyme activity was determined with 100 .mu.l of development solution (10% diethanolamine pH 9.8, 0.5 mM MgCl.sub.2, 0.05% NaN.sub.3) containing the reaction substrate p-nitrophenylphosphate (Sigma-Aldrich, USA). The enzyme activity was measured at optical densities of 405 nm and 620 nm by means of an automatic ELISA OD reader (Multiskan Labsystem, Finland) and the avidity calculation was done according to the mathematical analysis described in the literature (Jenum et al., 1997. J. Clin. Microbiol. 35, 1972-1977).

[0078] The following table 4 gives, by way of examples, the avidity of the human sera for a number of the antigen fragments selected.

[0079] The values should be interpreted as follows (commercial kit criterion): TABLE-US-00004 TABLE 4 Time from Infection Commercial kit Clones-GST Serum (months) bioMerleux tx-15.11 tx-1.11 tx-8.0 tx-4.18 tx-7.11 tx-1.16 T1 1 7.8% 20.0% 6.9% 12.0% -- -- 24.0% T2 1 5.7% 7.9% 2.3% 10.0% 9.8% 7.9% 2.7% T3 1-2 2.5% 5.4% 6.3% 9.5% 8.7% 11.5% 1.0% T4 1-2 8.1% 4.5% 9.0% 4.0% 10.3% 38.4% 9.5% T5 1-2 4.5% 2.4% 4.0% 9.3% 7.7% 6.7% 11.0% T6 1-2 2.6% 10.0% 4.7% 2.0% 10.0% 7.1% 12.4% T7 1-2 11.6% 9.1% 13.0% 8.0% 15.6% 4.2% 26.0% T8 1-2 6% 4.2% 8.7% 1.7% 7.5% 19.3% 26.2% T9 2-3 4.9% 17.0% 5.5% 3.0% 9.8% 4.8% 21.0% T10 2-3 13.7% 27.0% 30.8% 14.5% 28.1% 4.8% 52.0% T11 2-3 66.1% 41.0% 37.6% 15.7% 42.8% 59.0% 72.0% T12 3-4 16.2% 29.0% 25.1% 13.9% 28.7% 8.6% 56.0% T13 4-5 42.7% 20.1% 59.0% -- -- 28.6% 89.0% T14 4-5 59.5% 22.0% 32.8% 67.5% 50.9% 75.0% 79.5% T15 5-6 14.7% 25.0% 9.5% 14.6% 19.2% 8.3% 59.0% T16 6 55.1% 35.0% 75.8% 70.0% -- 63.5% 79.2% T17 6 15.6% -- -- -- 26.6% 10.2% 45.5% T18 6-7 45.8% 64.0% 59.1% -- 46.1% 50.7% 69.0% T19 6-7 25.7% 29.4% 23.0% 30.0% 24.6% 55.6% 62.3% T20 7-8 43.6% 44.0% 48.0% -- 63.9% 47.9% 90.0% T21 7-8 52.2% 22.0% 31.0% 16.4% 49.7% 48.2% 69.0% T22 7-8 26.2% 2.5% -- 9.0% -- -- 36.0% T23 8 26.2% 47.3% 47.2% -- -- 21.0% 42.6% T24 8 22.8% 26.5% 22.4% 82.8% -- 16.7% 40.5% T25 10 28.6% 46.0% 52.4% -- -- 23.2% 37.5% T26 24 25.6% 62.0% 35.3% -- -- -- 73.8% T27 38 41.8% 25.0% 34.1% 55.0% 35.2% 43.8% 58.0%

EXAMPLE 2

[0080] Using the vector .lamda.KM4 of Example 1, a library of DNA fragments of known Toxoplasma gondii genes was constructed.

[0081] Cells of Toxoplasma gondii (10.sup.6 parasites, strain ME49) were grown in vitro in monkey kidney cells ("VERO" African green monkey cells) using DMEM culture medium containing 10% foetal bovine serum, 2 mM glutamine and 0.05 mg/ml gentamicin (Gibco BRL, Canada). To have both forms of the parasite (tachyzoites and bradyzoites) present in the cell cultures, an experimental protocol was used based on the change in pH of the culture medium (Soete et al., 1994, Experimental Parasitology, 78, 361-370). The parasites were collected after complete lysis of the host cells and purified by filtration (filter porosity 3 .mu.m) followed by centrifuging. 2 .mu.g of mRNA were isolated from 5.times.10.sup.6 parasites using the "QuickPrep Micro mRNA Purification Kit" (Amersham Pharmacia Biotech, Sweden) and following the manufacturer's instructions. cDNA was synthesised from 200 ng of poly(A)+ RNA using the "SMART cDNA Library Construction Kit" (Clontech, CA, USA) and following the manufacturer's instructions. Genomic DNA was purified from the remaining 5.times.10.sup.6 cells using standard procedures (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY) and stored at -20.degree. C.

[0082] For the construction of the expression/exposure library the following genes, expressed only in the bradyzoite stage, were amplified by means of PCR with specific oligonucleotides: [0083] 1--SAG2D (Lekutis et al., 2000, Experimental Parasitology, 96, 89-96) was obtained from genomic DNA using the oligonucleotides 5'-ATGGCGGCTGCACACTCG-3' (SEQ ID No 39) and 5'-GAACATATTCCCTGTCACCAATG-3' (SEQ ID No 40); [0084] 2--SAG4 (Odberg-Ferragut et al., 1996, Molecular and Biochemical Parasitology, 82, 237-244) was obtained from genomic DNA using the oligonucleotides 5'-ATGACGAAAAATAAAATTCTTCTC-3' (SEQ ID No 41) and 5'-CATTGATATCAACACAAAGGCC-3' (SEQ ID No 42) [0085] 3--BSR4 (Manger et al., 1998, Infection and Immunity, 66, 2237-2244) was obtained from genomic DNA using the oligonucleotides 5'-ATGGTGATGATGGGCAGCATG-3' (SEQ ID No 43) and 5'-CGGCGGCCGCGCTAGAGG-3' (SEQ ID No 44); [0086] 4--MAG1 (Parmley et al., 1994, Molecular and Biochemical Parasitology, 66, 283-296) was obtained from genomic DNA using the oligonucleotides 5'-CGTTGGATCCTTGGATTGAGCCAAAGGGTGCCAG-3' (SEQ ID No 45) and 5'-CCCAGAATTCTCAAGCTGCCTGTTCCGCTAAGATCTG-3' (SEQ ID No 46); [0087] 5--LDH2 (Yang and Parmley, 1997, Gene, 184, 1-12) was obtained from cDNA using the oligonucleotides 5'-ATGACGGGTACCGTTAGCAG-3' (SEQ ID No 47) and 5'-ACCCAGCGCCGCTAAACTC-3' (SEQ ID No 48); [0088] 6--ENO1 (Dzierszinski et al., 2001, Journal of Molecular Biology, 309, 1017-1027) was obtained from genomic DNA using the oligonucleotides 5'-ATGGTGGTTATCAAGGACATCG-3' (SEQ ID No 49) and 5'-TTTTGGGTGTCGAAAGCTCTC-3' (SEQ ID No 50); [0089] 7--BAG1 (Bohne et al., 1995, Molecular Microbiology, 16, 1221-1230) was obtained from cDNA using the oligonucleotides 5'-ATGGCGCCGTCAGCATCG-3' (SEQ ID No 51) and 5'-CTTCACGCTGATTTGTTGCTTTG-3' (SEQ ID No 52); [0090] 8--p-ATPase (Holpert et al., 2001, Molecular and Biochemical Parasitology, 112, 293-296) was obtained from genomic DNA using the oligonucleotides 5'-ATGGACGAAGCGAGCAGAAGG-3' (SEQ ID No 53) and 5'-ACGCGTGATCGAAGGAACCG-3' (SEQ ID No 54).

[0091] 10 .mu.g of DNA deriving from a mixture of the amplification products of the above-mentioned genes were fragmented randomly using 0.5 ng of the endonuclease DNaseI (Sigma-Aldrich, USA). The mixture of DNA and DNaseI was incubated for 20 minutes at 15.degree. C. and the DNA fragments were purified by means of the "QIAquick PCR Purification Kit" (Qiagen, CA, USA), following the manufacturer's instructions. The 3 .mu.g ends of the cDNA fragments were "flattened" by incubating the DNA with 9 units of the enzyme T4 DNA polymerase (New England Biolabs, MA, USA) for 60 minutes at 15.degree. C. The fragments were then purified by means of extraction in phenol/chloroform and subsequent precipitation in ethanol. 500 ng of the resulting DNA were bound with a 20-fold molar excess of "synthetic adaptors" for the purposes of adding the restriction sites SpeI and NotI to the ends of the fragments. Six adaptors were used, obtained by hybridisation of the following pairs of oligonucleotides: K185 5'-CTAGTCGTGCTGGCCAGC-3' (SEQ ID No 5) and K186 5'-GCTGGCCAGCACGA-3' (SEQ ID No 6); K187 5'-CTAGTCGTGCTGGCCA GCT-3' (SEQ ID No 7) and K188 5'-AGCTGGCCAGCACGA-3' (SEQ ID No 8); K189 5'-CTAGTCGT GCTGGCCAGCTG-3' (SEQ ID No 9) and K190 5'-CAGCTGGCCAGCACGA-3' (SEQ ID No 10); K191 5'-TCTGGTGGCGGTAGC-3' (SEQ ID No 11) and K192 5'-GGCCGCTACCGCCACCAGA-3' (SEQ ID No 12); K193 5'-TTCTGGTGGCGGTAGC-3' (SEQ ID No 13) and K194 5'-GGCCGCTACCGCCACCAGAA-3' (SEQ ID No 14); K195 5'-TTTCTGGTGGCGGTAGC-3' SEQ ID No 15) and K196 5'-GGCCGCTACCGCCACCAGAAA-3' (SEQ ID No 16). The excess of unligated adaptors was removed from the ligation mixture by electropheresis on 2% agarose gel and the cDNA fragments with molecular weights ranging from 250 bp to 1000 bp were excised from the gel and purified by means of the "Qiaquick gel extraction kit" (Qiagen, CA, USA) following the manufacturer's instructions. The vector .lamda.KM4 was digested with SpeI/NotI and for the construction of the library 6 ligation mixtures were performed, each containing 0.4 .mu.g of vector and approximately 7 ng of insert. After overnight incubation at 4.degree. C. the ligation mixtures were packaged in vitro with the "Ready-To-Go lambda packaging kit" (Amersham Pharmacia Biotech, Sweden) and plated for infection of BB4 cells (bacterial cells of E. coli strain BB4; Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY). After overnight incubation at 37.degree. C. the phage was eluted from the plates with SM buffer (Sambrook et al., 1989, Molecular Cloning: a laboratory manual, Cold Spring Harbor Laboratory Press, NY), purified, concentrated and stored at -80.degree. C. in SM buffer containing 7% dimethylsulphoxide. The complexity of the library calculated as the number of total independent clones with inserts was 10.sup.6 clones.

