A potential peptide vaccine against two different strains of influenza virus isolated at intervals of about 10 years.

We have developed a strategy for making synthetic peptide vaccines, in which a peptide, HA127-133, derived from the hemagglutinin (HA) of A/Aichi/2/68(H3N2) influenza virus (Aichi/68) is introduced into the Ab binding component consisting of 43-46 and 54-58 residues of a pigeon cytochrome c analogue peptide, 46F50V54A. Indeed, this hybrid peptide, 46F/HA127-133/54A, induced impressive T-cell responses and antibody production neutralizing infectivity of Aichi/68 in vitro. In a subsequent study we found that 46F/HA127-133/54A(18mer) peptide antigen, which had been prepared by substitution at the central five residues of 46F50V54A with HA127-133, generated T-cell responses and neutralizing antibody responses as well. On the basis of these prior findings, in the present study we analyzed immunopotency of 46F/HA127-133/54A(18mer) in vivo administered in several ways to I-Ab mice. We show herein that this peptide vaccine loaded in multilamellar liposomes without adjuvant protects the mice against infection with Aichi/68 within 2 weeks after final immunization. Further, this peptide vaccine was shown to be effective in preventing infection with a naturally occurring antigenic variant, A/Texas/1/77(H3N2), carrying the same sequence at 127-133 of the HA as Aichi/68 virus. Since this part of the HA is relatively conserved among H3 subtype influenza viruses, our peptide vaccine may become the basis for a new strategy to prepare effective vaccines that will overcome the ineffectiveness of classical vaccines attributable to antigenic drift of influenza viruses.