Identification of SIV env-specific CTL in the jejunal mucosa in vaginally exposed, seronegative rhesus macaques (Macaca mulatta)

We previously reported major histocompatibility complex Class I-restricted cytotoxic T lymphocytes (CTL) in jejunal lamina propria (LP) of monkeys following colonic exposure to subinfectious SIV doses. Those monkeys with strong mucosal CTL responses specific for simian immunodeficiency virus (SIV) envelope (env) were protected from later colonic challenge with a heterologous pathogenic virus dose. Here, env-specific CTL were similarly induced in jejunal LP in five of eight non-progesterone treated macaques that were vaginally exposed to SIV, but not infected. Subsequent vaginal challenge following progesterone treatment produced systemic infection. The only two monkeys that had jejunal env-specific CTL detectable post-challenge developed significantly lower plasma virus loads, and had delayed disease progression. Either vaginal or colonic exposure to subinfectious SIV doses can induce CTL detectable in jejunal LP. The association of such CTL with protection or delayed disease upon challenge suggests that successful vaccine protection against SIV/HIV may require CTL responses in the mucosa.