Main > IMMUNOLOGY > Vaccines > Rubella. Vaccine > Peptide

Product Canada. C

PATENT ASSIGNEE'S COUNTRY Canada
UPDATE 03.00
PATENT NUMBER This data is not available for free
PATENT GRANT DATE 14.03.00
PATENT TITLE Synthetic peptides for a rubella vaccine

PATENT ABSTRACT Synthetic peptides have an amino acids sequence corresponding to at least one antigenic determinant of at least one protein, usually a structural protein, particularly the E1, E2 or C proteins, of rubella virus (RV), are used as is, in hybrid or chimeric tandem T-B form, in lipidated form, linked to a carrier molecule and/or polymerized to form molecular aggregates, in vaccines against rubella. Analogs of peptides which are human T-cell determinants are used to treat rubella-associated autoimmune disorders.

PATENT INVENTORS This data is not available for free
PATENT ASSIGNEE This data is not available for free
PATENT FILE DATE 06.10.94
PATENT CT FILE DATE 20.01.93
PATENT CT NUMBER This data is not available for free
PATENT CT PUB NUMBER This data is not available for free
PATENT CT PUB DATE 22.07.93
PATENT FOREIGN APPLICATION PRIORITY DATA This data is not available for free
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PATENT PARENT CASE TEXT This data is not available for free
PATENT CLAIMS What we claim is:

1. A synthetic peptide having an amino acid sequence of a portion of an E1, E2 or C protein of rubella virus (RV) and which contains a human T-cell determinant, wherein said amino acid sequence is at least one selected from:

(a) any of the amino acid sequences 1 to 22 (SEQ ID NO: 1), 38 to 57 (SEQ ID NO: 3), 54 to 74 (SEQ ID NO: 4), 106 to 125 (SEQ ID NO: 6), 140 to 159 (SEQ ID NO: 8), 157 to 176 (SEQ ID NO: 9), 174 to 193 (SEQ ID NO: 10), 190 to 209 (SEQ ID NO: 11), 207 to 226 (SEQ ID NO: 12), 224 to 243 (SEQ ID NO: 13), 240 to 250 (SEQ ID NO: 14), 256 to 275 (SEQ ID NO: 15), 272 to 291 (SEQ ID NO: 16), 307 to 326 (SEQ ID NO: 18), 324 to 343 (SEQ ID NO: 19), 341 to 360 (SEQ ID NO: 20), 358 to 377 (SEQ ID NO: 21), 374 to 390 (SEQ ID NO: 22), 391 to 412 (SEQ NO: 23) 196 to 212 (SEQ ID NO: 24) , 198 to 233 (SEQ ID NO: 25) 219 to 233 (SEQ ID NO: 26), 198 to 240 (SEQ ID NO: 27), and 212 to 240 (SEQ ID NO: 28) of E1 protein, set forth in Table 1,

(b) any of the amino acid sequences 1 to 20 (SEQ ID NO: 29), 15 to 36 (SEQ ID NO: 30), 124 to 145 (SEQ ID NO: 36), 156 to 177 (SEQ ID NO: 38), 176 to 199 (SEQ ID NO: 39), 218 to 239 (SEQ ID NO: 41) and 233 to 257 (SEQ ID NO: 42) of E2 protein, set forth in Table 2, and

(c) any of the amino acid sequences 1 to 30 (SEQ ID NO: 44), 52 to 78 (SEQ ID NO: 46), 74 to 100 (SEQ ID NO: 47), 96 to 123 (SEQ ID NO: 48), 119 to 152 (SEQ ID NO: 49), 151 to 179 (SEQ ID NO: 50), 177 to 204 (SEQ ID NO: 51), 205 to 233 (SEQ ID NO: 52), 231 to 257 (SEQ ID NO: 53) and 255 to 280 (SEQ ID NO: 54) of C protein, set forth in Table 3.

2. The synthetic peptide of claim 1 in an oxidized form and which is capable of eliciting a mammal to produce neutralizing antibodies against RV.

3. The synthetic peptide of claim 2 wherein said oxidized form has at least one disulfide bond between sulfur-containing amino acids.

4. The synthetic peptide of claim 1 modified with lipid to be in the form of a lipopeptide.

5. A synthetic peptide having an amino acid sequence of a portion of an E1, E2 or C protein of rubella virus (RV) and which contains a human T-cell determinant and which is modified with lipid to be in the form of a synthetic lipopeptide or a mixture of synthetic lipopeptides that, when used to form molecular aggregates, is capable of inducing mammals to produce immune responses against RV, wherein said synthetic lipopeptide is selected from those having the amino acid sequence set forth in Table 12.

6. The synthetic peptide of claim 1 wherein said selected amino acid sequence includes at least one virus neutralization epitope and/or haemagglutination inhibition epitope.

7. The synthetic peptide of claim 1 an analog of which is useful in the treatment of rubella-associated autoimmune disorders.

8. The synthetic peptide of claim 1 comprising at least one human T-cell determinant (T) and at least one viral neutralization B-cell epitope (B).

9. The synthetic peptide of claim 8 in the form of a hybrid or chimeric T-B tandem peptide.

10. The synthetic peptide of claim 8 in the form of a chimeric peptide comprising at least one human T-cell determinant of E1, E2 or C protein and at least one viral neutralization B-cell epitope of E1, E2 or C protein.

11. The synthetic peptide of claim 10 in the form of a chimeric lipopeptide.

12. The synthetic peptide of claim 11 in the form of a chimeric lipopeptide comprising at least one human T-cell determinant of E2 or C protein and at least viral neutralization B-cell epitope of E1 protein.

