Long term non-progressor-derived CD4+ T Cell In-Vitro susceptibility to HIV-1 infection
Introduction: World over, there are antiretroviral therapy naïve individuals infected with HIV who maintain their CD4+T cell count above 500 cells/μl over 7-10 years (termed as Long Term Non-progressors, LTNP). A subset referred to as elite controllers (ECs) have undetectable viral load (<50 copies of HIV RNA/mL). Others referred to as viremic controllers (VCs) maintain their viral load between 50 and 2,000copies/ml. Mechanisms responsible for these phenotypes have not been fully elucidated. We hypothesized that LTNP-derived CD4+T cells predominantly memory cells are naturally resistant to HIV-1 infection by blocking R-5 tropic viral entry. In this study, we determined LTNP derived-CD4+T cells susceptibility to HIV-1 infection and compared the proportion of their memory CD4+T cells with progressors. Methods: We conducted a case-control study in which archived peripheral blood mononuclear cells (PBMCs) obtained from 30 LTNPs and 15 progressors were studied. CD4+T cells were purified using EasySep CD4+ positive selection kit (Stem Cell technology) followed by activation with IL-2 and anti-human CD28 on anti-human CD3 coated plates. Three days post activation, cells were spinoculated and co-cultured with VSV-G, R5 and X4-tropic HIV-1 encoded with eGFP/YFP for 3 days. Percentage expression of GFP/YFP by cells as a marker of CD4+T cell infection and the proportion of memory CD4+T cell subset (defined as CD4+CD45RO+T cells) in both groups were determined by flow cytometric analysis. Results: We demonstrated that a subgroup of LTNPs (13%, 4/30) possess CD4+T cells that are specifically resistant to R5-tropic HIV-1. There was no statistically significant difference in the proportion of memory CD4+T cells between LTNPs and progressors. Conclusion: Our study revealed a subset of Ugandan LTNPs whose CD4+T cells are intrinsically resistant to R5 tropic HIV-1. This cellular resistance was independent of the proportion of memory CD4+T cells. This novel phenotype may provide critical information for the design of effective HIV-1 vaccines and for the development of therapeutic strategies to induce a functional cure of HIV in the general population. Recommendations: Further research is needed to explore mechanisms of CD4+T cell resistance to R5 tropic HIV.