Expression of MHC class II in T cells is associated with increased HIV-1 expression

HIV-1 replicates in activated T cells at significantly higher levels than i n resting cells. Thus, certain molecules up-regulated during T cell activat ion appear to be important for HIV-1 replication. In this study, we present evidence suggesting that expression of MHC class II (class II) molecules o n CD4(+) T cells facilitate HIV-1 replication. T cells that expressed class II supported greater virus replication than T cells lacking class II. The class II+ cells, when either infected with HIV-1 or transfected with an env -minus HIV-1 provirus plasmid, produced 10-20-fold greater virus expression than class II- cells. Anti-class II antibody markedly inhibited virus expr ession in class II+ cells (but not class II- cells) and also decreased the nuclear binding activity of AP-1, an inducible transcription factor importa nt in T cell activation and HIV-1 expression. Most importantly, the inducti on of class II expression by transfection of the MHC class II transactivato r (CIITA) stimulated HIV-1 replication in Jurkat T cells. Taken together, t hese data suggest that expression of MHC class II molecules and/or CIITA in T cells enhances HIV-1 transcription.