U.S. patent application number 10/251565 was filed with the patent office on 2003-08-07 for recombinant phages capable of entering host cells via specific interaction with an artificial receptor.
This patent application is currently assigned to VLAAMS INTERUNIVERSITAIR INSTITUUT VOOR BIOTECHNOLOGIE VZW, a Belgium corporation. Invention is credited to Muyldermans, Serge, Silence, Karen, Steyaert, Jan, Torreele, Els.
Application Number | 20030148508 10/251565 |
Document ID | / |
Family ID | 8242120 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030148508 |
Kind Code |
A1 |
Muyldermans, Serge ; et
al. |
August 7, 2003 |
Recombinant phages capable of entering host cells via specific
interaction with an artificial receptor
Abstract
The invention relates to a genetically modified bacteriophage,
pseudovirion or phagemid capable of entering a host cell by binding
of its artificial ligand to an artificial receptor present on said
host cell. The invention relates also to the use of the genetically
modified bacteriophage, pseudovirion or phagemid and of the host
cell to screen sequence libraries, including antibody library.
Inventors: |
Muyldermans, Serge;
(Hoeilaart, BE) ; Steyaert, Jan; (Beersel, BE)
; Silence, Karen; (Overijse, BE) ; Torreele,
Els; (Brussel, BE) |
Correspondence
Address: |
MARK S. ELLINGER, PH.D.
Fish & Richardson P.C., P.A.
Suite 3300
60 South Sixth Street
Minneapolis
MN
55402
US
|
Assignee: |
VLAAMS INTERUNIVERSITAIR INSTITUUT
VOOR BIOTECHNOLOGIE VZW, a Belgium corporation
|
Family ID: |
8242120 |
Appl. No.: |
10/251565 |
Filed: |
September 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10251565 |
Sep 19, 2002 |
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09433404 |
Nov 3, 1999 |
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6479280 |
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Current U.S.
Class: |
435/320.1 ;
424/199.1; 435/235.1; 435/239; 435/345; 435/5 |
Current CPC
Class: |
C07K 2317/50 20130101;
C12N 15/70 20130101; C07K 16/00 20130101; C12N 9/22 20130101; C07K
2317/22 20130101; C12N 15/1037 20130101 |
Class at
Publication: |
435/320.1 ;
424/199.1; 435/6; 435/235.1; 435/345; 435/239 |
International
Class: |
C12Q 001/68; A61K
039/12; C12N 007/00; C12N 007/01; C12N 007/02; C12N 015/00; C12N
015/09; C12N 015/63; C12N 015/70; C12N 015/74; C12N 005/06; C12N
005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 24, 1999 |
EP |
99402348.9 |
Claims
1. Genetically modified bacteriophage, pseudovirion or phagemid
capable of entering a host cell by binding of its artificial ligand
to an artificial receptor present on said host cell.
2. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 1, carrying a nucleotide sequence encoding an
artificial ligand, in condition enabling expression of said ligand
at the surface of the bacteriophage, pseudovirion or phagemid.
3. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 1 or 2, in which the artificial receptor is an
endogenous cell wall protein of the host cell.
4. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 1 or 2, in which the artificial receptor is a
fusion protein whereby the protein sequence or region of said
fusion protein, involved in the binding of the receptor with said
bacteriophage, pseudovirion or phagemid is free of peptide
sequences having 10 or more contiguous amino acid residues involved
in the wild type bacteriophage-host cell interaction.
5. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 1-3, where the binding is mediated by an
antigen--antibody reaction.
6. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 14, in which the said bacteriophage,
pseudovirion or phagemid is lytic.
7. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 6, in which the entering in the host cell of
said bacteriophage, pseudovirion or phagemid is inducing expression
of barnase in the host cell.
8. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 1-7, where the bacteriophage is M13.
9. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 8, where the artificial ligand is a pIII fusion
protein.
10. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 9, in which the phagemid is a pK7C3 derived
vector
11. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim anyone of claims 1 to 4, in which the fusion
protein is an pOrpl fusion protein.
12. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 11, in which the host cell is transformed with
an ptrc-Oprl derived vector.
13. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 12, in which the phagemid is a pK7C3 derived
vector.
14. Genetically modified bacteriophage, pseudovirion or phagemid
according to claim 5, in which the antibody is a camelid derived
antibody, or is a functional fragment thereof, including a fragment
comprising all or part of the VHH chain of a camelid heavy chain
antibody.
15. Use of a bacteriophage, pseudovirion or phagemid according to
claim 1-14 to detect and/or eliminate a specific bacterial
population.
16. Use of a bacteriophage, pseudovirion or phagemid according to
claim 1-14 to detect a artificial receptor-artificial ligand
interaction.
17. Use of a bacteriophage, pseudovirion or phagemid according to
claim 15 to screen an antigen and/or antibody library.
18. Method for selecting artificial receptor-artificial ligand
interactions, comprising: growing a host cell or a mixture of host
cells displaying one or more artificial receptors, contacting said
host cell or said mixture with a genetically modified
bacteriophage, pseudovirion or phagemid or a mixture of genetically
modified bacteriophages, pseudovirions or phagemids with one or
more artificial ligands, selecting those cells that have been
entered by one or more bacteriophages, pseudovirion of
phagemid.
19. Method for selecting artificial ligand-artificial receptor
interactions according to claim 18, in which the host cell is
transformed with an ptrc-Oprl derived vector.
20. Method for selecting artificial ligand-artificial receptor
interactions according to claim 18 or 19, in which the phagemid is
a pK7C3 derived vector.
21. Genetically modified host cell, carrying a nucleotide sequence
encoding an artificial receptor in conditions enabling that the
artificial receptor be expressed at the surface of the host cell,
said host cell being further transformed with a nucleotide sequence
encoding said artificial ligand whereby said nucleotide sequence
encoding the ligand entered the host cell as a consequence of the
interaction between said artificial ligand and a protein sequence
or region on said artificial receptor.
22. Genetically modified host cell according to claim 21, wherein
the nucleotide sequence encoding the artificial receptor and/or the
nucleotide sequence encoding the artificial ligand are not
known.
23. Genetically modified host cell according to claim 21 or 22,
which is a gram-negative bacterium, especially an E coli cell of
the F.sup.- strain.
24. Genetically modified host cell according to any of claims 21 to
23, wherein the nucleotide sequences of the artificial receptor and
the nucleotide sequence for the artificial ligand are respectively
coding sequences of an antibody or a functional fragment thereof
and coding sequence of an antigen, or are respectively coding
sequences of an antigen and coding sequence of antibody or a
functional fragment thereof.
25. Genetically modified host cell according to claim 24, wherein
the functional antibody fragment is a VHH fragment of a camelid
antibody or a functional portion of said VHH.
26. Genetically modified host cell according to anyone of claims 21
to 25, wherein the nucleotide sequence encoding the artificial
receptor comprises a sequence encoding Oprl or a part of Oprl
sufficient to enable the exposure, at the surface of the host cell,
of a protein sequence or region capable of interacting with the
artificial ligand.
27. A kit comprising a genetically modified host cell according to
anyone of claims 21 to 26 bacteriophage, pseudovirion or phagemid
according to anyone of claims 1 to 20, or comprising a host cell
and/or a bacteriophage, pseudovirion or phagemid and/or a cloning
vector enabling the construction of said genetically modified host
cell according to anyone of claims 21 to 26.
28. A kit according to claim 27 for in vivo panning of antibody or
antibody fragment library, or antigenic sequences library.
29. A kit according to claim 27 or 28, for the simultaneous in vivo
panning of both an antibody fragment library, and an antigenic
sequences library.
Description
[0001] The present invention relates to a recombinant
bacteriophage, pseudovirion or phagemid that is capable of entering
bacteria by specific binding to an artificial receptor. Said
receptor does not comprise at its active binding site elements such
as proteins or peptides that are derived from the natural receptor
used in the specific initial bacteriophage--bacterium
interaction.
BACKGROUND OF THE INVENTION
[0002] Bacteriophages, like bacteria, are very common in all
natural environments. Bacteriophages (phages) are intracellular
parasites. Bacteria and their phages have a common evolutionary
history and phages may have adapted to their host species by
multiple mechanisms. The phage genome may consist of
double-stranded DNA, single-stranded DNA, double-stranded RNA or
single-stranded RNA. Bacteriophages exist in several morphologies
and can be spherical, cubic, filamentous, pleomorphic or tailed.
