Detection of antibody responses against Mycobacterium avium subsp. paratuberculosis stress-associated proteins within 30 weeks after infection in cattle

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In this study, humoral immune responses in cattle against Mycobacterium avium subsp. paratuberculosis (MAP) stress-associated recombinant proteins were assessed longitudinally by ELISA during the first 30 weeks after MAP infection. A total of 11 MAP genes previously identified by proteomic analysis were selected for cloning and expression. These included possible general stress-associated proteins of MAP and proteins expressed in vivo in MAP-infected sheep at an early stage of infection. An increase in the antibody levels against 5 recombinant antigen preparations (MAP1027c, MAP1339, MAP1588c, MAP1589c and MAP2411) was seen in MAP-infected calves (n=16) but not in control calves (n=3) over the time examined. Antibody responses were recorded as early as two weeks post-inoculation, and 87.5% of the inoculated cattle responded to at least one of the five immunogenic antigen preparations within the first 30 weeks of infection, suggesting that these proteins identified in the in vitro models of stress were also expressed in vivo in MAP-infected cattle at a relatively early stage after infection and therefore stimulate the host's immune system. It has been assumed that the sensitivity of antibody ELISA tests is dependent on the stage of infection and the age of the animals. However, we have provided some evidence that humoral immunity occurs at an early stage of paratuberculosis and can be detected using appropriate antigens such as MAP stress-associated proteins.