Downregulation of CXCR5 in CD27^- B cells of HIV-1 infected patients

The CD27^- (naive) B cells of HIV-1 infected patients have been shown to be increased in frequency and to be activated, as indicated by high CD38 expression on the cell surface. CXCR5, a B cell chemokine receptor, is expressed on circulating CD27^- (naive) B cells and plays a pivotal role in peripheral B cell development. To investigate the effect of HIV-1 infection on the expression of this chemokine receptor on naive B cells, the expression level of CXCR5 on CD27^- B cells was examined in 19 drug-naive HIV-1 infected patients, 27 HAART-treated patients, and 20 controls. CXCR5 expression on CD27^- B cells was significantly lower in drug-naive patients than in HAART-treated patients and controls (P<0.01). CD27^- B cells with high CD38 expression exhibited low CXCR5 expression. The CXCR5 expression level on CD27^- B cells recovered to within the normal range after effective antiretroviral therapy. These findings suggested that HIV-1 infection induces a remarkable phenotypic alteration of naive B cells and that the activated naive B cells found in HIV-1 infection down-regulate CXCR5 on their surface. Impaired homing of naive B cells may contribute to HIV-1 induced immunological deficiencies.