Excretory Secretory Proteins Released during Growth of Mycobacterium tuberculosis (H37Ra), With Diagnostic Potential in Pulmonary and Extra Pulmonary Tuberculosis

Abstract

TB immunodiagnostics based on antibody and antigen detection for early detection and monitoring tubercular infections at low cost and flexible to adapt to field laboratories are a boon to developing countries. In this context we have explored in-house developed penicillinase based ELISA assays for the detection of antigen, antibody as well as immune-complexed antigen using various excretory secretory antigenic proteins and specific antibodies. Excretory secretory protein antigens such as ES-31, ES-41, ES-43, ES-6, ES-20, ES-100 and EST-6 were studied extensively and found to be useful in various pulmonary and extra pulmonary cases of tuberculosis infection. ES-31 has shown its diagnostic potential in chronic PTB cases, ES-43 in relapse cases and ES-41 in bone and joint TB. Elevated level of ES-20 antigen was observed in patients with weak immune response in TB lymphadenitis. Detection of ES-100 antigen and antibody by penicilinase ELISA was observed to be useful in detection of TB meningitis. ES-6 antigen was shown to be useful in detection of latent infection. These proteins with antigenic properties are utilized for production of specific antibodies against them and observed to be useful in immune diagnostics for detection of specific circulating and immune complexed antigens. Further user friendly peroxidase immunoassay has been standardised and is being routinely used for suspected TB cases attending 1000 bedded Kasturba Hospital attached to medical institute on physician’s request.