U.S. patent application number 13/268069 was filed with the patent office on 2012-03-15 for immunogenic composition and uses thereof.
This patent application is currently assigned to THE UNIVERSITY OF MELBOURNE. Invention is credited to Brendon Yew Loong Chua, David Charles Jackson, Weiguang Zeng.
Application Number | 20120064109 13/268069 |
Document ID | / |
Family ID | 42935575 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120064109 |
Kind Code |
A1 |
Jackson; David Charles ; et
al. |
March 15, 2012 |
IMMUNOGENIC COMPOSITION AND USES THEREOF
Abstract
The present invention provides an immunogenic composition
comprising an antigen and a dendritic cell targeting component. A
charged group is covalently attached to a dendritic cell ligand and
is electrostatically associated with the dendritic cell targeting
component.
Inventors: |
Jackson; David Charles;
(North Balwyn, AU) ; Zeng; Weiguang; (Kensington,
AU) ; Chua; Brendon Yew Loong; (Heidelberg Heights,
AU) |
Assignee: |
THE UNIVERSITY OF MELBOURNE
PARKVILLE
AU
|
Family ID: |
42935575 |
Appl. No.: |
13/268069 |
Filed: |
October 7, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/AU2009/000446 |
Apr 9, 2009 |
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13268069 |
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PCT/AU2009/000469 |
Apr 16, 2009 |
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PCT/AU2009/000446 |
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Current U.S.
Class: |
424/193.1 ;
530/300; 530/322; 536/123.1; 554/1 |
Current CPC
Class: |
A61K 45/06 20130101;
A61K 38/38 20130101; A61K 31/23 20130101; A61K 2039/6018 20130101;
C07K 14/77 20130101; A61K 38/03 20130101; A61P 37/04 20180101; C07K
2/00 20130101; A61K 31/23 20130101; A61K 2300/00 20130101; A61K
2300/00 20130101; A61K 2300/00 20130101; A61K 38/03 20130101; A61K
38/38 20130101; A61K 39/39 20130101; A61K 2039/55516 20130101 |
Class at
Publication: |
424/193.1 ;
530/300; 530/322; 554/1; 536/123.1 |
International
Class: |
A61K 39/00 20060101
A61K039/00; C08B 37/00 20060101 C08B037/00; C07C 53/126 20060101
C07C053/126; C07K 2/00 20060101 C07K002/00; A61P 37/04 20060101
A61P037/04 |
Claims
1. An immunogenic composition comprising an antigen and a dendritic
cell targeting component, wherein the antigen comprises a
negatively charged region and wherein the dendritic cell targeting
component comprises a positively charged group covalently attached
to a dendritic cell ligand and wherein the negatively charged
region of antigen is electrostatically associated with the
dendritic cell targeting component.
2. The immunogenic composition according to claim 1, wherein the
antigen has an overall negative charge.
3. The immunogenic composition according to claim 1, wherein the
positively charged group comprises at least one positively charged
amino acid.
4. The immunogenic composition according to claim 1, wherein the
positively charged group is a branched or linear peptide.
5. The immunogenic composition according to claim 4, wherein the
peptide comprises at least one arginine or lysine residue.
6. The immunogenic composition according to claim 4, wherein the
peptide comprises at least four arginine residues and/or at least
four lysine residues.
7. An immunogenic composition comprising an antigen and a dendritic
cell targeting component, wherein the antigen comprises a
positively charged region and wherein the dendritic cell targeting
component comprises a negatively charged group covalently attached
to a dendritic cell ligand and wherein the positively charged
region of antigen is electrostatically associated with the
dendritic cell targeting component.
8. The immunogenic composition according to claim 7, wherein the
antigen has an overall positive charge.
9. The immunogenic composition according to claim 7, wherein the
negatively charged group comprises at least one negatively charged
amino acid.
10. The immunogenic composition according to claim 7, wherein the
negatively charged group is a branched or linear peptide.
11. The immunogenic composition according to claim 10, wherein the
peptide comprises at least one aspartic acid or glutamic acid
residue.
12. The immunogenic composition according to claim 10, wherein the
peptide comprises at least four aspartic acid residues and/or at
least four glutamic acid residues.
13. The immunogenic composition according to claim 1, wherein the
antigen is not a nucleic acid.
14. The immunogenic composition according to claim 1, wherein the
antigen is associated with the dendritic cell targeting component
by electrostatic interaction only.
15. The immunogenic composition according to claim 1, wherein the
dendritic cell ligand is a TLR ligand.
16. The immunogenic composition according claim 15, wherein the TLR
ligand comprises a lipid or a peptidoglycan or a lipoprotein or a
lipopolysaccharide.
17. The immunogenic composition according to claim 15, wherein the
TLR ligand comprises palmitoyl, myristoyl, stearoyl, lauroyl,
octanoyl, or decanoyl.
18. The immunogenic composition according to claim 15, wherein the
TLR ligand is selected from the group consisting of: Pam.sub.2Cys,
Pam.sub.3Cys, Ste.sub.2Cys, Lau.sub.2Cys, and Oct.sub.2Cys.