[0092] Affinity selection, phage-ELISA, immunoscreening and phage clones preparation were performed exactly as described in Example 1

[0093] The following table 5 gives, by way of examples, the reactivity of a number of the recombinant bacteriophages selected. TABLE-US-00005 TABLE 5 Reactivity of phage clone with Reactivity of phage positive sera (positive/total clone with negative sera Name of clone positive) (negative/total negative) TxB-c121.2 10/20 1/10 TxB-c126.3 12/20 0/10 TxB-44.3 10/20 0/10 TxB-7.1 8/20 0/10 TxB-9.1 1/20 1/10 TxB-12.1 5/20 0/10

Characterisation of Positive Clones

[0094] The clones which showed multiple reactivity with the Toxoplasma gondii positive sera and which presented no reactivity with the negative sera were subsequently sequenced and compared with the sequences of the genes used to construct the library

[0095] The following table 6 gives, by way of examples, the sequences of some of the clones selected: TABLE-US-00006 TABLE 6 Name of clone Sequence TxB.26.3 GGATTGAGCCAAAGGGTGCCAGAGCTACCAGAAGT (SEQ ID No 55) GGAGCCCTTTGATGAAGTAGGCACGGGAGCTCGAC GGTCCGGGTCCATTGCGACCCTTCTTCCACAAGAC GCTGTTTTATATGAGAACTCAGAGGACGTTGCCGT TCCGAGTGATTCAGCATCGACCCCGTCATACTTTC ATGTGGAATCTCCAAGTGCTAGTGTGGAAGCCGCG ACTGGCGCTGTGGGAGAGGTGGTGCCGGACTGTGA AGAACAACAGGAACAGGGTGACACGACGTTATCCG ATCACGATTTCCATTCA TxB-c17.1 TCTTCAGAAAGATGACGTAACCATAGAAGTCGACAA (SEQ ID No 56) CGGAGCCATCGTTATCAAAGGAGAGAAGACCTCGAA AGAAGCGGAGAAAGTGGACGATGGCAAAACAAAGAA CATTTTGACTGAGCGAGTGTCCGGTTATTTTGCGCG CCGGTTCCAGCTCCCGAGTAATTACAAGCCCGACGG AATCAGTGCGGCAATGGACAACGGCGTTCTACGTGT CACGATCAAGGTCGAGGATTCAGGGGGCGCAAAGCA ACAAATCAGCGTG

[0096] The clone TxB-cl26.3 constitutes a fragment of the gene MAG1, a 65 kDa protein of the matrix and wall of T. gondii cysts (Parmley et al., 1994, Molecular and Biochemical Parasitology, 66, 283-296), the protein product of which has never been identified as an "antigen fragment" in the human humoral response. Said clone has the amino acid sequence GLSQRVPELPEVEPFDEVGTGARRSGSIATLLPQDAVLYENSEDVAVPSDSASTPSYFHVESPSASVEAATGA- VGEVVPDCEE QQEQGDTTLSDHDFH (SEQ ID No 57) and its use as a fragment containing an epitope is covered by the present invention.

[0097] The clone TxB-cl7.1 constitutes a fragment of the gene BAG1, a 30 kDa protein of the heat shock protein family of T. gondii (Bohne et al., 1995, Molecular Microbiology, 16, 1221-1230), the protein product of which has never been identified as an "antigen fragment" in the human humoral response. Said clone has the amino acid sequence LNPIDDMLFETALTANEMMEDITWRPRVDVEFDSKKKEMIILADLP GLQKDDVTIEVDNGAIVIKGEKTSKEAEKVDDGKTKNILTERVSGY FARRFQLPSNYIDGISAAMDNGVLRVTIKVEDSGGAKQQISV (SEQ ID No 58) and its use as a fragment containing an epitope is covered by the present invention.

Expression of DNA Fragments Selected from the Library as fusion Products with GST

[0098] The phage clones for which specific reactivity with sera of patients testing positive for Toxoplasma gondii was demonstrated, were amplified and then analysed with a substantial panel of positive and negative sera. After this ELISA study, the clones that showed multiple reactivity with Toxoplasma gondii-positive sera and presented no reactivity with the negative sera were cloned as fusion products with the protein Glutathione Sulphur Transferase (GST) and expressed in bacterial cells, for the purposes of determining their specificity and selectivity. To produce the fusion proteins each clone was amplified from a single phage plaque by PCR, using the following oligonucleotides: K47 5'-GGGCACTCGACCGGAATTATCG-3' (SEQ ID No 37) and K85 5'-GGGTAAAGGTTTCTTTGCTCG-3' (SEQ ID No 38). The resulting fragment was then purified by means of the "Qiagen Purification Kit" (Qiagen, CA, USA), digested with the restriction enzymes SpeI and NotI and cloned in the vector pGEX-SN to generate the fusion with GST. The corresponding recombinant proteins were then expressed in E. coli and purified by affinity using Glutathione-Sepharose resin (Amersham Pharmacia Biotech, Sweden) and following standard protocols (Sambrook et al., 1989, Molecular Cloning, Cold Spring Harbor Laboratory Press, Cold Spring Harbor).

[0099] The following table 7, by way of examples, presents the reactivity with negative and positive sera of a number of the clones selected, assayed in the form of fusion proteins: TABLE-US-00007 TABLE 7 Reactivity of GST fusion Reactivity of GST fusion protein with positive portein with negative Name of clone sera (pos./total neg.) sera (neg./totale neg.) TxB-c126.3 30/34 0/32 TxB-c17.1 17/34 0/32

EXAMPLE 3

[0100] By using the same strategy described in Example 2, a gene collection of DNA encoding for protein products of the Toxoplasma gondii microneme family was used to construct a "microneme-display library".

[0101] For the construction of the microneme-library the following genes were amplified by means of PCR with specific oligonucleotides: [0102] 1--MIC2 (Wan et al, 1997, Mol. Biochem. Parasitol. 84: 203-214) was obtained from single strand cDNA using the oligonucleotides 5'-ATGAGACTCCAACCGAGGCC-3' (SEQ ID No 69) and 5'-CTGCCTGACTCTTTCTTGGACTG-3' (SEQ ID No 70); [0103] 2--M2AP (Rabenau et al., 2001, Mol. Microbiol. 41: 537-547) was obtained from single strand cDNA using the oligonucleotides 5'-GGAAAGTTGGAAATCCGGCGGC-3' (SEQ ID No 71) and 5'-CGCCTCATCGTCACTCGGC-3' (SEQ ID No 72) [0104] 3--MIC4 (Brecht et al., 2001, J. Biol. Chem. 276:4119-412) was obtained from single strand cDNA using the oligonucleotides 5'-ATGAGAGCGTCGCTCCCGG-3' (SEQ ID No 73) and 5'-GTGTCTTTCGCTTCAAGCACCTG-3' (SEQ ID No 74); [0105] 4--AMA1 (Hehl et al., 2000, Infect. Immun. 68:7078-7086) was obtained from single strand cDNA using the oligonucleotides 5'-ATGGGGCTCGTGGGCGTAC-3' (SEQ ID No 75) and 5'-GATCAACGCAGTGTTAGAGCCAC-3' (SEQ ID No 76);

[0106] 10 .mu.g of DNA deriving from a mixture of the amplification products of the above-mentioned genes were fragmented randomly using 0.5 ng of the endonuclease DNaseI (Sigma-Aldrich, USA). The mixture of DNA and DNaseI was incubated for 20 minutes at 15.degree. C. and the DNA fragments were purified by means of the "QIAquick PCR Purification Kit" (Qiagen, CA, USA), following the manufacturer's instructions. Consequent steps for the construction of the microneme-library, and for the affinity selection were performed by following the procedure described in Example 2.

Selection of the Microneme-Library with Sera of Infants Who Were Infected by T. gondii During Pregnancy

[0107] To identify the antigenic domains of the T. gondii microneme proteins an affinity selection procedure was used consisting of two "panning" cycles with four sera collected from infants who were congenitally infected by the parasite, followed by an immunological screening procedure carried out with the same sera. The library was selected with sera T1, T2, T3, T4, generating, after a single selection cycle, the corresponding mixtures p1.sup.I, p2.sup.I, p3.sup.I and p4.sup.I. Each mixture was then subjected to a second affinity selection cycle with the same serum, giving rise to a second series of mixtures (called p1.sup.IIp2.sup.II, p3.sup.II and p4.sup.II). Various positive clones were identified by means of immunoplate screening per plaque of reactive mixtures.

[0108] Phage-Elisa, immunoscreening, and the preparation of phage clones were subsequently performed exactly as described in Examples 1 and 2.