13. A synthetic peptide in the form of a chimeric lipopeptide comprising at least one human T-cell determinant of E2 or C protein and at least one viral neutralization B-cell epitope of E1 protein and having the amino acid sequence tripalmityl-CSSVRAYNQPAGDVRGVWGKGERTYAEQDFRV PDPGDLVEYIMNYTGNQQSRWGLGSPNCHGPDWASPVCQRHSP (SEQ ID NO: 56), or any portion, variation or mutant thereof which retains the immunogenicity of said sequence.

14. The synthetic peptide claimed in any one of claims 1 to 3, 4, 5, 6, and 7, to 13, which is produced by chemical synthesis or by recombinant procedure.

15. A synthetic peptide having an amino acid sequence of a portion of an E1, E2 or C protein of rubella virus (RV) and which contains a human T-cell determinant.

16. The synthetic peptide of claim 15 wherein said RV protein is the E2 protein and said amino acid sequence is contained within amino acids 1 to 257 (SEQ ID NO:76) of the E2 protein of RV strain M33 or the corresponding amino acids of other strains of RV.

17. The synthetic peptide of claim 15 wherein said RV protein is the E2 protein and said amino acid sequence is contained within amino acids 1 to 40 of the E2 protein.

18. The synthetic peptide of claim 17 wherein said amino acids 1 to 40 (SEQ ID NO: 77) of the E2 protein are those set forth in Table 2 for RV strain M33 or the corresponding amino acids of other strains of RV.

19. A synthetic peptide having an amino acid sequence of a portion of an E2 protein of rubella virus (RV) and which contains a human T-cell determinant wherein said amino acid sequence is contained within the sequence GLQPRADMAAPPNPPQPPRAPQPPRAHGQHYGHHHHQLPFLG (SEQ ID NO: 78).
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PATENT DESCRIPTION FIELD OF INVENTION

The present invention relates to the development of synthetic vaccines against rubella viral infection. Particularly, the invention is related to the use of human T-helper determinants (THDs) and B-cell viral neutralization epitopes (BEs) from the rubella virus structural proteins E1, E2 and C, and their combination with other synthetic lipopeptides containing cytotoxic T-lymphocytes (CTL) epitopes to produce novel synthetic vaccine candidates, which can elicit neutralizing antibodies and a cell-mediated immune response against rubella virus.

BACKGROUND TO THE INVENTION

Rubella (German measles) is usually a benign childhood infection, but rubella virus (RV) can cause a persistent infection of the brain called progressive rubella panencephalitis (ref. 40,51--the literature references are listed at the end of the specification). RV has been isolated from synovial cells of some patients with juvenile rheumatoid arthritis (ref. 8,13). Several live attenuated rubella vaccines have been introduced since 1969 (ref. 2,41). Immunization of infants and susceptible women of child-bearing age against rubella virus is now a standard public health measure. However, there are serious medical concerns with the use of live attenuated rubella virus vaccine for routine immunization. These concerns include the risk of congenital infection of the fetus resulting in diabetis-related diseases (ref. 44) and rubella-associated arthritis following rubella vaccination (ref. 8,47), as well as the possibility of re-infection of vaccinees by wild-type RV due to antigenic differences between wild-type and vaccine virus strains (ref. 11,21). In addition to these problems, rubella virus grows to a relatively low titer in tissue cultures and its structural proteins are difficult to purify (ref. 27). Therefore, there is a clear requirement for preparing a non-infectious rubella vaccine by alternative means, such as recombinant DNA technology and peptides synthesis. Research efforts have recently focused on characterizing both the viral genome and the host immune responses.

RV is the sole member of the genus Rubivirus in the Togavirus family (ref. 29). The primary sequences of the rubella virus structural proteins decoded from cDNA clones have been reported (ref. 10). The RV virion contains an RNA genome enclosed within an icosahedral capsid composed of multiple copies of a basic capsid protein C of 33 kDa (ref. 38). Surrounding this nucleocapsid is a lipid bilayer in which viral glycoproteins E1 (58 kDa) and E2 (42 to 47 kDa) are embedded (ref. 38,43). Glycoprotein El has been shown to contain hemagglutinin and virus neutralization epitopes (ref. 50). The data accumulated to date suggest that none of these E1 neutralization epitopes is appropriate for use in a vaccine against RV since they failed to elicit high-titer neutralizing antibody responses against RV in animal studies. E2-specific antibodies are capable of neutralizing viral infection in vitro (ref. 17). However, neutralization epitopes of the E2 protein have not yet been mapped.

Studies have been carried out to characterize the specificity of the antibody response against rubella virus. The RV-specific IgM response is widely used for the diagnosis of recent rubella virus infection (ref. 19,37), and the production of RV-specific IgA antibodies has been shown to be important in the prevention of reinfection (ref. 19). Most of the RV-specific IgM antibodies react with the E1 protein while most of the IgA antibodies react with the C protein (ref. 42). IgG antibody responses can be elicited by all the structural proteins (ref. 30,42).

There is little known about the cellular immune response to RV structural proteins, although both T-helper cell proliferation (ref. 4, 22 to 24, 28, 49) and cytolytic T lymphocyte (CTL) responses (ref. 49) can be detected during viral infection. Studies cited above have neither identified the T-helper determinants nor the CTL epitopes of the rubella structural proteins. Therefore, the identification of these T-cell epitopes (T-helper and CTL) may lead to the design of a safe and effective rubella vaccine.

