ARS | Publication request: Mediation of host immune responses after immunization of neonatal calves with a heat-killed Mycobacterium avium subsp. paratuberculosis vaccine

Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 17, 2011
Publication Date: December 1, 2011
Citation: Stabel, J.R., Waters, W.R., Bannantine, J.P., Lyashchenko, K. 2011. Mediation of host immune responses after immunization of neonatal calves with a heat-killed Mycobacterium avium subsp. paratuberculosis vaccine. Clinical and Vaccine Immunology. 18(12):2079-2089.

Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle,sheep and wild ruminants, characterized by diarrhea, reduced feed intake, weight loss and death. Animals usually become infected when they are young by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced production by these animals through reduced milk production, they also present a potential infective threat to the rest of the herd. Vaccination is one method of managing the spread of this disease as it may reduce fecal shedding of the organism. However, some major disadvantages of vaccination are that animals become positive on serologic diagnostic tests for paratuberculosis. Vaccination against paratuberculosis may also cause false-positive reactions on tuberculin skin tests. In this paper, we present results from a study designed to evaluate effects of vaccination on current diagnostic tests for paratuberculosis and bovine tuberculosis. Further, we measured host immune responses to define protective immunity after vaccination. Results of this study suggest that vaccination does result in positive serologic tests for paratuberculosis, however, there was no interference with tests for bovine tuberculosis. These results are important considerations for producers considering the use of vaccination as a management tool in infected herds.

Technical Abstract: A major drawback of current whole-cell vaccines for Mycobacterium avium subsp. paratuberculosis(MAP) is the interference with diagnostic tests for bovine tuberculosis and paratuberculosis. The current study was designed to explore effects of immunization with a heat-killed whole cell vaccine (Mycopar) on diagnostic test performance and to characterize host immune responses to vaccination over a 12-month period. Neonatal dairy calves were assigned to treatment groups consisting of: 1) control – no vaccine (n = 5); and 2) vaccinate – Mycopar vaccine (n = 5). 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 responses to BoPPD, with minimal reactivity to ESAT-6/CFP-10, an M. bovis recombinant fusion protein. Interestingly, antigen-specific IL-4 and IL-10 secretion was markedly decreased in vaccinate calves between 7 and 90 days of the study but thereafter was similar to controls. Vaccinate calves began to seroconvert at 4 months with 4 of 5 calves having detectable MAP antibody by 6 months. Responses in test platforms for bovine TB were negligible in the vaccinate group as only one calf had a response in the suspect range of the comparative cervical skin test. Serum antibody responses to M. bovis antigens, ESAT-6, CFP-10, and MPB83 were negative on the STAT-PAK, DPP VetTB, and BovidTB STAT-PAK tests. These results suggest that vaccination with the Mycopar vaccine will interfere with diagnostic tools for the detection of paratuberculosis but result in low interference with M. bovis diagnostics.