Tuberculosis treatment effect on T-cell interferon-γ responses toMycobacterium tuberculosis-specific antigens

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Abstract
The hypothesis that T-cell interferon-γ responses toMycobacterium tuberculosis-specific antigens decline as disease activity diminishes with tuberculosis (TB) treatment has generated interest in the interferon-γ release assays (IGRAs) as treatment-monitoring tools. We studied the effect of TB treatment on these responses as measured by the QuantiFERON-TB® Gold In-tube (QFT-IT) and T-SPOT.TB® assays.275 sputum culture-positive, HIV-uninfected pulmonary TB patients were tested with QFT-IT and T-SPOT.TB® at baseline, treatment completion and 6 months thereafter. The QFT-IT was also performed at the end of the intensive phase. The time-treatment effect on the qualitative and quantitative IGRA results was determined.There were significant declines in the positivity rates and quantitative results of both IGRAs with treatment. The QFT-IT positivity rate was significantly lower than the T-SPOT.TB®. The test reversion rate was significantly different for the two assays (13.9% for T-SPOT.TB®versus39.2% for QFT-IT). 79% and 46% tested positive with T-SPOT.TB® and QFT-IT respectively at 6 months post-treatment completion. The kinetics of the quantitative responses was not significantly different between subjects with and without risk factors for disease relapse.That a substantial proportion of patients remained test-positive after TB treatment would suggest a limited role of IGRAs as treatment monitoring tools.

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