Induction of CD8+ cytotoxic T cells by immunization with killed influenza virus and effect of cholera toxin B subunit.

The MHC class I cytotoxic T-lymphocyte (CTL) response in mice given formalin-inactivated influenza whole-virus vaccine (WVV) with or without cholera toxin B subunit (CTB) was studied. Intraperitoneal injection of Balb/c (H-2d) mice with high doses of A/Taiwan/1/86 (H1N1) WVV stimulated influenza A virus-specific CTL response in a dose-dependent manner. A dose of 4.4 or 44 micrograms induced CTL response equal to or greater than live influenza virus infection. Coadministration of vaccine with 5 or 25 micrograms of CTB resulted in a higher level of CTL than with vaccine alone. CTL lysed A/Taiwan and A/Shanghai (H3N2) virus-infected class I-expressing P815 (H-2d) but not virus-infected EL-4 (H-2b) target cells nor B/Yamagata virus-infected target cells. Virus-infected MHC class II- and class I-expressing A20 (H-2d) targets were also lysed. Depletion of Lyt-2+ (CD8+) T cells with monoclonal antibody completely abrogated lysis of P815 target cells and resulted only in a slight reduction of lysis of A20 target cells. Depletion of L3T4+ (CD4+) T cells or NK cells had minimal effect on lysis of either P815 or A20 target cells. Using limiting dilution analysis, the precursor CTL (pCTL) frequency paralleled CTL activity. Significant CTL activity was detected 7 months after immunization. These results demonstrate that adequate doses of influenza WVV with or without CTB can induce long-lasting influenza A cross-reactive MHC class I-restricted CD8+ CTL response in mice. Thus, coadministration of influenza WVV with CTB may lead to an effective vaccine that stimulates both CTL and antibody responses.