RECOMBINANT MODIFIED VACCINIA VIRUS ANKARA-SIMIAN IMMUNODEFICIENCY VIRUS GAG POL ELICITS CYTOTOXIC T-LYMPHOCYTES IN RHESUS-MONKEYS DETECTEDBY A MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I PEPTIDE TETRAMER

The utility of modified vaccinia virus Ankara (MVA) as a vector for el iciting AIDS virus-specific cytotoxic T lymphocytes (CTL) was explored in the simian immunodeficiency virus (SIV)/rhesus monkey model. After two intramuscular immunizations with recombinant MVA-SIVSM gag pal, t he monkeys developed a Gag epitope-specific CTL response readily detec ted in peripheral blood lymphocytes by using a functional killing assa y. Moreover, those immunizations also elicited a population of CD8+ T lymphocytes in the peripheral blood that bound a specific major histoc ompatibility complex class I/peptide tetramer. These Gag epitope-speci fic CD8+ T lymphocytes also were demonstrated by using both functional and tetramer-binding assays in lymph nodes of the immunized monkeys. These observations suggest that MVA may prove a useful vector for an H IV-1 vaccine. They also suggest that tetramer staining may be a useful technology for monitoring CTL generation in vaccine trials in nonhuma n primates and in humans.