• S Banerjee, S Kumar, and B C Harinath.
• Department of Biochemistry, Jamnalal Bajaj Tropical Disease Research Centre, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Maharashtra, India.
• Int. J. Tuberc. Lung Dis. 2003 Mar 1; 7 (3): 278-83.

ObjectiveTo isolate and characterise in vivo released 41 kDa mycobacterial antigen in pulmonary and bone and joint tuberculosis (TB) and its identification with in vitro released ES-41 kDa antigen.DesignCirculating antigen was isolated from confirmed pulmonary tuberculosis serum (PTS) and bone and joint tuberculosis serum (BJS) by trichloroacetic acid precipitation and further fractionation by fast-protein liquid chromatography (FPLC).ResultsFractionation of PTS and BJS by gel filtration column gave six protein fractions each. PTS-G3 and BJS-G3 showed maximum antigenic activity with ELISA. Further fractionation of PTS-G3 and BJS-G3 on cation exchange FPLC gave four different fractions each, of which BJS-G3B was seroreactive similarly to in vitro released 41 kDa antigen (ES-41) isolated from culture medium, whereas PTS-G3C was slightly less seroreactive. BJS-G3B could inhibit binding of in vitro released ES-41 to affinity purified antibodies in inhibition ELISA at lower concentrations than PTS-G3C (2 vs. 20 ng/ml), showing the identical nature of the antigens. Biochemical characterisation showed that circulating antigen PTS-G3C, BJS-G3B and in vitro released ES-41 antigen were lipoproteins in nature.ConclusionThis study helped to demonstrate the presence of 41 kDa antigen in the serum of pulmonary and bone and joint TB patients and its identification with H37Ra in vitro released 41 kDa antigen.

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