ABSTRACT
M. bovis cell extract antigens as filter-sterilized lysozyme and sarkosyl extracts have been evaluated and successfully used in vitro for diagnosis of bovine tuberculosis. They were compared with the bovine PPD by measuring the cell mediated immunity using the lymphocyte blastogenesis assay [LBA] as detected by tetrazolism [MTT] reduction and skin sensitivity test, as well as measuring the serum antibody levels using ELISA in experimentally infected guinea pigs with M. bovis and M. tuberculosis. The lymphocytic proliferative response in the infected guinea pig groups 2 weeks post infection was higher than that obtained 4 weeks post infection. The use of lysozyme and sarkosyl extract antigens was found to be advantageousover the bovine PPD in lymphocytic blastogenesis assay due to their abilities to confirm specificity and to discriminate between animals infected with M. bovis and those infected with M. tuberculosis. The obtained results of the skin sensitivity test revealed that, the bovine PPD, sarkosyl and lysozyme extract antigens were able to differentiate the guinea pigs, infected with typical mycobacteria from those infected with atypical. ELISA results confirmed the superiority of sarkosyl extract over bovine PPD and lysozyme extract in distinguishing between guinea pigsinfected with typical and atypical mycobacteria at serum dilution of 1/80 [4, 6 and 9 weeks post infection]. Both sarkosyl extract and lysozyme extract antigens would be advantageous over bovine PPD in differentiating M. tuberculosis infected guinea pigs from M. bovis infected group at serum dilution 1/160 while bovine PPD, was not able to differentiate between those two groups. The results of ELISA in this work suggested, that M. bovis cell extract antigens [lysozyme and sarkosyl extracts] were useful antigens to minimize non-specific reactions in diagnosis of bovine tuberculosis. It was clear from the preliminary results of naturally infected cattle with M. bovis that, using the lysozyme and sarkosyl extract antigens could be of value in diagnosis of bovine tuberculosis