DNA vaccination of macaques with several different Nef sequences induces multispecific T cell responses

CD8(+) T lymphocytes play a key role in controlling viremia during primary human immunodeficiency virus-1 and in maintaining disease-free infection. I I has recently been shown that DNA immunization of rhesus monkeys can elici t strong, long-lived antigen-specific cytotoxic T lymphocyte (CTL) response s. In previous work, it was shown that macaque CTL responses to lipopeptide vaccination were directed against a limited number of epitopes. In the pre sent study, we used the DNA immunization approach to enlarge T cell respons es to several epitopes and to multiple isolates. We immunized macaques with a mixture of six plasmids reflecting the variability of Nef epitopic regio ns in the simian immunodeficiency virus (SIV) mac251 primary isolate. The N ef genes from viruses included in the SIVmac251 primary isolate were sequen ced and the six selected sequences were individually subcloned into the pCl vector, under cytomegalovirus enhancer/promoter control, and injected into macaques. We show that DNA immunization with Nef sequences induced interie ron-gamma (IFN-gamma) secreting cell responses directed against several reg ions of Nef. Reacting T cell lines were expanded in vitro and multispecific CTL responses mapping the 96-138 Nef region were analyzed. Several peptide s recognized by CTL were identified and studies using peptides reflecting t he variability of Nef indicated that all of the Nef variants were recognize d in the 96-138 region. Moreover, CTL responses were directed against an im munodominant epitope located in a functional region within the Nef protein that is essential for viral replication. This work shows that our approach of DNA immunization with several sequences induced multispecific T cell res ponses recognizing variants included in the SIVmac251 primary isolate. (C) 2001 Academic Press.