Methods for inducing immunity against disease are constantly improving and the current trend is to use smaller and well-defined materials as antigens. The objective is to minimize or eliminate the potential side-effects caused by certain native immunogens, while preserving both their immunogenicity and ability to confer protection against disease. Recent studies have indicated that immunization of experimental animals with synthetic peptides representing specific regions of viral or bacterial proteins can induce immune responses specific against the parent proteins, and neutralize their biological functions (ref. 3,18,25,33 to 36). Thus, synthetic peptides are potential candidate antigens for the production of inexpensive and safe vaccines against infectious diseases. Recent progress in fundamental immunology has revealed that, to be efficacious, immunogens should contain two distinct functional domains. One domain is responsible for B-cell recognition and antibody production and the second domain induce T-helper cell activity. Certainly, rubella-specific cytotoxic T-lymphocyte (CTL) epitopes should be included in the final synthetic vaccine constructs to provide necessary cellular immunity to rubella disease. A recent study (ref. 1) has demonstrated that peptides could prime mice for a CTL responses in vivo. Hence, a safe and effective synthetic peptide vaccine is conceivable.

To design a synthetic peptide-based rubella vaccine, the RV-specific CTL determinants, the viral neutralization B-cell epitopes (BE) and the functional T-helper epitopes of individual viral proteins must be identified. For a synthetic construct to be potent and efficacious, both functional T-helper and B-cell epitopes should be present. To this end, different T-B tandem synthetic peptides, both hybrid and chimeric, are synthesized to determine whether a preferential spatial relationship between T-helper determinants (THD) and B-cell epitopes in a synthetic construct is required for immunogenicity. In addition, the formulation of these synthetic constructs either with adjuvants or lipopeptides are studied to enhance immune responses.

The presentation of an appropriate processed T-cell epitope in the appropriate MHC context and the availability of an appropriate T-cell repertoire are necessary for induction of a cellular immune response. These factors vary among individuals of an outbred population and differences in T-cell responses to subunit vaccines have been reported (Zevering et al. Immunology, 2: 945-955, 1990). Other host factors, such as a possible selective T-cell tolerance to RV, also might influence antigen recognition by T-cells. Therefore, the identification of epitopes recognized by the T-cells of individuals of different genetic background and diverse immunologic experience with RV infection or immunization is important for the design of an effective synthetic vaccine.

To map the functional epitopes of rubella viral proteins, we have synthesized 28, 15 and 11 overlapping synthetic peptides covering most of the E1, E2 and C protein sequences, respectively (Tables 1, 2 and 3 below). The length of synthetic peptides was selected on the basis of their high index of hydrophilic .beta.-turns as judged by secondary structure prediction analysis according to the conventional algorithms (ref. 9,12,20) (FIGS. 1 to 3 ). Such segments are likely to be surface-exposed and antigenic. Long peptides were synthesized to better mimic the native epitopes of the protein as suggested by the work of Van Regenmortel (ref. 48). An additional cysteine residue was added to either the N-terminal or the C-terminal end of the peptides for conjugation purposes.

ASPECTS OF THE INVENTION

The present invention, in one aspect, is directed towards the provision of a synthetic peptide (or a mixture of synthetic peptides) that, when administrated as a free peptide, or linked to a carrier molecule, or polymerized to form molecular aggregates, is capable of eliciting high titers of antibodies against RV in mammals.

In another aspect, the present invention is directed towards the provision of a chimeric peptide (or a mixture of chimeric peptides) that, when administrated as a free chimeric peptide, or linked to a carrier molecule, or polymerized to form molecular aggregates, is capable of inducing an immune response against RV in mammals.

The present invention, in a further aspect, is directed towards the provision of a synthetic lipopeptide (or a mixture of synthetic lipopeptides) that is capable of producing cell-mediated immunity in mammals against RV.

In an additional aspect, the present invention is directed towards the provision of a synthetic lipopeptide (or a mixture of synthetic peptides and lipopeptides) that, when forming molecular aggregates, is capable of inducing both protective antibody and cell-mediated immune responses against RV in mammals.

The present invention, in further aspect, is directed towards the provision of a synthetic peptide (or a mixture of synthetic peptides) that can be used in a diagnostic immunoassay to detect the presence of anti-RV antibodies, for example, neutralizing antibodies, and a mixture of RV-specific polyclonal antibodies that can be used in immunoassays to detect the presence of RV in a biological sample.

In yet an additional aspect, the present invention is directed towards the provision of a synthetic peptide (or a mixture of synthetic peptides) that has been identified as human THDs to generate analogs which can be used as therapeutic agents for rubella-associated autoimmune diseases.

SUMMARY OF THE INVENTION

The present invention relates to the preparation of immunogens and candidate vaccines made of peptides containing the amino acid sequences of various antigenic determinants (THDs, BEs and CTLs) of the structural proteins (E1, E2 and C) of RV. Synthetic vaccines comprising one or more of these peptides either used as free peptides, or covalently coupled to a suitable carrier, or linked to a lipidic moiety, are disclosed.

Accordingly, in one aspect of the present invention, there is provided a synthetic peptide, which may be produced by chemical synthesis or recombinantly, having an amino acid sequence corresponding to at least one antigenic determinant of at least one protein, usually a structural protein, of rubella virus (RV).

