Researchers report that antiretroviral therapy (ART) for HIV infection restores some immune defense against tuberculosis.

Neil W. Schluger and colleagues at Columbia University in New York City evaluated antituberculosis T-cell activity in a group of ART-treated patients. Researchers measured T-cell activity in 10 HIV patients, who tested negative for TB, before and every two months after ART was initiated. ART was associated with modest improvements in cell-mediated responses to TB infection.

ART was highly effective in reducing viral loads to undetectable or very low levels in this cohort. T-cell gamma interferon responses to in vitro TB exposure also improved, as did proliferative responses by peripheral blood mononuclear cells, the data showed. TB-induced production of cytokines other than gamma interferon did not change during ART, the authors reported. Their full report, "Reconstitution of Immune Responses to Tuberculosis in Patients with HIV Infection Who Receive Antiretroviral Therapy," was published in the journal Chest (2002;122(2):597-602).

The authors noted that the improvements were not seen until several months after the start of ART treatment, and did not quite reach the threshold of statistical significance. "ART restores immune responses to M. tuberculosis, although this restoration is delayed and does not reach levels seen in healthy, HIV-negative control subjects," Schluger and colleagues concluded. "These results may explain in part the phenomenon of paradoxic reactions to antituberculosis therapy in patients with HIV infection."

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