Despite rapid advances in molecular genetics for detection of mycobacteria, it is clear that interest in serodiagnosis remains high, especially for those situations in which a specimen may not contain the infecting agent in particular in
extrapulmonary tuberculosis. Immune response to excretory-secretory (ES)
proteins of Mycobacterium tuberculosis (M.tb) has been of diagnostic interest in
tuberculosis. In earlier study from our laboratory, a secretory
protein M.tb ES-31 has been shown to have diagnostic potential in
pulmonary tuberculosis. Further, another M.tb H37Ra ES
protein (ES-41) was isolated and purified by
trichloroacetic acid solubilization followed by Fast Performance Liquid Chromatography (FPLC). These two
protein fractions viz ES-31 and ES-41 secreted by M.tb H37 Ra bacilli were employed in stick indirect
penicillinase ELISA to study seroreactivity in
extra pulmonary tuberculosis namely tuberculous
lymphadenopathy,
tuberculous meningitis, abdominal
tuberculosis and bone &
joint tuberculosis. While using ES-31
antigen 88% (22/25) of tuberculous
lymphadenopathy and 90% (9/10) of
tuberculous meningitis cases showed positive reaction for tuberculous
IgG antibody, ES-41 showed 80% positivity in both groups. In abdominal and bone &
joint tuberculosis cases, ES-41
antigen showed better sensitivity of 81.5% (22/27) and 84.6% (22/26) respectively in
IgG antibody detection compared to 70% (19/27) and 69.2% (18/26) shown by ES-31. This study is of interest that different
antigen protein fractions of M.tb exhibit differential seroreactivity, as ES-31
protein showed good potential in detecting tuberculous
IgG antibodies in tuberculous
lymphadenopathy (TBLN) &
tuberculous meningitis (TBM), while ES-41 in abdominal and bone &
joint tuberculosis cases.