Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/9/2003
Publication Date: N/A
Technical Abstract: M. subsp avium paratuberculosis (Map)is the causative agent of Johne's Disease, a chronic granulomatous inflammatory intestinal disease of ruminants. Currently available diagnostic assays including ELISAs and IFN- assays are not sufficiently sensitive to identify animals in the early stages of disease. In the present study, we show that infected animals can be detected as early as 6 months following infection, using flow cytometry and monoclonal antibodies to phenotype memory T cells responding to Map antigens in vitro. Calves were experimentally exposed to Map by the oral route at the time of birth and examined monthly for appearance of an immune response to Map (n = 5). A proliferative response to PPD and soluble antigens was detected 6 months after exposure, following 5 to 7 days of culture. CD4+/CD45R0+ memory T cells expressing activation molecules CD25 and CD26 were the primary cell type responding to the antigens. Few if any CD8+ and T cells proliferated in response to the antigens. The calves have remained positive for the last 7 months. Control calves have shown no response to the antigens over the same time course (n = 3). At this time point in the study, only three infected animals have been shown to be positive by ELISA. In addition, one of the control animals has been positive by ELISA. With the use of Map specific antigens it should now be possible to identify animals in the early stages of infection.