Based on their life cycle, bacteriophages can be divided into three
groups: the virulent phages capable of only lytic propagation
(called lytic phages), the so-called temperate phages capable of
either lytic propagation or lysogenic phase and the non-lysing
phages where the mature phage is continuously extruded. The
virulent life cycle of wild type phages consists of infection of
the host cell, i.e. attachment to a specific receptor in the
bacterial cell wall, followed by entering of the phage genome in
the cell, replication of the phage genome, production of the phage
structural components, phage assembly and release of the progeny
phages after lysis of the host cell. In the lysogenic life cycle,
the phage genome exists as a prophage resulting in coexistence of
phage and host cell without lysis. Usually, this is achieved by
integration of the phage genome into the bacterial chromosome. The
life cycle of the non-lysing phages, like e.g. Bacteriophage M13,
is similar to that of the lytic phages, but the infection is not
followed by lysis. Bacteriophages have been extensively used in
biotechnology. Phage genes or complete phages may be used to obtain
lysis and/or killing of bacteria.
[0003] U.S. Pat. No. 4,637,980 describes the use of an E. coli
strain containing defective temperature sensitive lambda lysogens
as a method for cell disruption. Smith and coworkers (Smith et al.,
1987, J. Gen. Microbiol. 133: 1111-1126) describe the use of
bacteriophages to treat diarrhoea in calves, caused by seven
different bovine enteropathogenic strains of E. coli. WO95/27043
describes a method to treat infectious diseases caused by several
bacterial genera, such as Mycobacterium, Staphylococcus, Vibrio,
Enterobacter, Enterococcus, Escherichia, Haemophilus, Neisseria,
Pseudomonas, Shigella, Serratia, Salmonella and Streptococcus,
comprising the administration of bacteriophages with delayed
inactivation by the animal host defence system. WO 98/51318
describes a diagnostic kit and a pharmaceutical composition,
comprising bacteriophages to diagnose and tro treat bacterial
diseases caused by bacteria, such as Listeria, Klebsiella,
Pneumococcus, Moraxella, Legionella, Edwardsiella, Yersinia,
Proteus, Heliobacter, Salmonella, Chlamydia, Aeromonas and
Renibacterium.
[0004] Another application of bacteriophages is the in vitro
selection of proteins displayed on the tip of filamentous phages on
immobilised target (=biopanning), which is a powerful technique for
the isolation of interacting protein-ligand pairs from large
libraries, such as antibody libraries (for a recent review: Rodi
and Makowski, 1999, Curr. Opin. Biotechn., 10: 87-93). However, for
optimal in vitro biopanning, a purified target protein is needed.
Moreover, high quality of the library is a prerequisite for
success. Enrichment for selfligated vector, phages carrying
incomplete sequences, incorrect reading frames, deletions and amber
stop codons are very often observed (Beekwilder et al, 1999, Gene,
228, 23-31 and de Bruin et al, 1999, Nature Biotechnology, 17:
397-399). In the search to avoid the problems encountered with
panning using imperfect libraries, several alternative techniques,
both bacteriophage based and non bacteriophage based,have been
developed. Non bacteriophage based techniques are, amongst others
ribosome display (Dall'Acqua and Carter, 1998, Curr. Opin. Struct.
Biol., 8: 443-450) and the yeast two-hybrid system (Drees, 1999,
Curr. Opin. Chem. Biol., 3: 64-70). Bacteriophage based techniques
comprise display on phage lambda, SIP (Spada and Pluckthun, 1997,
Biol. Chem., 378: 445-456; EP0614989) and CLAP (Malmborg et al,
1997, J. Mol. Biol., 273: 544-551; WO9710330). SIP and CLAP are in
vivo selection techniques and have the advantage that the F.sup.+
E.coli host cells can only be infected by bacteriophages or
pseudovirions when a matched pair is formed. Both systems are based
on the fact that pilin on the F-pili of E.coli cells serve as the
natural receptor for binding of the D2-domain of pill from the
phage (Deng et al., 1999, Virology, 253:271-277). This results in
retraction of the pilus, so that an interaction between the D1
domain of pill with the TOL protein complex located in the E. coli
cell membrane leads to the infection (Deng et al, 1999, Virology,
253: 271-277). SIP has the disadvantage that it only works for high
affinities of the binding pairs and that each target needs to be
cloned, expressed and purified as a fusion with the D2 domain of
pIII. Therefore, with SIP, normally only one target can be screened
at the time. For CLAP only small peptides (15-18 amino acids) can
be expressed on the F-pilus, hence, this technique can only be used
for small linear epitopes. An additional disadvantage is the need
for modified M13 to avoid natural infection of host cells.
Therefore, removal of the D2 domain of pIII is essential. This
results in a truncated form of M13 and concomitant difficulties to
obtain good titres.
[0005] It is known that bacteriophages use specific receptors on
the host cell wall as a way to recognise the host cell and to start
the infection process. In all the applications cited above, the
propagation of phages, pseudovirions or phagemids is dependent on
the use of the natural phage receptor, or part of it, on the host
cell wall. For M13, mainly used in these systems, the natural
receptor is pilin (Malmborg et al., 1997, J. Mol. Biol. 273:
544-551). Other examples of natural receptors are lamB for
bacteriophage lambda (Werts et al, 1994, J. Bacteriol. 176:
941-947), the outer membrane protein OmpA for bacteriophages K3,
O.times.2 and M1 (Montag et al, 1987, J. Mol. Biol., 196: 165-174),
the outer membrane proteins OmpF and Ttr for bacteriophage T2
(Montag et al, 1987, J. Mol. Biol., 196, 165-174), the outer
membrane protein OmpC for the T4 phage family (T4, Tula, Tulb)
(Montag et al., 1990, J. Mol. Biol., 216: 327-334). The T4
bacteriophage family is using a C-terminal region of protein 37 as
natural ligand (Montag et al., 1990, J. Mol. Biol., 216: 327-334),
bacteriophages T2, K3, O.times.2 and M1 are using protein 38 as
natural ligand (Montag et al, 1987, J. Mol. Biol., 196, 165-174)
whereas phage lambda is using the C-terminal portion of the lambda
tail fibre protein as natural ligand (Wang et al., 1998, Res.
Microbiol, 149: 611-624). Bacteriophage-receptor independent phage
binding to mammalian cells expressing the growth factor receptor
ErbB2 followed by receptor mediated endocytosis was also described:
Marks and collaborators (Poul and Marks, 1999, J. Mol. Biol., 288:
203-211 and Becceril and Marks, 1999, Biochem. Biophys. Res.
Commun., 255: 386-393) successfully isolated phage capable of
binding mammalian cells expressing the growth factor receptor ErbB2
and undergoing receptor mediated endocytosis by selection of a
phage antibody library on breast tumour cells and recovery of
infectious phage from within the cell. However, the phage could not
propagate in the mammalian cell, and the detection of the cells
carrying bacteriophage could only be realised in an indirect way,
by expression green fluorescent protein as a reporter gene.
SUMMARY OF THE INVENTION
[0006] One aspect of the invention is a genetically modified
bacteriophage, pseudovirion or phagemid that is not dependent upon
its natural receptor or parts thereof for entering a host cell.
[0007] Another aspect of the invention is a genetically modified
bacteriophage, pseudovirion or phagemid capable of entering a host
cell by specific binding to an artificial receptor. These
artificial receptors can be endogenous host cell proteins located
at the bacterial surface, or parts thereof, that are normally not
involved in the bacteriophage--bacterium interaction, but it may
also be heterologous proteins, preferentially fusion proteins
displaying an oligo- or polypeptide on the bacterial surface. The
genetically modified bacteriophage, pseudovirion or phagemid binds
to the artificial receptor preferentially by an artificial ligand.
A specific embodiment is a genetically modified bacteriophage that
is not dependent upon OmpA, OmpC, OmpF, Ttr or pilin for
interaction with and/or entering E.coli. A further specific
embodiment is a genetically modified M13 bacteriophage,
pseudovirion or phagemid that does not depend upon pilin, or
fragments thereof for specific interaction with and/or entering of
E. coli. Said M13 bacteriophage, pseudovirion or phagemid can enter
both F.sup.+ and F.sup.- E. coli cells, dependent upon an
artificial receptor that is displayed on the surface of said
cells.