In one embodiment, the present invention comprises an essentially pure form of at least one peptide containing an amino acid sequence corresponding to at least one antigenic determinant of an E1 structural protein of RV, which peptides are capable of eliciting polyclonal antibodies against RV in mammals. These E1-specific polyclonal antibodies are useful in test kits for detecting the presence of RV in any biological sample. The peptides can have, for example, the amino acid sequences corresponding to amino acids 1-22, 19-38, 38-57, 54-74, 71-91, 105-125, 122-141, 140-159, 157-176, 174-193, 190-209, 207-226, 224-243, 240-259, 256-275, 272-291, 289-308, 307-326, 324-343, 341-360. 358-377, 374-390, 391-412, 196-212, 198-233, 219-233, 198-240 and 212-240 of the E1 protein of the RV M33 strain, respectively,as set forth in Table 1 below (SEQ ID NOS. 1 to 28), or any portion, variant or mutant thereof which retains immunogenicity.

In another embodiment, the present invention comprises an essentially pure form of at least one peptide containing an amino acid sequence corresponding to at least one antigenic determinant of an E2 structural protein of RV, which peptides are capable of eliciting polyclonal antibodies against RV in mammals, These E2-specific polyclonal antibodies are useful in test kits for detecting the presence of RV in any biological sample. The peptides can have, for example, the amino acid sequences corresponding to amino acids 15-36, 33-57, 69-91, 104-124 and 195-220 of the E2 protein of the RV M33 strain, respectively, as set forth in Table 2 below (SEQ ID NOS: 30, 31, 33, 35 and 40), or any portion, variant or mutant thereof which retains immunogenicity.

In another embodiment, the present invention comprises an essentially pure form of at least one peptide containing an amino acid sequence corresponding to at least one antigenic determinant of a C structural protein of RV, which peptides are capable of eliciting polyclonal antibodies against RV in mammals. These C-specific polyclonal antibodies are useful in test kits for detecting the presence of RV in any biological sample. The peptides can have, for example, the amino acid sequences corresponding to amino acids 1-30, 28-56, 52-78, 74-100, 96-123, 119-152, 152-179, 177-204, 205-223, 231-257 and 255-280 of the C protein of the RV M33 strain, respectively, as set forth in Table 3 below (SEQ ID NOS: 44 to 54), or any portion, variant or mutant thereof which retains immunogenicity.

In yet another embodiment, the present invention comprises an essentially pure form of a peptide containing an amino acid sequence corresponding to at least one antigenic determinant of a protein of RV, which peptide is in an oxidized form, particularly to form disulfide bridges between sulfur-containing amino acids, and is capable of eliciting a mammal to produce antibodies against RV. One such oxidized peptide has an amino acid sequence corresponding to amino acids 198-240 of the E1 protein of the RV M33 strain (Table 1, SEQ ID NO: 27-RV-EP27). Peptides of the invention also can have sequences corresponding to the analogous RV-EP27 regions of RV isolates other than M33, this sequence is designated "RV-EP27-like".

The synthetic peptides of the invention further can be either modified with lipid as lipopeptides or linked to carrier molecules (and/or polymerized to molecular aggregates) to produce alternate vaccines. Vaccines comprising the synthetic peptides provided herein or such modified forms of the peptides may be formulated as vaccines to immunize against RV infection when administered to mammals, for example, by the intramuscular or parenteral route, or when delivered to the surface mucosal surface using microparticles, capsules, liposomes and targeting molecules, such as toxins and antibodies.

Accordingly, another aspect of the present invention provides a vaccine against rubella, comprising at least one immunogenic synthetic peptide as described herein, along with a physiological carrier therefor. The vaccine may further comprise at least one other immunogenic and/or immunostimulating molecule. The immunogenic synthetic peptide may form one component of a multivalent vaccine, for example, one formulated to provide protection against measles, mumps and rubella (MMR). The vaccine may further comprise an adjuvant. The invention also includes a method of immunizing a host against rubella, by administering to the host an effective amount of the vaccine.

In another embodiment, the present invention comprises a synthetic lipopeptide (or a mixture of synthetic lipopeptides) that, is capable of inducing immune responses against RV in mammals. Such lipopeptides can have, for example, the amino acid sequence set forth in Table 12 below (SEQ ID NOS: 57 to 75), or a portion, variant or mutant thereof which retains immunogenicity. One such lipopeptide is designated TPRV-C9 and can have, for example, the sequence Tripalmityl-CSSVRAYNQPAGDVRGVWGKGERTYAEQDFRV (SEQ ID NO: 55), corresponding to amino acids 205-233 of the C protein of the RV M33 strain, or any portion thereof.

In another embodiment, the present invention comprises at least one peptide that has an amino acid sequence corresponding to at least one B-cell neutralization epitope of a protein of RV, which may be an E1, E2 or C protein, and can be used as a component of a diagnostic kit to detect the presence of anti-RV antibodies, for example, neutralizing antibodies. The peptides can have, for example, the amino acid sequences corresponding to amino acids 240-259, 256-275, 272-291, 198-233 and 212-240 of the E1 protein of the RV M33 strain, respectively, (Table 1 below, SEQ ID NOS: 14, 15, 16, 25 and 28), or any portion thereof capable of detecting the presence of RV-specific antibodies in a biological sample.

In another embodiment, the present invention comprises peptides that have been identified as human THDs (T-cell determinants). Such T-cell determinants may be those of an E1, E2 or C protein of RV. Analogs of such THDs can be used, for example, as therapeutic agents, to treat rubella-associated autoimmune disorders.

