Red blood cell distribution width as an easily measurable biomarker of persistent inflammation and T cell dysregulation in antiretrovirally treated HIV-infected adults

Background: Chronic inflammation and immune dysfunction occur in human immunodeficiency virus (HIV)-infection despite stable antiretroviral therapy (ART). Red blood cell distribution width (RDW) has been shown to correlate with markers of inflammation in non-HIV conditions. The study objective was to determine associations between RDW with cellular markers of immune activation and immune dysfunction including soluble inflammatory mediators in ART treated HIV infection. Methods: We performed a cross-sectional analysis of the Hawaii Aging with HIV-Cardiovascular study. RDW was defined as one standard deviation of RBC size divided by mean corpuscular volume multiplied by 100%. Correlations were analyzed between RDW, soluble inflammatory biomarkers and T cell activation (CD38+HLA-DR+), senescence (CD28-CD57+), and immune exhaustion (PD-1, TIGIT, TIM-3 expression). Results: Of 158 participants analyzed, median age was 50 years, duration of ART 12.6 years, virally suppressed 84.4%, and CD4 count 503 cells/mm3. Significant positive correlations were identified between RDW and soluble biomarkers including sICAM, IL-8, IL-6, SAA, TNF-alpha, sE-selection, fibrinogen, D-dimer, CRP, CD4/CD8 ratio, and frequency of multiple CD8 T-cell populations such as CD38+HLA-DR+T-cells, single TIGIT+, and dual expressing of TIGIT+PD1+, TIGIT+TIM3+, and TIM3+PD1+ CD8+ T-cell subsets (p < .05). Frequencies of CD38+HLA-DR+CD8+ T-cells and TIGIT+CD8+ T-cells remained significant adjusting for baseline variables (p < .01). Conclusion: Our study revealed correlations between RDW with systemic inflammatory biomarkers and CD8+ T-cell populations related to immune activation and exhaustion in HIV-infected individuals on ART. Further studies are warranted to determine the utility of RDW as a marker of immune dysregulation in HIV.