Early Induction of Humoral and Cellular Immune Responses during

Johne’s disease (paratuberculosis) of cattle is widespread and causes significant economic losses for pro-ducers 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 peripheral colonization as detected by antemortem culture of feces and postmortem (320 days postchallenge) culture of intestinal tissues. Antigen-specific blastogenic, gamma interferon (IFN-), and nitric oxide responses by blood mononuclear cells from infected calves exceeded prechallenge responses beginning 194 days postchallenge. Upon in vitro stimulation with paratuberculosis antigens, CD4 cells from infected calves proliferated, produced IFN-, and increased expression of CD26 and CD45RO (indicative of an activated memory pheno-type). Utilizing a lipoarabinomannan-based enzyme-linked immunosorbent assay, specific serum immunoglob-ulin was detected as early as 134 days postchallenge and generally increased after this time point. Two antigens of 50 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 wil