19. The immunogenic composition according to claim 15, wherein the
TLR ligand binds either TLR-1, TLR-2 or TLR-6.
20. The immunogenic composition according to claim 15, wherein the
TLR ligand binds to TLR-2.
21. A method of raising an immune response in a subject, the method
comprising administering to a subject an immunogenic composition
according to claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of
International Patent Application No. PCT/AU2009/000446, filed Apr.
9, 2009, and is a continuation of International Patent Application
No, PCT/AU2009/000469, filed Apr. 16, 2009, the disclosures of
which are incorporated by reference herein in their entirety,
including any figures, tables, or drawings.
BACKGROUND OF INVENTION
[0002] There is an ever increasing interest in the development of
compositions which can be used to raise an immune response in
humans and other animals in particular to protect against disease.
In generating an immune response it is necessary for the antigen to
encounter dendritic cells. Dendritic cells are immune cells and
form part of the mammalian immune system. Their main function is to
process antigen material and present it on the surface to other
cells of the immune system, thus functioning as antigen-presenting
cells.
[0003] The targeting of antigens to dendritic cells has been
contemplated previously and lipopeptides which include lipids which
Toll-like receptors on dendritic cells have been shown to elicit
strong immune response (WO 2004/014956 & WO 2004/014957, the
disclosures of which are incorporated herein be reference)
[0004] For any peptide to be able to induce an effective antibody
response it must contain particular sequences of amino acids known
as epitopes that are recognised by the immune system. In
particular, for antibody responses, epitopes need to be recognised
by specific immunoglobulin (Ig) receptors present on the surface of
B lymphocytes. It is these cells which ultimately differentiate
into plasma cells capable of producing antibody specific for that
epitope. In addition to these B cell epitopes, the immunogen must
also contain epitopes that are presented by antigen presenting
cells (APC) to specific receptors present on helper lymphocytes,
the cells which are necessary to provide the signals required for
the B cells to differentiate into antibody producing cells.
[0005] In the case of viral infections and in many cases of cancer,
antibody is of limited benefit in recovery and the immune system
responds with cytotoxic T cells (CTL) which are able to kill the
virus-infected or cancer cell. Like helper T cells, CTL are first
activated by interaction with APC bearing their specific peptide
epitope presented on the surface, this time in association with MHC
class I rather than class II molecules. Once activated the CTL can
engage a target cell bearing the same peptide/class I complex and
cause its lysis. It is also becoming apparent that helper T cells
play a role in this process; before the APC is capable of
activating the CTL it must first receive signals from the helper T
cell to upregulate the expression of the necessary costimulatory
molecules.
[0006] Helper T cell epitopes are bound by molecules present on the
surface of APCs that are coded by class II genes of the major
histocompatibility complex (MHC). The complex of the class II
molecule and peptide epitope is then recognised by specific T-cell
receptors (TCR) on the surface of T helper lymphocytes. In this way
the T cell, presented with an antigenic epitope in the context of
an MHC molecule, can be activated and provide the necessary signals
for the B lymphocyte to differentiate.
[0007] In general then, an immunogen must contain epitopes capable
of being recognised by helper T cells in addition to the epitopes
that will be recognised by B cells or by cytotoxic T cells. It
should be realised that these types of epitopes may be very
different. For B cell epitopes, conformation is important as the B
cell receptor binds directly to the native immunogen. In contrast,
epitopes recognised by T cells are not dependent on conformational
integrity of the epitope and consist of short sequences of
approximately nine amino acids for CTL and slightly longer
sequences, with less restriction on length, for helper T cells. The
only requirements for these epitopes are that they can be
accommodated in the binding cleft of the class I or class II
molecule respectively and that the complex is then able to engage
the T-cell receptor. The class II molecule's binding site is open
at both ends allowing a much greater variation in the length of the
peptides bound (Brown, J. H., T. S. Jardetzky, J. C. Gorga, L. J.
Stern, R. G. Urban, J. L. Strominger and D. C. Wiley. 1993.
Three-dimensional structure of the human class II
histocompatibility antigen HLA-DR1. Nature 364: 33) although
epitopes as short as 8 amino acid residues have been reported
(Fahrer, A. M., Geysen, H. M., White, D. O., Jackson, D. C. and
Brown, L. E. Analysis of the requirements for class II-restricted
T-cell recognition of a single determinant reveals considerable
diversity in the T-cell response and degeneracy of peptide binding
to I-ED J. Immunol. 1995.155: 2849-2857).
BRIEF SUMMARY
[0008] The present inventors have developed immunogenic
compositions comprising an antigen and a dendritic cell targeting
component in which the antigen is electrostatically associated with
the dendritic cell targeting component.
[0009] In a first aspect the present invention provides an
immunogenic composition comprising an antigen and a dendritic cell
targeting component, wherein the antigen comprises a negatively
charged region and wherein the dendritic cell targeting component
comprises a positively charged group covalently attached to a
dendritic cell ligand and wherein the negatively charged region of
antigen is electrostatically associated with the dendritic cell
targeting component.