[0109] The following table 8 gives, by way of examples, the reactivity of a number of the recombinant bacteriophages selected. TABLE-US-00008 TABLE 8 Reactivity of phage Reactivity of phage clone with clone with positive sera negative sera (negative/total Name of clone (positive/total positive) negative) Tx-2.a 13/16 0/10 Tx-1.b 11/16 0/10 Tx-11.b 12/16 0/10 Tx-13.b 9/16 0/10 Tx-15.b 9/16 0/10

Characterisation of Positive Clones

[0110] The following table 9 gives the sequences of the clones selected: TABLE-US-00009 TABLE 9 Name of the clone Sequence Identification Classification Tx-2.a CCCCAGGATGCCATTT MIC2 Microneme (SEQ ID No 59) GCTCGGATTGGTCCGC protein ATGGAGCCCCTGCAGT unknown as GTATCCTGCGGTGACG antigen in GAAGCCAAATCAGGAC human response GCGAACTGAGGTTTCT GCTCCGCAACCTGGAA CACCAACATGTCCGGA CTGCCCTGCGCCCATG GGAAGGACTTGCGTGG AACAAGGCGGACTTGA AGAAATCCGTGAATGC AGTGCGGGGGTATGTG CTGTTGACGCTGGATG TGGCGTCTGGGTT Tx-1.b CCGTGTCCAATTAATG MIC2 Microneme (SEQ ID No 60) CAACTTGCGGTCAGTT protein TGAAGAATGGAGTACA unknown as TGCTCGGTCTCATGTG antigen in GTGGTGGACTGAAAAC human response GAGGTCGAGGAACCCT TGGAATGAAGACCAAC AACATGGAGGACTATC CTGCGAGCAGCAGCAT CCTGGTGGGCGGACGG AAACGGTAACTTGCAA TCCTCAAGCGTGTCCT GTGGATGAACGACCGG GGGAGTGGGCAGAGTG GGGGGAATGTAGTGTC ACGTGCGGCGACGGAG TGCGAGAGCGCAGGCG CGGGAAAAGTCTAGTT GAGGCTAAATTCGGCG GACGCACCATTGATCA GCAGAATGAGGCTCTT CCGGAAGACTTAAAAA TCAAAAACGTCGAGTA TGAGCCATGTTCGTAT CCTGCTTGTGGAGCTT CCTGCACGTACGTCTG GAGTGACTGGAACAAG Tx-11.b AACGAACCGGTGGCCC M2AP Microneme (SEQ ID No 61) TAGCTCAGCTCAGCAC protein unknown ATTCCTCGAGCTCGTC as antigen in GAGGTGCCATGTAACT human response CTGTTCATGTTCAGGG GGTGATGACCCCGAAT CAAATGGTCAAAGTGA CTGGTGCAGGATGGGA TAATGGCGTTCTCGAG TTCTATGTCACGAGGC CAACGAAGACAGGCGG GGACACAAGCCGAAGC CATCTTGCGTCGATCA TGTGTTATTCCAAGGA CATTGACGGCGTGCCG TCAGACAAAGCGGGAA AGTGCTTTCTGAAGAA CTTTTCTGGTGAAGAC TCGTCGGAAATAGACG AAAAAGAAGTATCTCT ACCCATCAAGAGCCAC AACGATGCGTTCATGT TCGTTTGTTCTTCAAA TGATGGATCCGCACTC CAGTGTGATGTTTTCG CCCTTGATAACACCAA CTCTAGCGACGGGTGG AAAGTGAATACCGTGG ATCTTGGCGTCAGCGT TAGTCCGGATTTGGCA TTCGGACTCACTGCAG ATGGGGTCAAGGTGAA GAAGTTGTACGCAAGC AGCGGCCTGACAGCGA TCAACGACGACCCTTC CTTGGGGTGCAAGGCT CCTCCCCATTCTCCGC CGGCCGGAGAGGAACC GAGTTTGGCGTCGCCT GAAAACAGCGGGTCTG CAACACCAGGGGAAGA AAGTCCGTCTGAGTCT GAATCT Tx-13.b CTTCGCGGGTACAGGT AMA1 Microneme (SEQ ID No 62) TCGGTGTTTGGAAGAA protein AGGCCGTTGCCTCGAC unknown as TACACTGAATTGACCG antigen in ACACTGTGATAGAACG human response TGTTGAGTCAAAGGCA CAGTGCTGGGTGAAAA CCTTTGAAAACGACGG GGTCGCGAGTGACCAA CCCCATACGTATCCAC TGACGTCGCAAGCATC ATGGAACGATTGGTGG CCTCTCCACCAGAGTG ACCAACCTCACTCAGG TGGCGTTGGGCGTAAT TACGGTTTCTACTACG TGGACACGACTGGAGA GGGCAAGTGTGCACTC TCTGACCAGGTACCCG ACTGCCTGGTGTCGGA TTCTGCCGCCGTGTCG TATACAGCAGCGGGGA GTTTGTCTGAAGAGAC GCCGAATTTCATAATT CCGTCAAATCCCTCTG TTACTCCGCCAACGCG CGAGACGGCACTTCAG TGCACGGCCGACAAGT TCCCCGACTCTTTCGG TGCCTGCGACGTTCAA GCCTGTAAAAGACAGA AGACGTCCTGCGTTGG CGGACAGATTCAAAGT ACTAGCGTCGACTGCA CCGCGGACGAACAAAA TGAATGTGGCTCTAAC ACTGCG Tx15.b AGTGCCAACGTAACAA MIC4 Microneme (SEQ ID No 63) GTTCGGAGCCTGCAAA protein- ACTTGATCTCTCTTGT unknown as GCGCACTCTGACAATA antigen in AGGGATCAAGGGCTCC human response CACAATAGGCGAGCCA GTGCCAGATGTGTCCC TGGAACAATGTGCTGC GCAATGCAAGGCTGTT GATGGCTGCACACATT TCACTTATAATGACGA TTCGAAGATGTGCCAT GTGAAGGAGGGAAAAC CCGATTTATACGATCT CACAGGAGGCAAAACA GCACCGCGCAGTTGCG ATAGATCATGCTTCGA ACAACACGTATCGTAT GAGGGAGCTCCTGACG TGATGACAGCGATGGT CACGAGCCAGTCAGCG GACTGTCAGGCTGCGT GTGCGGCTGACCCGAG CTGCGAGATCTTCACT TATAACGAACACGACC AGAAATGTACTTTCAA AGGAAGGGGGTTTTCT GCGTTTAAGGAACGAG GGGTGTTGGGTGTGAC TTCCGGGCCGAAACAG TTCTGCGATGAAGGCG GTAAATTAACT

[0111] The clones Tx-2.a e Tx-1.b represent two distinct fragments of the MIC2 gene (Wan et al, 1997, Mol. Biochem. Parasitol. 84: 203-214) and have never been identified as antigens of the human antibody response. Said clones have respectively the amino acid sequences PQDAICSDWSAWSPCSVSCGDGSQIRTRTEVSAPQPGTPTCPDCPA PMGRTCVEQGGLEEIRECSAGVCAVDAGCGVWV (SEQ ID No 64) and PCPINATCGQFEEWSTCSVSCGGGLKTRSRNPWNEDQQHGGLSCE QQHPGGRTETVTCNPQACPVDERPGEWAEWGECSVTCGDGVRER RRGKSLVEAIFGGRTIDQQNEALPEDLKIKNVEYEPCSYPACGASC TYVWSDWNK (SEQ ID No 65) and their use as fragments containing an epitope is covered by the present invention.

[0112] The clone Tx-11.b represents a distinct fragment of the M2AP gene (Rabenau et al., 2001, Mol. Microbiol. 41: 537-547) and has never been identified as antigen of the human antibody response. Said clone has the amino acid sequence NEPVALAQLSTFLELVEVPCNSVHVQGVMTPNQMVKVTGAGWDNGVLEFYVTRPTKTGGDTSRSHIASIMCYS- K DIDGVPSDKAGKCFLKNFSGEDSSEIDEKEVSLPIKSHNDAFMFVC SSNDGSALQCDVFALDNTNSSDGWKVNTVDLGVSVSPDLAFGLTA DGVKVLYASSGLTAINDDPSLGCKAPPHSPPAGEEPSLPSPENS GSATPAEESPSESES (SEQ ID No 66) and its use as fragment containing an epitope is covered by the present invention.

[0113] The clone Tx-13.b represents a fragment of the AMA1 gene (Hehl et al., 2000, Infect. Immun. 68:7078-7086). Said clone has the amino acid sequence LRGYRFGVWKKGRCLDYTELTDTVIERVESKAQCWVKTFENDGVASDQPHTYPLTSQASWNDWW- PLHQSDQPHSGGVGRNYG FYYVDTTGEGKCALSDQVPDCLVSDSAAVSYTAAGSLSEETPNFIIP SNPSVTPPTPETALQCTADKFPDSFGACDVQACKRQKTSCVGGQIQ STSVDCTADEQNECGSNTA (SEQ ID No 67) and its use as fragment containing an epitope is covered by the present invention.

[0114] The clone Tx-15.b represents a fragment of the MIC4 gene (Brecht et al., 2001, J. Biol. Chem. 276:4119-4127). Said clone has the amino acid sequence SANVTSSEPAKLDLSCAHSDNKGSRAPTIGEPVPDVSLEQCAAQCKAVDGCTHFTYNDDSKMCHVKEGKPDLY- DLTGGKTAPRS CDRSCFEQHVSYEGAPDVMTAIVTSQSADCQAACAADPSCEIFTY NEHDQKCTFKGRGFSAFKERGVLGVTSGPKQFCDEGGKLT (SEQ ID No 68) and its use as fragment containing an epitope is covered by the present invention.

Expression of DNA Fragments Selected from the Microneme-Library as Fusion Products with GST

[0115] Phage clones isolated from the microneme-library were cloned as fusion products with GST protein and expressed in bacterial cells, for the purposes of determining their specificity and selectivity. The procedure described in Examples 1 and 2 was used to produce the fusion proteins.

