IgA antibody responses to Mycobacterium tuberculosis recombinant MPT-64 and MT-10.3 (Rv3019c) antigens in pleural fluid of patients with tuberculous pleurisy.

SETTING

Microbiological tests lack sensitivity for pleural tuberculosis (TB) and histopathology is expensive, time consuming and needs specialised personnel. Immunoassay (ELISA) may be a promising approach in this respect.

OBJECTIVE

To evaluate the reactivity of IgA antibody to MPT-64 and MT-10.3 recombinant mycobacterial protein antigens in pleural fluid as a marker of pleural TB, based on the fact that IgA is the main antibody in the mucosa/serosa of the gastrointestinal and respiratory tract.

METHOD: Anti-MPT-64 and MT-10.3 IgA response was determined by ELISA in 72 patients with pleural TB and 27 with other pleural conditions.

RESULTS

High sensitivities for IgA were measured against MPT-64 (52/72, 72%) and MT-10.3 (52/72,72%) antigens. Combining the sensitivities of both antigens, further increase in sensitivity (55/72, 76%) was obtained with no loss of specificity (96%). Similar IgA reactivity was obtained from culture-negative and culture-positive specimens. In eight pleural TB patients with human immunodeficiency virus (HIV) co-infection, the sensitivity was 88% (7/8).

CONCLUSION

To our knowledge, this is the first description of the presence of IgA antibody pleural TB effusion reactive to MPT-64 and MT-10.3, with sensitivity similar to histopathological examination, which is presently considered the gold standard for pleural TB.