Specificity and cross-reactivity of synthetic peptides derived from a major antigenic site of influenza hemagglutinin

Construction and immunogenicity evaluation of an epitope-based antigen against swine influenza A virus using Escherichia coli heat-labile toxin B subunit as a carrier-adjuvant

Influenza A virus causes a highly contagious respiratory disease in a variety of avian and mammalian hosts, including humans and pigs. The primary means for preventing influenza epidemics is vaccination. Epitope-based vaccine represents a new approach to achieve protective immunity. The objective of this study was to construct and evaluate the immunogenicity of an epitope-based antigen for its potential application in future influenza vaccine development. The antigen, comprised of a set of consensus influenza A virus epitopes (IAVe), was genetically linked to a subunit of the bacterial heat-labile enterotoxin (LTB) as an adjuvant. Immunogenicity of this LTB-IAVe antigen was evaluated in a pig model. Despite an inability to detect neutralizing antibodies directed toward the whole virus, humoral immunity against the IAVe was demonstrated in both serum (IgA and IgG) and mucosal secretions (IgG) of immunized pigs. Specific cellular immunity was also induced after LTB-IAVe immunization, as evidenced by up-regulating of IL-1β, IL-8, and IL-4 expression in peripheral blood mononuclear cells (PBMCs) of vaccinated pigs. In comparison to the non-immunized pigs, pigs immunized with the LTB-IAVe showed improved protection against a pathogenic H1N1 swine influenza virus challenge, with about 50% decrease of pneumonic lesions and 10-fold reduction of the viral load in lung and nasal secretion at five days post challenge. This study establishes a platform for future construction of epitope-based vaccines against influenza A virus infection.

Development of a nucleoprotein-based enzyme-linked immunosorbent assay using a synthetic peptide antigen for detection of avian metapneumovirus antibodies in Turkey sera

Avian metapneumoviruses (aMPV) cause an upper respiratory tract disease with low mortality but high morbidity, primarily in commercial turkeys, that can be exacerbated by secondary infections. There are three types of aMPV, of which type C is found only in the United States. The aMPV nucleoprotein (N) amino acid sequences of serotypes A, B, and C were aligned for comparative analysis. On the basis of the predicted antigenicity of consensus sequences, five aMPV-specific N peptides were synthesized for development of a peptide antigen enzyme-linked immunosorbent assay (aMPV N peptide-based ELISA) to detect aMPV-specific antibodies among turkeys. Sera from naturally and experimentally infected turkeys were used to demonstrate the presence of antibodies reactive to the chemically synthesized aMPV N peptides. Subsequently, aMPV N peptide 1, which had the sequence 10-DLSYKHAILKESQYTIKRDV-29, with variations at only three amino acids among aMPV serotypes, was evaluated as a universal aMPV ELISA antigen. Data obtained with the peptide-based ELISA correlated positively with total aMPV viral antigen-based ELISAs, and the peptide ELISA provided higher optical density readings. The results indicated that aMPV N peptide 1 can be used as a universal ELISA antigen to detect antibodies for all aMPV serotypes.

Protection of mice against lethal viral infection by synthetic peptides corresponding to B- and T-cell recognition sites of influenza A hemagglutinin

Previously, we reported 12 synthetic T- and B-cell recognition regions representing surface areas of the hemagglutinin (HA) of X31 influenza virus. In the present study, four of these peptides were examined in Balb/c mice for their ability to produce protective immunity against lethal infection with a dose equivalent to 10 LD50 of influenza virus. These peptides corresponded to the following sequences: 23-36 (HA1-1); 138-152 (HA1-3); 183-199 (HA1-6) and 1-11 (HA2-10). Each of the selected peptides, in their free form, evoked anti-peptide antibodies that cross-react with intact X31 virus. Two of the peptides, HA1-1 and HA1-3, also elicited virus-specific delayed type hypersensitivity (DTH) responses. These two peptides, when injected into mice, not only failed to protect the immunized mice against challenge with influenza virus, but in fact caused greater susceptibility to viral infection as compared to control animals that had been injected with saline. In contrast, peptides HA1-6 and HA2-10, which were unable to induce adequate virus-specific DTH responses, conferred 42-46% and 54-73% protection, respectively, compared to the control group that received only saline (P < 0.03 to P < 0.01).

Engineered human vaccines

The limitations of human vaccines in use at present and the design requirements for a new generation of human vaccines are discussed. The progress in engineering of human vaccines for bacteria, viruses, parasites, and cancer is reviewed, and the data from human studies with the engineered vaccines are discussed, especially for cancer and AIDS vaccines. The final section of the review deals with the possible future developments in the field of engineered human vaccines and the requirement for effective new human adjuvants.