[0116] The following table 10, by way of example, presents the reactivity with negative and positive sera of a number of the clones selected, assayed in the form of fusion proteins: TABLE-US-00010 TABLE 10 Reactivity of GST fusion Reactivity of GST fusion protein with positive sera portein with negative sera Name of clone (pos./total neg.) (neg./totale neg.) Tx-2.a 29/30 0/15 Tx-1.b 15/30 0/15 Tx-11.b 23/30 0/15 Tx-13.b 24/30 0/15 Tx-15.b 12/30 0/15

[0117]

Sequence CWU 1

1

76 1 48 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 1 tttatctaga cccagcccta ggaagcttct cctgagtagg acaaatcc 48 2 32 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 2 gggtctagat aaaacgaaag gcccagtctt tc 32 3 56 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 3 ccgccttcca tgggtactag ttttaaatgc ggccgcacga gcaaagaaac ctttac 56 4 22 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 4 agcttcctag ggctgggtct ag 22 5 18 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 5 ctagtcgtgc tggccagc 18 6 14 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 6 gctggccagc acga 14 7 19 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 7 ctagtcgtgc tggccagct 19 8 15 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 8 agctggccag cacga 15 9 20 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 9 ctagtcgtgc tggccagctg 20 10 16 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 10 cagctggcca gcacga 16 11 15 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 11 tctggtggcg gtagc 15 12 19 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 12 ggccgctacc gccaccaga 19 13 16 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 13 ttctggtggc ggtagc 16 14 20 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 14 ggccgctacc gccaccagaa 20 15 17 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 15 tttctggtgg cggtagc 17 16 21 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 16 ggccgctacc gccaccagaa a 21 17 348 DNA Toxoplasma gondii 17 agtggaggga cagggcaggg attaggaatc ggagaatctg tagatttgga gatgatgggg 60 aacacgtatc gtgtggagag acccacaggc aacccggact tgctcaagat cgccattaaa 120 gcttcagatg gatcgtacag cgaagtcggc aatgttaacg tggaggaggt gattgatact 180 atgaaaagca tgcagaggga cgaggacatt ttccttcgtg cgttgaacaa aggcgaaaca 240 gtagaggaag cgatcgaaga cgtggctcaa gcagaagggc ttaattcgga gcaaaccctg 300 caactggaag atgcagtgag cgcggtggcg tctgttgttc aagacgag 348 18 165 DNA Toxoplasma gondii 18 tactcttcac cacgaatagt tgttttgatt agatattgct tcttctccac atatcgcctc 60 acaatgttcg ccgtaaaaca ttgtttgctg gttgttgccg ttggcgccct ggtcaacgtc 120 tcggtgaggg ctgccgagtt ttccggagtt gttaaccagg gacct 165 19 297 DNA Toxoplasma gondii 19 gctgccttgg gaggccttgc ggcggatcag cctgaaaatc atcaggctct tgcagaacca 60 gttacgggtg tgggggaagc aggagtgtcc cccgtcaacg aagctggtga gtcatacagt 120 tctgcaactt cgggtgtcca agaagctacc gccccaggtg cagtgctcct ggacgcaatc 180 gatgccgagt cggataaggt ggacaatcag gcggagggag gtgagcgtat gaagaaggtc 240 gaagaggagt tgtcgttatt gaggcgggaa ttatatgatc gcacagatcg ccctggt 297 20 234 DNA Toxoplasma gondii 20 cagttcgcta ccgcggccac cgcgtcagat gacgaactga tgagtcgaat ccgaaattct 60 gactttttcg atggtcaagc acccgttgac agtctcagac cgacgaacgc cggtgtcgac 120 tcgaaaggga ccgacgatca cctcaccacc agcatggata aggcatctgt agagagtcag 180 cttccgagaa gagagccatt ggagacggag ccagatgaac aagaagaagt tcat 234 21 104 DNA Toxoplasma gondii 21 gagaacccgg tgagaccgcc tcctcccggt ttccatccaa gcgttattcc caatcccccg 60 tacccgctgg gcactccagc gggcatgcca cagccagagg ttcc 104 22 219 DNA Toxoplasma gondii 22 aggaggactg gatgtcatgc cttcagggag aactgcagcc ctggtagatg tattgatgac 60 gcctcgcatg agaatggcta cacctgcgag tgccccacag ggtactcacg tgaggtgact 120 tccaaggcgg aggagtcgtg tgtggaagga gtcgaagtca cgctggctga gaaatgcgag 180 aaggaattcg gcatcagcgc gtcatcctgc aaatgcgat 219 23 270 DNA Toxoplasma gondii 23 gcacccactc aatctgaaat gaaagaattc caagaggaaa tcaaagaagg ggtggaggaa 60 acaaagcatg aagacgatcc tgagatgacg cggctcatgg tgaccgagaa gcaggagagc 120 aaaaatttca gcaagatggc gaaatcccag agttttagca cgcgaatcga agagctcggg 180 ggatccattt cgtttctaac tgaaacgggg gtcacaatga tcgagttgcc caaaactgtc 240 agtgaacatg acatggacca actactccac 270 24 456 DNA Toxoplasma gondii 24 gttatggcat cggatccccc tcttgttgcc aatcaagttg tcacctgccc agataaaaaa 60 tcgacagccg cggtcattct cacaccgacg gagaaccact tcactctcaa gtgccctaaa 120 acagcgctca cagagcctcc cactcttgcg tactcaccca acaggcaaat ctgcccagcg 180 ggtactacaa gtagctgtac atcaaaggct gtaacattga gctccttgat tcctgaagca 240 gaagatagct ggtggacggg ggattctgct agtctcgaca cggcaggcat caaactcaca 300 gttccaatcg agaagttccc cgtgacaacg cagacgtttg tggtcggttg catcaaggga 360 gacgacgcac agagttgtat ggtcacggtg acagtacaag ccagagcctc atcggtcgtc 420 aataatgtcg caaggtgctc ctatggtgcg gacagc 456 25 393 DNA Toxoplasma gondii 25 ccatcggtcg tcaataatgt cgcaaggtgc tcctacggtg cagacagcac tcttggtcct 60 gtcaagttgt ctgcggaagg acccactaca atgaccctcg tgtgcgggaa agatggagtc 120 aaagttcctc aagacaacaa tcagtactgt tccgggacga cgctgactgg ttgcaacgag 180 aaatcgttca aagatatttt gccaaaatta actgagaacc cgtggcaggg taacgcttcg 240 agtgataagg gtgccacgct aacgatcaag aaggaagcat ttccagccga gtcaaaaagc 300 gtcattattg gatgcacagg gggatcgcct gagaagcatc actgtaccgt gaaactggag 360 tttgccgggg ctgcagggtc agcaaaatcg gct 393 26 116 PRT Toxoplasma gondii 26 Ser Gly Gly Thr Gly Gln Gly Leu Gly Ile Gly Glu Ser Val Asp Leu 1 5 10 15 Glu Met Met Gly Asn Thr Tyr Arg Val Glu Arg Pro Thr Gly Asn Pro 20 25 30 Asp Leu Leu Lys Ile Ala Ile Lys Ala Ser Asp Gly Ser Tyr Ser Glu 35 40 45 Val Gly Asn Val Asn Val Glu Glu Val Ile Asp Thr Met Lys Ser Met 50 55 60 Gln Arg Asp Glu Asp Ile Phe Leu Arg Ala Leu Asn Lys Gly Glu Thr 65 70 75 80 Val Glu Glu Ala Ile Glu Asp Val Ala Gln Ala Glu Gly Leu Asn Ser 85 90 95 Glu Gln Thr Leu Gln Leu Glu Asp Ala Val Ser Ala Val Ala Ser Val 100 105 110 Val Gln Asp Glu 115 27 55 PRT Toxoplasma gondii 27 Tyr Ser Ser Pro Arg Ile Val Val Leu Ile Arg Tyr Cys Phe Phe Ser 1 5 10 15 Thr Tyr Arg Leu Thr Met Phe Ala Val Lys His Cys Leu Leu Val Val 20 25 30 Ala Val Gly Ala Leu Val Asn Val Ser Val Arg Ala Ala Glu Phe Ser 35 40 45 Gly Val Val Asn Gln Gly Pro 50 55 28 99 PRT Toxoplasma gondii 28 Ala Ala Leu Gly Gly Leu Ala Ala Asp Gln Pro Glu Asn His Gln Ala 1 5 10 15 Leu Ala Glu Pro Val Thr Gly Val Gly Glu Ala Gly Val Ser Pro Val 20 25 30 Asn Glu Ala Gly Glu Ser Tyr Ser Ser Ala Thr Ser Gly Val Gln Glu 35 40 45 