[0010] In a second aspect the present invention provides an
immunogenic composition comprising an antigen and a dendritic cell
targeting component, wherein the antigen comprises a positively
charged region and wherein the dendritic cell targeting component
comprises a negatively charged group covalently attached to a
dendritic cell ligand and wherein the positively charged region of
antigen is electrostatically associated with the dendritic cell
targeting component.
[0011] In a third aspect the present invention provides a method of
raising an immune response in a subject, the method comprising
administering to a subject an immunogenic composition of the first
or second aspect of the present invention.
BRIEF DESCRIPTION OF DRAWINGS
[0012] In the following, OVA=ovalbumin; HEL=hen egg white lysozyme;
R.sub.4(S.sub.2Pam.sub.2Cys)=construct shown at 1 in FIG. 5;
E.sub.4(S.sub.2Pam.sub.2Cys)=construct shown at 2 in FIG. 5;
CFA=complete Freund's adjuvant.
[0013] FIG. 1. Antibody and cell-mediated responses elicited by
vaccination with R.sub.4(S.sub.2Pam.sub.2Cys-OVA) complexes. (A)
Groups of BALB/c mice were inoculated sub-cutaneously with 25 .mu.g
of OVA alone, OVA emulsified in CFA or OVA that had been mixed with
an equimolar or a 5-fold molar excess of
R.sub.4(S.sub.2Pam.sub.2Cys). Animals received a second and similar
dose of antigen 26 days later. Sera were obtained from blood taken
27 days after the primary (.largecircle.) and 13 days following the
secondary ( ) inoculation of antigen. Antibody levels were
determined by ELISA and individual antibody titres presented with
the mean value represented by the horizontal bar. (B) Mice were
inoculated a third time on day 50 and spleens obtained 7 days
later. Intracellular cytokine staining was performing on
splenocytes to detect the presence of SIINFEKL-specific IFN-.gamma.
producing CD8.sup.+ T cells. Data are presented as the mean and
standard deviation of triplicate samples.
[0014] FIG. 2. OVA and HEL-specific antibody responses elicited by
vaccination with cationic and anion lipopeptide-protein complexes.
BALB/c mice were inoculated sub-cutaneously with 25 .mu.g of HEL
(A) or OVA (B) alone, emulsified in CFA or with an equal amount of
R.sub.4(S.sub.2Pam.sub.2Cys) or E.sub.4(S.sub.2Pam.sub.2Cys that
had been mixed with the antigen. Mice were bled 28 days after the
primary (.largecircle.) inoculation, boosted on day 32 and bled
again on day 46 ( ). Antibody levels were then determined by ELISA.
Individual animal titres are presented with the mean value
represented by the horizontal bar.
[0015] FIG. 3. Sedimentation of ovalbumin-lipopeptide complexes.
Increasing amounts of the branched R.sub.4(S.sub.2Pam.sub.2Cys) or
linear Pam.sub.2Cys-SK.sub.4 lipopeptide were mixed with 1 nmole of
ovalbumin (OVA) in a total volume of 100 .mu.l PBS in a flat
flat-bottom 96-well plate. The turbidity of the solution was then
measured by determining the optical density of the solution at 450
nm.
[0016] FIG. 4. HPLC analysis of
ovalbumin-R.sub.4(S.sub.2Pam.sub.2Cys) lipopeptide solution. HPLC
analysis was performed on supernatants of solutions containing
either (A) 100 nmoles of branched R.sub.4(S.sub.2Pam.sub.2Cys)
lipopeptide, (B) 1 nmole of ovalbumin (OVA) or (C) a mixture of
R.sub.4(S.sub.2Pam.sub.2Cys) lipopeptide and ovalbumin in a total
volume of 100 .mu.l PBS following centrifugation
(1.2.times.10.sup.5 G). (D) Sedimented material from the mixture
containing both the lipopeptide and OVA was dissolved in a solution
of 50% acetonitrile in water and then analysed by HPLC. In all
samples containing R.sub.4(S.sub.2Pam.sub.2Cys), the identity of
the peak corresponding to the lipopeptide was verified by mass
spectrometry.
[0017] FIG. 5 Schematic representations of some examples of
branched (structures 1-5) and linear (structures 6-8) immunogenic
compositions comprising of positively charged (Arginine, R; Lysine,
K) or negatively charged (Aspartic acid, D; Glutamic acid, E) amino
acids in terminal positions such that their respective
electrostatic charges are displayed to the environment. Each
immunogenic composition also contains dipalmitoyl-S-glyceryl
cysteine (Pam2Cys) which is a ligand for Toll-Like Receptor 2. Two
serine residues (Ser) are also incorporated. In the case of
construct 2 the peptide structure was assembled in the direction
N.fwdarw.C, all other structures shown in the figure were assembled
C.fwdarw.N. Positive and negative electrostatic charges are shown
as 2-, 2+, 1-, 1+ etc. depending on the size of charge. Ac=acetyl
group used to suppress the positive charge of alpha amino groups in
the case of N-terminally situated Glutamic acid.
DETAILED DISCLOSURE
[0018] The present inventors have found that a charged moiety
covalently attached to a dendritic cell targeting group associate
with an antigen electrostatically to form an immunogenic complex
which can be used to raise an immune response.
