Anti-feline immunodeficiency virus (FIV) soluble factor(s) produced from antigen-stimulated feline CD8+ T lymphocytes suppresses FIV replication

Feline immunodeficiency virus (FIV causes AIDS-like symptoms in infected cats. Concanavalin A (ConA)stimulated peripheral blood mononuclear cells (PBMC) from chronically FIV strain PPR-infected cats readily expressed FIV, In contrast, when PBMC from these animals were stimulated with irradiated, autologous antigen-presenting cells (APC), at least a 10-fold drop in viral production was observed. In addition to FIV-specific cytotoxic T lymphocytes, anti-FIV activity was demonstrated in the cell-free supernatants of effector T lymphocytes stimulated with APC. The FIV-suppressive activity was induced from APC stimulated PBMC of either FIV-infected or uninfected cats but not from ConA-stimulated PBMC. Suppression of FIV strain PPR replication was observed for both autologous and heterologous feline PBMC, was dose dependent, and demonstrated cross-reactivity and cell specificity. It was also demonstrated that the anti-FIV activity originated from CD8(+) T lymphocytes and was mediated by a noncytolytic mechanism.