Ala Thr Ala Pro Gly Ala Val Leu Leu Asp Ala Ile Asp Ala Glu Ser 50 55 60 Asp Lys Val Asp Asn Gln Ala Glu Gly Gly Glu Arg Met Lys Lys Val 65 70 75 80 Glu Glu Glu Leu Ser Leu Leu Arg Arg Glu Leu Tyr Asp Arg Thr Asp 85 90 95 Arg Pro Gly 29 78 PRT Toxoplasma gondii 29 Phe Ala Thr Ala Ala Thr Ala Ser Asp Asp Glu Leu Met Ser Arg Ile 1 5 10 15 Arg Asn Ser Asp Phe Phe Asp Gly Gln Ala Pro Val Asp Ser Leu Arg 20 25 30 Pro Thr Asn Ala Gly Val Asp Ser Lys Gly Thr Asp Asp His Leu Thr 35 40 45 Thr Ser Met Asp Lys Ala Ser Val Glu Ser Gln Leu Pro Arg Arg Glu 50 55 60 Pro Leu Glu Thr Glu Pro Asp Glu Gln Glu Glu Val His Phe 65 70 75 30 35 PRT Toxoplasma gondii 30 Glu Asn Pro Val Arg Pro Pro Pro Pro Gly Phe His Pro Ser Val Ile 1 5 10 15 Pro Asn Pro Pro Tyr Pro Leu Gly Thr Pro Ala Gly Met Pro Gln Pro 20 25 30 Glu Val Pro 35 31 73 PRT Toxoplasma gondii 31 Arg Arg Thr Gly Cys His Ala Phe Arg Glu Asn Cys Ser Pro Gly Arg 1 5 10 15 Cys Ile Asp Asp Ala Ser His Glu Asn Gly Tyr Thr Cys Glu Cys Pro 20 25 30 Thr Gly Tyr Ser Arg Glu Val Thr Ser Lys Ala Glu Glu Ser Cys Val 35 40 45 Glu Gly Val Glu Val Thr Leu Ala Glu Lys Cys Glu Lys Glu Phe Gly 50 55 60 Ile Ser Ala Ser Ser Cys Lys Cys Asp 65 70 32 90 PRT Toxoplasma gondii 32 Ala Pro Thr Gln Ser Glu Met Lys Glu Phe Gln Glu Glu Ile Lys Glu 1 5 10 15 Gly Val Glu Glu Thr Lys His Glu Asp Asp Pro Glu Met Thr Arg Leu 20 25 30 Met Val Thr Glu Lys Gln Glu Ser Lys Asn Phe Ser Lys Met Ala Lys 35 40 45 Ser Gln Ser Phe Ser Thr Arg Ile Glu Glu Leu Gly Gly Ser Ile Ser 50 55 60 Phe Leu Thr Glu Thr Gly Val Thr Met Ile Glu Leu Pro Lys Thr Val 65 70 75 80 Ser Glu His Asp Met Asp Gln Leu Leu His 85 90 33 152 PRT Toxoplasma gondii 33 Val Met Ala Ser Asp Pro Pro Leu Val Ala Asn Gln Val Val Thr Cys 1 5 10 15 Pro Asp Lys Lys Ser Thr Ala Ala Val Ile Leu Thr Pro Thr Glu Asn 20 25 30 His Phe Thr Leu Lys Cys Pro Lys Thr Ala Leu Thr Glu Pro Pro Thr 35 40 45 Leu Ala Tyr Ser Pro Asn Arg Gln Ile Cys Pro Ala Gly Thr Thr Ser 50 55 60 Ser Cys Thr Ser Lys Ala Val Thr Leu Ser Ser Leu Ile Pro Glu Ala 65 70 75 80 Glu Asp Ser Trp Trp Thr Gly Asp Ser Ala Ser Leu Asp Thr Ala Gly 85 90 95 Ile Lys Leu Thr Val Pro Ile Glu Lys Phe Pro Val Thr Thr Gln Thr 100 105 110 Phe Val Val Gly Cys Ile Lys Gly Asp Asp Ala Gln Ser Cys Met Val 115 120 125 Thr Val Thr Val Gln Ala Arg Ala Ser Ser Val Val Asn Asn Val Ala 130 135 140 Arg Cys Ser Tyr Gly Ala Asp Ser 145 150 34 131 PRT Toxoplasma gondii 34 Pro Ser Val Val Asn Asn Val Ala Arg Cys Ser Tyr Gly Ala Asp Ser 1 5 10 15 Thr Leu Gly Pro Val Lys Leu Ser Ala Glu Gly Pro Thr Thr Met Thr 20 25 30 Leu Val Cys Gly Lys Asp Gly Val Lys Val Pro Gln Asp Asn Asn Gln 35 40 45 Tyr Cys Ser Gly Thr Thr Leu Thr Gly Cys Asn Glu Lys Ser Phe Lys 50 55 60 Asp Ile Leu Pro Lys Leu Thr Glu Asn Pro Trp Gln Gly Asn Ala Ser 65 70 75 80 Ser Asp Lys Gly Ala Thr Leu Thr Ile Lys Lys Glu Ala Phe Pro Ala 85 90 95 Glu Ser Lys Ser Val Ile Ile Gly Cys Thr Gly Gly Ser Pro Glu Lys 100 105 110 His His Cys Thr Val Lys Leu Glu Phe Ala Gly Ala Ala Gly Ser Ala 115 120 125 Lys Ser Ala 130 35 31 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 35 gatccttact agttttagta gcggccgcgg g 31 36 31 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 36 aattcccgcg gccgctacta aaactagtaa g 31 37 22 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 37 gggcactcga ccggaattat cg 22 38 21 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 38 gggtaaaggt ttctttgctc g 21 39 18 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 39 atggcggctg cacactcg 18 40 23 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 40 gaacatattc cctgtcacca atg 23 41 24 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 41 atgacgaaaa ataaaattct tctc 24 42 22 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 42 cattgatatc aacacaaagg cc 22 43 21 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 43 atggtgatga tgggcagcat g 21 44 18 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 44 cggcggccgc gctagagg 18 45 34 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 45 cgttggatcc ttggattgag ccaaagggtg ccag 34 46 37 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 46 cccagaattc tcaagctgcc tgttccgcta agatctg 37 47 20 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 47 atgacgggta ccgttagcag 20 48 19 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 48 acccagcgcc gctaaactc 19 49 22 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 49 atggtggtta tcaaggacat cg 22 50 21 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 50 ttttgggtgt cgaaagctct c 21 51 18 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 51 atggcgccgt cagcatcg 18 52 23 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 52 cttcacgctg atttgttgct ttg 23 53 21 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 53 atggacgaag cgagcagaag g 21 54 20 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 54 acgcgtgatc gaaggaaccg 20 55 297 DNA Toxoplasma gondii 55 ggattgagcc aaagggtgcc agagctacca gaagtggagc cctttgatga agtaggcacg 60 ggagctcgac ggtccgggtc cattgcgacc cttcttccac aagacgctgt tttatatgag 120 aactcagagg acgttgccgt tccgagtgat tcagcatcga ccccgtcata ctttcatgtg 180 gaatctccaa gtgctagtgt ggaagccgcg actggcgctg tgggagaggt ggtgccggac 240 tgtgaagaac aacaggaaca gggtgacacg acgttatccg atcacgattt ccattca 297 56 265 DNA Toxoplasma gondii 56 tcttcagaaa gatgacgtaa ccatagaagt cgacaacgga gccatcgtta tcaaaggaga 60 gaagacctcg aaagaagcgg agaaagtgga cgatggcaaa acaaagaaca ttttgactga 120 gcgagtgtcc ggttattttg cgcgccggtt ccagctcccg agtaattaca agcccgacgg 180 aatcagtgcg gcaatggaca acggcgttct acgtgtcacg atcaaggtcg aggattcagg 240 gggcgcaaag caacaaatca gcgtg 265 57 98 PRT Toxoplasma gondii 57 Gly Leu Ser Gln Arg Val Pro Glu Leu Pro Glu Val Glu Pro Phe Asp 1 5 10 15 Glu Val Gly Thr Gly Ala Arg Arg Ser Gly Ser Ile Ala Thr Leu Leu 20 25 30 Pro Gln Asp Ala Val Leu Tyr Glu Asn Ser Glu Asp Val Ala Val Pro 35 40 45 Ser Asp Ser Ala Ser Thr Pro Ser Tyr Phe His Val Glu Ser Pro Ser 50 55 60 Ala Ser Val Glu Ala Ala Thr Gly Ala Val Gly Glu Val Val Pro Asp 65 70 75 80 Cys Glu Glu Gln Gln Glu Gln Gly Asp Thr Thr Leu Ser Asp His Asp 85 90 95 Phe His 58 135 PRT Toxoplasma gondii 58 Leu Asn Pro Ile Asp Asp Met Leu Phe Glu Thr Ala Leu Thr Ala Asn 1 5 10 15 Glu Met Met Glu Asp Ile Thr Trp Arg Pro Arg Val Asp Val Glu Phe 20

