High levels of CD2 expression identify HIV-1 latently infected resting memory CD4⁺ T cells in virally suppressed subjects

Resting memory CD4⁺ T cells are the largest reservoir of persistent infection in HIV-1-positive subjects. They harbor dormant, stably integrated virus despite suppressive antiretroviral therapy, posing an obstacle to a cure. Surface markers that identify latently infected cells remain unknown. Microarray analyses comparing resting latently infected and uninfected CD4⁺ T cells generated in vitro showed profound differences in the expression of gene programs related to transcriptional and posttranscrip- tional regulation, cell proliferation, survival, cycle progression, and basic metabolism, suggesting that multiple biochemical and metabolic blocks contribute to preventing viral production in latently infected cells. We identified 33 transcripts encoding cell surface markers that are differentially expressed between latently infected and uninfected cells. Quantitative reverse transcriptase PCR (RT-QPCR) and flow cytometry analyses confirmed that the surface marker CD2 was expressed at higher levels on latently infected cells. To validate this result in vivo, we sorted resting memory CD4⁺ T cells expressing high and low surface levels of CD2 from six HIV-1-infected subjects successfully treated with antiretroviral drugs for at least 3 years. Resting memory CD4⁺ CD2^high T cells from all subjects harbored higher HIV-1 DNA copy numbers than all other CD4⁺ T cell subsets. Moreover, after ex vivo viral reactivation, robust viral RNA production was detected only from resting memory CD4⁺ CD2^high T cells but not from other cell subsets. Altogether, these results show that a high CD2 expression level is a hallmark of latently infected resting memory CD4⁺ T cells in vivo.