Prevention of infection of influenza virus in DQ6 mice, a human model, by a peptide vaccine prepared according to the cassette theory.

We proposed a strategy (cassette theory) in which non-binding peptides for murine major histocompatibility complex (MHC) class II molecules are introduced into a MHC-binding component to render the resultant hybrid peptides bound to the MHC and thus immunogenic in animals carrying the relevant MHC. It was shown that 46F/HA127-133/54A(18mer) peptide which was prepared by introducing hemagglutinin (HA)127-133 of influenza virus into the H-2Ab binding component induced significant T cell responses and antibodies (Ab) specific for HA127-133 in H-2Ab mice. Further we found that the H-2Ab binding component had a supermotif for human class II molecules (i.e. HLA-DQ6). In the present study, a new peptide vaccine, H3-H3, was prepared by combining 46F/HA127-133/54A(18mer) as a carrier and HA127-133 attached to the C terminus of 46F/HA127-133/54A(18mer) as a hapten and the effect of vaccine was examined in DQ6 mice which carry HLA-DQ6 alone as MHC class II molecules and thus may be regarded as a model of the DQ6 positive individuals. Since 46F/HA127-133/ 54A(18mer) induced merely Ab against HA127-133, it was assumed that H3-H3 induced mainly HA127-133 specific Ab in DQ6 mice without undesirable Ab production against the carrier. Indeed, H3-H3 elicited T cell responses and induced HA127-133 specific Ab in DQ6 mice. Furthermore, administration of H3-H3 inhibited growth of influenza virus until 9 weeks after the last immunization in DQ6 mice.