Identification of antigens of Mycobacterium tuberculosis using human monoclonal antibodies.

Pleural tuberculosis constitutes a human model of local protective immunity to mycobacterial infection as the disease is usually self-limited and recurrent pleurisy is rare. To identify potentially protective antigens of Mycobacterium tuberculosis, 37 human pleural fluid B cell clones were established using EBV and their supernatants assayed by ELISA and Western blot for antibody reactivity with M. tuberculosis sonicate and culture filtrate. One antibody identified 29,000, 31,000, and 33,000 bands in culture filtrate, and 31,000, 33,000, and 47,000 bands in sonicate; its species reactivity by ELISA was limited to M. tuberculosis. Eight antibodies identified a 31,000 band in culture filtrate and a 68,000 band in M. tuberculosis sonicate, suggesting recognition of a secreted antigen. The species crossreactivity of these eight antibodies extended to M. avium. Six antibodies identified multiple bands and had crossreactivity that included M. avium and M. kansasii. There was no reactivity with recombinant M. tuberculosis 65,000 antigen. Tuberculous pleurisy may prove useful in the identification of potentially protective mycobacterial antigens, particularly those secreted during active infection, and thus accessible to the human immune response.

Evaluation of an enzyme-linked immunosorbent assay (ELISA) using an IgG antibody to Mycobacterium tuberculosis antigen 5 in the diagnosis of active tuberculosis in children.

An enzyme-linked immunosorbent assay (ELISA) using Mycobacterium tuberculosis antigen 5 has been evaluated as a serodiagnostic test for active tuberculosis in children. Forty children of either sex, ages 1 to 14 yr, were studied, including 21 bacteriologically confirmed tuberculous patients and 19 control subjects who were evaluated for tuberculosis and found to be free of disease. At a 1:20 dilution, the test showed a sensitivity of 0.857 and a specificity of 1.000, with an accuracy value of 0.925, a positive predictive value of 1.000, and a negative predictive value of 0.864. The prevalence of disease calculated directly from the data of the study was found to be of 0.525. The geometric mean ELISA titer of the tuberculosis group was 1:58, and the difference in antibody titers between patient and control groups was found to be statistically significant (p less than 0.001). From our results, we conclude that ELISA using M. tuberculosis antigen 5 may be useful in those situations of high prevalence of disease when children suspected of tuberculosis are being evaluated.