[0008] Still another aspect of the invention is a bacteriophage,
pseudovirion or phagemid that enters the host cell mediated by an
antigen--antibody reaction, whereby in the binding complex no
proteins or parts of the natural receptor are involved.
[0009] A preferred embodiment of the invention is a genetically
modified M13 phage, pseudovirion or phagemid displaying an
antibody, preferentially the variable part of a camel heavy chain
antibody for instance disclosed in international patent application
WO 94/04678 and in Hamers-Casterman C et al Nature, vol 363, Jun.
3, 1993.p 446-448, on its tip, which can enter an E.coli host cell,
displaying the antigen, preferentially as an pOprl fusion protein.
The use of Oprl as a protein for the expression of an amino acid
sequence at the surface of the cell wall of a host cell is
disclosed for example in international patent application WO
95/04079 which is incorporated herewith by reference.
[0010] A further aspect of the invention is the use of said
bacteriophage, pseudovirion or phagemid for selective entering of a
subpopulation of bacteria. Using the specific artificial receptor
interaction, in a mixed culture, the bacteriophage, pseudovirion or
phagemid will only enter those bacteria that carry said artificial
receptor. By this, the subpopulation of bacteria can be identified
and/or eliminated. One embodiment of the invention is the specific
elimination of pathogenic bacteria by directing a recombinant
bacteriophage, pseudovirion or phagemid to a specific bacterial
surface protein of said pathogenic bacteria. The pathogenic
bacteria can be gram positive, gram negative or gram variable and
can belong, amongst other to the genera Aeromonas, Chlamydia
Edwardsiella, Enterobacter, Enterococcus, Escherichia, Haemophilus,
Heliobacter, Klebsiella, Legionella, Listeria, Moraxella,
Mycobacterium, Neisseria, Pneumococcus, Proteus, Pseudomonas,
Renibacterium, Salmonella, Serratia, Shigella, Staphylococcus,
Vibrio or Yersinia, without that this summation is limitative.
[0011] Elimination can be obtained by the lytic cycle of the
bacteriophage, but is not limited this method. Other methods of
eliminating the host cell may be the production of a toxic product
encoded by the recombinant bacteriophage genome in the host cell. A
preferred embodiment is the production of barnase placed after an
inducible promoter, such as the barnase--barstar cassette described
by Jucovic and Hartley (Protein engineering, 8: 497-499, 1995).
[0012] Another aspect of the invention is a host cell, entered by
the genetically modified bacteriophage, pseudovirion or phagemid.
Such host cell comprises the nucleotide sequence encoding the
artificial receptor and the nucleotide sequence encoding the
artificial ligand. Such sequences may be expressed in the host cell
in combination with marker sequences, especially sequences encoding
antibiotic resistance genes. A preferred embodiment is an E. coli
cell, preferentially transformed with a plasmid encoding a
pOprl-fusion protein, more preferentially transformed with a
plasmid derived from ptrc-Oprl, carrying a genetically modified M13
phage, pseudovirion or phagemid, preferentially a pK7C3 derived
phagemid, wherein said genetically modified M13 phage is modified,
especially by in vitro construction, with a nucleotide sequence
encoding a protein capable of specifically binding to the
pOprl-fusion protein.
[0013] In a particular embodiment of the invention, the Oprl-fusion
protein is carried out in introducing the nucleotide sequence of
the fusion partner acting as the region for interaction with the
ligand expressed on the bacteriophage, pseudovirion or phagemid,
especially as disclosed in WO 95/04678.
[0014] Still a further aspect of the invention is the use of said
bacteriophage,psseudovirion or phagemid to identify interacting
proteins, including cases where none of the members of the
interacting protein is known.
[0015] In different embodiments, the bacteriophage, pseudovirion or
phagemid can be used to screen (1) a host cell, displaying a bait
against a library of bacteriophages, pseudovirions or phagemids
displaying the prays, (2) a bacteriophage, pseudovirion or phagemid
displaying a bait against a library of host cells displaying the
prays, (3) a library of bacteriophages, pseudovirions or phagemids
displaying different prays or baits against a library of host
cells, displaying different baits or prays (As illustrated in FIG.
1).
[0016] A preferred embodiment is where pOprl is used as fusion
partner for the display of bait or pray on the surface of the
F.sup.- E.coli strains (Williams & Meynell 1971. Mol. Gen.
Genet. 113: 222-227) such as DH5.alpha. and UT5600 as host cell and
where the phagemid pK7C3 is used for cloning the pray or bait as a
pill fusion protein. Another embodiment of the invention is the
construction of a subtraction library, with the use of lytic
bacteriophages, preferentially barnase expressing bacteriophages.
In this embodiment, a part of the host cell library is recognised
by lytic phages such as barnase expressing phages and killed upon
recognition of the artificial receptor by the artificial ligand,
entering of the bacteriophage, pseudovirion or phagemid and
expression of the lytic gene.
[0017] Another aspect of the invention is a method for selecting
artificial receptor-artificial ligand interactions, comprising
[0018] growing a host cell or a mixture of host cells displaying
one or more artificial receptors,
[0019] contacting said host cell or said mixture with a genetically
modified bacteriophage, pseudovirion or phagemid or a mixture of
genetically modified bacteriophages, pseudovirions or phagemids
with one or more artificial ligands,
[0020] selecting those cells that have been entered by one or more
bacteriophages, pseudovirion of phagemid.
[0021] One embodiment of the invention is said method, whereby the
selection is based on an antibiotic resistance marker. Another
embodiment is said method whereby the cells are selected by killing
of the host cell, preferentially by expression of barnase. A
preferred embodiment is said method, whereby the host cell is an E.
coli cell, displaying the artificial receptor as a pOprl fusion
protein, and the genetically modified bacteriophage, pseudovirion
or phagemid is a genetically modified M13, displaying an artificial
ligand as a pill fusion protein.
Definitions
[0022] The following definitions are set forth to illustrate and
define the meaning and scope of the various terms used to describe
the invention herein.
[0023] Genetically modified bacteriophage: a bacteriophage of which
the genome has been modified, at least by the introduction of the
gene encoding for an artificial ligand. This introduction can be as
a replacement of one of the endogenous genes or as an additional
gene besides the endogenous genes.
[0024] Natural receptor: protein domain, protein or protein complex
situated on the host cell wall, involved in the natural initial
interaction between a bacteriophage and said host cell, whereby
this interaction is followed by introduction of the genetic
material of the bacteriophage into the host cell.
[0025] Artificial receptor: protein domain, protein, fusion protein
or protein complex on the host cell wall whereby said protein
domain, protein, fusion protein or protein complex does not contain
one or more peptide fragments of at least 10 contiguous amino acids
derived from the natural bacteriophage receptor in the protein
sequence or region that is involved in the interaction between
bacteriophage, pseudovirion or phagemid and the artificial
receptor.
[0026] Protein: encompasses peptide, protein, glycoprotein,
lipoprotein or another form of modified protein, including
chemically modified protein.
[0027] Protein complex: protein--protein complex, but also
protein--compound complex, whereby said compound may be any
chemical or biological compound, including simple or complex
inorganic or organic molecules, peptido-mimetics, carbohydrates,
nucleic acids or derivatives thereof.
[0028] Natural ligand: protein, protein domain or protein complex
of the bacteriophage, pseudovirion, or phagemid involved in the
natural initial interaction between said bacteriophage,
pseudovirion, or phagemid, and a host cell, including recognition
of and possibly binding to the natural receptor, whereby this
interaction is followed by introduction of the genetic material of
the bacteriophage into the host cell.
[0029] Artificial ligand: protein, protein domain or protein
complex of the bacteriophage, pseudovirion, or phagemid, whereby
said protein domain, protein, fusion protein or protein complex
does not contain one or more peptide fragments of at least 10
contiguous amino acids derived from the natural ligand of the
bacteriophage in the protein sequence or region that is involved in
the interaction between bacteriophage, pseudovirion or phagemid and
the artificial receptor.
[0030] Host cell: any bacterial cell that can allow a
bacteriophage, pseudovirion or phagemid to enter said cell after
interaction of a said bacteriophage, pseudovirion or phagemid with
a natural or artificial receptor. As example, host cells include
gram-negative or gram-positive bacteria, especially including E
coli cells and in particular F.sup.- cells which do not permit
entering of bacteriophages, pseudovirions or phagemids through the
pillin mechanism.
