Immunological response to PPD and phosphatide antigens in buffaloes experimentally infected with Mycobacterium bovis

Abstract

Antibody response to PPD and phosphatide antigens of Mycobacterium bovis was monitored at monthly intervals by ELISA in buffaloes experimentally infected with 10 mg (wet weight) of M. bovis (field isolate) intratracheally. The cellular immune response was evaluated by leukocyte migration inhibition test using PPD antigen and intradermal tuberculin test. Antibody titres detected by ELISA using PPD antigen increased with progression of the disease, but statistically significant high titres were found only in the later stages (450 DPI) of the disease. ELISA using phosphatide antigen, however, detected significant increase from 15 DPI onwards. Cell mediated immune responses revealed maximum inhibition of leukocyte migration at 135 DPI and gradual decline thereafter. Tuberculin test was positive at 30 DPI and before death or sacrifice at 450 DPI. An inverse relationship between ELISA and LMIT responses was evident between 255 and 480 DPI.