Search

Little attention has been given to the role of antibodies against Mycobacterium tuberculosis ( Mtb) infection. We have compared the levels of Ig A and Ig G against ESAT-6/ CFP-10 and Rv2031c antigens in sera of patients with culture-confirmed pulmonary tuberculosis ( PTB), healthy Mtb-infected and non-infected individuals in endemic TB settings. Venous blood samples were collected from 166 study participants; sera were separated and assayed by an enzyme-linked immunosorbent assay ( ELISA). Quanti FERON- TB Gold In- Tube ( QFTGIT) assay was used for the screening of latent TB infection. The mean optical density ( OD) values of Ig A against ESAT-6/ CFP-10 and Rv2031 were significantly higher in sera of patients with culture-confirmed PTB compared with healthy Mtb-infected and non-infected individuals ( P < 0.001). The mean OD values of Ig G against ESAT-6/ CFP-10 and Rv2031 were also significantly higher in sera of patients with culture-confirmed PTB compared with healthy Mtb-infected and non-infected individuals ( P < 0.05). The mean OD values of Ig A against both antigens were also higher in sera of healthy Mtb-infected cases compared with non-infected individuals. There were positive correlations ( P < 0.05) between the level of IFN-γ induced in QFTGIT assay and the OD values of serum Ig A against both antigens in healthy Mtb-infected subjects. This study shows the potential of Ig A response against ESAT-6/ CFP-10 and Rv2031 antigens in discriminating clinical TB from healthy Mtb-infected and non-infected cases. Nevertheless, further well-designed cohort study is needed to fully realize the full potential of this diagnostic marker. [ABSTRACT FROM AUTHOR]

One-third of the world population is estimated to have Mycobacterium tuberculosis infection. Accurate and timely identification of infected individuals is critical for treatment and control. The current diagnostic methods lack the desired sensitivity and specificity, require sophisticated equipment and skilled workforce or take weeks to yield results. Diagnosis of extrapulmonary TB, TB-HIV co-infection, childhood TB and sputum smear-negative pulmonary TB pose serious challenges. Interest in developing serodiagnostic methods is increasing because detection of antibody is rapid, simple and relatively inexpensive, and does not require a living cell for detection. Three types of tests, namely screening tests to overcome diagnostic delay, specific tests for diagnosis of extrapulmonary TB and other bacteriologically negative cases, and tests for vaccine-induced immunity need critical consideration. Several factors must be considered to develop serodiagnostic methods for TB. Antigen recognition by infected individuals is highly heterogeneous due to stage of disease, differences in HLA types, strain of the bacilli, health of the patient and bacillary load. With advances in molecular biological techniques, a number of novel antigens have been identified. Some of these antigens have proven valuable in detecting specific antibodies in some of the most challenging TB patients. The best example is a fusion protein containing several M. tuberculosis proteins (e.g. CFP-10, MTB8, MTB48, MTB81 and the 38-kDa protein) which showed encouraging results in detecting antibodies in sera of patients, including TB-HIV co-infection. This review presents progress made in the serodiagnosis of TB during the last decade. [ABSTRACT FROM AUTHOR]