Interferon gamma response to combinations 38 kDa/CFP-10, 38 kDa/MPT-64, ESAT-6/MPT-64 and ESAT-6/CFP-10, each related to a single recombinant protein of Mycobacterium tuberculosis in individuals from tuberculosis endemic areas.

Several antigens of Mycobacterium tuberculosis have been identified and specificity to one or multiple antigens could determine the distinction between protective and pathogenic host reaction. Therefore T cell immune response to combinations 38 kDa/CFP-10, 38 kDa/MPT-64, ESAT-6/MPT-64 and ESAT-6/CFP-10 (each related to a single protein of Mycobacterium tuberculosis) in individuals from tuberculosis endemic areas have been examined. ELISA was used to detect IFN-gamma production in PBMC priming with single proteins and combinations in a panel of 105 individuals: 38 tuberculosis patients (6 untreated and 32 treated) and 67 healthy controls with tuberculin skin test positive or negative (TST). Brazilian TB patients highly recognized ESAT-6 (66%), but combinations improved response in the following order: ESAT-6/MPT-64 (89%) > ESAT-6/CFP-10 (73%) > 38 kDa/CFP-10 (70%), the last combination showing the highest specificity (TST(/) = 42% and TST(-) = 83%). Average IFN-gamma production in TB patients was signifi-cantly higher for 38 kDa/CFP-10 (P = 0.012) and 38 kDa/MPT-64 (P <0.035), when compared to single antigens. None of the combinations was able to discriminate TB patients from TST(+) controls; however, 38 kDa/CFP-10 displayed a borderline significance (P = 0.053). Similar to the ESAT-6/CFP-10 combination, IFN-gamma response to 38 kDa/CFP-10 showed an increased tendency in treated patients, although not signifi-cant (P = 0.16). We demonstrated for the first time that 38 kDa/CFP-10 had prediction sensitivity for TB patients similar to the ESAT-6/CFP-10 combination and also significant response improvement related to the single proteins with more selective reactivity among TST-positive individuals, which could be of potential interest for diagnostic evaluation for tuberculosis infection.

Use of the 2,3-diacyl-trehalose and the purified protein derivative in the serodiagnosis of tuberculosis in AIDS

The effect of the human immunodeficiency virus (HIV) infection on IgG production against purified protein derivative (PPD) and 2,3-diacil-trehalose (SL-IV) was investigated by an enzyme-linked immunosorbent assay (ELISA) test. Comparison between the antigens showed that immunocompetent patients produce preferentially antibodies to SL-IV than to PPD (73.3 por cento versus 63.3 por cento). Combination of the these results showed an increase of the sensitivity to 80 por cento, which decreased over the spectrum of immunodepression caused by HIV. In the tuberculous HIV seropositive group the sensitivities of SL-IV and PPD were 36.4 por cento versus 40 por cento and 0 por cento versus 22.2 por cento in the tuberculosis/acquired immunodeficiency syndrome (TB/AIDS) group. Combination of these results gave respectively 54.5 por cento and 20 por cento, showing that serological tests have limited value for diagnosis of tuberculosis in HIV infected patients. High antibody levels were observed in HIV seropositive asymptomatic group, but only two individuals were positive for both antigens. In the follow up, one of them tuberculous lymphadenitis, indicating that further work is needed to access the value of serological tests in predicting tuberculosis in HIV infected individuals.