Robust reconstitution of TB-specific polyfunctional CD4+ T-cell responses and rising systemic IL-6 in paradoxical TB-IRIS.

Background. The immunopathogenesis of paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) remains unclear. We determined the association between pathogen-specific T-cell responses and development of paradoxical TB-IRIS on antiretroviral therapy (ART). Methods. This study was nested within a prospective cohort study of HIV-infected patients with active pulmonary tuberculosis and baseline CD4 counts <= 125 cells/mu L initiating ART. T-cell immune activation (CD38, HLA-DR, and PD-1 expression), phenotype, and polyfunctional pathogen-specific cellular immune responses prior to and 4 weeks after ART initiation were determined by flow cytometry. Patients with TB-IRIS were compared to non-IRIS controls using chi(2) and rank-sum tests and logistic regression. Results. TB-IRIS patients and controls had similar CD4 counts, levels of T-cell-associated immune activation, frequencies of T-cell memory subsets, and frequencies of interferon gamma (IFN-gamma(+))/interleukin 2 (IL-2(+))/tumor necrosis factor alpha (TNF-alpha(+)) CD4(+) T-cells prior to ART initiation. After ART initiation, cellular immune activation and T-cell subsets also were similar in TB-IRIS patients and controls. In contrast, TB-IRIS patients had significantly greater early increases in the frequency of tuberculosis-specific polyfunctional IFN-gamma(+)/IL-2(+)/TNF-alpha(+) CD4(+) T-cells on ART (P =.02); each quartile increase in the percentage of these cells was independently associated with a 2.8-fold increased risk of TB-IRIS (95% confidence interval, 1.1 to 7.5-fold). In a secondary analysis, patients with TB-IRIS had rapid, concomitant increases in tuberculosis-specific adaptive immune responses and interleukin 6 (IL-6) levels, whereas controls with similarly rapid increases in cellular immune function had IL-6 levels that tended to decrease on ART. Conclusions. Rapid expansion of tuberculosis-specific polyfunctional CD4(+) T-cell responses, likely linked to increases in IL-6, is associated with development of paradoxical TB-IRIS.