Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/2/2003
Publication Date: N/A
Technical Abstract: Johne's disease (paratuberculosis) of cattle is widespread and causes significant economic losses for producers due to decreased production and poor health of affected animals. The chronic nature of the disease and the lack of a reproducible model of infection hinder research efforts. In the present study, instillation of Mycobacterium avium subsp. paratuberculosis into the tonsillar crypts of neonatal calves resulted in chronic infection with peripheral colonization detected by ante-mortem culture of feces and post-mortem (320 d postchallenge) culture of intestinal tissues. Antigen-specific blastogenic, IFN-g, and nitric oxide responses by blood mononuclear cells from infected calves exceeded prechallenge responses beginning 194 d postchallenge. Upon in vitro stimulation with paratuberculosis antigens, CD4+ cells from infected calves proliferated, produced IFN-g, and increased expression of CD26 and CD45RO (i.e., indicative of an activated memory phenotype). Utilizing a lipoarabinomannan-based ELISA, specific serum immunoglobulin was detected as early as 134 d postchallenge and generally increased after this time point. Two antigens of ~50-kDa and ~60-kDa were particularly immunodominant early in infection as shown by immunoblot with serum collected within 2 weeks postchallenge. Findings indicate that the intratonsillar inoculation route will prove useful as an experimental model for paratuberculosis pathogenesis, diagnosis, and vaccine efficacy studies. Additionally, this study confirms that mycobacteria-specific antibody is detectable early in the course of experimental Johne's disease, even preceeding the development of specific cell-mediated responses.