CD27 and PD-1 expression patterns and exploratory ratio-based immunophenotypic indices in people living with HIV

Chronic immune activation and T-cell exhaustion persist in people living with HIV (PLWH) despite effective antiretroviral therapy (ART). We investigated CD27 and PD-1 expression and evaluated ratio-based indices as exploratory immunophenotypic indices related to T-cell differentiation and exhaustion. In this single-center, analytical cross-sectional study, 199 PLWH were categorized into BIC/FTC/TAF (n = 57), DTG/TDF/FTC (n = 51), DTG/3TC (n = 39), viremic (n = 22), and treatment-naive (n = 30) groups. CD27 and PD-1 expression on CD4⁺ and CD8⁺ T cells was assessed by flow cytometry. The CD4⁺CD27⁺/CD4⁺PD-1⁺ and CD8⁺CD27⁺/CD8⁺PD-1⁺ ratios were calculated and correlated with selected clinical and immunological parameters. Significant differences were observed in CD4⁺ T-cell count (p < 0.001), CD8⁺ T-cell count (p = 0.041), CD4⁺PD-1⁺ percentage (p = 0.022), CD8⁺CD27⁺ percentage (p = 0.004), and CD8⁺PD-1⁺ percentage (p = 0.001). The CD4⁺CD27⁺/CD4⁺PD-1⁺ ratio (p = 0.019) and CD8⁺CD27⁺/CD8⁺PD-1⁺ ratio (p = 0.010) were highest in the DTG/3TC group and lowest in treatment-naive individuals. Both ratios showed inverse correlations with age, diagnostic delay, and HIV RNA levels at diagnosis, whereas positive correlations were observed with baseline CD4/CD8 ratio. Higher CD27/PD-1 ratios were associated with more favorable immunological profiles and preserved immune balance. These ratio-based indices may have potential as exploratory immunophenotypic indices associated with immune status in PLWH and warrant further validation in prospective studies.