Synthetic peptides corresponding to the F protein of RSV stimulate murine B and T cells but fail to confer protection.

We have previously located a major neutralization site of the fusion protein of respiratory syncytial virus (RSV) in the polypeptide region extending from amino acids Ile221 to Glu232. In this report, 8 peptides corresponding to the six major hydrophilic regions of the F1 subunit were selected to analyse their immunogenic and protective capacities as well as their ability to block the high neutralization activities of 4 monoclonal antibodies (MAbs). Only 5 of the 8 peptides tested induced specific antibodies while all induced an in vitro interleukin-2 response of splenocytes from immunized mice. Peptide 3 (Ile221-Phe237) was able to elicit neutralizing antibodies, confirming our previous hypothesis concerning the location of a neutralization site. However, immunization with the latter did not induce significant reduction of virus in lungs of BALB/c mice upon challenge, probably due to an inadequate level of circulating neutralizing antibodies. Interestingly, peptides 2 (Asn216-Glu232), 3 (Ile221-Phe237), and 5 (Ser275-Ile288) blocked in vitro neutralization by four different F1 specific MAbs. A hypothesis is proposed to explain these results.

[Synthetic immunogenic complexes containing a peptide from the surface protein of the foot-and-mouth disease virus]. / Sinteticheskie immunogennye kompleksy na osnove peptida poverkhnostnogo belka virusa iashchera.

Synthetic constructions containing a peptide antigenic determinant (C-terminal peptide 205-213 of the surface VP1 protein of the foot-and-mouth disease virus, O1K strain), glucosaminylmuramayl dipeptide (GMDP), and polyionic synthetic carriers were prepared. The polymerized peptide and peptide-BSA conjugates were synthesized as well. Among the constructions obtained only peptide-BSA conjugate proved to be highly immunogenic. Application of synthetic constructions to design immunogenic complexes is discussed.

Serologically defined linear epitopes in the E2 envelope glycoprotein of Semliki Forest virus.

A set of 41 overlapping peptides, representing the complete sequence of SFV-E2 protein were synthesized and analyzed in the ELISA test against murine anti-SFV sera. No single peptide was recognized by all antisera. Eight peptides were found to be highly reactive with hyperimmune anti-SFV sera. Six out of the eight peptide sequences coincide with the most hydrophilic regions of SFV-E2. Out of these, four peptides (amino acid positions 16-35, 61-80, 166-185, 286-305) that contain the least number of alphavirus conserved residues were selected. This panel constitutes the minimal number of peptides necessary and sufficient for specific recognition of hyperimmune mouse anti-SFV sera.

Serological prospects for peptide vaccines against foot-and-mouth disease virus.

Antibodies to a synthetic peptide corresponding to the 141 to 160 amino acid sequence of the protein VP1 of type O foot-and-mouth disease virus (FMDV) neutralize a wider range of type O isolates than anti-virion serum. Extending this peptide at the amino terminus reduced the number of strains neutralized by the antipeptide sera. Reactions with antisera to peptides representing non-contiguous native sequences showed that it was also possible to increase the number of strains effectively neutralized. Selected substitutions of a single amino acid at position 148 markedly altered the neutralizing specificity of antibodies elicited by the 141 to 160 peptide. In particular, a peptide with an L----S substitution at this position induced antibodies which neutralized a type O and a type A virus equally, and guinea-pigs inoculated with it were protected from challenge with either virus. Attempts to isolate variant viruses resistant to neutralization with anti-peptide antibody indicated that these occurred at low frequency, and there was some evidence that resistance may be partially conferred by mutations outside the peptide sequence.

Peptides as potential virus inhibitors. Synthesis and bioassay of five respiratory syncytial virus peptide analogs with antimeasles activity.

Five carbobenzoxylated and D-amino acid containing-peptide analogs of the respiratory syncytial virus (RSV) F1 glycoprotein amino terminus were chemically synthesized by solution and FMOC-solid phase peptide synthesis methods. Several of these peptides, ranging from 3 to 6 residues in length, raised the bilayer to hexagonal phase transition temperature of dielaidoylphosphatidylethanolamine. None of these peptides were specific inhibitors of RSV or herpes simplex virus infection. Two of the series, CBZ-D-Phe-L-Leu-Gly-D-Phe-D-Leu-D-Leu and CBZ-D-Phe-L-Leu-Gly-D-Phe-D-Leu-D-Leu-Gly, were active in reducing measles virus-induced cytopathic effect at 62 micrograms/mL. Others in the series showed some activity at higher doses or activity simultaneously with some cell toxicity. These results support the view that membrane-stabilizing agents may have non-specific effects on membranes which are responsible for their antimeasles activity.

Cellular and humoral immune responses to synthetic peptides deduced from the amino-acid sequences of Epstein-Barr virus-encoded proteins in EBV-transformed cells.

Ten synthetic peptides containing 18-22 residues deduced from the amino-acid sequences of the EBV-encoded latent-infection-associated membrane protein (LMP) and the 2 principal nuclear antigens, EBNA-1 and EBNA-2, were tested for their ability to induce lymphokine release from sensitized T-cells of EBV-seropositive donors, as measured by the leukocyte migration inhibition assay (LMI). Only one of the 10 free peptides induced EBV-specific LMI. After Sepharose-coupling, 4 additional peptides were regularly active. In parallel, the sera of the same and other donors were screened for synthetic peptide-binding antibodies, as measured by an ELISA assay. Antibodies to 9 of the 10 peptides were detected in 25-80% of EBV-antibody-positive, but not in EBV-antibody-negative sera. A comparison of the two responses indicates that the humoral immune system tends to react with more epitopes on a given protein than the cellular immune system. Furthermore, the antibody reactivity pattern to different epitopes is more variable from individual to individual than the T-cell response. Also, the epitopes detected by antibodies and sensitized T-cells are often not identical.

Cytotoxic T lymphocytes recognize a fragment of influenza virus matrix protein in association with HLA-A2.

Both human and murine cytotoxic T cells (CTL) elicited in response to infection with influenza A viruses have been shown to be specific for internal viral proteins, such as the matrix and nucleoprotein. Individual CTL epitopes have been identified in the nucleoprotein by successfully substituting short synthetic peptides for the intact virus in the preparation of target cells in cytotoxicity assays. The defined peptide epitopes have each been recognized by CTL in association with individual class I major histocompatibility complex (MHC) proteins, H-2Db, H-2Kk, H-2Kd (Taylor, P. et al., unpublished data) and HLA-B37. A logical strategy to investigate the molecular details of the interaction between antigen and MHC class I proteins would be to define an epitope recognized by the MHC class I molecule HLA-A2. This is because the amino-acid sequence is known, several variants of A2 have been characterized and the protein has been purified and crystallized. Here we describe a peptide derived from the influenza matrix protein that is recognized by human CTL in association with the HLA-A2 molecule.