Association of Anisocytosis with Markers of Immune Activation and Exhaustion in Treated HIV

Background: Treated HIV infection is associated with heightened inflammation which can contribute to increased risk of cardiovascular disease (CVD). We have previously shown that anisocytosis, as measured by red cell distribution width (RDW), is independently associated with prevalent CVD in people living with HIV (PLHIV). In this study, we sought to identify immune correlates of RDW in PLHIV receiving antiretroviral therapy.

Methods: We performed a cross-sectional and longitudinal analysis of 147 virally-suppressed PLHIV, who had LDL < 130 mg/dL and evidence of heightened inflammation, in a randomized trial of statin therapy. A complete blood count and biomarkers of inflammation and immune activation/exhaustion were measured in peripheral blood at entry and after 24 and 48 weeks. Associations with RDW were estimated using linear regression and linear mixed models.

Results: The median age (IQR) for the cohort at enrollment was 46 (40-53) years; 78% were male and 68% were African American. The median RDW for the cohort was 13.4% (12.9-14.0). Compared with the lowest RDW tertile, patients in the highest tertile were less likely to be male, and more likely to be African American, have lower hemoglobin, lower mean corpuscular volume, and higher platelet counts (all P < 0.05). At baseline, RDW weakly correlated with C-reactive protein (r = 0.196), d-dimer (r = 0.214), fibrinogen (r = 0.192), IL-6 (r = 0.257), CD4+DR+38+ T cells (r = 0.195), and CD4+PD1+ T cells (r = 0.227), all P < 0.05. Only IL-6, CD4+38+DR+ T cells, and CD4+PD1+ T_cells remained associated after adjustment for clinical factors known to affect RDW in the general population. Over 48 weeks, RDW did not change and there was no significant effect of statin (P = 0.45). After adjustment for clinical parameters, RDW remained positively associated with CD4+38+DR+ and CD4+PD1+ T cells across all time points (P = 0.05).

Conclusion: In this population of treated HIV+ subjects, anisocytosis was associated with biomarkers of inflammation and T-cell activation/exhaustion over time and independent of clinical confounders. Therefore, RDW may be a useful prognostic biomarker of cardiovascular risk that partially reflects chronic inflammation and immune exhaustion in PLHIV receiving antiretroviral therapy.