25 30 Asp Ser Lys Lys Lys Glu Met Ile Ile Leu Ala Asp Leu Pro Gly Leu 35 40 45 Gln Lys Asp Asp Val Thr Ile Glu Val Asp Asn Gly Ala Ile Val Ile 50 55 60 Lys Gly Glu Lys Thr Ser Lys Glu Ala Glu Lys Val Asp Asp Gly Lys 65 70 75 80 Thr Lys Asn Ile Leu Thr Glu Arg Val Ser Gly Tyr Phe Ala Arg Arg 85 90 95 Phe Gln Leu Pro Ser Asn Tyr Lys Pro Asp Gly Ile Ser Ala Ala Met 100 105 110 Asp Asn Gly Val Leu Arg Val Thr Ile Lys Val Glu Asp Ser Gly Gly 115 120 125 Ala Lys Gln Gln Ile Ser Val 130 135 59 237 DNA Toxoplasma gondii 59 ccccaggatg ccatttgctc ggattggtcc gcatggagcc cctgcagtgt atcctgcggt 60 gacggaagcc aaatcaggac gcgaactgag gtttctgctc cgcaacctgg aacaccaaca 120 tgtccggact gccctgcgcc catgggaagg acttgcgtgg aacaaggcgg acttgaagaa 180 atccgtgaat gcagtgcggg ggtatgtgct gttgacgctg gatgtggcgt ctgggtt 237 60 432 DNA Toxoplasma gondii 60 ccgtgtccaa ttaatgcaac ttgcggtcag tttgaagaat ggagtacatg ctcggtctca 60 tgtggtggtg gactgaaaac gaggtcgagg aacccttgga atgaagacca acaacatgga 120 ggactatcct gcgagcagca gcatcctggt gggcggacgg aaacggtaac ttgcaatcct 180 caagcgtgtc ctgtggatga acgaccgggg gagtgggcag agtgggggga atgtagtgtc 240 acgtgcggcg acggagtgcg agagcgcagg cgcgggaaaa gtctagttga ggctaaattc 300 ggcggacgca ccattgatca gcagaatgag gctcttccgg aagacttaaa aatcaaaaac 360 gtcgagtatg agccatgttc gtatcctgct tgtggagctt cctgcacgta cgtctggagt 420 gactggaaca ag 432 61 678 DNA Toxoplasma gondii 61 aacgaaccgg tggccctagc tcagctcagc acattcctcg agctcgtcga ggtgccatgt 60 aactctgttc atgttcaggg ggtgatgacc ccgaatcaaa tggtcaaagt gactggtgca 120 ggatgggata atggcgttct cgagttctat gtcacgaggc caacgaagac aggcggggac 180 acaagccgaa gccatcttgc gtcgatcatg tgttattcca aggacattga cggcgtgccg 240 tcagacaaag cgggaaagtg ctttctgaag aacttttctg gtgaagactc gtcggaaata 300 gacgaaaaag aagtatctct acccatcaag agccacaacg atgcgttcat gttcgtttgt 360 tcttcaaatg atggatccgc actccagtgt gatgttttcg cccttgataa caccaactct 420 agcgacgggt ggaaagtgaa taccgtggat cttggcgtca gcgttagtcc ggatttggca 480 ttcggactca ctgcagatgg ggtcaaggtg aagaagttgt acgcaagcag cggcctgaca 540 gcgatcaacg acgacccttc cttggggtgc aaggctcctc cccattctcc gccggccgga 600 gaggaaccga gtttgccgtc gcctgaaaac agcgggtctg caacaccagc ggaagaaagt 660 ccgtctgagt ctgaatct 678 62 582 DNA Toxoplasma gondii 62 cttcgcgggt acaggttcgg tgtttggaag aaaggccgtt gcctcgacta cactgaattg 60 accgacactg tgatagaacg tgttgagtca aaggcacagt gctgggtgaa aacctttgaa 120 aacgacgggg tcgcgagtga ccaaccccat acgtatccac tgacgtcgca agcatcatgg 180 aacgattggt ggcctctcca ccagagtgac caacctcact caggtggcgt tgggcgtaat 240 tacggtttct actacgtgga cacgactgga gagggcaagt gtgcactctc tgaccaggta 300 cccgactgcc tggtgtcgga ttctgccgcc gtgtcgtata cagcagcggg gagtttgtct 360 gaagagacgc cgaatttcat aattccgtca aatccctctg ttactccgcc aacgcccgag 420 acggcacttc agtgcacggc cgacaagttc cccgactctt tcggtgcctg cgacgttcaa 480 gcctgtaaaa gacagaagac gtcctgcgtt ggcggacaga ttcaaagtac tagcgtcgac 540 tgcaccgcgg acgaacaaaa tgaatgtggc tctaacactg cg 582 63 507 DNA Toxoplasma gondii 63 agtgccaacg taacaagttc ggagcctgca aaacttgatc tctcttgtgc gcactctgac 60 aataagggat caagggctcc cacaataggc gagccagtgc cagatgtgtc cctggaacaa 120 tgtgctgcgc aatgcaaggc tgttgatggc tgcacacatt tcacttataa tgacgattcg 180 aagatgtgcc atgtgaagga gggaaaaccc gatttatacg atctcacagg aggcaaaaca 240 gcaccgcgca gttgcgatag atcatgcttc gaacaacacg tatcgtatga gggagctcct 300 gacgtgatga cagcgatggt cacgagccag tcagcggact gtcaggctgc gtgtgcggct 360 gacccgagct gcgagatctt cacttataac gaacacgacc agaaatgtac tttcaaagga 420 agggggtttt ctgcgtttaa ggaacgaggg gtgttgggtg tgacttccgg gccgaaacag 480 ttctgcgatg aaggcggtaa attaact 507 64 79 PRT Toxoplasma gondii 64 Pro Gln Asp Ala Ile Cys Ser Asp Trp Ser Ala Trp Ser Pro Cys Ser 1 5 10 15 Val Ser Cys Gly Asp Gly Ser Gln Ile Arg Thr Arg Thr Glu Val Ser 20 25 30 Ala Pro Gln Pro Gly Thr Pro Thr Cys Pro Asp Cys Pro Ala Pro Met 35 40 45 Gly Arg Thr Cys Val Glu Gln Gly Gly Leu Glu Glu Ile Arg Glu Cys 50 55 60 Ser Ala Gly Val Cys Ala Val Asp Ala Gly Cys Gly Val Trp Val 65 70 75 65 144 PRT Toxoplasma gondii 65 Pro Cys Pro Ile Asn Ala Thr Cys Gly Gln Phe Glu Glu Trp Ser Thr 1 5 10 15 Cys Ser Val Ser Cys Gly Gly Gly Leu Lys Thr Arg Ser Arg Asn Pro 20 25 30 Trp Asn Glu Asp Gln Gln His Gly Gly Leu Ser Cys Glu Gln Gln His 35 40 45 Pro Gly Gly Arg Thr Glu Thr Val Thr Cys Asn Pro Gln Ala Cys Pro 50 55 60 Val Asp Glu Arg Pro Gly Glu Trp Ala Glu Trp Gly Glu Cys Ser Val 65 70 75 80 Thr Cys Gly Asp Gly Val Arg Glu Arg Arg Arg Gly Lys Ser Leu Val 85 90 95 Glu Ala Lys Phe Gly Gly Arg Thr Ile Asp Gln Gln Asn Glu Ala Leu 100 105 110 Pro Glu Asp Leu Lys Ile Lys Asn Val Glu Tyr Glu Pro Cys Ser Tyr 115 120 125 Pro Ala Cys Gly Ala Ser Cys Thr Tyr Val Trp Ser Asp Trp Asn Lys 130 135 140 66 226 PRT Toxoplasma gondii 66 Asn Glu Pro Val Ala Leu Ala Gln Leu Ser Thr Phe Leu Glu Leu Val 1 5 10 15 Glu Val Pro Cys Asn Ser Val His Val Gln Gly Val Met Thr Pro Asn 20 25 30 Gln Met Val Lys Val Thr Gly Ala Gly Trp Asp Asn Gly Val Leu Glu 35 40 45 Phe Tyr Val Thr Arg Pro Thr Lys Thr Gly Gly Asp Thr Ser Arg Ser 50 55 60 His Leu Ala Ser Ile Met Cys Tyr Ser Lys Asp Ile Asp Gly Val Pro 65 70 75 80 Ser Asp Lys Ala Gly Lys Cys Phe Leu Lys Asn Phe Ser Gly Glu Asp 85 90 95 Ser Ser Glu Ile Asp Glu Lys Glu Val Ser Leu Pro Ile Lys Ser His 100 105 110 Asn Asp Ala Phe Met Phe Val Cys Ser Ser Asn Asp Gly Ser Ala Leu 115 120 125 Gln Cys Asp Val Phe Ala Leu Asp Asn Thr Asn Ser Ser Asp Gly Trp 130 135 140 Lys Val Asn Thr Val Asp Leu Gly Val Ser Val Ser Pro Asp Leu Ala 145 150 155 160 Phe Gly Leu Thr Ala Asp Gly Val Lys Val Lys Lys Leu Tyr Ala Ser 165 170 175 Ser Gly Leu Thr Ala Ile Asn Asp Asp Pro Ser Leu Gly Cys Lys Ala 180 185 190 Pro Pro His Ser Pro Pro Ala Gly Glu Glu Pro Ser Leu Pro Ser Pro 195 200 205 Glu Asn Ser Gly Ser Ala Thr Pro Ala Glu Glu Ser Pro Ser Glu Ser 210 215 220 Glu Ser 225 67 194 PRT Toxoplasma gondii 67 Leu Arg Gly Tyr Arg Phe Gly Val Trp Lys Lys Gly Arg Cys Leu Asp 1 5 10 15 Tyr Thr Glu Leu Thr Asp Thr Val Ile Glu Arg Val Glu Ser Lys Ala 20 25 30 Gln Cys Trp Val Lys Thr Phe Glu Asn Asp Gly Val Ala Ser Asp Gln 35 40 45 Pro His Thr Tyr Pro Leu Thr Ser Gln Ala Ser Trp Asn Asp Trp Trp 50 55 60 Pro Leu His Gln Ser Asp Gln Pro His Ser Gly Gly Val Gly Arg Asn 65 70 75 80 Tyr Gly Phe Tyr Tyr Val Asp Thr Thr Gly Glu Gly Lys Cys Ala Leu 85 90 95 Ser Asp Gln Val Pro Asp Cys Leu Val Ser Asp Ser Ala Ala Val Ser 100 105 110 Tyr Thr Ala Ala Gly Ser Leu Ser Glu Glu Thr Pro Asn Phe Ile Ile 115 120 125 Pro Ser Asn Pro Ser Val Thr Pro Pro Thr Pro Glu Thr Ala Leu Gln 130 135 140 Cys Thr Ala Asp Lys Phe Pro Asp Ser Phe Gly Ala Cys Asp Val Gln 145 150 155 160 Ala Cys Lys Arg Gln Lys Thr Ser Cys Val Gly Gly Gln Ile Gln Ser 165 170 175 Thr Ser Val Asp Cys Thr Ala Asp Glu Gln Asn Glu Cys Gly Ser Asn 180 185 190 Thr Ala 68 169 PRT Toxoplasma gondii 68 Ser Ala Asn Val Thr Ser Ser Glu Pro Ala Lys Leu Asp Leu Ser Cys 1 5 10 15 Ala His Ser Asp Asn Lys Gly Ser Arg Ala Pro Thr Ile Gly Glu Pro 20 25 30 Val Pro Asp Val Ser Leu Glu Gln Cys Ala Ala Gln Cys Lys Ala Val 35 40 45 Asp Gly Cys Thr His Phe Thr Tyr Asn Asp Asp Ser Lys Met Cys His 50 55 60 Val Lys Glu Gly Lys Pro Asp Leu Tyr Asp Leu Thr Gly Gly Lys Thr 65 70 75 80 Ala Pro Arg Ser Cys Asp Arg Ser Cys Phe Glu Gln His Val Ser Tyr 85 90 95 Glu Gly Ala Pro Asp Val Met Thr Ala Met Val Thr Ser Gln Ser Ala 100 105 110 Asp Cys Gln Ala Ala Cys Ala Ala Asp Pro Ser Cys Glu Ile Phe Thr 115 120 125 Tyr Asn Glu His Asp Gln Lys Cys Thr Phe Lys Gly Arg Gly Phe Ser 130 135 140 Ala Phe Lys Glu Arg Gly Val Leu Gly Val Thr Ser Gly Pro Lys Gln 145 150 155 160 Phe Cys Asp Glu Gly Gly Lys Leu Thr 165 69 20 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 69 atgagactcc aaccgaggcc 20 70 23 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 70 ctgcctgact ctttcttgga ctg 23 71 22 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 71 ggaaagttgg aaatccggcg gc 22 72 19 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 72 cgcctcatcg tcactcggc 19 73 19 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 73 atgagagcgt cgctcccgg 19 74 23 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 74 gtgtctttcg cttcaagcac ctg 23 75 19 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 75 atggggctcg tgggcgtac 19 76 23 DNA Artificial Sequence Description of Artificial Sequence Synthetic oligonucleotide 76 gatcaacgca gtgttagagc cac 23

