6-Mercaptopurine inhibits HIV expression and improves CD4+ T cell immune function by downregulating mTOR

Background The persistence of the immunodeficiency virus (HIV) reservoir and chronic immune activation and inflammation are major obstacles to achieving a functional cure for AIDS. Despite antiretroviral therapy (ART), some patients still experience inadequate immune reconstitution. Recent studies suggest that dysregulated purine metabolism is associated with HIV disease progression, but its underlying mechanism and therapeutic implications are unclear. Methods We integrated single-cell sequencing data of peripheral blood mononuclear cells (PBMCs) from people living with HIV (PLWH) with public database analysis to identify key metabolic pathways. Using an HIV latency model (J-Lat 10.6) and primary PBMCs from ART-treated PLWH, we evaluated the effects of the purine antimetabolite 6-mercaptopurine (6-MP) on viral suppression and immune modulation via quantitative viral outgrowth assay (qVOA), flow cytometry, western blotting, Seahorse metabolic analysis, and molecular docking simulations. Results The purine metabolic pathway was significantly upregulated in immunological non-responders (INRs). 6-MP treatment not only effectively suppressed HIV replication (reducing viral RNA, p24 protein, and infectious viral particles) but also reduced basal HIV expression without exogenous stimulation, exhibiting characteristics of a latency-promoting agent (LPA) in a "Block and Lock" strategy. More importantly, 6-MP significantly improved immune function: it increased the CD4⁺ T cell proportion, optimized the CD4/CD8 ratio, and suppressed key pro-inflammatory cytokines (TNF-α, IFN-γ). Mechanistic studies revealed that 6-MP and its active metabolite TIMP (6-thioinosinic acid) directly bind to and inhibit mTOR kinase activity, leading to a global downregulation of cellular energy metabolism (reduced OCR and ECAR) and deprivation of resources essential for viral replication. The mTOR agonist MHY1485 can reverse all potential effects of 6-MP, confirming the central causal role of the mTOR pathway. Furthermore, 6-MP demonstrated synergistic effects when combined with ART drugs (DTG/FTC/TAF). Conclusion Our study repurposes 6-mercaptopurine as a dual-function agent acting through direct mTOR inhibition, concurrently providing antiviral and immunomodulatory benefits. Given its established clinical safety profile, our work provides a solid mechanistic foundation for considering 6-MP as an adjunctive therapy to ART to reduce the viral reservoir and promote immune reconstitution.