Recombinant vaccinia viruses expressing an immunodominant epitope of HIV-1 envelope protein within an influenza hemagglutinin cassette predominantly prime epitope-specific CD8+ CTL.

We constructed recombinant vaccinia viruses (RVV) expressing a 15-residue peptide (P18IIIB; RIQRGPGRAFVTIGK) of gp160 envelope protein from a human immunodeficiency virus type-1 (HIV-1) IIIB isolate using an H1 influenza virus hemagglutinin (HA) gene cassette. Immunofluorescent tests with antisera against both H1N1 influenza virus and P18IIIB localized chimeric HA molecules comprising influenza virus HA and P18IIIB peptide intracellularly, but the P18IIIB could not be seen on the outer surfaces of infected cells though weak fluorescence was detected regarding HA molecule. Consistent with these findings, Western blotting confirmed the expression of a polypeptide of about 74-kDa protein representing chimeric HA molecule in the infected cells. These recombinants markedly primed CD8⁺ cytotoxic T lymphocytes (CTL) specific for P18IIIB as well as HA protein of the influenza virus, but failed to elicit P18IIIB-specific antibody despite stimulating production of HA-specific antibody. In addition, the P18IIIB-specific CTL could strongly lyse target cells expressing the whole HIV-1 envelope gene of IIIB strain. Thus, the influenza virus chimeric HA cassette vector system used in the present study appeared to be a useful tool for constructing vaccine candidates which will predominantly prime CD8⁺ CTL specific for immunodominant determinants of various infectious agents. [ABSTRACT FROM AUTHOR]