The role of CD8-positive lymphocytes from HIV-1-seropositive individuals in the inhibition of HIV-1 replication in CD4-positive lymphocytes, either from HIV-1-seropositive or -seronegative individuals, has been described. It has been suggested that CD8-positive lymphocytes isolated from HIV-1-seropositive individuals are 'primed' against certain HIV-1 antigens, hence inducing HIV-1-specific resistance. In the present studies, we show that CD8-positive lymphocytes from HIV-1-uninfected individuals also induce a significant decrease in HIV-I replication from peripheral blood mononuclear cells (PBMC) acutely infected with HIV-1 in vitro. Unfractionated PBMC from 16 HIV-1-seronegative individuals were infected with HIV-1. In parallel experiments, PBMC from these individuals were depleted of CD8-positive lymphocytes. Viral replication was measured by a syncytia-formation assay, as well as by measuring HIV-1 p24 antigen levels in the culture supernatants on day 10 post-infection. Removal of CD8-positive lymphocytes resulted in the increased replication of HIV-1 in vitro. Reconstitution with syngeneic CD8-positive lymphocytes to CD8-positive lymphocyte-depleted wells resulted in significant decreases in HIV-1 replication. Reconstitution with allogeneic CD8-positive lymphocytes or supernatants from syngeneic or allogeneic CD8-positive lymphocyte cultures also resulted in some decrease in HIV-1 production, but it was not statistically significant. The status of HIV-1 replication in unfractionated, CD8-positive lymphocyte-depleted and CD8-positive lymphocyte-reconstituted PBMC cultures was further confirmed at the level of HIV-1 transcription. In situ hybridization of cultured cells, with a biotinylated HIV-1 gag probe, revealed increased numbers of cells actively transcribing HIV-1-specific RNA in the CD8-positive lymphocyte-depleted cell cultures, as compared with unfractionated PBMC. Thus, removal of CD8-positive lymphocytes from PBMC obtained from HIV-1-seronegative individuals resulted in a significant enhancement of HIV-1 replication in vitro.
