T lymphocyte responses to Mycobacterium avium subspecies paratuberculosis (Map)-derived culture filtrate proteins and membrane vesicles during early intestinal Map infection in calves
Johne’s disease (JD) is a chronic granulomatous enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (Map). T lymphocytes play a significant role in JD control; however anti‐mycobacterial T cell responses during early intestinal Map infection remain poorly understood. Crude Map antigen preparations have been studied to detect T cell responses during subclinical JD; however, use of secreted Map antigens remains unexplored. Our hypothesis was that exposure of Map sensitized T cells to Map-secreted antigens would evoke T cell responses that could be assessed by flow cytometry and ELISA. We screened T lymphocytes from blood of experimentally Map-infected calves against Map whole cell sonicate, Map culture filtrate and Map membrane vesicles. Our data supported the hypothesis and secreted IFNγ was detected in supernatants of cells from only Map-infected calves upon exposure to Map antigens. Results demonstrated that CD4 T cells from Map-infected calves were a source of IFNγ produced in response to Map antigens. CD4 and WC1+ γδ T cells from Map infected calves and WC1- γδ T cells from uninfected calves proliferated after stimulation with Map antigens, which was consistent with the previous findings.