Claims

1. Method for the identification of antigen fragments and/or fragments containing epitopes of Toxoplasma gondii proteins, particularly phase-specific antigen fragments, by means of selection of libraries of cDNA or DNA fragments of specific genes of the parasite with sera of subjects who have been infected, using the phage display technique, characterised in that it uses the vector .lamda.KM4.

2. Antigen fragments and/or fragments containing epitopes of Toxoplasma gondii proteins obtainable with the method according to claim 1.

3. Antigenic portions of the fragments according to claim 2.

4. Antigen fragment and/or fragment containing an epitope according to claim 3 with the following amino acid sequence: TABLE-US-00011 RRTGCHAFRENCSPGRCIDDASHENGYTCECPTG (SEQ ID NO: 31) YSREVTSKAEESCVEGVEVTLAEKCEKEFGISAS SCKCD LNPIDDMLFETALTANEMMEDITWRPRVDVEFDS (SEQ ID NO: 58) KKKEMIILADLPGLQKDDVTIEVDNGAIVIKGEK TSKEAEKVDDGKTKNILTERVSGYFARRFQLPSN YKPDGISAAMDNGVLRVTIKVEDSGGAKQQISV SGGTGQGLGIGESVDLEMMGNTYRVERPTGNPDL (SEQ ID NO: 26) LKIAIKASDGSYSEVGNVNVEEVIDTMKSMQRDE DIFLRALNKGETVEEAIEDVAQAEGLNSEQTLQL EDAVSAVASVVQDE AALGGLAADQPENHQALAEPVTGVGEAGVSPVNE (SEQ ID NO: 28) AGESYSSATSGVQEATAPGAVLLDAIDAESDKVD NQAEGGERMKKVEEELSLLRRELYDRTDRPG FATAATASDDELMSRIRNSDFFDGQAPVDSLRPT (SEQ ID NO: 29) NAGVDSKGTDDHLTTSMDKASVESQLPRREPLET EPDEQEEVHF PQDAICSDWSAWSPCSVSCGDGSQIRTRTEVSAP (SEQ ID NO: 64) QPGTPTCPDCPAPMGRTCVEQGGLEEIRECSAGV CAVDAGCGVWV PCPINATCGQFEEWSTCSVSCGGGLKTRSRNPWN (SEQ ID NO: 65) EDQQHGGLSCEQQHPGGRTETVTCNPQACPVDER PGEWAEWGECSVTCGDGVRERRRGKSLVEAKFGG RTIDQQNEALPEDLKIKNVEYEPCSYPACGASCT YVWSDWNK LRGYRFGVWKKGRCLDYTELTDTVIERVESKAQC (SEQ ID NO: 67) WVKTFENDGVASDQPHTYPLTSQASWNDWWPLHQ SDQPHSGGVGRNYGFYYVDTTGEGKCALSDQVPD CLVSDSAAVSYTAAGSLSEETPNFIIPSNPSVTP PTPETALQCTADKFPDSFGACDVQACKRQKTSCV GGQIQSTSVDCTADEQNECGSNTA NEQVALAQLSTFLELVEVPCNSVHVQGVMTPNQM (SEQ ID NO: 66) VKVTGAGWDNGVLEFYVTRPTKTGGDTSRSHLAS IMCYSKDIDGVPSDKAGKCFLKNFSGEDSSEIDE KEVSLPIKSHNDAFMFVCSSNDGSALQCDVFALD NTNSSDGWKVNTVDLGVSVSPDLAFGLTADGVKV KKLYASSGLTAINDDPSLGCKAPPHSPPAGEEPS LPSPENSGSATPAEESPSESES GLSQRVPELPEVEPFDEVGTGARRSGSIATLLPQ (SEQ ID NO: 57) DAVLYENSEDVAVPSDSASTPSYFHVESPSASVE ATTGAVGEVVPDCEEQQEQGDTTLSDHDFH PSVVNNVARCSYGADSTLGPVKLSAEGPTTMTLV (SEQ ID NO: 34) CGKDGVKVPQDNNQYCSGTTLTGCNEKSFKDILP KLTENPWQGNASSDKGATLTIKKEAFPAESKSVI IGCTGGSPEKHHCTVKLEFAGAAGSADSA VMASDPPLVANQVVTCPDKKSTAAVILTPTENHF (SEQ ID NO: 33) TLKCPKTALTEPPTLAYSPNRQICPAGTTSSCTS KAVTLSSLIPEAEDSWWTGDSASLDTAGIKLTVP IEKFPVTTQTFVVGCIKGDDAQSCMVTVTVQARA SSVVNNVARCSYGADS APTQSEMKEFQEEIKEGVEETKHEDDPEMTRLMV (SEQ ID NO: 32) TEKQESKNFSKMAKSQSFSTRIEELGGSISFLTE TGVTMIELPKTVSEHDMDQLLH SANVTSSEPAKLDLSCAHSDNKGSRAPTIGEPVP (SEQ ID NO: 68) DVSLEQCAAQCKAVDGCTHFTYNDDSKMCHVKEG KPDLYDLTGGKTAPRSCDRSCFEQHVSYEGAPDV MTAMVTSQSADCQAACAADPSCEIFTYNEHDQKC TFKGRGFSAFKERGVLGVTSGPKQFCDEGGKLT ENPVRPPPPGFHPSVIPNPPYPLGTPAGMPQPEV (SEQ ID NO: 30) P YSSPRIVVLIRYCFFSTYRLTMFAVKHCLLVVAV (SEQ ID NO: 27) GALVNVSVRAAEFSGVVNQGP.