[0031] Entering bacteria: means that the bacteriophage,
pseudovirion or phagemid can enter as a whole or as a part (e.g.
only the genetic material) the host cell after specific binding to
the artificial receptor. The mechanism by which the material is
entering the host cell is not limited to specific ways and can be
amongst others an active infection process or a passive uptake by
the host cell. Methods for determination of the specific binding of
the artificial ligand with the artificial receptor are illustrated
in the examples.
[0032] Specific binding: means that the initial step of the
entering is mediated by a specific interaction between the
artificial receptor on the host cell wail and the artificial ligand
of the bacteriophage, pseudovirion or phagemid. This specific
interaction is preferentially a protein--protein interaction. This
entering after specific interaction should be distinguished from
the Calcium dependent pilus independent infection that can be
detected with M13 bacteriophages in which the second N-terminal
domain of glllp has been removed (Krebber et al., 1997, J. Mol.
Biol. 268: 607-618).
[0033] According to particular embodiments, the invention relates
to a genetically modified host cell, transformed with a nucleotide
sequence encoding an artificial receptor in conditions enabling
that the artificial receptor be expressed at the surface of the
host cell, said host cell being further transformed with a
nucleotide sequence encoding said artificial ligand whereby said
nucleotide sequence encoding the ligand entered the host cell as a
consequence of the interaction between said artificial ligand and a
protein sequence or region on said artificial receptor.
[0034] Particular genetically modified host cells are those wherein
the nucleotide sequence encoding the artificial receptor and/or the
nucleotide sequence encoding the artificial ligand are not
initially known.
[0035] According to another specific embodiment, the genetically
modified host cell is a gram-negative bacterium, especially an E
coli cell of the F.sup.- type.
[0036] According to another particular embodiment, the genetically
modified host cell is a transformed cell wherein the nucleotide
sequences of the artificial receptor and the nucleotide sequence
for the artificial ligand are respectively coding sequences of an
antibody or a functional fragment thereof and coding sequence of an
antigen, or are respectively coding sequences of an antigen and
coding sequence of antibody or a functional fragment thereof.
[0037] In said genetically modified host cell of the invention, the
functional antibody fragment can be a variable fragment of an
antibody, encompassing four-chain antibodies or two-chain antibody
as defined in international patent application WO 94/04678,
including native or modified, especially truncated chains thereof.
In a preferred embodiment the variable chain is a VHH fragment of a
camelid antibody or a functional portion of said VHH, as disclosed
in the above cited patent application which is incorporated by
reference.
[0038] The invention relates also to the above defined genetically
modified host cell, wherein the nucleotide sequence encoding the
artificial receptor comprises a sequence encoding Oprl or a part of
Oprl sufficient to enable the exposure, at the surface of the host
cell, of a protein sequence or region capable of interacting with
the artificial ligand.
[0039] A further object of the invention is a kit comprising a
genetically modified host cell according to the above proposed
definitions and specific embodiments or comprising a host cell
and/or a bacteriophage, pseudovirion or phagemid and/or means
including a cloning vector enabling the construction of said host
cell and/or a bacteriophage, pseudovirion or phagemid according to
the above definitions.
[0040] A particular kit is designed to be used for in vivo panning
of antibody or antibody fragment library, or antigenic sequences
library.
[0041] Said kit can also be used for the simultaneous in vivo
panning of both an antibody fragment library, and an antigenic
sequences library.
[0042] The invention therefore provides means for the
identification of target sequences or molecules including
especially amino acid sequences capable of interacting with a
determined receptor, whether the nature or sequences of said
receptor is known or unknown. Especially the invention can be used
for the identification of therapeutic targets.
SHORT DESCRIPTION OF THE FIGURES
[0043] FIG. 1 gives a schematic representation of the screening of
a proteome expression library against a camel VHH anti-proteome
antibody library. FIG. 2: schematic representation of phagemid
pK7C3. FIG. 3: schematic representation of plasmid ptrc-Oprl
[0044] FIG. 4: Results of the Western blot. From left to right:
lane 1 shows the molecular weight markers. Lane 2 and 3 show the
total lysate of E. coli, transformed with ptrc-Oprl, respectively
after growth in LB (lane 2) and M9 (lane 3). Lane 4 and 5 show the
total lysate of E. coli, transformed with ptrc-Oprl-OVA,
respectively after growth in LB (lane 4) and M9 (lane 5). Proteins
are visualised with anti-Oprl, as described in example II.
[0045] FIGS. 5(a and b): Schematic representation of barnase
activation by inversion of the expression cassette, due to
integrase activity induced by heat shock.
EXAMPLES
Example I
[0046] Construction of M13 Pseudovirions Displaying Camel Heavy
Chain Antibodies (VHH)
[0047] Immunisation of Camels
[0048] A camel (B) was immunised with 1 mg hen-egg ovalbumin
(Sigma) in the presence of complete Freund adjuvant, and boosted in
the presence of incomplete Freund adjuvant at days 7,14, 28, 35 and
42. Anticoagulated blood was collected for lymphocyte isolation on
day 45. This results in VHH library CAMELB
[0049] Construction of Phagemid Library
[0050] Peripheral blood lymphocytes were prepared using Unisep (WAK
Chemie, Germany). The camelid heavy chain antibodies (VHH's) from
10.sup.7 lymphocytes were cloned after RT-PCR amplification in the
Ncol-Notl site of the pK7C3 vector (FIG. 2) and transformed in TG1
(Lauwereys et al, 1998, the EMBO Journal, 17: 3512-3520). The
primers for the amplification are
1 CATGCGATGACTCGCGGCCCAGCCGGCCATGGC and
GTGTGCGGCCGCTGAGGAGACRGTGACCWG.
[0051] The pK7C3 vector is a pHEN4 (Ghahroudi et al, 1997, FEBS
letters, 414: 521-526) derivative where the ampicillin resistance
gene was replaced by the chloramphenicol resistance gene and the
haemaglutinin tag was replaced by a histidine and c-myc tag
(Ghahroudi et al, 1997, FEBS letters, 414: 521-526)
[0052] Construction of M13 Pseudovirions Displaying Camel VHH
[0053] VHH's from the CAMELB library were expressed on phage after
infection of the library with M13KO7 helper phage (pK7C3-VHHB) as
described by Ghahroudi et al, 1997, FEBS letters, 414: 521-526. A
library of 3.times.10.sup.6 individual colonies was obtained of
which 85% had the correct insert size, and 90% of these could
produce a fusion protein between VHH and pIII.
[0054] Selection of Ovalbumin Specific Pseudovirions by
Biopanning
[0055] The CAMELB library was panned for the presence of binders on
ovalbumin coated in wells of microtitre plates (10 .mu.g
ovalbumin/well). Bound phages were eluted and allowed to infect TG1
cells (Stratagene). After two or three rounds of panning,
individual colonies were grown, periplasmic extracts were prepared
and screened for the presence of ovalbumin binders in ELISA.
(Skerra and Pluckthun, 1988, Science, 240: 1038-1041). The plasmid
of these binders was prepared and sequenced. We obtained 2 VHH
binders of which 1DBOVA1 (DVQLVESGGGSVPAGSLRLSCAVSGYTYENRY-
MAWFRQAPGKEREGVAAIWR
GGNNPYYADSVKGRFTISQDNAKNIVSLLMNSLKPEDTAIYYCAAQAGRFSGP- LY
ESTYDYWGQGTQVTVSS) was the most abundant.
[0056] Titre Determination
[0057] The titre of the phages was determined by incubation of 150
.mu.l TG1 (F.sup.+) cells at OD600 nm=0.5 with 10 .mu.l of phages
of different dilutions, for 30 minutes at 37.degree. C. This was
plated on LB-agar plates containing 25 .mu.g/ml chloramphenicol and
2% glucose.
[0058] The background for infection of DH5.alpha. (Gibco BRL) was
determined under the same conditions as described above for
TG1.
