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 healthy HIV-1 uninfected, 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 as compared to treated individuals in LNs and a large proportion(up to 50%) of CD32+ cells co-expressed PD-1 and were enriched within T follicular helper cells(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 as 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 not enrichment of latently infected cells with inducible HIV-1 in CD32+ versus PD-1+ cells in 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 as compared to CD32-PD-1-(average 5.2 fold in treated and 86.6 fold in viremics), to CD32+PD-1-(2.2 fold in treated and 4.3 fold in viremics) and to CD32-PD-1+ cell populations(2.2 fold in ART treated and 4.6 fold in viremics). 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 while positively correlated with viremia. Therefore, the expression of CD32 identifies, independently of PD-1, a CD4 T cell population with persistent HIV-1 transcription and CD32 and PD-1 co-expression the CD4 T cell population with the highest levels of HIV-1 transcription in both viremic and treated individuals.\n\nImportanceThe 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 co-expressing CD32 and PD-1 identify a CD4 T cell population with high levels of persistent HIV-1 transcription.