Establishment and Reversal of HIV-1 Latency in Naive and Central Memory CD4+ T Cells In Vitro

The latent HIV-1 reservoir primarily resides in resting CD4 + T cells which are a heterogeneous population composed of both naive (T N ) and memory cells. In HIV-1-infected individuals, viral DNA has been detected in both naive and memory CD4 + T cell subsets although the frequency of HIV-1 DNA is typically higher in memory cells, particularly in the central memory (T CM ) cell subset. T N and T CM cells are distinct cell populations distinguished by many phenotypic and physiological differences. In this study, we used a primary cell model of HIV-1 latency that utilizes direct infection of highly purified T N and T CM cells to address differences in the establishment and reversal of HIV-1 latency. Consistent with what is seen in vivo , we found that HIV-1 infected T N cells less efficiently than T CM cells. However, when the infected T N cells were treated with latency-reversing agents, including anti-CD3/CD28 antibodies, phorbol myristate acetate/phytohemagglutinin, and prostratin, as much (if not more) extracellular virion-associated HIV-1 RNA was produced per infected T N cell as per infected T CM cell. There were no major differences in the genomic distribution of HIV-1 integration sites between T N and T CM cells that accounted for these observed differences. We observed decay of the latent HIV-1 cells in both T cell subsets after exposure to each of the latency-reversing agents. Collectively, these data highlight significant differences in the establishment and reversal of HIV-1 latency in T N and T CM CD4 + T cells and suggest that each subset should be independently studied in preclinical and clinical studies. IMPORTANCE The latent HIV-1 reservoir is frequently described as residing within resting memory CD4 + T cells. This is largely due to the consistent finding that memory CD4 + T cells, specifically the central (T CM ) and transitional memory compartments, harbor the highest levels of HIV-1 DNA in individuals on suppressive therapy. This has yielded little research into the contribution of CD4 + naive T (T N ) cells to the latent reservoir. In this study, we show that although T N cells harbor significantly lower levels of HIV-1 DNA, following latency reversal, they produced as many virions as did the T CM cells (if not more virions). This suggests that latently infected T N cells may be a major source of virus following treatment interruption or failure. These findings highlight the need for a better understanding of the establishment and reversal of HIV-1 latency in T N cells in evaluating therapeutic approaches to eliminate the latent reservoir.