[0019] Accordingly the present invention provides an immunogenic
composition comprising an antigen and a dendritic cell targeting
component, wherein the antigen comprises a negatively charged
region and wherein the dendritic cell targeting component comprises
a positively charged group covalently attached to a dendritic cell
ligand and wherein the negatively charged region of antigen is
electrostatically associated with the dendritic cell targeting
component.
In this aspect of the invention it is important that the antigen
includes a negatively charged region or domain which can
electrostatically interact with the charged targeting component. It
is however not essential that the antigen has an overall negative
charge, although this is preferred. It is also possible to increase
the negative charge of the antigen by adding negatively charged
groups. For example with a polypeptide antigen a chain of aspartic
acid or glutamic acid residues could be added to the
polypeptide.
[0020] It is preferred that the positively charged group comprises
at least one positively charged amino acid. It is also preferred
that the positively charged group is a branched or linear peptide,
preferably branched. In various embodiments the peptide will
include at least one arginine, histidine, ornithine or lysine
residue or combinations thereof. It is preferred that the peptide
comprises at least four arginine residues and/or at least four
lysine residues. It is particularly preferred that the positively
charged group comprises a branched peptide comprising at least 4
arginine residues.
[0021] In a second aspect the present invention provides an
immunogenic composition comprising an antigen and a dendritic cell
targeting component, wherein the antigen comprises a positively
charged region and wherein the dendritic cell targeting component
comprises a negatively charged group covalently attached to a
dendritic cell ligand and wherein the positively charged region of
antigen is electrostatically associated with the dendritic cell
targeting component.
[0022] In this aspect of the invention it is important that the
antigen includes a positively charged region or domain which can
electrostatically interact with the charged targeting component. It
is however not essential that the antigen has an overall positive
charge, although this is preferred. It is also possible to increase
the positive charge of the antigen by adding positively charged
groups. For example with a polypeptide antigen a chain of lysine,
arginine or histidine residues could be added to the
polypeptide.
[0023] It is preferred that the negatively charged group comprises
at least one negatively charged amino acids. It is also preferred
that the negatively charged group is a branched or linear peptide,
preferably branched. In various embodiments the peptide will
include at least one aspartic acid or glutamic acid residue or
combinations thereof. It is preferred that the peptide comprises at
least four aspartic acid residues and/or at least four glutamic
acid residues. It is particularly preferred that the positively
charged group comprises a branched peptide comprising at least 4
glutamic acid residues.
[0024] In a preferred embodiment of the present invention the
antigen is not a nucleic acid. It is also preferred that the
antigen is associated with the dendritic cell targeting component
by electrostatic interaction only.
[0025] A range of dendritic cell ligands which may be used in the
present invention are set out in Table 1. It is preferred however
that the dendritic cell ligand is a TLR ligand. The TLR ligand may
comprise a lipid or a peptidoglycan or a lipoprotein or a
lipopolysaccharide. In particular, the TLR ligand may comprise
palmitoyl, myristoyl, stearoyl, lauroyl, octanoyl, or decanoyl.
Preferably the TLR ligand is selected from the group consisting of:
Pam2Cys, Pam3Cys, Step 2Cys, Lau2Cys, and Oct2Cys.
[0026] In certain embodiments the TLR ligand binds TLR-2, which may
be associated TLR-1, or TLR-6.
[0027] In a third aspect the present invention provides a method of
raising an immune response in a subject, the method comprising
administering to a subject an immunogenic composition according to
the first or second aspects of the present invention.
TABLE-US-00001 TABLE 1 Pathogen Associated Molecular Pattern (PAMP)
receptors expressed by DCs Family Receptor Ligand References
Toll-like TLR-1 triacylated bacterial lipids (Takeuchi 2002)
receptors (TLR-1 & 2) TLR-2 peptidoflycan, yeast (Schwandner
zymosan, bacterial 1999, Ozinsky lipoproteins 2000, Takeuchi 2000)
TLR-3 double stranded RNA (Alexopoulou 2001) TLR-4 LPS, hsp60 &
hsp70 (Poltorak 1998, Chow 1999, Asea 2002, Bulut 2002) TLR-5
flagellin (Hayashi 2001) TLR-6 diacylated bacterial lipids (Morr
2002, (TLR-2 & 6) Okusawa 2004) TLR-7 imidazoquinoline (Hemmi
2002) compounds TLR-8 single stranded RNA (Heil 2004) TLR-9 CpG DNA
(Hemmi 2000) TLR-10 yet to be discovered C-type Mannose Mannose-,
fucose-, (Kery 1992, lectins Receptor glucose-, GlcNAc- Engering
1997) containing carbohydrates Langerin, Mannose-, fucose-
(Feinberg 2001, DC-SIGN containing carbohydrates Frison 2003,
Stambach 2003) Dectin-1 .beta.-glucans (Brown 2001) DEC-205 yet to
be discovered Abbreviations: CpG, cytosine phosphate guanine; Fc,
fragment crystallisable; GlcNAc, N-acetyl glucosamine; hsp, heat
shock protein; LPS, lipopolysaccharide; RNA, ribonucleic acid
[0028] An exemplary dendritic cell targeting compound of the
present invention is the lipopeptide "Pam.sub.2Cys". One of skill
in the art would understand that the term "lipopeptide" means any
composition of matter comprising one or more lipid moieties and one
or more amino acid sequences that are conjugated. "Pam.sub.2Cys"
(also known as dipalmitoyl-S-glyceryl-cysteine or S-[2, 3
bis(palmitoyloxy)propyl] cysteine has been synthesised (Metzger, J.
