CD8+ cell-derived anti-human immunodeficiency virus inhibitory factor

CD8+ cells in human immunodeficiency virus (HIV)-infected individuals develop the ability to control HIV replication not only by destruction of the infected cells but also by controlling the virus in a noncytotoxic fashion that leaves the infected cell functionally intact. The CD8+ noncytotoxic response is mediated by a novel soluble factor known as CD8+ cell antiviral factor (CAF). CAF suppresses HIV replication in the infected cell at the level of viral transcription by interrupting the ability of Tat or host cellular factors to interact with the HIV long terminal repeats. Unlike some strain-specific anti-HIV cytokines, CAF is active against many different virus isolates, including HIV strains that are nonsyncytium- and syncytium-inducing. Of importance, the ability of CD8+ cells to produce CAF and suppress HIV replication plays a critical role in preventing disease progression following HIV infection.