Increased negative immune checkpoint receptors (NCR) on T cells are linked to T cell exhaustion, dysfunctional effector responses, and HIV viral persistence. Metformin, an oral hypoglycemic agent used for diabetes, may have previously unrecognized beneficial immunologic effects. Using cryopreserved blood from a 24-week pilot study involving 12 virally suppressed HIV-infected individuals randomized 1:1 to metformin versus observation (OBS), we assessed change in the frequencies of T cell activation (CD38+HLA-DR+) and NCR [programmed cell death protein 1 (PD1), T cell immunoreceptor with Ig and ITIM domains (TIGIT), and T cell mucin-domain containing-3 (TIM3)]. No differences in 24-week change were seen between arms in CD4 or CD8 T cells, in the CD4/CD8 ratio, or in activated (CD38+HLA-DR+) CD4 or CD8 T cells. However, metformin over 24 weeks led to decreases compared with OBS in single PD1+ (percent decrease: -9.6% vs. 7.5%, p = .015), in dual PD1+TIGIT+ (-15.0% vs. 10.4%, p = .002), and in triple PD1+TIGIT+TIM3+ (-24.0% vs. 8.1%, p = .041) CD4 T cells. Metformin led to no changes in CD8 T cell NCR frequencies. Metformin decreases the frequency of PD1+, PD1+TIGIT+, and PD1+TIGIT+TIM3+ expressing CD4 T cells. This may have relevance to HIV cure strategies and to efforts to mitigate the risk of chronic complications of HIV.
Keywords: CD4 T cell; metformin; negative immune checkpoint receptors.