W. et al. 1995. J Pept Sci 1: 184) and corresponds to the lipid
moiety of MALP-2, a macrophage-activating lipopeptide isolated from
Mycoplasma fermentans (Sacht, G. et al. 1998. Eur J Immunol 28:
4207; Muhiradt, P. F. et al. 1998. Infect Immun 66: 4804; Muhiradt,
P. F. et al. 1997. J Exp Med 185: 1951). Pam.sub.2Cys is known to
be a ligand of TER-2. Pam.sub.2Cys has the structure of Formula
(I):
##STR00001##
Other lipid moieties which may be used to target cell surface TLRs
include palmitoyl, myristoyl, stearoyl, lauroyl, octanoyl, or
decanoyl. Preferred groups include Pam.sub.2Cys, Pam.sub.3Cys,
Ste.sub.2Cys, Lau.sub.2Cys, and Oct.sub.2Cys.
[0029] Reference to "immune response" as used herein means a
reference to the concerted action of lymphocytes, antigen
presenting cells, phagocytic cells, granulocytes, and soluble
macromolecules produced by the above cells or the liver (including
antibodies, cytokines, and complement) that results in selective
damage to, destruction of, or elimination from the human body of
invading pathogens, cells or tissues infected with pathogens,
cancerous cells, or, in cases of autoimmunity or pathological
inflammation, normal human cells or tissues.
[0030] Throughout this specification the word "comprise", or
variations such as "comprises" or "comprising", will be understood
to imply the inclusion of a stated step or element or integer or
group of steps or elements or integers but not the exclusion of any
other step or element or integer or group of elements or
integers.
[0031] All the references cited in this application are
specifically incorporated by reference herein.
[0032] Reference to any prior art in this specification is not, and
should not be taken as, an acknowledgment or any form of suggestion
that this prior art forms part of the common general knowledge in
Australia.
[0033] It would be appreciated that the person of skill in the art
may introduce any combination of positively charged group and TLR
ligand as befits the desired application.
[0034] The present invention will now be described further with
reference to the following non-limiting examples:
Methods and Materials
Synthesis of Lipopeptides
[0035] The synthesis of branched and linear lipopeptides was
carried out on PEG-S RAM resin (Rapp Polymere, Tubingen, Germany;
substitution factor 0.27 mmol/g). For the synthesis of the branched
lipopeptides R.sub.4(S.sub.2Pam.sub.2Cys)(construct 1) and
E.sub.4(S.sub.2Pam.sub.2Cys)(construct 2; see schematic
representations), Fmoc-lysine(Mtt)-OH (Novabiochem, Laufelfingen,
Switzerland) was first coupled to the resin at a 4-fold excess with
equimolar amounts of
O-benzotriazole-N,N,N,N',N'-tetamethyl-uronium-hexafluorophosphate
(HBTU; Novabiochem, Darmstadt, Germany), 1-hydroxybenzotriazole
(HOBt) and a 1.5-fold molar excess of diisopropylethylamine (DIPEA;
Sigma, Castle Hill, Australia). Acylation was carried out for 40
minutes. The Fmoc protective group on the .quadrature.-amino was
then removed and Fmoc-lysine(Fmoc)-OH was coupled such that
following removal of these Fmoc groups, two primary amino groups
were exposed to act as branching points. Subsequent coupling of
another round of Fmoc-lysine(Fmoc)-OH at an 8-fold excess yielded
four branch points to which four arginine (R) or glutamic acid (E)
residues were coupled at a 16-fold excess.
[0036] For the lipidation of branched constructs, the amino groups
of the N-terminal arginine acid residues were protected using a
10-fold molar excess of di-tert-butyl dicarbonate (Fluka Chemika,
Switzerland) in the presence of DIPEA. The Boc protective groups
were removed upon successful lipidation and cleavage. The glutamic
acid residues are acetylated with acetic anhydride to block the
a-amino groups and also suppress the positive charges of the
a-amino groups of the final product. The Mtt protective group
present on the .epsilon.-amino group of the C-terminal lysine was
then removed and two serines were coupled. The Pam.sub.2Cys lipid
moiety was then coupled according to Zeng et al (Zeng 2003) to
generate branched R.sub.4(S.sub.2Pam.sub.2Cys) or branched
E.sub.4(S.sub.2Pam.sub.2Cys).
[0037] In the case of the linear lipopeptide Pam.sub.2Cys-SK.sub.4,
Fmoc-lysine(Boc)-OH and Fmoc-Serine(tBu)-OH were used to synthesise
the linear peptide followed by coupling of the Pam.sub.2Cys lipid
moiety.
