Background
Anti-PD-1 immunotherapy (API) can potentially reverse T-cell exhaustion, reinvigorate HIV-specific T-cell responses, and reduce the HIV reservoir in people living with HIV (PLHIV). API responsiveness is not direct associated with PD-1 expression on T-cells, suggesting that receptor heterogeneity might influence therapeutic outcomes. Therefore, we aimed to assess 1. whether PD-1 expression varies among T-cells subsets, 2. which host factors contributed to PD-1 heterogeneity, 3. correlate PD-1 expression with cell functionality.
Methods
High-dimensional flowcytometric PD-1 measurements from viral suppressed PLHIV using ART of the 2000HIV cohort (NCT03994835) were analyzed, separated into discovery cohort (n=1147) and validation cohort (n=225). We assessed percentages and MFI of PD1 in 21 T-cell subsets (Tc). Participants were categorized into high, intermediate, and low consistent PD-1 expression groups when >75% of Tc had PD-1 values in one of the following tertiles of PD-1 distribution, T3, T2 and T1 respectively. We explored the relationship of PD-1 expression with clinical and HIV-related factors as well as ex-vivo PBMC cytokine production capacity after stimulation using Spearman-rank correlation analysis.
Results
Less than 40% of the participants had a consistent PD1 expression (both proportions and MFI) across Tc evaluated, regardless of the category. Lower percentage of exhausted CD4Tc was significantly correlated with female sex, high CD4 nadir, COVID-19 vaccination, and spontaneous HIV control (HIC) phenotype, while higher percentage of exhausted cells was significantly correlated with older age, immunological non-responders (INR) phenotype, CMV titers and larger HIV reservoir size (Fig.A). Exhausted CD8+ naïve Tc were linked to older age, CMV titers and intact HIV reservoir. Higher PD-1 expression on CD4 Tc was negatively correlated with IFN-γ, IL-17, IL-22, and IL-10 secretion upon microbial stimulation (Fig.B, FDR < 0.05, discovery; p < 0.05, validation).
Conclusions
PLHIV exhibited a heterogeneous PD-1 expression across all Tc subsets, which negatively impacted cytokines production, indicating immune exhaustion. Notably, our study suggests that PLHIV with higher CMV reactivity, higher HIV reservoir size, males and immunological non-responders show highest PD-1 expression and may react differently to API than other groups. A careful consideration of clinical host factors and functional immune response is crucial for an effective API in PLHIV.