ARS | Publication request: Immune responses and safety after dart or booster vaccination of bison with Brucella abortus strain RB51

Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 19, 2012
Publication Date: May 1, 2012
Citation: Olsen, S.C., Johnson, C.S. 2012. Immune responses and safety after dart or booster vaccination of bison with Brucella abortus strain RB51. Clinical and Vaccine Immunology. 19(5):642-648.

Interpretive Summary: Brucella abortus is an intracellular pathogen that causes reproductive losses in cattle, bison and elk and which also causes zoonotic infections in people. Regulatory programs in domestic livestock, which include vaccination of livestock, are the most cost-efficient way to control Brucella abortus and prevent human infection. The persistence of brucellosis in bison in Yellowstone National Park may pose a threat for reintroduction of brucelloss to cattle in the United States. In this paper, we evaluated the safety and immunologic responses of bison to single vaccination, booster vaccination, or vaccine delivered by a dart system. All three vaccination schemes induced immunologic responses that were greater than responses of non-vaccinated bison. Surprisingly, immunologic responses after booster vaccination did not demonstrate robust increases. Booster vaccination of bison in early pregnancy did not induce abortions or fetal infection. This data will be of interest to regulatory personnel, people with responsibilities for management of brucellosis in bison, livestock owners, and other parties with interests regarding brucellosis management.

Technical Abstract: One alternative in the Bison remote vaccination environmental impact statement (EIS) for Yellowstone National Park includes inoculation of both calves and yearlings. Although RB51 vaccination of bison does protect against experimental challenge, it was unknown whether booster vaccination might enhance protective immunity. In this study, we characterized immunologic responses and protection against experimental challenge after dart or booster vaccination of bison or Brucella abortus strains RB51 (RB51). In two studies, 8 to 10 month old, female bison were vaccinated with saline (n=14), hand vaccinated with 1.1-2.0 x 10**10 CFU of RB51 (n=21) or dart vaccinated with 1.8 x 10**10 CFU of RB51 (n=7). A subgroup of hand vaccinates in study 1 were randomly selected for booster vaccination 15 months later with 2.2 x 10**10 CFU of RB51. When compared to single vaccinates, booster vaccinated bison had greater serologic titers to RB51 However, there was a trend for antigen-specific proliferative responses of PBMC from booster vaccinates to be reduced when compared to responses of PBMC from single vaccinates. PBMC from booster vaccinates did tend to have greater production of interferon-gamma when compared to single vaccinates. In general, dart vaccination with RB51 induces similar serologic, proliferative, and interferon-gamma responses in bison as hand vaccination. All vaccinates (single hand, dart, or booster) demonstrated greater (P<0.05) immunologic responses at various times after vaccination when compared to non-vaccinated bison. Booster vaccination with RB51 in early gestation did not induce abortion or fetal infection. Our data suggests that booster vaccination does not induce strong anamnestic responses as measured by the assays used in this study. However, phenotypic data on resistance to experimental challenge will be required to fully assess the effect of booster vaccination on protective immunity.