Patients with inefficient CD4+ T-cell recovery on virogically suppressive highly active antiretroviral therapy constitute a major clinical hurdle given the threat of HIV/AIDS disease progression. We show heightened circulating lipopolysaccharide associated with plasma enterobacterial DNA and highly activated Ki67+CD4+CD8+ in 24 immunologic-nonresponders (CD4+ T-cell < or = 200; HIV-RNA < or = 50) compared with 11 full responders (CD4+ T-cell > or= 400; HIV-RNA < or = 50). These data provide novel insight into INRs pathogenesis, since they correlate augmented systemic translocation of microbial bioproducts with T-cell hyperactivation.