[0059] Preparation of the Phages Cultures of TG1 containing
pK7C3-VHHB or 1 DBOVA1 were grown at 37.degree. C. in 100 ml
2.times.TY medium containing 2% glucose, and 25 .mu.g/ml
chloramphenicol, until the OD600 nm reached 0.5. M13KO7 phages
(10.sup.12) were added and the mixture was incubated in a water
bath at 37.degree. C. for 2.times.30 minutes, first without
shaking, then with shaking at 100 rpm. The culture was centrifuged
(15', 4300 rpm, room temperature). The bacterial pellet was
dissolved in 600 ml of 2.times.TY medium containing 25 .mu.g/ml
chloramphenicol and 25 .mu.g/ml kanamycin, and incubated overnight
at 30.degree. C., vigorously shaking at 250 rpm.
[0060] These overnight cultures were centrifuged for 15 minutes at
4300 rpm at 4.degree. C. Phages were precipitated for 1 hour on ice
with PEG (20% poly-ethylene-glycol and 1.5 M NaCl), pelleted by
centrifugation (30', 4300 rpm, 4.degree. C.), dissolved in 10 ml
PBS and centrifuged for another 10 minutes at 4300 rpm and
4.degree. C. The supernatant was loaded on 2 ml Ni-NTA (QIAGEN),
washed extensively with 50 mM Na.sub.2HPO.sub.4. 1M NaCl pH=7.0,
eluted with 50 mM NaAc, 1M NaCl pH=4.5 and neutralised with 1 M
Tris pH=7.4. Phages were again PEG precipitated by immediate
centrifugation for 30 minutes at 4300 rpm and 4.degree. C. after
PEG addition. The pellet (invisible) was dissolved in 1 ml PBS+100
.mu.l PBS-caseine. 15% glycerol was added and the phages were
stored at -80.degree. C. for maximally 1 week, until further
use.
Example II
[0061] Display of Oprl and Oprl-ovalbumin Fusion Protein on E.
coli
[0062] The ptrc-Oprl (Cote-Sierra et al., 1998, Gene, 221:25-34;
FIG. 3) or ptrc-Oprl-ova (obtained by amplifying the gene encoding
for hen-egg ovalbumin, digesting the product with BamHI and EcoRI
and cloning the digest in BgIII/EcoRI digested ptrc-Oprl) plasmids
were transformed in E.coli Top10F' (Invitrogen) and tested for
expression in M9CAA and LB-medium in Western blot. Cells were
induced with 1 mM ITPG (Calbiochem) at OD600 nm=0.6 and grown
overnight at 37.degree. C. on a rotary shaker at 200 rpm. Cells
were centrifuged and concentrated 10-fold. Total cell lysates,
obtained by sonication were loaded on a 12% SDS-PAGE and
transferred to nitrocellulose for Western blotting. Transferred
proteins were detected using a monoclonal anti-Oprl antibody QB2
(De Vos D. et al, Journal of general microbiology 1993, 139:
2215-2223). An anti-mouse IgG conjugated with alkaline phosphatase
(Sigma) was applied and the blots were developed with the BCIP/NBT
substrate. The results are shown in FIG. 4. A band at the position
of intact fusion protein is clearly observed. However, large
amounts of degradation products demonstrate the instability of the
pOprl-ova form. Since these degradation products might interfere
with the infection, conditions for growth and infection were
optimised, amongst others by the use of UT5600 (F.sup.-, ara-14,
leuB6, azi-6, lacY1, proC14, tsx-67, entA403, trpE38, rfbD1,
rpsL109, xyl-5, mtl-1, thi1, .DELTA. ompT, fepC266) (Biolabs).
UT5600 is an outer membrane protease T-deficient E. coli strain,
which was used for the stable presentation of Ig scFv fusions
(Maurer and Meyer, J. Bacteriol., 1997, 179: 794-804)
Example III
[0063] Receptor Independent Entering of E.coli by M13
Pseudovirions.
[0064] Cultures of E.coli strain DH5.alpha. containing ptrc-Oprl
(Cote-Sierra et al, 1998, Gene, 221: 25-34) or ptrc-Oprl-OVA
(indicated as DH5.alpha.{ptrc-Oprl-OVA}) were incubated at
37.degree. C. at 220 rpm until the OD600 nm reached 0.6. Cells were
centrifuged at 4300 rpm for 5 minutes and resuspended in the
original volume and in the same medium (=washed cells*). A fraction
of the cells was induced with 1 mM IPTG and grown at 37.degree. C.
for another 4 hours (**).
[0065] To test the pilus independent entering of E.coli displaying
ovalbumin on its surface by M13 phages displaying ovalbumin
specific antibodies, we incubated 150 .mu.l of E.coli cells with 10
.mu.l phages from pK7C3-VHHB of different dilutions for 1 hour at
37.degree. C. without shaking.
[0066] Infection of E.coli was screened for by selection of
incubation mixtures on LB-agar plates containing 100 .mu.g/ml
ampicilline, 25 .mu.g/ml chloramphenicol and 2% glucose.
[0067] Individual colonies were screened in ELISA. Therefore, large
single colonies (resistant to ampicilline and chloramphenicol) were
inoculated in 10 ml TB medium containing 0.1% glucose, 100 .mu.g/ml
ampicilline and 25 .mu.g/ml chloramphenicol for 8 hours. IPTG was
added at a final concentration of 10 mM and the cultures were grown
overnight at 37.degree. C. at 200 rpm.
[0068] Individual colonies in TG1 and DH5.alpha. were picked and
grown in 10 ml TB medium containing 0.1% glucose and 25 .mu.g/ml
chloramphenicol for 4 hours. IPTG was added at a final
concentration of 1 mM and the cultures were grown overnight at
28.degree. C. at 200 rpm.
[0069] Periplasmic fractions were prepared by pelleting the
overnight cultures, and dissolving the pellet in 200 .mu.l TES (0.2
M Tris-HCl, pH=8.0, 0.5 mM EDTA, 0.5 M sucrose). This was incubated
on ice for 20 minutes. 300 .mu.l TES/4 was added and incubated at
4.degree. C. for 25 minutes. This suspension was centrifuged for 25
minutes at maximal speed in an eppendorf centrifuge and the
supernatant was used for testing in ELISA.
[0070] Periplasmic fractions were tested in NUNC-plates coated
overnight with ovalbumin (5 .mu.g/ml) or casein as a negative
control (1% w/v in PBS) and blocked overnight with 1% (w/v) casein.
Samples were incubated for 2 hours at room temperature and
ovalbumin binding VHH's were detected with a mouse
anti-Histidine-tag (SEROTEC), anti-mouse-alkaline phosphatase
conjugate (Sigma) and a chromogenic substrate (Sigma). The results
are summarised in Table I
2 TABLE 1 Positives in ELISA TG1 1/337 DH5.alpha. 0/7 DH5.alpha. +
ptrc-Oprl 2/141 DH5.alpha.{ptrc-Oprl-OVA} 7/16, 17/38, 7/24
DH5.alpha.{ptrc-Oprl-OVA}, washed* 14/19 DH5.alpha.{ptrc-Oprl-ova-
} + IPTG** 3/12 Table 1: The numbers indicate the number of
positive clones in ELISA versus the number of clones that were
tested. Extracts were scored positive if the OD405 nm was at least
double the OD of the background (coated caseine at 1%). Numbers
separated by a comma are from independent experiments. *The cells
were washed 1 time with fresh medium before infection with phages
as described above. **Cells were induced with IPTG as described
above.
Example IV
[0071] Receptor Independent Entering of E.coli by Pseudovirions is
Specific for the Artificial Receptor
[0072] 150 .mu.l of washed UT5600 containing ptrc-Oprl-OVA
(indicated as UT5600{ptrc-Oprl-OVA}) or DH5.alpha.{ptrc-Oprl-OVA}
cells at OD600 nm=0.6 were incubated with 10 .mu.l phages of
pK7C3-VHHB of different dilutions for 1 hour at 37.degree. C.
without shaking.
[0073] The same experiment was repeated after pre-incubation of the
phages with 1ml ovalbumin (2 mg/ml) for 1 hour at room temperature.
The phages were mixed with 150 .mu.l of washed
UT5600{ptrc-Oprl-OVA} or DH5.alpha.{ptrc-Oprl-OVA} cells at OD600
nm=0.6 and incubated for 1 hour at 37.degree. C.
[0074] This was plated on LB agar plates containing 25 .mu.g/ml
chloramphenicol, 100 .mu.g/ml ampicilline and 2% glucose.
Expression of 25-45 clones in UT5600 cells and DH5.alpha. was
carried out as described above.