The peptides identified as human THDs can have, for example, the amino acid sequences corresponding to amino acids 1-22, 122-141, 140-159, 157-176, 174-193, 190-209, 207-226, 224-243, 240-259, 256-275, 272-291, 289-308, 307-326, 324-343, 341-360. 358-377, 374-390, 196-212, 198-233, and 198-240 of the E1 protein of the RV M33 strain, respectively, (Table 1 below, SEQ ID NOS: 1, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 24, 25 and 27), or any portion thereof analogs of which are useful for therapeutic treatment of rubella-associated autoimmune disorders; the amino acid sequences corresponding to amino acids 1-20, 54-74, 139-159, 156-177, 176-199, 218-239 and 233-259 of the E2 protein of the RV M33 strain, respectively, (Table 2 below, SEQ ID NOS: 29, 32, 37, 38, 39, 41 and 42), or any portion thereof analogs of which are useful for therapeutic treatment of rubella-associated autoimmune disorders; or the amino acid sequences corresponding to amino acids 1-30, 96-123, 119-152, 151-179, 177-204, 205-233 and 255-280 of the C protein of the RV M33 strain, respectively, (Table 3 below, SEQ ID NOS: 44, 48, 49, 50, 51, 52 and 54), or any portion thereof analogs of which are useful for therapeutic treatment of rubella-associated autoimmune disorders.

In another aspect of the present invention, there is provided a method of treatment of a rubella-associated autoimmune disorder, by administering to a host an effective amount of a synthetic analog of a peptide identified as a human THD.

In another embodiment, the present invention provides a process to identify human T-cell epitopes associated with rubella-related autoimmune diseases. Such procedure involves synthesizing overlapping peptides corresponding to an RV protein, generating RV-specific T-cell lines from a panel of hosts having been exposed to RV antigens, and performing RV antigen specific T-cell proliferation assays. Results obtained from this process are used towards a rational design of synthetic peptide-based RV vaccines.

In another embodiment of the invention, the synthetic peptides comprise at least one human T-cell determinant (T) and at least one viral neutralization B-cell epitope (B), which may be in the form of hybrid or chimeric T-B tandem peptides. Such tandem peptide may be chimeric, comprising at least one human T-cell determinant of E1, E2 or C protein and at least one viral neutralization B-cell epitope of E1, E2 or C protein. Preferably, the synthetic peptide is in the form of chimeric peptide, particularly a chimeric lipopeptide, comprising at least one human T-cell determinant of E2 or C protein and at least one viral neutralization B-cell epitope of E1 protein The peptide can have, for example, sequences Tripalmityl-CSSVRAYNQPAGDVRGVWGKGERTYAEQDFRVPDPGDLVEYIMNYTGNQQSRWGL GSPNCHGPDWASPVCQRHSP (SEQ ID NO: 56), or any portion thereof that retains immunogenicity. Peptides of the invention can also have sequences corresponding to the analogous RV-EP27 regions of RV isolates other than M33, this sequence is designated "RV-EP27-like lipopeptide".

As mentioned above, the synthetic peptides described herein can be further either modified with lipid as lipopeptides or linked to carrier molecules (and/or polymerized to form aggregates) to produce alternate vaccines. These vaccines can be used to immunize against RV infection when administered to mammals, for example, by the intramuscular or parenteral route, or when delivered to the surface mucosal surface using microparticles, capsules, liposomes and targeting molecules, such as toxins and antibodies.

In a yet further aspect of the invention, there is provided a live vector for antigen delivery comprising a gene having a nucleotide sequence coding for an amino acid sequence of a synthetic peptide as provided herein. Such live vector may be a viral vector, such as poxviral, adenoviral, palioviral or retroviral viral vector, or a bacterial vector, such as salmonella or mycobacteria. The live vector may be provided in a vaccine against rubella with a physiologically-acceptable carrier.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1a-b show structure prediction analysis of rubella E1 protein. The upper panel shows the secondary structure analysis of local average .alpha.-helix and .beta.-turn potentials according to Chou and Fasman (ref. 9). The lower panel shows hydrophilicity plots according to Hopp and Woods (ref. 20). The values are derived from the average of heptapeptide windows and are plotted at the midpoint of each segment.

FIG. 2 shows structure prediction analysis of rubella E2 protein. The upper panel shows the secondary structure analysis of local average .alpha.-helix and .beta.-turn potentials according to Chou and Fasman (ref. 9). The lower panel shows hydrophilicity plots according to Hopp and Woods (ref. 20). The values are derived from the average of heptapeptide windows and are plotted at the midpoint of each segment.

FIG. 3 shows structure prediction analysis of rubella C protein. The upper panel shows the secondary structure analysis of local average .alpha.-helix and .beta.-turn potentials according to Chou and Fasman (ref. 9). The lower panel shows hydrophilicity plots according to Hopp and Woods (ref. 20). The values are derived from the average of heptapeptide windows and are plotted at the midpoint of each segment.

FIG. 4 comprising panels A and B, shows recognition of E1 peptides RV-EP24, -EP25, and -EP26 by MAbs 21B9H, 16A10E and 3D9F (panel A) and RV-EP24, -EP27, -EP28 by MAbs 21B9H and 3D9F (panel B). One hundred ug/mL of synthetic peptides were bound to Immulon-2 plates and probed with all MAbs except 3D9F at 1:200 dilutions of ascites fluids. Hybridoma cell culture supernatant was the source of antibody for MAb 3D9F and used at 1:50 dilution. The negative sera are normal Balb/C mouse sera not exposed to rubella;

FIG. 5 comprising panels A and B, shows peptide ELISA reactivity of mouse (panel A) and rabbit (panel B) anti-capsid antisera with rubella capsid peptides;

FIGS. 6a-b show immunoblot analysis of the antipeptide sera from rabbit immunized with C peptides. Immunoblot analysis was carried out under non-reducing (A) and reducing (B) conditions. Mab is the blot probed with monoclonal antibodies against C protein. The relative mobilities of protein standards (kDa) are indicated on the left. E1, E2 and C denote the structural proteins of RV. The antipeptide sera were used at a dilution 1:100; and

