A novel chimeric Rev, Tat, and Nef (Retanef) antigen as a component of an SIV/HIV vaccine

The human immunodeficiency virus type 1 (HIV-1) regulatory proteins Rev, Tat, and Nef are expressed at early time post-infection and represent attractive targets to be included in a vaccine candidate for AIDS. However, the putative immunosuppressive activities of some of these proteins may limit their immunogenicity. To circumvent these issues, a novel chimeric polyprotein vaccine candidate (Retanef), comprising genetically modified and re-assorted rev, tat, and nef open reading frames of simian immunodeficiency virus (SIV), was constructed and optimized for its expression in mammalian cells. Retanef encodes a protein of approximately 55 kDa localized primarily in the cytoplasm of transfected cells. The Retanef gene expressed in context of an eucaryotic expression vector (DNA-SIV-Retanef) or cloned into a highly attenuated poxvirus-based NYVAC vector (NYVAC-SIV-Retanef) was used to immunize either naive rhesus macaques or macaques chronically infected with SIVmac251 undergoing anti-retroviral therapy (ART). Three immunizations of naive macaques with DNA-SIV-Retanef followed by a single NYVAC-SIV-Retanef boost induced a response to the Mamu-A*01-restricted Tat epitope (Tat_SL8, TTPESANL) demonstrated by staining with a specific tetramer and by direct cytolytic activity assays, as well as responses to Rev, Tat and Nef proteins demonstrated by ELISPOT assays using overlapping peptide pools encompassing the entire proteins. Immunization of infected macaques with either DNA-SIV-Retanef or NYVAC-SIV-Retanef expanded the frequency of Tat-specific tetramer-staining cells by two- to seven-fold. No adverse effects were observed in either naive or SIV-infected rhesus macaques. Thus, an analogous HIV-1-based chimeric vaccine may represent useful component of an HIV-1 vaccine. Published by Elsevier Science Ltd.