High CD45 expression of CD8+ and CD4+ T cells correlates with the size of HIV-1 reservoir in blood.

Using mass cytometry, we investigated the expression of 28 markers on CD8+ and CD4+ T cells from HIV-1 infected patients with a variable size of HIV-1 reservoir defined as high (HR) and low (LR) reservoir; we aimed at identifying phenotypic associations of T cells with size of HIV-1 reservoir. We showed that the frequency of CD45+ CD8+ and CD4+ T cells was directly proportional to the size of HIV-1 reservoir; HR patients had a significantly larger frequency of blood CD45high T cells and higher CD45 expression on both CD8+ and CD4+ T cells. CD45 is a receptor-type protein tyrosine phosphatase essential in TCR signaling. Functional and phenotypical analysis of CD45high cells revealed that they express activation and proliferation markers (CD38 + HLA-DR + and Ki-67) and produce cytokines upon in vitro activation. CD45high T cells also expressed high levels of immune check-point PD-1. Our results link CD45 expression on T cells to HIV-1 reservoir; PD-1 expression on CD45high T cells may contribute to their exhaustion.