FIGS. 7a-b show proliferation response of RV-C9-specific murine T-cells to synthetic peptides, anti-CD4 antibodies and anti-CD8 antibodies. RV-C9B which is an C-terminal truncated analog of RV-C9, has amino acids sequence, VRAYNQPAGDV corresponding to residues 205-216 of C protein.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to peptides corresponding to immunogenic epitopes of RV and synthetic vaccines made therefrom. These novel immunogenic agents are prepared by chemically synthesizing peptides sharing antigenic determinants with the structural proteins of RV. The peptides or lipopeptides are used individually or linked to carrier molecules (and/or are polymerized) as vaccines. These vaccines can be used to immunize against RV infection when administered to mammals, for example, by the intramuscular or parenteral route, or when delivered to the surface mucosal surface using microparticles, capsules, liposomes and targeting molecules such as toxins and antibodies.

Synthesis of Peptides

To design a synthetic peptide-based rubella vaccine, the RV-specific CTL determinants, the viral neutralization B-cell epitopes (BE) and the functional T-helper epitopes (THDs) of individual viral proteins must be identified. Fifty-four overlapping synthetic peptides covering most of the E1, E2 and C protein sequences, respectively (Tables 1, 2 and 3 below) were chemically synthesized using an automated ABI 430A solid-phase peptide synthesizer, as described in Example 2 below. The length of synthetic peptides was selected on the basis of their high index of hydrophilic .beta.-turns as judged by secondary structure prediction analysis according to conventional algorithms (ref. 9,12,20) (FIGS. 1 to 3). Such segments are likely to be surface-exposed and antigenic. Long peptides were synthesized to better mimic the native epitopes on the protein as suggested by the work of Van Regenmortel (ref. 48). Occasionally, an additional cysteine residue was added to either the N-terminal or the C-terminal end of the peptides for conjugation purposes.

Generation and Characterization of RV-specific Monoclonal Antibodies

The production of murine RV-specific MAbs is described in Example 3 below. Antibodies were purified from ascites fluids using the Bio-Rad Affi-gel protein A MAPS II system. The subclass of the IgG monoclonal antibodies was determined by double immunodiffusion in agar using monospecific goat anti-mouse IgG subclass antisera (Tago, Burlinghams, Calif.). The results obtained are summarized in Table 4 below. The immunological properties of each MAbs were characterized by the haemagglutination inhibition (HI) and virus neutralization (VN) assays. Of the 25 monoclonal antibodies (MAbs) 3D9F, 3D5D, 12B2D and 16A10E were characterized to have HI activity of 1:16384, 1:8192, 1:4096 and 1:32, respectively (Table 4). 21B9H and 16A10E were found to have VN activity. 21B9H neutralized both the M33 and RA-27/3 strains in the presence of complement. The specificity of each MAb was determined using immunoblot analysis. The results summarized in Table 4 indicate that E1-specific MAbs such as 16A10E, 21B9H and 3D9F may be used to fine map the VN and HI epitopes of the E1 protein.

Identification of HA and VN Epitopes Using Linear Synthetic Peptides

Overlapping synthetic peptides covering most of the sequence of E1 was prepared, were coated onto ELISA plates and probed with E1-specific MAbs. Although MAb 21B9H reacted strongly with RV-EP25, -EP27 and -EP28, it failed to recognize RV-EP24 and -EP26 in the peptide-specific ELISAs (FIG. 4). This results suggest that MAb 21B9H recognizes an epitope which is located in the amino acid sequence PDPGDLVEYIMNYTGNQQSRWGLGSPNCHGPDWASP (SEQ ID NO: 25) corresponding to residues 198-233. However, another viral neutralizing MAb 16A10E reacted with both EP25 and EP26. This indicates that there is at least another neutralization epitope which is present in the amino acid sequence GLGSPNCHGPDWASP (SEQ ID NO: 26) coresponding to residues 219-233. MAb 3D9F which had strong HI activity against RV, reacted with peptide RV-EP28 corresponding to residues 212-240 (GNQQSRWGLGSPNCHGPDWASPVCQRHSP--SEQ ID NO: 28) (FIG. 4B), but not the long peptide RV-EP27. We do not know why RV-EP27 is not recognized by MAb 3D9F. In addition, two other MAbs 3D5D and 12B2D which had HI activities against RV, failed to recognize any of the synthetic peptides tested. Perhaps the hemagglutinin epitope(s) recognized by these two MAbs is conformational and could not be mimicked by linear peptides.

On the basis of the results, two conclusions can be drawn: (1) Two distinct virus neutralization epitopes were mapped to residues 198-233 (PDPGDLVEYIMNYTGNQQSRWGLGSPNCHGPDWASP--SEQ ID NO: 25) and 219-233 (GLGSPNCHGPDWASP--SEQ ID NO: 26) as defined by their reactivity with MAbs 21B9H and 16A10E, respectively. (2) A haemagglutinin epitope defined by MAb 3D9F was mapped to residues 212-240 (GNQQSRWGLGSPNCHGPDWASPVCQRHSP--SEQ ID NO: 28).

Therefore, a mixture of peptides that comprises amino acid sequences corresponding to these E1 epitopes, can be used in a diagnostic kit to detect the presence of RV neutralizing and HI antibodies. Peptides of the instant invention can also be used in standard immunoassays to detect the presence of RV antibodies.

