CD32⁺ and PD-1⁺ Lymph Node CD4 T Cells Support Persistent HIV-1 Transcription in Treated Aviremic Individuals

A recent study conducted in blood has proposed CD32 as the marker identifying the "elusive" HIV reservoir. We have investigated the distribution of CD32⁺ CD4 T cells in blood and lymph nodes (LNs) of HIV-1-uninfected subjects and viremic untreated and long-term-treated HIV-1-infected individuals and their relationship with PD-1⁺ CD4 T cells. The frequency of CD32⁺ CD4 T cells was increased in viremic compared to treated individuals in LNs, and a large proportion (up to 50%) of CD32⁺ cells coexpressed PD-1 and were enriched within T follicular helper (Tfh) cells. We next investigated the role of LN CD32⁺ CD4 T cells in the HIV reservoir. Total HIV DNA was enriched in CD32⁺ and PD-1⁺ CD4 T cells compared to CD32^- and PD-1^- cells in both viremic and treated individuals, but there was no difference between CD32⁺ and PD-1⁺ cells. There was no enrichment of latently infected cells with inducible HIV-1 in CD32⁺ versus PD-1⁺ cells in antiretroviral therapy (ART)-treated individuals. HIV-1 transcription was then analyzed in LN memory CD4 T cell populations sorted on the basis of CD32 and PD-1 expression. CD32⁺ PD-1⁺ CD4 T cells were significantly enriched in cell-associated HIV RNA compared to CD32^- PD-1^- (averages of 5.2-fold in treated individuals and 86.6-fold in viremics), CD32⁺ PD-1^- (2.2-fold in treated individuals and 4.3-fold in viremics), and CD32^- PD-1⁺ (2.2-fold in ART-treated individuals and 4.6-fold in viremics) cell populations. Similar levels of HIV-1 transcription were found in CD32⁺ PD-1^- and CD32^- PD-1⁺ CD4 T cells. Interestingly, the proportion of CD32⁺ and PD-1⁺ CD4 T cells negatively correlated with CD4 T cell counts and length of therapy. Therefore, the expression of CD32 identifies, independently of PD-1, a CD4 T cell population with persistent HIV-1 transcription and coexpression of CD32 and PD-1, the CD4 T cell population with the highest levels of HIV-1 transcription in both viremic and treated individuals.IMPORTANCE The existence of long-lived latently infected resting memory CD4 T cells represents a major obstacle to the eradication of HIV infection. Identifying cell markers defining latently infected cells containing replication-competent virus is important in order to determine the mechanisms of HIV persistence and to develop novel therapeutic strategies to cure HIV infection. We provide evidence that PD-1 and CD32 may have a complementary role in better defining CD4 T cell populations infected with HIV-1. Furthermore, CD4 T cells coexpressing CD32 and PD-1 identify a CD4 T cell population with high levels of persistent HIV-1 transcription.