Naive CD4+T Cells Harbor a Large Inducible Reservoir of Latent, Replication-competent Human Immunodeficiency Virus Type 1

Background. The latent human immunodeficiency virus type 1 (HIV-1) reservoir represents a major barrier to a cure. Based on the levels of HIV-1 DNA in naive (T-N) vs resting memory CD4+ T cells, it is widely hypothesized that this reservoir resides primarily within memory cells. Here, we compared virus production from T-N and central memory (T-CM) CD4+ T cells isolated from HIV-1-infected individuals on suppressive therapy. Methods. CD4+ T-N and T-CM cells were purified from the blood of 7 HIV-1-infected individuals. We quantified total HIV-1 DNA in the CD4+ T-N and TCM cells. Extracellular virion-associated HIV-1 RNA or viral outgrowth assays were used to assess latency reversal following treatment with anti-CD3/CD28 monoclonal antibodies (mAbs), phytohaemagglutinin/interleukin-2, phorbol 12-myristate 13-acetate/ionomycin, prostratin, panobinostat, or romidepsin. Results. HIV-1 DNA was significantly higher in T-CM compared to T-N cells (2179 vs 684 copies/10(6) cells, respectively). Following exposure to anti-CD3/CD28 mAbs, virion-associated HIV-1 RNA levels were similar between T-CM and T-N cells (15 135 vs 18 290 copies/mL, respectively). In 4/7 donors, virus production was higher for T-N cells independent of the latency reversing agent used. Replication-competent virus was recovered from both T-N and T-CM cells. Conclusions. Although the frequency of HIV-1 infection is lower in T-N compared to T-CM cells, as much virus is produced from the T-N population after latency reversal. This finding suggests that quantifying HIV-1 DNA alone may not predict the size of the inducible latent reservoir and that T-N cells may be an important reservoir of latent HIV-1.