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.