HIV-specific CD4+Th17 cells from HIV infected long-term non-progressors exhibit lower CTLA-4 expression and reduced apoptosis

Progressive HIV infection is marked with reduced frequency and impaired function of Th17 cells. Since T-cell functional responses are regulated by various inhibitory receptors; we examined the expression profile of CTLA-4, PD-1, Tim-3 and apoptotic marker: Caspase-3 on virus-specific Th17 cells from HIV-infected Long-Term Non-Progressors (LTNPs), chronic disease progressors and HIV-uninfected healthy controls (HC) using flowcytometry. Real-time PCR was done to analyze the mRNA expression of Th17 and Treg specific genes. LTNPs showed higher frequencies of HIV-specific Th17 cells; higher mRNA expression of IL-17, IL-22 while lower expression of IL-10; along with lower Caspase-3 expression than the progressors. Among inhibitory receptors, expression of CTLA-4 was 27 and 8 fold; PD-1 was 8 and 6 fold while Tim-3 was 7 and 6 fold higher in progressors and LTNPs respectively than HC. Among HIV-infected patients, LTNPs had 3-fold lower expression of CTLA-4 on HIV-specific Th17 cells than progressors (p = 0.06). Caspase-3+ve Th17 cells were associated with HIV-specific Th17 cells expressing CTLA-4 (r = 0.66;p < 0.0001), PD-1 (r = 0.40;p = 0.02) and Tim-3 (r = 0.35;p = 0.04). To conclude, virus-specific Th17 cells from LTNP maintained IL-17 production, expressed low levels of CTLA-4 and reduced apoptosis. The study suggests that such functional competence of Th17 cells could be one of the factors in maintenance of non-progressive HIV infection.