Immunogenicity of RV peptides

The ability of RV peptides to elicit peptide-specific antibody responses in mammals was examined by immunizing mice, guinea pigs and rabbits with individual peptides emulsified in Freund's adjuvant. After three injections (5 to 100 .mu.g peptide per injection), IgG antibody responses were tested by peptide-specific ELISAs and immunoblotting against RV. All rabbit anti-E1 and anti-C peptide antisera reacted specifically with the immunizing peptide, and also recognized the corresponding parental protein in immunoblots (for example, see FIGS. 5 and 6). On the contrary, only certain rabbit anti-E2 peptide antisera reacted with E2 in immunoblots. These antisera were raised against E2-2, E2-3, E2-5, E2-7, and E2-12. Since free RV peptides can elicit strong IgG antibody responses, these results indicate that all synthetic peptides derived from the E1 and C proteins, as well as E2-2 (residues 15-36--SEQ ID NO: 31) E2-3 (residues 33-57--SEQ ID NO: 33), E2-5 (residues 69-91--SEQ ID NO: 35), E2-7 (residues 104-124--SEQ ID NO: 35), and E2-12 (residues 195-220--SEQ ID NO: 40) from the E2 protein comprise of both T- and B-cell epitopes. Furthermore, the presence of T-cell epitope(s) in these peptides was confirmed by human T-cell proliferation studies as described below.

Therefore, the ability of rabbit anti-RV peptide antisera to recognize RV structural proteins indicates that RV peptides (or a mixture of RV synthetic peptides) are capable of eliciting high titers of antibodies against RV in mammals. The RV-specific polyclonal antibodies raised against the peptides of the instant invention, can be used in immunoassays to detect the presence of RV in any biological sample.

Neutralization of RV by Guinea Pig Anti-E1 peptides Antisera

The immunological properties of each anti-E1 and anti-E2 peptides antisera were further characterized using haemagglutination inhibition (HI) and virus neutralization (VN) assays. All antisera raised against linear peptides failed to neutralize RV. However, guinea pig antisera raised against the oxidized form of either peptide RV-EP27 (PDPGDLVEYIMNYTGNQQSRWGLGSPNCHGPDWASPVCQRHSP--SEQ ID NO: 27) or its N-terminal truncated analog RV-EP28 (GNQQSRWGLGSPNCHGPDWASPVCQRHSP--SEQ ID NO: 28) were capable of neutralizing M33 in the absence of complement (Table 11 below). The oxidized RV-EP28 appears to be more immunogenic than the long peptide RV-EP27. Although Terry et al. (Arch. Virol. 98: 189-197, 1988) have identified three neutralization epitopes within residues 245 to 285 of E1, none of these epitopes (RV-EP 14, residues 240-259--SEQ ID NO: 14; -EP15, residues 256-275 --SEQ ID NO: 15; and -EP16, residues 272-291--SEQ ID NO: 16) elicited neutralizing antibody responses in our studies (Table 11 below). In addition, three distinct human T-cell epitopes (RV-EP11, residues 190-209--SEQ ID NO: 11; RV-EP12, residues 207-226--SEQ ID NO: 12; and RV-EP13, residues 224-243--SEQ ID NO: 13) were identified within the RV-EP27 peptide as described below. RV-EP27 can be used as a novel vaccine candidate since it is capable of eliciting a neutralizing antibody response in mammals and contains three distinct human T-cell epitopes.

Therefore, peptides of the instant invention can have, for example, the sequence PDPGDLVEYIMNYTGNQQSRWGLGSPNCHGPDWASPVCQRHSP (SEQ ID NO: 27), corresponding to amino acids 198-240 of E1 of the RV M33 strain, or any portion, variant or mutant thereof. Peptides of the invention also can have sequences corresponding to the analogous RV-EP27 regions of RV isolates other than M33, these sequences being designated "RV-EP27-like". Peptides described in the invention can be further either modified with lipid as lipopeptides or linked to carrier molecules (and/or polymerized) to produce alternate vaccines. These vaccines can be used to immunize against RV infection when administered to mammals, for example, by the intramuscular or parenteral route, or when delivered to the mucosal surface using microparticles, capsules, liposomes and targeting molecules, such as toxins and antibodies.

Human T-cell response to RV peptides

Human RV-specific T-cell epitopes were determined using RV peptides and T-cell lines obtained from a panel of individuals of diverse immunologic experience with RV infection or immunization. The lymphocyte proliferative responses of the RV-specific T-cell lines to overlapping E1 peptides (the first 23 peptides), E2 peptides (15 peptides) and C peptides (11 peptides) were determined in conventional proliferation assays. The results indicated that each individal in the four study groups exhibited different responses to E1, E2 and C peptides (see Tables 5 to 10 below). Not all the synthetic peptides elicited proliferative responses, and the recognition of T-cell epitopes was found to be MHC-restricted. Synthetic peptides corresponding to residues 1-22, 38-57, 54-74, 106-125, 140-159, 157-176, 174-193, 190-209, 207-226, 224-243, 240-259, 256-275, 272-291, `307-326, 324-343, 341-360, 358-377, 374-390, and 391-412 of E1; residues 1-20, 15-36, 54-74, 124-145, 156-177, 176-199, 218-239 and 233-257 of E2, and residues 1-30, 52-78, 74-100, 96-123, 119-152, 151-178, 177-204, 205-233, 231-257 and 255-280 of the C protein, when presented in the appropriate human MHC context, were shown to be highly stimulatory for RV-specific human T-cell lines. Nineteen out of 23 E1 peptides, 8 out of 15 E2 peptides and 10 out 11 C peptides were active in the proliferation assays. These results suggest that dominant T-cell epitopes are presented mainly on the E1 and C proteins, and to a lesser extent in the E2 protein.

