Understanding the mechanisms underlying the establishment, persistence, and location of the HIV latent reservoir is a key step for developing cure interventions. T-cell activation and HIV reservoir size are higher in rectal tissue and lymph nodes (LN) compared with peripheral blood mononuclear cells (PBMC). However, the relative contribution of CD4 T cell subsets to this anatomic difference is unknown and it could identify critical targets for an intervention. We sought to identify the relationship between PBMC and LN HIV DNA and activation markers on key T cell subsets: naïve, central memory (CM), transitional memory (TM) and effector memory (EM).
T cell subsets were sorted from 32 people with HIV on ART, including 11 with matched PBMCs and LN, 5 virologically suppressed immunologic responders (IR, CD4 cell count >500 cells/?L <2 years after ART initiation) and 6 virologically suppressed suboptimal responders (ISR, CD4 cell count <500 cells/?L <2 years after ART initiation). We measured HIV DNA, PD-1 and CD38+HLA-DR+expression on T cell subsets.
Total HIV DNA was significantly higher in all CD4 T cell subsets from LN compared with those from PBMCs, except for the naïve subset (CM p=0.002; TM p=0.02, EM p=0.002). For subgroups, this difference was significant in CM and TM of ISR while only significant in EM of IR (Figure 1A,B). PD-1 expression was significantly higher in naïve and CM CD4 from LN compared with PBMC (Figure 1C). This difference was maintained in ISR, while IR had significantly higher LN levels of PD1 expression on CM and TM subsets (p=0.016, p=0.047, respectively). Expression of PD-1 on CD8 T-cells was significantly higher in all subsets derived from LNs as compared to PBMC. Similarly, CD38+HLA-DR+ was significantly higher in CD4 T-cells from LNs compared with those from PBMC in all subsets (naïve p=0.011; CM p=0.005; TM p=0.049) except for EMs and mainly driven by ISR participants (Figure 1D). The same differences were seen in CD38+HLA-DR+ for CD8+ T cells but these were mainly driven by IR participants.
HIV-DNA content, T cell immune activation and PD-1 expression, particularly for long-lived CD4 T-cell subsets such as CM and TM, are higher in LN than PBMCs. The differences in those parameters between the two anatomic compartments are further pronounced in or specific for ISR, thus highlighting increased residual disease in LN as a critical feature of and a potential mechanism for individuals with poor CD4 T cell reconstitution during ART.