Long-lasting anti-viral cytotoxic T lymphocytes induced in vivo with chimeric-multirestricted lipopeptides.

Cytotoxic T lymphocytes (CTL) play a major role in protective immunity against viral diseases. However, the antigenic formulations that can be used in vaccinations able to generate virus-specific CTL responses in vivo have yet to be defined. We have previously shown that HIV-1-specific CTL can be elicited in mice by injecting without adjuvant a synthetic peptide of the envelope glycoprotein that has been modified by the addition of a simple lipid tail to the end of the sequence (lipopeptide). The present study set out to address the question of whether such immunogens may be appropriate for preparing a human synthetic vaccine. We first showed that CTL were effectively induced by lipopeptides when given s.c. or i.p. We evidenced that the in vivo induction required stimulation of a concomitant specific T helper cell response, implying the presence of at least one CD4 epitope in the synthetic sequence used. Bearing in mind the particular properties that would be required in a prospective human peptide vaccine, we conceived a strategy in which a virus-specific CTL response could be generated in mice of different haplotypes using a single lipopeptide. We therefore tested a lipopeptide construct that integrated a synthetic sequence having three colinear epitopes of the influenza virus nucleoprotein, each restricted to a different H-2 haplotype. We found that a CTL response could be elicited to all three epitopes of this chimeric multirestricted lipopeptide construct. Finally, we have attempted to estimate the duration of the responses; strong CTL activities were still present up to six months after the last injection. These findings indicate that this approach may be suitable for developing a synthetic vaccine for human use.