Synthetic peptides corresponding to residues 207-226, 324-343 and 358-377 of E1, residues 54-74 of E2 and residues 119-152, 205-233 and 255-280 of the C protein were recognized by five or more human RV-specific T-cell lines. Four E1-specific T-cell clones (clones R9 and R20 specific for RVEP-10 peptide, clones R2 and R12 specific for RVEP-18), two E2-specific T-cell clones (both clones A3 and A8 specific for peptide E2-4) and nine C-specific T-cell clones (clones R5, R8, R10, R11 and R18 specific for C6 peptide; clones A2 and A11 specific for C9 peptide; clones A10 and A12 specific for C11 peptide) have been established. Three C-specific T-cell clones have cytolytic activities against various targets prepared with EBV-transformed autologous lymphoblastoid cells in the presence of RV or C protein, or peptide C6 (residues 119-151). Thus, a cytotoxic T-cell epitope was mapped to residues 119-151 of the C protein.

Delesi and Berzofsky et al. (ref. 12) proposed that T-cell epitopes were amphipathic .alpha.-helices. Rothbard and Taylor (EMBO J. 7: 93-100, 1988) suggested a different basic structure for T-cell epitope motives. A structure prediction analysis was performed with RV peptides containing functional human T-cell epitopes to determine whether their activity correlated with the presence of such structural features. We found that 5 out of 25 peptides with .alpha.-helical segments and 7 out of 29 peptides with a Rothbard's T-cell receptor-binding motif did not stimulate any of the 20 T-cell lines tested. Conversely, three peptides with no characterictic T-cell epitope structure (RV-EP19, -EP23 and E2-13) were found stimulatory. These results indicate the conventional structure prediction algorithms for T-cell epitopes are not absolute criteria for identifying T-cell determinants and that only in vitro proliferation studies can determine whether a peptide contains a functional T-cell epitope. Therefore, the identification of epitopes recognized by the T-cells of individuals of different genetic background and diverse immunologic experience with RV infection or immunization is important for the design of an effective synthetic vaccine.

Among the four subject groups tested, peptides containing human T-cell epitopes were more frequently detected in the group of healthy seropositive individuals and rubella vaccinees. Of particular interest, three of the five patients with congenital rubella syndrome (CRS) did not respond to any peptide. It is possible that in a proportion of CRS patients there is a defective T-cell recognition of RV antigen that may lead to failure or delay in the termination of RV replication, and thus may play a critical role in the persistence of the virus. In view of the increasing recognition that rubella infector or immunization may be associated with the induction of autoimmune diseases, it is possible that particular immunoreactive T-cell epitopes need to be excluded from any RV vaccine. Synthetic peptide-based RV vaccines can offer the flexibility to include of a mixture of potent human T-cell epitopes while excluding putative T-cell epitopes responsible for autoimmunity.

Immunogenicity of Lipopeptide

Generation of cell-mediated immunity (CMI) is a critical component of the immune response to RV. Nineteen lipopeptides (RV peptide modified with a lipid-linkage, N-palmitoyl-S-[2,3-bis(palmitoyloxy)-propyl]-cysteine-serine-serine) were selected from the structural proteins of RV and synthesized (Table 12 below). Some of these lipopeptides contain a CTL epitope allele-specific motif: x(Y)xxxxx(L,I,M)x or x(L,I,M)xxxxxYx (Falk et al.

Nature, 351:290, 1991; Romero et al. J Exp. Med. 174: 603-612, 1991). These RV lipopeptides were assessed for their ability to elicit peptide-specific antibody and T-cell responses in three different strains of mice with MHC H-2.sup.a, H-2.sup.b and H-2.sup.d haplotypes. For example, in two strains of mice Balb/c and A/J, lipopeptides TPRV-C9 in Freund's adjuvant induced strong T-cell proliferations (FIG. 7).

RV-C9 induced RV-C9-specific antibody responses only when injected in the presence of CFA, but not with saline. By contrast, TPRV-C9 lipopeptide in saline induced strong peptide-specific IgG antibody response, although the best response was induced by priming with CFA. These results demonstrate that lipopeptides can be applied successfully to induce both T- and B-cell responses. Thus, the present invention comprises a synthetic lipopeptide (or a mixture of synthetic lipopeptides) that, is capable of inducing both humoral and cell-mediated immunity responses against RV in vivo. The lipopeptide can have, for example, the sequence Tripalmityl-CSSVRAYNQPAGDVRGVWGKGERTYAEQDFRV (SEQ ID NO: 74), corresponding to amino acids 205-233 of C protein of the RV M33 strain.

It is understood that within the scope of the invention are any variants or functionally equivalent variants of the above peptides. The terms "variant" or "functionally equivalent variant" as used above, mean that if the peptide is modified by addition, deletion or derivatization of one or more of the amino acid residues, in any respect, and yet acts in a manner similar to that of E1, E2 and C peptides for any rubella virus isolates, then it falls within the scope of the invention.

Given the amino acid sequence of these peptides (Tables 1 to 3 and 12) and any similar peptide, these are easily synthesized employing commercially available peptide synthesizers, such as the Applied Biosystems Model 430A, or may be produced by recombinant DNA technology.

The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific Examples. These Examples are described solely for purposes of illustration and are not intended to limit the scope of the invention. Changes in form and substitution of equivalents are contemplated as circumstances may suggest or render expedient. Although specific terms have been employed herein, such terms are intended in a descriptive sense and not for purposes of limitations. Immunological and virological methods may not explicitly described in this disclosure but are well within the scope of those skilled in the art.

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