HIV‐infected CD4+ T Cells Use T‐bet‐dependent Pathway for Production of IL‐10 Upon Antigen Recognition

Interleukin (IL)‐10 has been implicated in persistence of pathogens in a number of chronic infections. Infected CD4+ cells upon reactivation with HIV antigens were also shown to produce IL‐10, which might contribute to their persistence. Hence, it is crucial to determine mechanisms regulating IL‐10 production after activation with HIV antigens for devising effective blocking strategies. In this study, ERK‐, T‐bet‐ and FoxP3‐dependent pathways were evaluated for their possible roles in IL‐10 production by infected CD4+ cells after reactivation with HIV Env. Intracellular and secreted IL‐10 levels were determined by flow cytometry and Bioplex assay after treating PBMCs with PD98059, tipifarnib and cyclosporin A for blocking of ERK‐, T‐bet‐and FoxP3‐dependent pathways, respectively. Baseline levels of T‐bet, pERK were higher in P24+ CD4+ cells as compared to uninfected CD4+ cells, which increased further after activation with Env. Inhibition of T‐bet resulted in 2.3‐fold reduction of IL‐10 expression whereas ERK and FoxP3 inhibition failed to cause suppression of IL‐10 expression. Conversely, IL‐10 secreted by PBMCs was inhibited maximally after ERK inhibition suggesting its role in regulation of cytokine secretory pathway. IFN‐γ was found to be suppressed after treatment with inhibitors of all these pathways. Thus, the study highlighted need for IL‐10 blockade along with the use of antigens for therapeutic vaccinations or latency reversal and identified the T‐bet‐dependent pathway as an important pathway regulating IL‐10 production by infected CD4+ cells. However, simultaneous blockade of IFN‐γ precludes use of inhibitor of this pathway as an IL‐10 blocking strategy.