Peptide Vaccine Design Research Articles

A rational design of synthetic peptide vaccine with a built-in adjuvant. A modular approach for unambiguity.

We describe a peptide vaccine model containing a built-in adjuvant. This model used a multiple antigen peptide system (MAPS) to amplify peptide antigens and a lipoamino acid, tripalmitoyl glyceryl cysteine (P3C), as a built-in adjuvant. An 18-residue peptide antigen (B2) derived from the third variable domain (amino acid 312-329) of the glycoprotein gp120 of type I human immunodeficiency virus (HIV-1) was used in this model. This peptide antigen is a suitable target since it consists of neutralizing, T-helper, and T-cytotoxic epitopes. The peptide antigen in a tetravalent MAPS format (B2M-P3C) with a lipophilic attachment was synthesized by two routes for comparison: a direct stepwise approach and an indirect modular approach. In the stepwise approach, each residue was sequentially added to the peptide resin to give B2M-P3C and the P3C was incorporated to the side chain of a carboxyl terminal lysine as Fmoc-Lys(P3C). In the modular approach, a module containing a chloroacetylated core matrix of MAPS (M-P3C) with a carboxyl tetrapeptide bearing Lys(P3C) and a second module containing the peptide antigen B2 with a cysteine at its terminus were synthesized and purified separately, and then coupled to each other to form B2M-P3C. In the modular approach, the molecular ion of B2M-P3C was unambiguously identified by ion-spray mass spectrometry. B2M-P3C, administered in liposomes without any adjuvant such as Freund's complete adjuvant, was used to immunize mice and found to induce gp120-specific antibodies in vitro, and prime cytotoxic T lymphocytes in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum angiotensin-1 converting enzyme activity processes a human immunodeficiency virus 1 gp160 peptide for presentation by major histocompatibility complex class I molecules.

T cell stimulation by the human immunodeficiency virus 1 gp160-derived peptide p18 presented by H-2Dd class I major histocompatibility complex molecules in a cell-free system was found to require proteolytic cleavage. This extracellular processing was mediated by peptidases present in fetal calf serum. In vitro processing of p18 resulted in a distinct reverse phase high performance liquid chromatography profile, from which a biologically active product was isolated and sequenced. This peptide processing can be specifically blocked by the angiotensin-1 converting enzyme (ACE) inhibitor captopril, and can occur by exposing p18 to purified ACE. The ability of naturally occurring extracellular proteases to convert inactive peptides to T cell antigens has important implications for understanding cytotoxic T lymphocyte responses in vivo, and for rational peptide vaccine design.

Antibodies raised against peptide fragments of bovine αs1‐casein cross‐react with the native protein, but recognize sites distinct from the determinants on the protein

Bovine alpha s1-casein (alpha s1-CN) and its peptides 61-110 and 91-110, which contain both T and B cell determinants on alpha s1-CN and can elicit peptide-native protein cross-reactive antibodies, were selected as model antigens to study whether or not the immune response to the peptides is similar to that to the corresponding regions of the native protein, because they both have a similar disordered conformation in solution. Both alpha s1-CN- and peptide 61-110-primed T cells responded to peptides 61-80 and 91-100, but not to peptides 76-95 and 101-110. In addition, T cells immunized with peptide 91-110 were also stimulated by peptide 91-100, but not by peptide 101-110. These results suggest that the location of the T cell determinant was almost the same in alpha s1-CN and its peptides. On the contrary, antibodies raised against alpha s1-CN bound to peptides 76-95 and 91-100, but not to peptides 61-80 nor 101-110, while anti-peptide 61-110 antibodies preferentially reacted with peptides 61-80 and 101-110, and anti-peptide 91-110 antibodies also bound to peptide 101-110 but not to peptide 91-100. These results indicate that the B cell epitopes were not similar between alpha s1-CN and its peptides. This difference may have arisen because the antigen-B cell or T-B interactions required for the development of a specific antibody response occurred in a different manner between alpha s1-CN and its peptides. These findings may be useful for basic studies on immunology, and could also be applied to the design of new peptide vaccines.

Helper T-cell determinants in vaccine design

Mice belonging to the H-2 d haplotype do not respond to the 141–160 peptide of foot-and-mouth disease virus protein VP1. However, when defined ‘foreign’ helper T-cell determinants from ovalbumin or sperm whale myoglobin are added they do respond. These observations are likely to have important implications for the design of peptide vaccines.

Synthetic peptide vaccine design: synthesis and properties of a high-density multiple antigenic peptide system.

