Humoral response to low molecular weight antigens of Mycobacterium tuberculosis by tuberculosis patients and contacts.

Much effort has been devoted to the identification of immunologically important antigens of Mycobacterium tuberculosis and to the combination of target antigens to which antibodies from serum of tuberculous patients could react specifically. We searched for IgG antibodies specific for antigens of 45 to 6 kDa obtained after sonication of the well-characterized wild M. tuberculosis strain in order to detect differences in the antibody response to low molecular weight antigens from M. tuberculosis between patients with pulmonary tuberculosis and contacts. Specific IgG antibodies for these antigens were detected by Western blot analysis of 153 serum samples collected from 51 patients with confirmed pulmonary tuberculosis. Three samples were collected from each patient: before therapy, and after 2 and 6 months of treatment. We also analyzed 25 samples obtained from contacts, as well as 30 samples from healthy individuals with known tuberculin status, 50 samples from patients with other lung diseases and 200 samples from healthy blood donors. The positive predictive value for associated IgG reactivity against the 6-kDa and 16-kDa antigens, 6 and 38 kDa, and 16 and 38 kDa was 100% since simultaneous reactivity for these antigens was absent in healthy individuals and individuals with other lung diseases. This association was observed in 67% of the patients, but in only 8% of the contacts. The humoral response against antigens of 16 and 6 kDa seems to be important for the detection of latent tuberculosis since the associated reactivity to these antigens is mainly present in individuals with active disease.

Combined use of Western blot/ELISA to improve the serological diagnosis of human tuberculosis.

Two recombinant antigens and a crude bacterial antigen of a wild M. tuberculosis strain were used to detect specific IgG antibodies in sera from 52 patients with pulmonary tuberculosis, confirmed by an acid-fast smear and serum culture of these patients and that of 25 contacts. The patients were not infected with HIV. We evaluated the sensitivity and specificity of ELISA, based on the recombinant TbF6 and TbF6/DPEP antigen and a search for reactivity patterns in the Western blot technique, using whole mycobacterium antigen. Serum samples from 22 healthy individuals and from 30 patients with lung diseases other than tuberculosis were used as controls. The best ELISA results were obtained with the TbF6/DPEP antigen combination, which gave 85% sensitivity and 91% specificity. ELISA sensitivity improved from 85% to 92% when the Western blot results were used. Western blot specificity was 100% when antibody reactivity with different antigenic bands was analyzed and associated. The association of TbF6/DPEP antigens used in ELISA with specific patterns of reactivity determined by Western blot can help make an identification when classic methods for the diagnosis of pulmonary tuberculosis are not sufficient.

Humoral response to low molecular weight antigens of Mycobacterium tuberculosis by tuberculosis patients and contacts

Much effort has been devoted to the identification of immunologically important antigens of Mycobacterium tuberculosis and to the combination of target antigens to which antibodies from serum of tuberculous patients could react specifically. We searched for IgG antibodies specific for antigens of 45 to 6 kDa obtained after sonication of the well-characterized wild M. tuberculosis strain in order to detect differences in the antibody response to low molecular weight antigens from M. tuberculosis between patients with pulmonary tuberculosis and contacts. Specific IgG antibodies for these antigens were detected by Western blot analysis of 153 serum samples collected from 51 patients with confirmed pulmonary tuberculosis. Three samples were collected from each patient: before therapy, and after 2 and 6 months of treatment. We also analyzed 25 samples obtained from contacts, as well as 30 samples from healthy individuals with known tuberculin status, 50 samples from patients with other lung diseases and 200 samples from healthy blood donors. The positive predictive value for associated IgG reactivity against the 6-kDa and 16-kDa antigens, 6 and 38 kDa, and 16 and 38 kDa was 100 percent since simultaneous reactivity for these antigens was absent in healthy individuals and individuals with other lung diseases. This association was observed in 67 percent of the patients, but in only 8 percent of the contacts. The humoral response against antigens of 16 and 6 kDa seems to be important for the detection of latent tuberculosis since the associated reactivity to these antigens is mainly present in individuals with active disease.

Combined use of Western blot/ELISA to improve the serological diagnosis of human tuberculosis

Two recombinant antigens and a crude bacterial antigen of a wild M. tuberculosis strain were used to detect specific IgG antibodies in sera from 52 patients with pulmonary tuberculosis, confirmed by an acid-fast smear and serum culture of these patients and that of 25 contacts. The patients were not infected with HIV. We evaluated the sensitivity and specificity of ELISA, based on the recombinant TbF6® and TbF6/DPEP antigen and a search for reactivity patterns in the Western blot technique, using whole mycobacterium antigen. Serum samples from 22 healthy individuals and from 30 patients with lung diseases other than tuberculosis were used as controls. The best ELISA results were obtained with the TbF6/DPEP antigen combination, which gave 85 percent sensitivity and 91 percent specificity. ELISA sensitivity improved from 85 percent to 92 percent when the Western blot results were used. Western blot specificity was 100 percent when antibody reactivity with different antigenic bands was analyzed and associated. The association of TbF6/DPEP antigens used in ELISA with specific patterns of reactivity determined by Western blot can help make an identification when classic methods for the diagnosis of pulmonary tuberculosis are not sufficient.