Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2011
Publication Date: February 19, 2012
Citation: Stabel, J.R., Waters, W.R., Bannantine, J.P., Lyashcnenko, K. 2012. Activation of host immune responses in neonatal calves and interference with TB diagnostics after immunization with a commercial heat-killed vaccine [abstract]. International Colloquium on Paratuberculosis. p. 126. Technical Abstract: A major drawback of current whole-cell vaccines for Mycobacterium avium subsp. paratuberculosis (MAP) is the potential interference with diagnostic tests for bovine tuberculosis and paratuberculosis. The current study was designed to explore cross-reactivity of the current USDA commercial vaccine for MAP with diagnostic tools for bovine TB and to assess host responses to vaccination. Neonatal dairy calves were assigned to treatment groups consisting of: 1) Control – no vaccine (n = 5); and 2) Vaccinate – Mycopar vaccine (n = 5). Blood and fecal samples were collected prior to the initiation of the study for pre-vaccination measurements. Calves were vaccinated subcutaneously with a 0.5 ml dose in the dewlap-brisket area as per standard procedure with the wild-type commercial vaccine that consists of a heat-killed whole cell suspension of MAP in oil (Mycopar). Calves were sampled throughout the study on days 7, 14, 28, and at 3, 6, 9, and 12 months. Comparative cervical skin testing was performed at 6 months both as a diagnostic tool and to determine in vivo cell-mediated response to vaccination. For determination of M. bovis-specific antibody, the TB Stat-Pak assay and the dual-path platform (DPP) VetTB assay (Chembio Diagnostic Systems) were performed. Peripheral blood mononuclear cells were isolated before and after vaccination and stimulated in vitro for measurement of interferon-(IFN)-gamma, interleukin (IL)-4, IL-10, and IL-12, and to assess differences in lymphocyte populations by flow cytometry. Results from this study demonstrated a rapid initiation of MAP-specific IFN-gamma in Vaccinate calves by 7 days, with robust responses continuing throughout the study. Vaccinate calves also had IFN-gamma responses to BoPPD, with moderate reactivity to ESAT-6/CFP-10, an M. bovis recombinant fusion protein. Interestingly, IL-4 and IL-10 were markedly decreased in Vaccinate calves only on days 7 and 14 of the study and thereafter were similar to Controls. Vaccinate calves began to seroconvert at 4 months with all calves having detectable MAP antibody by 6 months. Only one Vaccinate calf had a positive (suspect) skin test response to M. bovis PPD and none of these calves reacted in M. bovis serologic tests. These results suggest that vaccination with Mycopar will interfere with diagnostic tools for the detection of paratuberculosis but have low interference with M. bovis diagnostics.