CTLA-4+PD-1− Memory CD4+ T Cells Critically Contribute to Viral Persistence in Antiretroviral Therapy-Suppressed, SIV-Infected Rhesus Macaques

Summary Antiretroviral therapy (ART) suppresses viral replication in HIV-infected individuals but does not eliminate the reservoir of latently infected cells. Recent work identified PD-1 + follicular helper T (Tfh) cells as an important cellular compartment for viral persistence. Here, using ART-treated, SIV-infected rhesus macaques, we show that CTLA-4 + PD-1 − memory CD4 + T cells, which share phenotypic markers with regulatory T cells, were enriched in SIV DNA in blood, lymph nodes (LN), spleen, and gut, and contained replication-competent and infectious virus. In contrast to PD-1 + Tfh cells, SIV-enriched CTLA-4 + PD-1 − CD4 + T cells were found outside the B cell follicle of the LN, predicted the size of the persistent viral reservoir during ART, and significantly increased their contribution to the SIV reservoir with prolonged ART-mediated viral suppression. We have shown that CTLA-4 + PD-1 − memory CD4 + T cells are a previously unrecognized component of the SIV and HIV reservoir that should be therapeutically targeted for a functional HIV-1 cure.