Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/28/2006
Publication Date: 10/1/2006
Citation: Olsen, S.C., Fach, S.J., Palmer, M.V., Sacco, R.E., Stoffregen, W.C., Waters, W.R. 2006. Immune Responses of Elk to Initital and Booster Vaccinations with Brucella abortus Strain RB51 or 19. Clinical and Vaccine Immunology. 13(10):1098-1103. Interpretive Summary: At the present time, there is a high seroprevalence of brucellosis in elk that overwinter on feedgrounds in the GYA. In recent outbreaks of brucellosis in cattle in Wyoming, elk were implicated as the source for transmission to livestock. Vaccination of elk with strain 19 induces only moderate protection, whereas strain RB51 induces no protection against brucellosis. In an effort to understand why brucellosis vaccines are poor at protecting elk against brucellosis, we characterized immunologic responses after vaccination of elk with RB51 or strain 19. Although elk develop strong antibody responses after brucellosis vaccination, our data indicates that elk develop poor cell mediated immune responses. This may explain the results of efficacy studies as cell-mediated responses are associated with long-term protection against brucellosis. Our data suggest immune responses of elk to brucellosis vaccines are profoundly different when compared to responses of other domestic livestock or wildlife species.
Technical Abstract: To study the immunologic responses of elk to brucellosis vaccines, 21 elk were innoculated with saline, SRB51, or S19. Elk were booster vaccinated at 65 wks. Blood was obtained after initial and booster vaccination for measurement of antibody responses and/or Brucella-specific proliferative responses. When compared to nonvaccinates, elk vaccinated with SRB51 or S19 had greater antibody responses after initial and booster vaccination. Proliferative responses to autologous antigen after initial or booster vaccination, as measured by 3H-thymidine incorporation, were greater in peripheral blood mononuclear cells (PBMC) from SRB51- and S19-vaccinated elk in only a few sampling times when compared to responses of nonvaccinated elk. With one exception, proliferative responses to non-autologous antigens did not differ from responses of nonvaccinated elk. Flow cytometric techniques demonstrated greater responses to Brucella antigens by PBMC obtained from SRB51- and S19-vaccinated elk after initial and booster vaccination when compared to responses of nonvaccinated elk. However, flow cytometric techniques suggested the greatest responses occurred in IgM+ subsets. Overall data indicated that proliferative responses to Brucella antigens in S19- or SRB51 vaccinates were reduced when compared to other species. Our data suggest that although immunologic responses can be detected in elk after initial or booster vaccination with SRB51 or S19, cellular immunologic responses tend to be transient and much less robust than previously reported in SRB51-vaccinated cattle or bison.