Noncytotoxic suppression of human immunodeficiency virus type 1 transcription by exosomes secreted from CD8+ T cells.

CD8(+) T cells display a noncytotoxic activity that suppresses transcription of human immunodeficiency virus type 1 (HIV-1) in an antigen-independent and major histocompatibility complex-unrestricted manner. To date, the precise cellular and molecular factors mediating this CD8(+) T-cell effector function remain unsolved. Despite evidence indicating the dependence of the activity on cell-cell contact, the possibility of a membrane-mediated activity that represses transcription from the viral promoter remains unexplored.