T cell expression of inhibitory receptors (IR) has been associated with measures of HIV persistence and immune responses to HIV. In a cohort of persons with HIV (PWH) with suppressed plasma viremia on ART for at least 4 years, we evaluated which specific combinations of IR were associated with HIV persistence and HIV-specific immune responses.
Using flow cytometry, we measured frequencies of CD4+ and CD8+ T cells expressing combinations of 6 different IR: PD1, PDL1, TIM3, CTLA4, TIGIT, LAG3. In samples from the same time points, we evaluated viral persistence, including residual viremia (by single copy assay; SCA), cell-associated RNA (CA-RNA), total HIV DNA (CA-DNA), and intact proviral DNA (IPD). Similarly, we assessed responses to HIV peptide pools (Gag, Pol, Env, Nef/Tat/Rev, Vif/Vpr/Vpu) and CMV/EBV by interferon gamma (IFN?) ELISPOT.
Participants (N=95) were on ART for a median of 6.8 years with median age of 48 (range 23-74) and a median CD4+ T cell count of 665 cells/mm3. We observed nominally significant correlations between CA-DNA (N=89) and the frequency of CD4+ T cells expressing PD1/TIM3 (r=0.26; p=0.013, Spearman), PD1/PDL1/TIM3 (r=0.26; p=0.014), and TIM3 alone (0.31; p=0.004). CA-DNA also correlated with %CD8+ T cells expressing PD1/TIM3 (r=0.21; p=0.045) and PD1/PDL1/TIM3 (r=0.23; p=0.033). The correlations of the frequency of T cells expressing these IR combinations were not evident with CA-RNA, SCA, or IPD (IPD assay N=42). CD8+ T cell expression of combinations of PD1, PDL1, TIM3, and TIGIT was associated with IFN? ELISPOT responses to Pol (r=0.23-0.27; p=0.021-0.046; N=73) and to Nef/Tat/Rev (r=0.23-26; p=0.029-0.046), but not to Gag and Env peptide pools. Frequencies of CD4+ T cells expressing IR combinations did not correlate with HIV-specific immune responses. None of the combinations of IR expressed on the T cells were associated with CMV or EBV-specific responses.
After long-term suppressive ART, multiple IR expression on CD4+ and CD8+ T-cells is associated with greater persistence of HIV-infected cells and stronger IFN? responses to specific HIV peptides. These seemingly contradictory findings suggest that persistent antigen expression from infected cells can stimulate both IFN? and IR expression, the net effect of which is failure to clear HIV-infected cells. Determining whether expression of specific combinations of IR facilitates HIV persistence is a priority.