Synthetic approaches to vaccines for infectious and autoimmune diseases

The development is outlined of some synthetic vaccines against infectious diseases, in particular cholera, shigella and influenza. In the last case, use of the synthetic adjuvant MDP in combination with a haemagglutinin peptide has led to a synthetic vaccine with built-in adjuvanticity. The production of vaccines both by chemical synthesis and genetic engineering is described. The successful use of the synthetic amino acid copolymer COP-1 as an immunomodulatory vaccine to suppress the onset of allergic encephalomyelitis in experimental animals has led to clinical trials with patients suffering from exacerbating remitting multiple sclerosis. T-cell vaccination is an alternative approach to immunization against autoimmune diseases.

Synthetic recombinant vaccine expressing influenza haemagglutinin epitope in Salmonella flagellin leads to partial protection in mice

The influenza virus haemagglutinin epitope 91-108, which is a conserved amino acid sequence in all type A H3 strains, was expressed in Salmonella flagellin, to evaluate its potential as a vaccine. For that purpose, a synthetic oligonucleotide comprising 54 bases coding for the corresponding sequence was inserted into the plasmid pLS408 and transformed into Escherichia coli JM101. Colonies containing the recombinant plasmid were used to transform Salmonella typhimurium LB5000 and were then transduced to a flagellin negative 'live vaccine' aroA mutant of Salmonella dublin. Rabbits immunized either with the live recombinant S. dublin or with the flagellin isolated from it, showed significant levels of IgG response against the synthetic peptide 91-108 as well as against the intact A/Texas/77 influenza virus. Mice immunized with the same preparations developed influenza-specific IgG antibodies in the blood and secreted IgA antibodies in their lungs. Furthermore, these mice showed about 50% protection against challenge infection with the virus. The most successful results were achieved by intranasal immunization with the isolated recombinant flagellin, when employed without the aid of adjuvant.

Antigenic properties and protective capacity of a cyclic peptide corresponding to site A of influenza virus haemagglutinin

Two cyclic peptide analogues corresponding to residues 139-146 (site A) of influenza A virus haemagglutinin (strain X31) were synthesized. The ability of these peptides to react with anti-influenza virus antibodies was found to depend on the conformation of the loop and on the orientation in which the peptide was presented to antibodies. Antibodies raised to the peptides were able to bind in ELISA with influenza virus antigen that had been allowed to dry on the microtitre plate. When OF1 mice were immunized with cyclic peptides, approximately 80% of the animals were protected against an intranasal challenge with influenza virus.

Synthesis of cyclic peptides on solid support. Application to analogs of hemagglutinin of influenza virus

In order to mimic a well-known loop structure (site A) of the hemagglutinin of influenza virus, a series of cyclic peptides derived from the region 139-147 were synthesized. The lactam analogs cyclised between the N-terminus Cys 139 and the beta-carboxyl of aspartic acid 148 (small loop) or the epsilon-NH2 of lysine 148 via succinimidyl linker (large loop) were synthesized by the solid phase method. Cyclisation was directly performed on the solid support prior to final cleavage of the peptide. We describe two protection schemes which allow us to obtain different loop sizes derived from the same sequence. Eight of the analogs contained relatively large ring structures (up to 38 membered). For protection of the side chain of aspartic acid in combination with N-alpha-Fmoc protection, the cyclohexyl ester was more satisfactory than the benzyl ester with respect to imide formation. When the rate of cyclodimerisation, as a function of resin substitution, was compared to the rate of cyclic monomer formation, it was found that dimerisation was proportional to the charge of the resin. Furthermore, a comparison of the recently reported BOP reagent over the classical DIPC/HOBt method for the cyclisation reaction shows that in our case the reaction proceeded more rapidly by the BOP procedure although it gave a less pure crude product.

Development and application of synthetic peptides as vaccines

Vaccination against bacterial and viral diseases has been one of the major achievements in medicine and immunology since the beginning of this century. Extensive vaccination programs have been able to control or, in the case of smallpox, virtually wipe out some of the most dangerous infectious diseases e.g. poliomyelitis, measles, whooping cough, diphtheria and tetanus. However, as this success has been limited mainly to the developed, affluent countries, infectious diseases still remain the worlds largest health problem. Furthermore, vaccines against human parasites are non-existent. Recent advances in immunology and molecular biology including recombinant DNA technology have provided the basis for new approaches to vaccine development.

Integrity of the C-terminal part of tyrosine aminotransferase revealed by an anti-peptide serum

A synthetic peptide corresponding to the seven carboxy-terminal amino acids of tyrosine aminotransferase was coupled to ovalbumin or keyhole limpet haemocyanin, and the resulting conjugates were used to raise anti-peptide antibodies by immunization of rabbits. The crude sera were purified and tested for recognition of the whole enzyme by enzyme-linked immunosorbent assay and immunoprecipitation in extracts from [35S] methionine labeled hepatoma cells. Our results support the existence of an intact C-terminus. If processing takes place, it will rather occur at the N-terminus of this hepatic enzyme.