|HENNAGER, S - Animal And Plant Health Inspection Service (APHIS)|
Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2015
Publication Date: 4/1/2015
Publication URL: https://handle.nal.usda.gov/10113/61355
Citation: Olsen, S.C., McGill, J.L., Sacco, R.E., Hennager, S.G. 2015. Immune responses of bison and efficacy after booster vaccination with Brucella abortus strain RB51. Clinical and Vaccine Immunology. 22(4):440-447. doi: 10.1128/CVI.00746-14.
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 or booster vaccination. Both vaccination schemes induced immunologic responses that were greater than responses of non-vaccinated bison. Booster vaccination of bison dramatically increased protection against experimental challenge and reduced bacterial colonization in tissues. 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: Thirty-one bison heifers were randomly assigned to saline (control; n=7) or single vaccination (n=24) with 1010 CFU of B. abortus strain RB51 (RB51). Some vaccinated bison were randomly selected for booster vaccination with 10**10 CFU of RB51 at 11 months after initial vaccination (n=16). When compared to non-vaccinated bison, mean titers to RB51 were greater (P<0.05) in bison after initial vaccination, and in booster vaccinates after the second inoculation. Proliferative responses by peripheral blood mononuclear cells (PBMC) from RB51 vaccinates were greater (P<0.05) than proliferation responses to RB51 antigens at 16 and 24 weeks after initial vaccination, but not after booster vaccination when compared to non-vaccinated bison. Relative gene expression of gamma-IFN was increased (P<0.05) in RB51 vaccinates at 8, 16, and 24 weeks after initial vaccination, and at 8 weeks after booster vaccination when compared to non-vaccinates. Although not increased after initial vaccination, relative gene expression of IL-2, IL-10, IL-15, and Il-17 were increased in vaccinated as compared to control bison at either 8 or 16 weeks after booster vaccination. Vaccinated bison had greater (P<0.05) production of gamma-IFN at all sampling times after initial or booster vaccination when compared to control bison. In a similar comparison, vaccinates also had greater (P<0.05) antigen-specific production of IL-1 beta at various times after initial and booster vaccination, and greater IL-6 production at one sampling time after booster vaccination. Between 170 and 180 days of gestation, as determined by rectal palpation, bison were intraconjunctivally challenged with approximately 1 x 10**7 CFU of B. abortus strain 2308. After experimental challenge, the incidence of abortion, uterine infection, or mammary infection was greater (P<0.05) in non-vaccinated bison as compared to either vaccination treatment. Booster vaccinates, but not single vaccinates, had reduced (P<0.05) incidence of infection in fetal tissues and maternal tissues not associated with uterine or mammary systems when compared to controls. When compared to non-vaccinated bison, both vaccination treatments had lower colonization (CFU/gm) of Brucella in all tissues except retropharyngeal and supramammary lymph nodes. Booster and single vaccinates demonstrated 7.5 and 5.6 log reductions, respectively, in mean Brucella colonization in the placentome/cotyledon at necropsy as compared to non-vaccinates. Our study suggests that a booster vaccination protocol is currently the most effective vaccination strategy for enhancing herd immunity in bison against brucellosis.