5. Collection of antigen fragments obtainable with the method according to claim 1.

6. Nucleotide sequence coding for an antigen fragment according to claim 2.

7. Nucleotide sequence coding for an antigen fragment according to claim 4 selected from the group consisting of: TABLE-US-00012 AGGAGGACTGGATGTCATGCCTTCAGGGAGAACT (SEQ ID NO: 22) GCAGCCCTGGTAGATGTATTGATGACGCCTCGCA TGAGAATGGCTACACCTGCGAGTGCCCCACAGGG TACTCACGTGAGGTGACTTCCAAGGCGGAGGAGT CGTGTGTGGAAGGAGTCGAAGTCACGCTGGCTGA GAAATGCGAGAAGGAATTCGGCATCAGCGCGTCA TCCTGCAAATGCGAT TCTTCAGAAAGATGACGTAACCATAGAAGTCGAC (SEQ ID NO: 56) AACGGAGCCATCGTTATCAAAGGAGAGAAGACCT CGAAAGAAGCGGAGAAAGTGGACGATGGCAAAAC AAAGAACATTTTGACTGAGCGAGTGTCCGGTTAT TTTGCGCGCCGGTTCCAGCTCCCGAGTAATTACA AGCCCGACGGAATCAGTGCGGCAATGGACAACGG CGTTCTACGTGTCACGATCAAGGTCGAGGATTCA GGGGGCGCAAAGCAACAAATCAGCGTG AGTGGAGGGACAGGGCAGGGATTAGGAATCGGAG (SEQ ID NO: 17) AATCTGTAGATTTGGAGATGATGGGGAACACGTA TCGTGTGGAGAGACCCACAGGCAACCCGGACTTG CTCAAGATCGCCATTAAAGCTTCAGATGGATCGT ACAGCGAAGTCGGCAATGTTAACGTGGAGGAGGT GATTGATACTATGAAAAGCATGCAGAGGGACGAG GACATTTTCCTTCGTGCGTTGAACAAAGGCGAAA CAGTAGAGGAAGCGATCGAAGACGTGGCTCAAGC AGAAGGGCTTAATTCGGAGCAAACCCTGCAACTG GAAGATGCAGTGAGCGCGGTGGCGTCTGTTGTTC AAGACGAG GCTGCCTTGGGAGGCCTTGCGGCGGATCAGCCTG (SEQ ID NO: 19) AAAATCATCAGGCTCTTGCAGAACCAGTTACGGG TGTGGGGGAAGCAGGAGTGTCCCCCGTCAACGAA GCTGGTGAGTCATACAGTTCTGCAACTTCGGGTG TCCAAGAAGCTACCGCCCCAGGTGCAGTGCTCCT GGACGCAATCGATGCCGAGTCGGATAAGGTGGAC AATCAGGCGGAGGGAGGTGAGCGTATGAAGAAGG TCGAAGAGGAGTTGTCGTTATTGAGGCGGGAATT ATATGATCGCACAGATCGCCCTGGT CAGTTCGCTACCGCGGCCACCGCGTCAGATGACG (SEQ ID NO: 20) AACTGATGAGTCGAATCCGAAATTCTGACTTTTT CGATGGTCAAGCACCCGTTGACAGTCTCAGACCG ACGAACGCCGGTGTCGACTCGAAAGGGACCGACG ATCACCTCACCACCAGCATGGATAAGGCATCTGT AGAGAGTCAGCTTCCGAGAAGAGAGCCATTGGAG ACGGAGCCAGATGAACAAGAAGAAGTTCAT CCCCAGGATGCCATTTGCTCGGATTGGTCCGCAT (SEQ ID No: 59) GGAGCCCCTGCAGTGTATCCTGCGGTGACGGAAG CCAAATCAGGACGCGAACTGAGGTTTCTGCTCCG CAACCTGGAACACCAACATGTCCGGACTGCCCTG CGCCCATGGGAAGGACTTGCGTGGAACAAGGCGG ACTTGAAGAAATCCGTGAATGCAGTGCGGGGGTA TGTGCTGTTGACGCTGGATGTGGCGTCTGGGTT CCGTGTCCAATTAATGCAACTTGCGGTCAGTTTG (SEQ ID No: 60) AAGAATGGAGTACATGCTCGGTCTCATGTGGTGG TGGACTGAAAACGAGGTCGAGGAACCCTTGGAAT GAAGACCAACAACATGGAGGACTATCCTGCGAGC AGCAGCATCCTGGTGGGCGGACGGAAACGGTAAC TTGCAATCCTCAAGCGTGTCCTGTGGATGAACGA CCGGGGGAGTGGGCAGAGTGGGGGGAATGTAGTG TCACGTGCGGCGACGGAGTGCGAGAGCGCAGGCG CGGGAAAAGTCTAGTTGAGGCTAAATTCGGCGGA CGCACCATTGATCAGCAGAATGAGGCTCTTCCGG AAGACTTAAAAATCAAAAACGTCGAGTATGAGCC ATGTTCGTATCCTGCTTGTGGAGCTTCCTGCACG TACGTCTGGAGTGACTGGAACAAG CTTCGCGGGTACAGGTTCGGTGTTTGGAAGAAAG (SEQ ID No: 62) GCCGTTGCCTCGACTACACTGAATTGACCGACAC TGTGATAGAACGTGTTGAGTCAAAGGCACAGTGC TGGGTGAAAACCTTTGAAAACGACGGGGTCGCGA GTGACCAACCCCATACGTATCCACTGACGTCGCA AGCATCATGGAACGATTGGTGGCCTCTCCACCAG AGTGACCAACCTCACTCAGGTGGCGTTGGGCGTA ATTACGGTTTCTACTACGTGGACACGACTGGAGA GGGCAAGTGTGCACTCTCTGACCAGGTACCCGAC TGCCTGGTGTCGGATTCTGCCGCCGTGTCGTATA CAGCAGCGGGGAGTTTGTCTGAAGAGACGCCGAA TTTCATAATTCCGTCAAATCCCTCTGTTACTCCG CCAACGCCCGAGACGGCACTTCAGTGCACGGCCG ACAAGTTCCCCGACTCTTTCGGTGCCTGCGACGT TCAAGCCTGTAAAAGACAGAAGACGTCCTGCGTT GGCGGACAGATTCAAAGTACTAGCGTCGACTGCA CCGCGGACGAACAAAATGAATGTGGCTCTAACAC TGCG AACGAACCGGTGGCCCTAGCTCAGCTCAGCACAT (SEQ ID NO: 61) TCCTCGAGCTCGTCGAGGTGCCATGTAACTCTGT TCATGTTCAGGGGGTGATGACCCCGAATCAAATG GTCAAAGTGACTGGTGCAGGATGGGATAATGGCG TTCTCGAGTTCTATGTCACGAGGCCAACGAAGAC AGGCGGGGACACAAGCCGAAGCCATCTTGCGTCG ATCATGTGTTATTCCAAGGACATTGACGGCGTGC CGTCAGACAAAGCGGGAAAGTGCTTTCTGAAGAA CTTTTCTGGTGAAGACTCGTCGGAAATAGACGAA AAAGAAGTATCTCTACCCATCAAGAGCCACAACG ATGCGTTCATGTTCGTTTGTTCTTCAAATGATGG ATCCGCACTCCAGTGTGATGTTTTCGCCCTTGAT AACACCAACTCTAGCGACGGGTGGAAAGTGAATA CCGTGGATCTTGGCGTCAGCGTTAGTCCGGATTT GGCATTCGGACTCACTGCAGATGGGGTCAAGGTG AAGAAGTTGTACGCAAGCAGCGGCCTGACAGCGA TCAACGACGACCCTTCCTTGGGGTGCAAGGCTCC TCCCCATTCTCCGCCGGCCGGAGAGGAACCGAGT TTGCCGTCGCCTGAAAACAGCGGGTCTGCAACAC CAGCGGAAGAAAGTCCGTCTGAGTCTGAATCT GGATTGAGCCAAAGGGTGCCAGAGCTACCAGAAG (SEQ ID NO: 55) TGGAGCCCTTTGATGAAGTAGGCACGGGAGCTCG ACGGTCCGGGTCCATTGCGACCCTTCTTCCACAA GACGCTGTTTTATATGAGAACTCAGAGGACGTTG CCGTTCCGAGTGATTCAGCATCGACCCCGTCATA CTTTCATGTGGAATCTCCAAGTGCTAGTGTGGAA GCCGCGACTGGCGCTGTGGGAGAGGTGGTGCCGG ACTGTGAAGAACAACAGGAACAGGGTGACACGA CGTTATCCGATCACGATTTCCATTCA CCATCGGTCGTCAATAATGTCGCAAGGTGCTCCT (SEQ ID NO: 25) ACGGTGCAGACAGCACTCTTGGTCCTGTCAAGTT GTCTGCGGAAGGACCCACTACAATGACCCTCGTG TGCGGGAAAGATGGAGTCAAAGTTCCTCAAGACA ACAATCAGTACTGTTCCGGGACGACGCTGACTGG TTGCAACGAGAAATCGTTCAAAGATATTTTGCCA AAATTAACTGAGAACCCGTGGCAGGGTAACGCTT CGAGTGATAAGGGTGCCACGCTAACGATCAAGAA GGAAGCATTTCCAGCCGAGTCAAAAAGCGTCATT ATTGGATGCACAGGGGGATCGCCTGAGAAGCATC ACTGTACCGTGAAACTGGAGTTTGCCGGGGCTGC AGGGTCAGCAAAATCGGCT GTTATGGCATCGGATCCCCCTCTTGTTGCCAATC (SEQ ID NO: 24) AAGTTGTCACCTGCCCAGATAAAAAATCGACAGC CGCGGTCATTCTCACACCGACGGAGAACCACTTC ACTCTCAAGTGCCCTAAAACAGCGCTCACAGAGC CTCCCACTCTTGCGTACTCACCCAACAGGCAAAT CTGCCCAGCGGGTACTACAAGTAGCTGTACATCA AAGGCTGTAACATTGAGCTCCTTGATTCCTGAAG CAGAAGATAGCTGGTGGACGGGGGATTCTGCTAG TCTCGACACGGCAGGCATCAAACTCACAGTTCCA ATCGAGAAGTTCCCCGTGACAACGCAGACGTTTG TGGTCGGTTGCATCAAGGGAGACGACGCACAGAG TTGTATGGTCACGGTGACAGTACAAGCCAGAGCC TCATCGGTCGTCAATAATGTCGCAAGGTGCTCCT ATGGTGCGGACAGC GCACCCACTCAATCTGAAATGAAAGAATTCCAAG (SEQ ID NO: 23) AGGAAATCAAAGAAGGGGTGGAGGAAACAAAGCA TGAAGACGATCCTGAGATGACGCGGCTCATGGTG ACCGAGAAGCAGGAGAGCAAAAATTTCAGCAAGA TGGCGAAATCCCAGAGTTTTAGCACGCGAATCGA AGAGCTCGGGGGATCCATTTCGTTTCTAACTGAA ACGGGGGTCACAATGATCGAGTTGCCCAAAACTG TCAGTGAACATGACATGGACCAACTACTCCAC AGTGCCAACGTAACAAGTTCGGAGCCTGCAAAAC (SEQ ID NO: 63) TTGATCTCTCTTGTGCGCACTCTGACAATAAGGG ATCAAGGGCTCCCACAATAGGCGAGCCAGTGCCA GATGTGTCCCTGGAACAATGTGCTGCGCAATGCA AGGCTGTTGATGGCTGCACACATTTCACTTATAA TGACGATTCGAAGATGTGCCATGTGAAGGAGGGA AAACCCGATTTATACGATCTCACAGGAGGCAAAA CAGCACCGCGCAGTTGCGATAGATCATGCTTCGA ACAACACGTATCGTATGAGGGAGCTCCTGACGTG ATGACAGCGATGGTCACGAGCCAGTCAGCGGACT GTCAGGCTGCGTGTGCGGCTGACCCGAGCTGCGA GATCTTCACTTATAACGAACACGACCAGAAATGT ACTTTCAAAGGAAGGGGGTTTTCTGCGTTTAAGG AACGAGGGGTGTTGGGTGTGACTTCCGGGCCGAA ACAGTTCTGCGATGAAGGCGGTAAATTAACT GAGAACCCGGTGAGACCGCCTCCTCCCGGTTTCC (SEQ ID NO: 21) ATCCAAGCGTTATTCCCAATCCCCCGTACCCGCT GGGCACTCCAGCGGGCATGCCACAGCCAGAGGTT CC TACTCTTCACCACGAATAGTTGTTTTGATTAGAT (SEQ ID NO: 18) ATTGCTTCTTCTCCACATATCGCCTCACAATGTT CGCCGTAAAACATTGTTTGCTGGTTGTTGCCGTT GGCGCCCTGGTCAACGTCTCGGTGAGGGCTGCCG AGTTTTCCGGAGTTGTTAACCAGGGACCT

8. Nucleotide sequences that hybridise with the sequences coding for the sequences according to claim 4, under stringent hybridisation conditions.

9. Nucleotide sequences that hybridise with the sequences coding for the antigen fragments according to claim 2 under stringent hybridisation conditions.

10. Use of an antigen fragment according to claim 4 as active agents for the diagnosis of Toxoplasma gondii infections.

11. Use according to claim 10 for the diagnosis of the time of infection.

12. Use according to claim 11, where said time of infection is determined by the IgG avidity assay.

13. Specific ligand for an epitope according to claim 2.

14. Anti-epitope antibody raised against an epitope according to claim 2.

15. Ligands for the collection according to claim 5.

16. Anti-collection antibody raised against a collection according to claim 5.

17. Use of at least one ligand according to claim 13 for the preparation of means for the diagnosis of Toxoplasma gondii infection.

18. Use of ligands according to claim 15 for the preparation of means for the diagnosis of Toxoplasma gondii infection.

19. Method for the diagnosis of Toxoplasma gondii infection, comprising the selection of sera of subjects affected by or suspected of being affected by said infection with the antigen fragments of claim 1 and/or with at least one ligand of said antigen and/or at least one antibody to the same.

20. Use of antigen fragments according to claim 2 as medicaments.

21. Use of antigen fragments of claim 2 as active agents for the preparation of medicaments for the prevention or treatment of Toxoplasma gondii infections.

22. Use of the sequences according to claim 6 as medicaments.

23. Use of the sequences according to claim 6 for the preparation of medicaments useful for the treatment and prevention of Toxoplasma gondii infections.

24. Diagnostic kit for the diagnosis of Toxoplasma gondii infection, containing at least one antigen fragment according to claim 2.

25. Kit for the diagnosis of an acute and/or chronic Toxoplasma gondii infection, containing at least one antigen fragment according to claim 4.

26. Pharmaceutical composition, particularly in the form of a vaccine, containing at least one antigen fragment according to claim 2.

27. Pharmaceutical composition, particularly in the form of a vaccine, containing at least one sequence according to claim 6.

28. Composition according to claim 26 suitable for human and/or veterinary use.