[0075] The results are summarised in Table 2.
3 TABLE 2 DH5.alpha. UT5600 c.sup.r, a.sup.r c.sup.r, a.sup.r E.
coli (ptrc-Oprl-ova) + pK7C3- 150 90, 73 VHHB phages E. coli
(ptrc-Oprl-ova) + 1 2, 2 ovalbumin pretreated pK7C3- VHHB phages
Table2: number of colonies on plates after infection of washed
UT5600{ptrc-Oprl-OVA) or DH5.alpha.{ptrc-Oprl-OVA} cells with
phages with or without pre-incubation with ovalbumin. Numbers
separated by a comma are from independent experiments. c.sup.r:
chloramphenicol resistant; a.sup.r: ampicilline resistant
[0076] Infection of washed UT5600{ptrc-Oprl-OVA} or
DH5.alpha.{ptrc-Oprl-OVA} cells with phages from pK7C3-VHHB
pre-incubated with hen-egg ovalbumin protein, reduced the number of
transformants significantly, which means that infection is
dependent upon ovalbumin display on the host cell wall.
Example V
[0077] Survival of E.coli Cells and Phages Upon Coincubation
[0078] 150 .mu.l of washed UT5600{ptrc-Oprl-OVA} or
DH5.alpha.{ptrc-Oprl-OVA} cells at OD600 nm=0.6 were incubated with
10 .mu.l phages of PK7C3-VHHB for 1 hour at 37.degree. C. without
shaking.
[0079] This was plated on LB agar plates containing 25 .mu.g/ml
chloramphenicol, 100 .mu.g/ml ampicilline and 2% glucose (C).
[0080] Cells were also checked for survival upon growth (A) and
upon incubation with phages (B) by dilution and plating on LB agar
plates containing 100 .mu.g/ml ampicilline and 2% glucose. The
results are shown in Table 3.
4 TABLE 3 number of cells DH5.alpha. UT5600 Before incubation (A) 2
.times. 10.sup.8 10.sup.9 After incubation (B) 5 .times. 10.sup.7 3
.times. 10.sup.8 entered (C) 64 150 Table3: Number of cells upon
incubation of washed UT5600{ptrc-Oprl-OVA}_or
DH5.alpha.{ptrc-Oprl-OVA} cells with pK7C3-VHHB phages.
[0081] The titre of pK7C3-VHHB phages was determined before
incubation with washed DH5.alpha.{ptrc-Oprl-OVA} cells. Cells were
centrifuged after incubation for 1 hour at 37.degree. C. and the
supernatant was used to determine the titre of unentered phages.
The titres were determined by incubation of 150 .mu.l TG1 cells at
OD600 nm=0.5 with 10 .mu.l of phages of different dilutions for 30
minutes at 37.degree. C. This was plated on LB-agar plates
containing 25 .mu.g/ml chloramphenicol and 2% glucose. The number
of transformants are listed in Table4.
5 TABLE 4 number of phages Before incubation 5.6 .times. 10.sup.7
After incubation 1.2 .times. 10.sup.7 Table4: Number of pK7C3-VHHB
phages before and after incubation with washed
DH5.alpha.{ptrc-Oprl-OVA} cells
[0082] UT5600{ptrc-Oprl-OVA} or DH5.alpha.{ptrc-Oprl-OVA} cells
survived very well when incubated with and entered by pK7C3-VHHB
phages. The pK7C3-VHHB phages which did not enter
UT5600{ptrc-Oprl-OVA} or DH5.alpha.{ptrc-Oprl-OVA} cells are still
able to infect TG1 cells and are therefore stable under the
conditions used.
Example VI
[0083] Individual E.coli Cells Displaying Ovalbumin on the Surface
are Entered by a single Ovalbumin Specific Phaqe.
[0084] Positive clones were selected from experiment 2 for UT5600
(clone number 10, 11, 12, 13, 16, 17). They were inoculated in 5 ml
LB containing 25 .mu.g/ml chloramphenicol, and grown overnight at
37.degree. C. Plasmid was prepared, transformed in TG1 and plated
on LB agar plates containing 25 .mu.g/ml chloramphenicol and 2%
glucose. Individual colonies were tested in ELISA as described
before (in TB containing 25 .mu.g/ml chloramphenicol and 0.1%
glucose).
6 TABLE 5 Positives in ELISA 10 8/8 11 8/8 12 8/8 13 7/8 16 8/8 17
8/8 Table5: number of positive clones in ELISA versus the number of
clones that were tested for individual colonies.
[0085] Individual positive clones were selected and grown overnight
for plasmid preparation. After transformation in TG1 individual
colonies were tested in ELISA. All clones scored positive,
therefore we can be sure that ovalbumin specific phages have
entered the cell. Colony PCR on these individual colonies showed
that they have the same length if they originate from the same
original clone.
Example VII
[0086] Optimisation of the Conditions of Receptor Independent
Entering
[0087] Cells of DH5.alpha.{ptrc-Oprl-OVA} and UT5600{ptrc-Oprl-OVA}
were grown at 37.degree. C. A 150 .mu.l sample was removed at
different time intervals, washed and 5.times.10.sup.8 phages of
pK7C3-VHHB were added. This suspension was incubated for 1 hour at
37.degree. C. and plated on LB-agar plates with 2% glucose, 25
.mu.g/ml chloramphenicol and 100 .mu.g/ml ampicillin. Single
colonies were tested in ELISA as described above. The results are
shown in Table 6a and 6b.
7TABLE 6a UT5600 Time of Positives growth OD600 in ELISA (minutes)
nm tfu pK7C3-VHHB 30 0.062 20 7/15 60 0.076 56 7/15 90 0.142 100
11/15, 2/3 120 0.273 130 11/16 150 0.555 150 8/15 210 1.24 120 2/13
270 2.25 30 7/12
[0088]
8TABLE 6b DH5.alpha. Time of Positives growth OD600 in ELISA
(minutes) nm tfu pK7C3-VHHB 60 0.010 0 -- 120 0.038 23 5/13 210
0.197 97 3/8 270 0.600 84 3/5 300 0.665 64 2/8 Tables 6a and 6b:
Number of positive clones in ELISA versus the number of clones that
were tested and the number of transformants (tfu) as a function of
the OD600 nm of the cells. Numbers separated by a comma are from
independent experiments.
[0089] Cells of DH5.alpha.{ptrc-Oprl-OVA} and UT5600{ptrc-Oprl-OVA}
were grown at 37.degree. C. Increasing concentrations of pK7C3-VHHB
phages were added to 150 .mu.l of washed cells at OD600 nm=0.2-0.3
for UT5600{ptrc-Oprl-OVA} and 0.6 for DH5.alpha.{ptrc-Oprl-OVA}.
This mixture was incubated for 1 hour at 37.degree. C. and plated
on B-agar plates with 2% glucose, 25 .mu.g/ml chloramphenicol (Chl)
and 100 .mu.g/ml ampicillin (Amp). Single colonies were tested in
ELISA as described before.
9TABLE 7a UT5600 Number of Number Number of Number of positives of
phages transformants positives in in ELISA added on Amp/Chl ELISA
(%) 7 .times. 10.sup.6 30 0/2 -- 1 .times. 10.sup.7 20 0/2 -- 7
.times. 10.sup.7 85, 90, 150 0/5, 1/24, 2/24 --, 4, 8 1 .times.
10.sup.8 70 1/4 25 4 .times. 10.sup.8 67 4/29 14 7 .times. 10.sup.8
300, 300 18/24, 20/20 75, 100
[0090]
10TABLE 7b DH5.alpha. Number of Number Number of Number of
positives of phages transformants positives in in ELISA added on
Amp/Chl ELISA (%) 5 .times. 10.sup.7 85 10/28 36 2 .times. 10.sup.5
250 21/43 49 5 .times. 10.sup.8 110 17/40 43 Table7a-b: Increasing
concentrations of pK7G3-VHHB phages were mixed with 150 .mu.l
UT5600{ptrc-Oprl-OVA} at OD600 nm = 0.2-0.3 or with
DH5.alpha.{ptrc-Oprl-OVA) cells at OD600 nm = 0.6. Individual
colonies were tested in ELISA. Numbers separated by a comma are
from independent experiments.
[0091] Optimal conditions for uptake of phages were tested by
mixing pK7C3-VHHB phages with UT5600{ptrc-Oprl-OVA} or
DH5.alpha.{ptrc-Oprl-OVA} cells at different optical densities.
