TTV Species Diversity as a Novel Biomarker of Immune Dysregulation in Aging

Torquetenovirus (TTV) is a prevalent virus whose clinical significance remains unclear, potentially linked to immunosenescence. This study examines TTV species in relation to immune impairment, inflammation, and cellular stress response in aging. A subset of recruited age-stratified individuals (RASIG) from the MARK-AGE study was divided into three groups: Cohort 1 A (healthy young adults), Cohort 1B (older adults with mild immune decline), and Cohort 1 C (older adults with marked immune impairment). Analyses included TTV load, species diversity, lymphocyte subpopulations, inflammatory markers, Poly-(ADP-ribose) polymerase (PARP-1) expression/activity. Alpha- and beta-diversity analyses showed the highest TTV species diversity in Cohort 1 C, with significant cohort-dependent differences and partially cohort-specific clustering patterns. Increased TTV species number correlated with higher TTV load, elevated CMV IgG levels, and greater immune impairment risk. Specific TTV species were associated with CD4/CD8, and reduced T-cell receptor excision circles, suggesting impaired T-cell homeostasis. TTV viremia positively correlated with C-reactive protein (CRP) and α2-macroglobulin. PARP-1 expression and activity increased in individuals with higher TTV diversity, particularly in the presence of TTV9 and TTV20. TTV load and species diversity are associated with immunosenescence, inflammation, and PARP-1 activation suggesting their potential as biomarkers of age-related immune decline. Longitudinal studies are needed to clarify underlying mechanisms.