Identification of linear epitopes on Semliki Forest virus E2 membrane protein and their effectiveness as a synthetic peptide vaccine

Abstract

Semliki Forest virus (SFV) infection of mice was used as a model to study the applicability of synthetic peptides containing only linear epitopes as viral vaccines. The identification of linear epitopes with vaccine potential on the E2 membrane protein of SFV was based on the binding of SFV-specific antibodies to a set of overlapping synthetic hexapeptides (Pepscan) representing the whole E2 amino acid sequence. The 14 available E2-specific monoclonal antibodies which were protective in vivo proved to be unsuitable for the identification of linear epitopes because they recognized only conformational epitopes, as indicated by their lack of reactivity with unfolded, reduced E2 protein on immunoblots. Three epitopes were detected with polyclonal anti-SFV serum at amino acid positions 135 to 141,177 to 185 and 240 to 246 of the E2 protein. Synthetic peptides containing these epitopes were coupled to a carrier protein and tested as a vaccine. Mice immunized with the peptide containing amino acids 240 to 255 of protein E2 were protected against a challenge with virulent SFV but protection of mice immunized with the peptides containing amino acids 126 to 141 or 178 to 186 was only marginally better than that of controls. The prechallenge sera of most peptide-immunized mice reacted with SFVinfected cells but none of these sera neutralized the virus in vitro. However, protection of mice correlated well with SFV-specific antibody titre, suggesting antibody-mediated protection.

Two‐dimensional structure of the Opc invasin from Neisseria meningitidis

“…Forest virus (Snijders et al, 1991) and terminating in compatible BamHI ends were cloned in frame into the Bgl II sites. Because of the manipulations, these insertions were flanked by 1-3 additional amino acids ( Table 2).…”

Immunogenicity and vaccine efficacy of synthetic peptides containing Semliki Forest virus B and T cell epitopes

“…Peptides were either synthesized by E. Freund (Hubrecht Laboratory, Utrecht, The Netherlands) as described (Snijders et al, 1991) or (peptides e and f) by Waters, Millipore on a Milligen/Biosearch 9050 Peptide Synthesizer. The amino acid sequences of the peptides were derived from the nucleotide sequence of the prototype strain ofSFV (Garoffet al, 1980) or the A/PR/8/34 strain of influenza virus (Hackett et al, 1983).…”

“…These peptides contain previously identified SFV B cell epitopes (Snijders et al, 1991) and H-2a-restricted Th cell epitopes of either SFV (A. Snijders et al, unpublished results) or influenza virus (Hackett et al, 1985).…”

“…Antibody titres were determined by indirect ELISA with horseradish peroxidase-coupled goat anti-mouse IgG on coated peptide or prototype SFV-infected L cells as described (Snijders et al, 1991). The titre was defined as -log~o of the highest serum dilution that resulted in an extinction value obtained for a specific coat (homologous peptide or SFV-infected cells) that was > 0.20 and at least 0-10 higher than the extinction obtained for the corresponding control coat (heterologous peptide or uninfected L cells).…”

“…Two different linear B cell epitopes of SFV were used as were three different Th cell epitopes, two of SFV (A. Snijders et al, unpublished results) and one of influenza virus (Hackett et al, 1985). One of the two linear B cell epitopes of SFV was shown previously to protect mice against SFV by evoking (when conjugated to a carrier) high titres of non-neutralizing antibodies, whereas the other evoked low titres of SFV-reactive antibodies and was only marginally protective (Snijders et al, 1991). The role of the Th cell epitopes and the anti-peptide antibodies in the observed protection was assessed.…”