T-reg are the Predominant CD4+ T-Cell Subset Productively Infected with HIV-1 at Sites of Dual HIV/TB Infection

Abstract

Background: Regulatory T-cells (T-reg) are expanded during active tuberculosis (TB) regardless of HIV-1-infection, particularly at sites of M. tuberculosis infection. In HIV-1 disease, T-reg are targeted by HIV-1 infection. However, whether they contribute to promotion of HIV-1 infection at sites of HIV/TB is unknown. Methods: Pleural fluid mononuclear cells (PFMC) from HIV/TB patients with pleural TB were characterized by immunostaining and FACS analysis for surface markers CD4, CD127, CCR5, CXCR4 and intracellular expression of Foxp3, HIVp24, IFN-g and Bcl-2. T-reg purified by immunomagnetic bead separation were assessed for HIV-1 strong stop (SS) DNA expression by real-time PCR. Results: High numbers of T-reg (defined as CD4 + Foxp3 + or CD4 + Foxp3 + CD127 - ), that were HIV-1-infected were found in PFMC. T-reg displayed higher expression of the cellular activation marker, HLA-DR (p<0.001), and HIV-1 co-receptors (CCR5 and CXCR4) (p<0.05 for both) as compared to non-T-reg. Purified T-reg exhibited higher HIV-1 infection, as measured by HIV-1 SS DNA, when compared to whole PFMC, and as compared to PFMC T-reg from an HIV-infected subject with mesothelioma. HIV- infected CD4 + Foxp3 + T-reg were significantly higher in Bcl-2 expression as compared to CD4 + Foxp3 - cells (p<0.001). Further, HIV-1-infected T-reg showed significantly higher Bcl-2 reactivity than un-infected T-reg (p<0.001). A small fraction of HIV-1-infected T-reg were also IFN-g+ .