[0038] Following assembly, lipopeptides were cleaved from the solid
phase support with 88% TFA, 5% phenol, 2% TIPS, 5% water for 3
hours at room temperature and were analysed by reversed phase
high-pressure liquid chromatography (RP-HPLC) using a Vydac C4
column (4.6.times.300 mm) installed in a Waters HPLC system. The
chromatogram was developed at a flow rate of 1 ml/min using 0.1%
TFA in H.sub.2O and 0.1% TFA in acetonitrile as the limit solvent.
Products were purified if necessary and presented as a single major
peak on analytical RP-HPLC and had the expected mass when analysed
using an Agilent series 1100 ion trap mass spectrometer.
[0039] Immunization Protocols
[0040] Groups of five female, 8-12 week old BALB/c mice were
inoculated sub-cutaneously in the base of the tail on day 0 and
again on day 28 unless otherwise stated with either 25 .mu.g of
ovalbumin (OVA; Sigma Aldrich, USA) or hen egg lysozyme (HEL; Sigma
Aldrich, USA) in saline or emulsified in CFA, or mixed with
different amounts of R.sub.4(S.sub.2Pam.sub.2Cys) or
E.sub.4(S.sub.2Pam.sub.2Cys) in saline. Sera were prepared from
blood taken at approximately 4 weeks following the primary
inoculation and 2 weeks following the secondary inoculation unless
otherwise stated.
[0041] Enzyme-Linked Immunosorbent Assay (ELISA)
[0042] Flat bottom well polyvinyl plates (Thermo, USA) were coated
with either OVA or HEL (5 .mu.l g/ml) in PBS containing w/v 0.1%
sodium azide (Chem Supply, Australia) for 18-20 hours at room
temperature in a humidified atmosphere. The antigen was removed and
PBS containing 10 mg/ml bovine serum albumin (BSA.sub.10PBS) was
added for 1 hour before washing with PBS containing v/v 0.05%
Tween-20 (Sigma Aldrich, Milwaukee, USA)(PBST). Serial dilutions of
sera obtained from immunised mice were added to wells and incubated
overnight at room temperature. After washing with PBST, bound
antibody was detected using horseradish peroxidase-conjugated
rabbit anti-mouse IgG antibodies (Dako, Glostrup, Denmark) in
conjunction with enzyme substrate (0.2 mM 2,2'-azino-bis
3-ethylbenzthiazoline-sulfonic acid [Sigma Aldrich, Milwaukee, USA]
in 50 mM citric acid [M&B, England] containing 0.004% hydrogen
peroxide [Ajax Chemicals, Australia]). Colour development induced
by the enzyme-substrate reaction was allowed to proceed for 15
minutes and was stopped by the addition of 50 mM sodium fluoride
(BDH Chemicals, Australia). A Labsystems Multiscan Multisoft
microplate reader (Pathtech Diagnostics, Australia) was used to
determine the absorbance readings at 405 nm (with wavelength
correction at 450 nm). The titers of antibody are expressed as the
reciprocal of the highest dilution of serum required to achieve an
optical density of 0.2.
[0043] Detection of IFN-.gamma. Production by Intracellular
Cytokine Staining
[0044] For the detection of specific CD8.sup.+ T cell-mediated
cytokine production, mice were administered with a third dose of
OVA (25 .mu.g) in saline or emulsified in CFA, or mixed with
different amounts of R.sub.4(S.sub.2Pam.sub.2Cys). Seven days later
spleens were obtained from inoculated mice and pressed through a
metal sieve to obtain single cell suspensions. Splenocytes
(1.times.10.sup.6) were then cultured with syngeneic irradiated
(2200 rad, .sup.60Co source) naive splenocytes (5.times.10.sup.5)
with or without the OVA.sub.258-265 peptide SIINFEKL (2 .mu.g/ml)
in the presence of recombinant IL-2 (10 U/ml; Roche, Mannheim,
Germany). Brefeldin A (1 .mu.g/ml) in the form of BD GolgiPlug from
the Cytofix/Cytoperm Plus Kit (Becton Dickinson, USA) was also
included in this culture. After 6 hours, lymphocytes were washed
with FACs wash and stained with a PerCP-conjugated rat anti-mouse
CD8 antibody (Clone 53-6.7; Becton Dickinson, USA) for 30 minutes
at 4.degree. C. Fixation and permeabilization was then performed
for 20 minutes at 4.degree. C. using Cytofix/Cytoperm solution
(Cytofix/Cytoperm Plus Kit, Becton Dickinson, USA) according to the
manufacturer's instructions. Cells were washed once with the
kit-supplied Perm/Wash solution and stained with a FITC-conjugated
rat anti-mouse IFN-.gamma. antibody (Clone XMG1.2; Becton
Dickinson, USA) for 30 minutes at 4.degree. C. before analysis by
flow cytometry. Data analysis was performed using FlowJo software
(Treestar Inc, USA). Live viable cells were gated based on their
forward and side scattering properties and a total of
1.times.10.sup.5 CD8+ cells counted.
[0045] Sedimentation of OVA-Lipopeptide Complexes
[0046] OVA (1 nmole) was mixed with increasing amounts of the
branched R.sub.4(S.sub.2Pam.sub.2Cys) or linear
Pam.sub.2Cys-SK.sub.4 lipopeptide in a total volume of 100 .mu.l
PBS in a flat-bottom 96-well plate. The turbidity of solution in
each well was then determined by measuring its optical density at
450 nm on a Labsystems Multiscan Multisoft microplate reader.
