Latent Tuberculosis Infection Treatment and T-Cell Responses to Mycobacterium tuberculosis–specific Antigens

Rationale: There is currently no available test for monitoring the effect of treatment of latent tuberculosis infection (LTBI) to indicate cure or predict risk of subsequent progression to disease.Objective: We used the T-SPOT.TB assay, which measures T-cell interferon-γ responses to the Mycobacterium tuberculosis–specific peptides early secretory antigenic target 6-kD protein (ESAT-6) and culture filtrate protein 10 (CFP-10), to determine the effect of LTBI treatment on these responses.Methods: A total of 226 tuberculosis contacts with positive T-SPOT.TB results underwent repeat testing on LTBI treatment completion. The majority (96%) received 6 months of isoniazid. The pre- and post-treatment T-SPOT.TB results were analyzed according to the combined and separate responses to ESAT-6 and CFP-10 antigens.Results: The T-SPOT.TB reverted to negative in 85 (37.6%) contacts at treatment completion. Treatment had a significant effect on the response to CFP-10 (p < 0.001; reversion rate, 48.6%), but not on the r...