Altered expression of the tetraspanin CD81 on B and T lymphocytes during HIV‐1 infection

Summary CD81 is a member of the tetraspan superfamily and plays a role in immune responses and in hepatitis C virus (HCV) pathogenesis. We analysed CD81 cell surface and mRNA expression in different lymphocytic subpopulations in human immunodeficiency virus (HIV)‐1, HCV and dually infected subjects. CD81 cell surface expression was evaluated with fluorescence activated cell sorter (FACS) analysis; mRNA quantification was performed with semiquantitative polymerase chain reaction (PCR). CD81 cell surface expression on CD4 + T lymphocytes was significantly different by analysis of variance ( anova ) test ( P  < 0·001), with reduced expression in HIV‐1 + patients. In B lymphocytes, higher cell surface expression was present in HIV‐1, in HCV and in dually infected subjects compared to healthy controls. CD81 expression on B lymphocytes showed a positive correlation with plasma HIV‐RNA. CD81 mRNA levels in B lymphocytes were significantly higher in HIV‐1 + patients compared to healthy controls. The potential consequence of the down‐regulation of CD81 in CD4 + cells during HIV‐1 infection in conjunction with diverted CD28, CD4 and CD3 expression is the disruption of T cell function. Increased CD81 expression on B lymphocytes might explain the higher prevalence of lymphoproliferative disorders in HIV‐1 and HCV infection. Up‐regulation of CD81 mRNA on CD4 + T cells indicates that down‐regulation of CD81 occurs at the post‐transcriptional/translational level.