[0047] Solutions containing either 100 nmoles of
R.sub.4(S.sub.2Pam.sub.2Cys), 1 nmole of OVA or a mixture of
R.sub.4(S.sub.2Pam.sub.2Cys) and OVA were also centrifuged
(1.2.times.10.sup.5G) and HPLC analysis performed on supernatants.
Sedimented material from the mixture containing both the
lipopeptide and OVA was also dissolved in a solution of 50%
acetonitrile in water and then analysed by HPLC. In all samples,
the identity of the peak corresponding to the lipopeptide was
verified by mass spectrometry and that of OVA based on its
retention time in the solution containing OVA alone.
[0048] All patents, patent applications, provisional applications,
and publications referred to or cited herein, supra or infra, are
incorporated by reference in their entirety, including all figures
and tables, to the extent they are not inconsistent with the
explicit teachings of this specification.
[0049] Following are examples which illustrate procedures for
practicing the invention. These examples should not be construed as
limiting. All percentages are by weight and all solvent mixture
proportions are by volume unless otherwise noted.
Example 1
Introduction
[0050] Protein antigens, particularly recombinant proteins, are
often not immunogenic and formulation with adjuvant is necessary to
enhance their immunogenicity although concerns about adjuvant
toxicity and their mechanism of action need to be resolved before
they can be licensed for use in humans. Therefore the development
of novel systems that can facilitate the delivery of protein
antigens by directly targeting and concurrently activating
antigen-presenting cells, such as the dendritic cell, could prove
to be advantageous.
[0051] In this example, we describe the use of a charged and
branched lipopeptide structure that can electrostatically bind
protein antigens and deliver them to dendritic cells. The charge of
the lipopeptide is mediated by the presence of four N-terminal
arginine (R.sub.4) or glutamic acid residues (E.sub.4) imparting
either an overall positive or negatively charge respectively to the
delivery module. Hence R.sub.4 can be used to bind negatively
charged proteins and E.sub.4 used for those that are positively
charged. The incorporation of the TLR-2 targeting lipid moiety,
Pam.sub.2Cys, to the cationic (R.sub.4(S.sub.2Pam.sub.2Cys)) or
anionic version (E.sub.4(S.sub.2Pam.sup.2Cys)) of the branched
lipopeptide ensures targeted delivery of bound protein to dendritic
cells.
[0052] Results
[0053] The lipopeptide R.sub.4(S.sub.2Pam.sub.2Cys) has an overall
charge of +8 due to the presence of four N-terminal arginine
residues (each arginine having a +2 charge). To determine whether
R.sub.4(S.sub.2Pam.sub.2Cys) can enhance protein immunogenicity
through electrostatic interaction, ovalbumin (OVA), which has an
overall negative charge of 11, was used as a model protein
antigen.
[0054] Vaccination with OVA pre-incubated with an equimolar or a
5-fold molar excess of R.sub.4(S.sub.2Pam.sub.2Cys) elicited
significantly higher titres of anti-OVA antibodies in the primary
and secondary response than did vaccination with OVA alone (FIG.
1A) indicating that association of the cationic lipopeptide with
the protein can enhance its immunogenicity. The level of antibody
elicited appears to be proportional to the amount of
R.sub.4(S.sub.2Pam.sub.2Cys) used because a 5-fold excess of
R.sub.4(S.sub.2Pam.sub.2Cys) resulted in higher antibody levels
compared to those achieved when an equal amount
R.sub.4(S.sub.2Pam.sub.2Cys) was used. Although the antibody levels
in the primary response of mice in these groups were less than
those obtained when mice were inoculated with OVA emulsified in
complete Freund's adjuvant (CFA), the antibody levels obtained
following a second dose of antigen in R.sub.4(S.sub.2Pam.sub.2Cys)
were almost as high as those induced by FCA.
[0055] Cell-mediated responses were also analysed following
vaccination with R.sub.4(S.sub.2Pam.sub.2Cys)+OVA. The secretion of
the pro-inflammatory cytokine, interferon-.gamma. (IFN-.gamma.) by
CD8.sup.+ T cells was measured as an indication of T cell
activation. Vaccination with R.sub.4(S.sub.2Pam.sub.2Cys)+OVA
induced significantly more specific IFN-.gamma. producing CD8.sup.+
T cells in the spleen of inoculated mice than did inoculation with
OVA alone and similar levels of IFN-.gamma. producing CD8.sup.+ T
cells were elicited with R.sub.4(S.sub.2Pam.sub.2Cys) and CFA (FIG.
1B). In contrast to the antibody results where an increase in the
amount of R.sub.4(S.sub.2Pam.sub.2Cys) used was associated with a
higher antibody response, the opposite appears to be the case for
cell-mediated responses; higher cytokine-secreting T cells were
detected when an equimolar amount of R.sub.4(S.sub.2Pam.sub.2Cys)
was used in comparison to when 5-fold excess was used. This
observation suggests that by altering the ratio of
R.sub.4(S.sub.2Pam.sub.2Cys) to protein antigen, it may be possible
to select the appropriate (cellular vs humoral) type of immune
response required for the clearance of a particular pathogen.