Individual colonies were tested in ELISA. For UT5600{ptrc-Oprl-OVA}
the optimal density is between 0.15 and 0.3 and for
DH5.alpha.{ptrc-Oprl-OVA} between 0.2 and 0.6.
UT5600{ptrc-Oprl-OVA} cells grow much faster than
DH5.alpha.{ptrc-Oprl-OV- A} and are easier infected by
anti-ovalbumin expressing phages (positive clones in ELISA) (73%
versus 30-50% table 6a-b). When increasing amounts of phages were
mixed with UT5600[ptrc-Oprl-OVA] cells (OD600 nm=0.2-0.3), more
positive clones were obtained in ELISA (table 7a). 75-100% positive
clones were obtained when 5-10.times.10.sup.8 phages were mixed
with 0.5.times.10.sup.8 UT5600{ptrc-Oprl-OVA} cells resulting in
150-500 individual colonies. However, in DH5.alpha.{ptrc-Oprl-OVA},
no increase in positive clones in ELISA was observed upon addition
of increasing amounts of phages (table 7b).
Example VIII
[0092] Selective Elimination by Killer Phases
[0093] Barnase is a extracellular ribonuclease from Bacillus
amyloliquefaciens (Hartley & Rogerson 1972, Prep. Biochem. 2:
229-242). A very low level of intracellular expression of barnase
in E.coli is lethal because barnase depolymerizes the RNA of its
host. Jucovic & Hartley developed a tightly controlled system
(pMI47a) for the intracellular expression of barnase in E.coli
(Protein engineering, 8: 497-499, 1995). The plasmid encodes
barstar (a strong polypeptide inhibitor of barnase) under the
transcriptional control of the Tac promotor. A barnase gene
(without secretion signal) has been cloned in the inverse
orientation downstream from barstar. In pMI47a, the Tac promotor is
followed by attP, followed by barstar, followed by the inversed
gene for barnase, followed by attB. AttP and attB are derived from
the phage lambda attachment site. pMI47a is not toxic for E.coli
because it overproduces barstar and no barnase (OFF configuration,
FIG. 5a). The Integrase protein (INT function) from phage lambda
recognises the attB and attP sequences and inverses the DNA
fragment that is located between the attB and attP sites in vivo.
In the resulting plasmid pMI47b the Tac promotor is followed by
attR, followed by barnase, followed by the inversed gene for
barstar, followed by attL. Sites attR and attL are the products of
recombination between attP and attB (Jucovic & Hartley, 1995,
Protein Engineering 8: 497-499). This plasmid is toxic for E.coli
because it produces active barnase in the cytoplasm of the host (ON
configuration, FIG. 5b). The system can be switched in vivo from
the OFF to the ON configuration in the E.coli strain D1210HP
(supE44 ara14 galK2 lacY1 D(gpt-proA)62 rpsL20 (Str.sup.r) xyl-5
mtl-1 recA13 D(mrcC-mrr)HsdS.sup.-(r.sup.-m.sup.-) lacl.sup.q
LacY.sup.+ lxis-kil-cl857) (Stratagene) by a short incubation at
42.degree. C. This strain encodes the integrase function (Int;
lxis) from phage lambda, whereas D1210 doesn't have this
function.
[0094] A conditionally lethal phage particle was made by cloning
the conditionally lethal cassette of pMI47a into a phagemid. A DNA
fragment of pMI47a including the Tac promotor, followed by attP,
followed by barstar, followed by the inversed gene for barnase, and
followed by attB was amplified by PCR. This PCR product was cloned
as a blunt end fragment within the EcoRI site of the pK7C3-1DBOVA1
vector (example I) to give pK7C3BB-1DBOVA1 (Before ligation,
pK7C3-1DBOVA1 was linearized with EcoRI and filled-in with Klenow
DNA polymerase).
[0095] Plasmids of pK7C3BB-1DBOVA1, pK7C3, ptrc-Oprl-OVA and pMI47a
were transformed in D1210 and D1210HP electrocompetent cells.
Individual colonies were grown in LB with 25 .mu.g/ml
chloramphenicol or 100 .mu.g/ml ampicilline and 2% glucose at
37.degree. C. until the OD600 nm=1.2-1.3. Half of the culture was
exposed to thermal induction (15 minutes at 42.degree. C.). Both
fractions (before and after induction) were spread after
appropriate dilutions, on LB agar plates containing 25 .mu.g/ml
chloramphenicol or 100 .mu.g/ml ampicilline and 2% glucose. The
numbers of transformants were counted and are listed in table
8.
11TABLE 8 Number of transformants with or without thermoinduction
of D1210 or D1210HP cells containing PM147a, ptrc-Oprl-OVA, pK7C3
or pK7C3BB-1DBOVA1. Number of construct E. coli strain temperature
transformants/ml PM147a D1210 37.degree. C. 3 .times. 10.sup.8
Amp.sup.r 37.degree. C.-42.degree. C. 2 .times. 10.sup.8 Amp.sup.r
D1210HP 37.degree. C. 2 .times. 10.sup.8 Amp.sup.r 37.degree.
C.-42.degree. C. 280 Amp.sup.r Ptrc-Oprl-OVA D1210 37.degree. C. 3
.times. 10.sup.8 Amp.sup.r 37.degree. C.-42.degree. C. 2 .times.
10.sup.8 Amp.sup.r D1210HP 37.degree. C. 3 .times. 10.sup.8
Amp.sup.r 37.degree. C.-42.degree. C. 2 .times. 10.sup.8 Amp.sup.r
pK7C3 D1210 37.degree. C. 5 .times. 10.sup.8 Chl.sup.r 37.degree.
C.-42.degree. C. 4 .times. 10.sup.8 Chl.sup.r D1210HP 37.degree. C.
6 .times. 10.sup.8 Chl.sup.r 37.degree. C.-42.degree. C. 3 .times.
10.sup.8 Chl.sup.r pK7C3BB- D1210 37.degree. C. 4 .times. 10.sup.8
Chl.sup.r 1DBOVA1 37.degree. C.-42.degree. C. 3 .times. 10.sup.8
Chl.sup.r D1210HP 37.degree. C. 5 .times. 10.sup.8 Chl.sup.r
37.degree. C.-42.degree. C. 560 Chl.sup.r
[0096] The results show that D1210 cells (lacking the Int gene)
transformed with PMI47a, ptrc-Oprl-OVA, pK7C3 or pK7C3BB-1DBOVA1
survive well upon thermoinduction, which indicates that PMI47a,
ptrc-Oprl-OVA, pK7C3 and pK7C3BB-1DBOVA1 are not harmful for
E.coli. PMI47a, ptrc-Oprl-OVA, pK7C3 and pK7C3BB-1DBOVA1 can be
transformed and maintained in D1210HP if the cells are maintained
at 37.degree. C. (OFF configuration). However, when cells are
incubated at 42.degree. C. for 15 minutes (ON configuration), the
integrase function is activated, and D1210HP cells containing
PMI47a or pK7C3BB-1DBOVA1 do not longer survive. These experiments
show that the phagemid pK7C3BB-1 DBOVA1 is toxic for E.coli strain
D1210HP if inversion is induced by thermoinduction of the Int
gene.
[0097] Elimination Upon Recognition of an Artificial Receptor
[0098] D1210 and D1210HP electrocompetent cells were transformed
with ptrc-Oprl-OVA. A single colony was used to inoculate a culture
in LB containing 100 .mu.g/ml ampicilline. Phages of pK7C3-1DBOVA1
or pK7C3BB-1DBOVA1 were prepared as described above. 150 .mu.l of
washed cells were incubated with 5.times.10.sup.8 pK7C3-1DBOVA1 or
pK7C3BB-1DBOVA1 phages for 1 hour at 37.degree. C. Half of these
mixtures was exposed to thermal induction (15 minutes at 42.degree.
C.). An aliquot (before and after induction) was spread on LB agar
plates containing 25 .mu.g/ml chloramphenicol and 100 .mu.g/ml
ampicilline and 2% glucose. The numbers of transformants were
counted and are listed in table 9.
