Effects of influenza virus-specific cytotoxic T-lymphocyte responses induced by a synthetic nucleoprotein peptide on the survival of mice challenged with a lethal dose of virus.

Even though virus-induced cytotoxic T lymphocytes (CTLs) recognize antigens as peptides presented on infected cells, short synthetic peptides without any modifications are generally considered unsuitable for inducing antigen-specific CTLs in vivo. Our results demonstrate rapid induction of influenza virus-specific CTLs in Balb/c mice by an unmodified core protein peptide known to be a dominant H-2d-restricted CTL epitope. Additionally, the immunization procedure we employed in these studies produced significant influenza virus-specific CTLs in lymph nodes, spleen and lungs. When challenged with a lethal dose of influenza virus, a statistically significant delay in the day of death was observed in peptide-immunized mice. However, viral clearance was only slightly different from that in control mice. While these results are encouraging, they suggest a requirement for multiple CTL-inducing peptides, helper T cell-inducing peptides and/or virus-specific IgA responses in order to achieve protection from influenza infection.