Tetraspanin CD63 is a regulator of HIV-1 replication.

Macrophages and CD4(+) T-cells are the major reservoirs for HIV-1 infection. CD63 is a tetraspanin transmembrane protein, which has been shown to play an essential role during HIV-1 replication in macrophages. In this study, we further confirm the requirement of CD63 in HIV-1 replication events in primary human CD4(+) T-cells, dendritic cells, and a CD4(+) cell line. Most interestingly, we also show the evidences for the co-localization and internalization of CD63 and HIV-1 major receptor CD4 in primary human macrophages and CD4(+) cell line by confocal microscopy and Co-Immunoprecipitation assay. Analysis revealed that CD63-depleted CD4(+) T-cells, dendritic cells, and a cell line showed significant decrease in HIV-1 production. Further analysis showed that CD63 down regulation reduced production of the early HIV protein Tat, and affected HIV protein Gag by CD63-Gag interaction. In agreement, CD63 silencing also inhibited production of the late protein p24. Furthermore, we revealed that CD63 silencing has no effect on HIV-1 replication with extensive viral challenge (MOI > 0.2). These findings suggest that CD63 plays a dual-role both in early and late HIV-1 life cycle with a range of HIV-1 infection (MOI < 0.2).