12TABLE 9 Number of transformants when D1210 or D1210HP cells
containing ptrc-Oprl-OVA were incubated with pK7C3-1 DBOVA1 or
pK7C3BB- 1DBOVA1 phages with or without thermal incubation. type of
phages E. coli strain temperature Number of transformants pK7C3-
D1210 37.degree. C. 8000 1DBOVA1 37.degree. C.-42.degree. C. 7800
D1210HP 37.degree. C. 8100 37.degree. C.-42.degree. C. 8300
pK7C3BB- D1210 37.degree. C. 7800 1DBOVA1 37.degree. C.-42.degree.
C. 7900 D1210HP 37.degree. C. 7600 37.degree. C.-42.degree. C.
2
[0099] D1210HP cells displaying ovalbumin on their surface are
killed by pseudovirions containing phagemid pK7C3BB-1DBOVA1 after
thermoinduction. This experiment clearly demonstrates that coli
cells, expressing an artificial receptor can be recognised and
killed by a bacteriophage with an artificial ligand that recognises
the artificial receptor.
Example IX
[0100] Library Versus Library Screening ("Picup" Screening)
[0101] Fission yeast (Schizosaccharomyces pombe p2, h.sup.+,
arg.sup.3-, ura.sup.4-) was grown in YES medium (0.5% (w/v) yeast
extract, 3.0% (w/v) glucose +225 mg/l adenine, histidine, leucine,
uracil and lysine hydrochloride). Cells were harvested by low speed
centrifugation. 15 g wet cells were washed with 100 ml S-buffer
(1.4 M sorbitol, 40 mM HEPES, 0.5 mM MgCl.sub.2 adjusted to pH
6.5). After centrifugation the pellet was resuspended in 100 ml
S-buffer containing 10 mM 2-mercaptoethanol and 1 mM PMSF and
incubated at 30.degree. C. for 10 minutes. After centrifugation,
the pellet was resuspended in 60 ml S-buffer containing 1 mM PMSF,
and 460 mg Zymolase 20T (ICN Biomedicals) was added to prepare
spheroplasts. After incubation for 3 hours at 30.degree. C., the
pellet was washed five times with 100 ml S-buffer containing 1 mM
PMSF. Spheroplasts were resuspended in 60 ml Tris (25 mM, pH=7.5),
100 mM NaCl, 2 mM EDTA supplemented with 1 tablet protease
inhibitor mix (Boehringer) and lysed by two passages in French
press. The supernatant was recovered after centrifugation for 30
minutes at 15.000 rpm in SS34 rotor. 15.5 g solid ammoniumsulfate
was added to 30 ml of the supernatant. After incubation on ice for
1 hour, precipitated material was recovered by centrifugation and
resuspended in 20 ml PBS. The solution was equilibrated in PBS by
passage over PD10 columns. Following this treatment, the protein
concentration was determined with Bio-Rad protein assay kit, using
BSA as reference protein. Six aliquots, each 5 ml in volume, with a
protein concentration of 8 mg/ml, were prepared for camel
immunisation.
[0102] The immunisation and blood withdrawal scheme is as
follows:
13 Day 0 Collect preimmune serum Day 0 inject subcutaneously 1 tube
(40 mg protein) + complete freund adjuvant Day 7 inject
subcutaneously 1 tube + incomplete freund adjuvant Day 14 inject
subcutaneously 1 tube + incomplete freund adjuvant Day 21 Collect
anticoagulated blood and serum Day 21 inject subcutaneously 1 tube
+ incomplete freund adjuvant Day 28 inject subcutaneously 1 tube +
incomplete freund adjuvant Day 35 inject subcutaneously 1 tube +
incomplete freund adjuvant Day 38 Collect anticoagulated blood and
serum
[0103] A cDNA library of Schizosaccharomyces pombe is constructed
by recloning the S.pombe cDNA bank that is used in Two-hybrid
system (Clontech). The cDNA inserts are amplified with specific
primers harbouring restriction enzyme sites compatible for cloning
into the multiple cloning site of ptrc-Oprl. The library is
transformed in UT5600 or in D1210HP electro-competent cells.
[0104] The serum immunoglobulins from the immunised animal (day 21
or 38) are passed over protein A and protein G columns to purify
the conventional antibodies and the heavy chain antibodies. Each
fraction is used in a Western blot to evaluate the presence and
titre of anti-S.pombe protein immunoglobulins.
[0105] Peripheral blood lymphocytes from the immunised camel are
prepared using Unisep (WAK Chemie, Germany) from the anticoagulated
blood isolated at days 21 and 42. The camel heavy chain antibodies
(VHH's) from 10.sup.7 lymphocytes are ligated after RT-PCR
amplification in the Sfil-Notl sites of the pK7C3 or pK7C3-BB
(pK7C3 with the barnase-barstar inversion system) vector and
transformed in TG1 as described above, in order to obtain a library
of 10.sup.8 individual clones. The VHH phages is prepared by
infection of the E.coli culture with M13K07 and enriched for
virions with a VHH-gpIII fusion by IMAC chromatography (see
before).
[0106] For the PICUP experiment, 10.sup.7-10.sup.8 UT5600 cells
from the cDNA library of S.pombe are mixed with 10.sup.12 phages
obtained from the camel VHH library. The mixture is incubated for 1
hour at 37.degree. C. and plated on LB agar plates containing 100
.mu.g/ml ampicillin, 25 .mu.g/ml chloramphenicol and 2% glucose.
Colonies can only grow on this medium if the UT5600 cells are
expressing a S.pombe antigen that is recognised and subsequently
infected by a virion carrying an antigen-specific VHH. For each
colony the VHH insert is sequenced with a primer annealing in the
gene pill sequence, while the cDNA coding for the antigen is
directly sequenced with an Oprl specific primer. The latter
sequence is screened in a BLAST on the S.pombe genome sequence
database to identify the gene. The specificity of the VHH (having a
his-tag) is also tested in a Western blot in which the S.pombe
extracted proteins are separated on SDS gels. The presence of the
VHH is revealed with an anti-His monoclonal antibody (SEROTEC),
[0107] As a positive control, individual colonies from the cDNA
library are used in a separate PICUP experiment. One single clone
that is capable to produce a fusion protein with the lipoprotein
(as seen by Western blot) is grown and challenged with the VHH
phages from the library. The VHH from clones growing on Ampicilline
and Chloramphenicol are induced with IPTG, extracted from the
periplasm and it's binding to the yeast protein tested in Western
blot and ELISA.
[0108] To eliminate particular antigens dominantly present in the
matched pairs (S.pombe antigen--specific VHH) or particular VHH
over-represented in the matched pairs, the killer phage strategy is
used. To this end the UT5600 cells carrying the S.pombe cDNA
library are incubated with the phages from the pK7C3-BB library of
VHH. After infection the suspension is incubated at 42.degree. C.
to eliminate the E.coli cells that are infected with phages. The
surviving cells are carrying S.pombe antigens that are less
frequent represented in the ptrc-Oprl or pK7C3-BB libraries. In a
second step these surviving cells are used to inoculate fresh
medium and to restart the PICUP experiment as before.
Sequence CWU 1
1
3 1 33 DNA Artificial Sequence primer 1 catgcgatga ctcgcggccc
agccggccat ggc 33 2 30 DNA Artificial Sequence primer 2 gtgtgcggcc
gctgaggaga crgtgaccwg 30 3 124 PRT Camel 3 Asp Val Gln Leu Val Glu
Ser Gly Gly Gly Ser Val Pro Ala Gly Ser 1 5 10 15 Leu Arg Leu Ser
Cys Ala Val Ser Gly Tyr Thr Tyr Glu Asn Arg Tyr 20 25 30 Met Ala
Trp Phe Arg Gln Ala Pro Gly Lys Glu Arg Glu Gly Val Ala 35 40 45
Ala Ile Trp Arg Gly Gly Asn Asn Pro Tyr Tyr Ala Asp Ser Val Lys 50
55 60 Gly Arg Phe Thr Ile Ser Gln Asp Asn Ala Lys Asn Ile Val Ser
Leu 65 70 75 80 Leu Met Asn Ser Leu Lys Pro Glu Asp Thr Ala Ile Tyr
Tyr Cys Ala 85 90 95 Ala Gln Ala Gly Arg Phe Ser Gly Pro Leu Tyr
Glu Ser Thr Tyr Asp 100 105 110 Tyr Trp Gly Gln Gly Thr Gln Val Thr
Val Ser Ser 115 120
* * * * *