Correlates of protection against SIVmac239 infection in rhesus macaques immunized with chimpanzee-derived adenovirus vectors

An efficacious vaccine to HIV-1 remains elusive. We tested two vaccine regimens based on prime-boosting with two chimpanzee-origin adenovirus (Ad) vectors (SAdV) of serotypes SAdV24 and SAdV23 or two distinct human serotype Ad vectors (HAdV), i.e., HAdV5 and HAdV26, expressing Gag and gp160 of SIVmac239 for induction of protection against repeated low dose rectal SIVmac251 challenges in Indian rhesus macaques (RMs). Animals were rendered seropositive to the HAdV vectors prior to vaccination. In RMs with non-controller genotypes, the SAdV vectors achieved significant reduction in viral acquisition. In RMs with controller genotypes, both vaccine regimens reduced set-point and peak viral loads and accelerated viral clearance. In SAdV-vaccinated RMs resistance against infection correlated with levels of circulating envelope (Env)-specific antibody (Ab) titers. In both vaccine groups CD8+T cells controlled viral loads upon infection. Circulating CD4+ and CD8+ T cells showed significant changes in their transcriptome over time following vaccination, which differed between the vaccine groups. T cells from SIV-resistant RMs had unique transcriptional profiles indicating that both follicular T helper (TFH) cell responses and highly activated CD8+ T cells may play a role in protection. Our results demonstrate that SAdV-based candidate AIDS vaccines provide protection from virus acquisition and replication in a stringent SIV challenge model in RMs and may thus outperform HIV-1 vaccines that have undergone large-scale clinical efficacy testing in humans. Samples were hybridized to Affymetrix GeneChip® Rhesus Macaque Genome Arrays. CD4+ and CD8+ T lymphocytes were collected by cell sorting from 103 Rhesus macaques. The data from 21 samples suggested low RNA quality and were excluded.