Antibody response to culture filtrate antigens of Mycobacterium tuberculosis during and after treatment of tuberculosis patients

SETTING: Many authors have shown rising titres of antimycobacterial antibod ies after a few months of antituberculosis treatment. This humoral response might persist for years, making the discrimination between current and old disease difficult. OBJECTIVE: Characterisation of the humoral response to culture filtrates of Mycobacterium tuberculosis before and after treatment of tuberculous patie nts in order to identify those antigens that could provide information abou t disease activity. METHODS: Anti-mycobacterial IgG response was determined during and after tr eatment of tuberculous patients by ELISA and immunoblot. Serum was taken fr om 71 active tuberculous patients (59 newly acquired and 12 relapse), 15 ol d tuberculous patients and 45 nontuberculous control subjects. RESULTS: By ELISA, antibody response increased after 2 months of treatment. After chemotherapy was completed, the estimated number of antibodies remai ned at the same level. The level of specific antibodies in patients seems t o reach the same level as that of control subjects 3 years after initiation of treatment. In Western blot, although each patient serum had its own cha racteristic banding pattern, differences between tuberculous patients and c ontrol subjects were found in the area below 20 kDa. Serum from tuberculous patients showed high levels of antibodies at the 14 kDa region. After the beginning of treatment, the intensity of the 14 kDa region band and the per centage of positive recognition tended to decrease. Therefore, one year aft er initiation of treatment, only seven of 13 cases who demonstrated antimyc obacterial antibodies in ELISA revealed a mild but still positive reaction at the 14 kDa region; this reactivity disappeared 2 years after initiation of chemotherapy. CONCLUSIONS: The 14 kDa region antigen seems to induce a humoral response t hat evolves in relation with the disease activity.