[0056] In order to determine if the electrostatic interaction
between a negatively charged lipopeptide and a positively charged
antigen can also provide the same immunogenic enhancement, the
lipopeptide E.sub.4(S.sub.2Pam.sub.2Cys) (which has an overall
charge of +4 due to the presence of four N-terminal glutamic acid
residues) was incubated with hen egg lysozyme (HEL) which has an
overall charge of +8. Inoculation of mice with these complexes
resulted in higher antibody titres than those that were achieved
with HEL alone indicating that the strategy of using Pam2Cys imbued
with an electric charge opposite to the antigen with which it is
administered can also be applied to accommodate protein antigens of
the opposite charge (FIG. 2A).
[0057] It was also found that inoculation of mice with
R.sub.4(S.sub.2Pam.sub.2Cys) and HEL, both of which have positive
charges, did not result in the production of antibody indicating
that the enhancement is charge specific. It remains to be seen
however, whether the unexpected antibody results seen with
E4(S.sub.2Pam.sub.2Cys) and the negatively charged OVA are due to
the E.sub.4(S.sub.2Pam.sub.2Cys) binding to positively charged
patches present on OVA.
[0058] Discussion
[0059] The findings indicate that branched positively or negatively
charged lipopeptides can be used to enhance the immunogenicity of
oppositely charged proteins. This is especially highlighted through
the use of R.sub.4(S.sub.2Pam.sub.2Cys), which although capable of
inducing OVA-specific responses, is unable to augment HEL-specific
responses. Considering the positive charge of this lipopeptide and
those of the proteins examined, the effects observed are possibly
due to electrostatic interactions, or lack of therein, between the
Pam2Cys moiety and the antigen. Further investigations to confirm
this hypothesis can be achieved through chromatographic methods of
analysis and additional in vivo studies using similarly or
oppositely charged protein antigens as well as the inclusion of a
branched lipopeptide that has a neutral charge.
[0060] The results of these experiments also suggest that the type
of immune response that can be induced i.e. humoral or cellular may
depend on the ratio of charged lipopeptide and protein used. This
could be a particularly significant finding because the successful
clearance of particular pathogens can depend on the type of immune
response that is elicited The lipopeptides that we describe here
may therefore provide a means to tailor the desired immune response
against the particular antigen according to the disease.
Example 2
[0061] In order to measure the ability of the branched
R.sub.4(S.sub.2Pam.sub.2Cys) and the linear Pam.sub.2Cys-SK.sub.4
lipopeptide to form a complex with the model antigen ovalbumin
(OVA), the light absorbances of solutions containing increasing
amounts of each lipopeptide and OVA were determined by measuring
the optical density at 450 nm (FIG. 3). The ability of each
lipopeptide to allow complex formation with OVA would therefore
indicate an association between the two compounds.
[0062] It was found that the addition of 5 nmoles of branched
R.sub.4(S.sub.2Pam.sub.2Cys) to a solution containing 1 nmole of
OVA resulted in the formation of complexes which appeared as a
turbid or opalescent solution. Increasing the amount of branched
lipopeptide resulted in an increase in optical density readings
with the highest achieved when 20 to 40 nmoles of lipopeptide was
used. In contrast, very little increase in optical density was
observed when the linear Pam2Cys-SK4 lipopeptide was added at all
concentrations investigated indicating that branched
R.sub.4(S.sub.2Pam.sub.2Cys) is superior to the linear lipopeptide
at binding to the antigen.
[0063] To confirm the binding of R.sub.4(S.sub.2Pam.sub.2Cys) to
OVA, solutions containing either of these compounds individually or
a mixture of both were centrifuged to sediment any complex. HPLC
analysis was then performed on the supernatant and on the
sedimented material.
[0064] In the supernatant of solutions containing either OVA or
R.sub.4(S.sub.2Pam.sub.2Cys) (FIG. 4A), the resulting chromatograms
revealed major peaks corresponding to each individual compound in
solution. After mixing both compounds, a dramatic decrease in the
size of the peak corresponding to OVA in solution was obvious
suggesting that the protein had been sedimented out of solution as
a result of association with the R.sub.4(S.sub.2Pam.sub.2Cys)
lipopeptide. This was confirmed in the HPLC analysis of the
reconstituted material (FIG. 4B) which revealed the presence of two
major peaks corresponding to both OVA and lipopeptide confirming
the sedimented material is a complex of lipopeptide and
protein.
[0065] It should be understood that the examples and embodiments
described herein are for illustrative purposes only and that
various modifications or changes in light thereof will be suggested
to persons skilled in the art and are to be included within the
spirit and purview of this application and the scope of the
appended claims. In addition, any elements or limitations of any
invention or embodiment thereof disclosed herein can be combined
with any and/or all other elements or limitations (individually or
in any combination) or any other invention or embodiment thereof
disclosed herein, and all such combinations are contemplated with
the scope of the invention without limitation thereto.
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