A convenient and versatile approach to the direct synthesis of a peptide-antigen matrix by the solid-phase method is described. The approach is called the multiple antigen peptide system (MAP) and it utilizes a simple scaffolding of a low number of sequential levels (n) of a trifunctional amino acid as the core matrix and 2n peptide antigens to form a macromolecule with a high density of peptide antigens of final Mr 10,000. The MAP model chosen for study was an octa-branching MAP consisting of a core matrix made up of three levels of lysine and eight amino terminals for anchoring peptide antigens. The MAP, containing both the core matrix and peptides of 9-16 amino acids, was prepared in a single synthesis by the solid-phase method. Six different MAPs elicited specific antibodies in rabbits and mice, of which five produced antibodies that reacted with their corresponding native proteins. In rabbits, the sera had a considerably higher titer of antibodies than sera prepared from the same peptides anchored covalently to keyhole limpet hemocyanin as carrier. Thus, the MAP provided a general, but chemically unambiguous, approach for the preparation of carrier-bound antigens of predetermined and reproducible structure and might be suitable for generating vaccines.

Knowledge‐based protein modelling and design

A systematic technique for protein modelling that is applicable to the design of drugs, peptide vaccines and novel proteins is described. Our approach is knowledge-based, depending on the structures of homologous or analogous proteins and more generally on a relational data base of protein three-dimensional structures. The procedure simultaneously aligns the known tertiary structures, selects fragments from the structurally conserved regions on the basis of sequence homology, aligns these with the 'average structure' or 'framework', builds on the loops selected from homologous proteins or a wider database, substitutes sidechains and energy minimises the resultant model. Applications to modelling an homologous structure, tissue plasminogen activator on the basis of another serine proteinase, and to modelling an analogous protein, HIV viral proteinase on the basis of aspartic proteinases, are described. The converse problem of ab initio design is also addressed: this involves the selection of an amino acid sequence to give a particular tertiary structure, in this case a symmetrical domain of two Greek-key motifs.

Non-responsiveness to a foot-and-mouth disease virus peptide overcome by addition of foreign helper T-cell determinants

Study of the immune response to synthetic antigens has shown that uncoupled peptides can realize their potential as vaccines only if they contain domains that react with helper T-cell receptors and Ia antigens in addition to antibody binding sites. Here we consider whether genetically restricted non-responsiveness to an uncoupled peptide could be overcome by synthesizing a peptide with an additional helper T-cell epitope from a different protein. We demonstrate that H-2d mice, which are non-responders to the 141-160 VP1 peptide of foot-and-mouth disease virus (FMDV), can be converted into responders by immunization with peptides containing the FMDV sequence with defined 'foreign' helper T-cell determinants from ovalbumin or sperm whale myoglobin. Furthermore, the virus-neutralizing activity of the antibody raised against peptide was dependent on the determinant used. Thus, FMDV peptides with the added sequences 323-339 from ovalbumin and 132-148 from sperm-whale myoglobin elicited a high degree of neutralizing activity in B10.D2 mice. The sera from mice which received the peptide with the added sequence 105-121 from sperm whale myoglobin did not neutralize the virus, although they had high levels of anti-141-160 FMDV peptide activity. Our data indicate that the T-cell help given by the 'foreign' epitopes is B-cell clone specific. These results are likely to have important implications for the design of peptide vaccines.

Identification of a Synthetic Peptide as Part of a Major Neutralization Epitope of Respiratory Syncytial Virus

A 7000 Mr cleavage fragment of the F1 subunit that carries the major neutralization epitope has been identified by chemical and enzymatic cleavage of the fusion protein of respiratory syncytial (RS) virus (Long strain) with an efficient RS virus-neutralizing monoclonal antibody. Based on the published mRNA-deduced sequence of the A2 strain, coupled to the hydropathicity profile and prediction of protein conformation, the neutralization epitope has tentatively been localized on the first third of the F1 protein N-terminal, probably in the region of amino acids 215Ser to 236Glu. Analysis of three peptides covering different portions of the 212Cys to 236Glu region of the F1 fusion protein identified a peptide (Cys X 216Asn to 236Glu) that reacted strongly with the neutralizing monoclonal antibody and that was efficient in blocking neutralization and in plaque-reducing assays, confirming that the neutralization epitope was localized in that region. Further analysis with two other synthetic peptides (212Cys to 222Glu and Cys X 221Ile to 236Glu) indicated that the dodecapeptide Ile-Glu-Phe-Gln-Lys-Asn-Asn-Arg-Leu-Leu-Glu mimicked either the whole or a major part of the neutralization epitope. This opens a promising avenue for the simple design of a synthetic peptide vaccine to control RS virus infection.

Prediction of antigenic determinants and secondary structures of the major AIDS virus proteins

Criteria for the design of peptide vaccines to prevent AIDS are presented. The best vaccine candidates contain both B and T lymphocyte-defined epitopes in regions conserved in sequence between viral isolates. We propose that attention should focus on proteins specified by the gag and, possibly, pol genes in addition to the env gene envelope glycoproteins being actively studied. The predictions of B- and T-epitopes are refined by consideration of secondary structure prediction and inter-isolate sequence variability to suggest peptides from env, gag and pol that would be the best vaccine candidates.