The mechanisms underlying abnormalities in B cell maturation and antibody response in HIV-1 infection have been only partially elucidated. The large majority of the studies have been performed in blood B cells while limited information is available on B cell populations in lymph nodes and on the association between the functional profile of T follicular helper (Tfh) cells and the maturation of B cell populations in lymph nodes.
In the present study, we have investigated the phenotype and function of T follicular helper cells (Tfh) and B cells in lymph nodes of healthy and HIV-1 infected individuals using cutting-edge technologies such as mass cytometry and single cell gene expression. Lymph node biopsies were obtained from 21 HIV-1 infected viremic individuals naive to antiretroviral therapy and 18 healthy HIV negative individuals undergoing surgery for vascular pathologies or herniorrhaphy. Lymph node mononuclear cells (LNMC) were stimulated with phorbol-12-myristate-13-acetate (PMA) and ionomycin for 6 hours and stained with a unique panel of 32 markers primarily defining memory CD4 T cell and B cell populations including antibodies measuring differentiation, trafficking receptors and function.
In HIV-1 infected individuals, we demonstrate a significant increase (2-3 fold) in the Tfh cells defined by the CXCR3+T-bet+ phenotype and IFN-γ production along with a significant decrease (2-3 fold) in Tfh cells expressing CCR4, CCR6 and producing IL-4. The CXCR3, T-bet and IFN-γ signatures of Tfh cells in HIV infection were strongly associated with the appearance of memory B cells expressing CXCR3 and T-bet, which accounted for 30% of memory B cells. CXCR3+ B cells had decreased expression of CXCR4 and CXCR5 and antibody production by CXCR3+ cells was different both quantitatively, e.g. higher producer cells, and qualitatively, e.g. lower levels of hyper somatic mutations, as compared to CXCR3- B cells. We then identified IFN-γ as the causative factor inducing the differentiation of the CXCR3+T-bet+ memory B cells and as a strong suppressive factor of antibody production.
The identification of Th1-like Tfh cells and IFN-γ as the main mechanisms affecting B cell maturation and antibody production in HIV infection will provide novel insights into strategies to develop optimal antibody responses in HIV infection and following vaccination.