Immune responses and efficacy of Brucella abortus strain RB51 in bison after delivery in a dry dart formulation or by parenteral inoculation

Authors: Olsen, Steven; Boggiatto, Paola; NOL, PAULINE - Colorado Parks And Wildlife; MCCOLLUM, MATT - Colorado State University; RHYAN, JACK - Animal And Plant Health Inspection Service (APHIS)

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2021
Publication Date: 7/20/2021
Citation: Olsen, S.C., Boggiatto, P.M., Nol, P., Mccollum, M., Rhyan, J. 2021. Immune responses and efficacy of Brucella abortus strain RB51 in bison after delivery in a dry dart formulation or by parenteral inoculation. Frontiers in Veterinary Science. 8. Article 706160. https://doi.org/10.3389/fvets.2021.706160.
DOI: https://doi.org/10.3389/fvets.2021.706160

Interpretive Summary: Brucellosis is a disease in livestock that causes reproductive failure but can also cause clinical disease in humans. Development of intervention strategies to reduce disease in animal hosts of brucellosis is the most efficient way to reduce infection of humans. In this study we evaluated a Brucella abortus dry dart vaccine for immunogenicity and efficacy in protecting bison against brucellosis. Our data demonstrates that the dry dart formula provided some protection in bison, but efficacy was not as great as parenteral vaccination with a commercial RB51 vaccine. This data provides information on a vaccine formulation that may be useful for remote delivery to free-ranging bison. The work will be of interest to researchers working on vaccines for bison, bison producers, and state and federal agencies with responsibilities for managing bison herds.

Technical Abstract: Bison heifer calves (n equals 32) were randomly assigned to control or vaccination with 1010 colony-forming units of B. abortus strain RB51 (RB51) vaccine by single or boostered parenteral delivery, or by surgical implantation of a dry dart formulation (n equals 8/trt). Serum and/or peripheral blood mononuclear cells (PBMC) were obtained at 0, 4, 8, 13, 16, 21, and 24 wk after initial vaccination and at 0, 4, 8, 12, 15, 22 and 27 wks after booster vaccination to characterize humoral and cellular immune responses to RB51. Bison in both RB51 vaccination treatments demonstrated greater (P less than 0.05) serum humoral responses when compared to non-vaccinates, with parenteral vaccinates demonstrating greater (P less than 0.05) responses when compared to mean responses of bison inoculated with the dry dart. Only the booster vaccinated treatment demonstrated greater (P less than 0.05) humoral responses than control bison in samples collected after re-inoculation. At 4, 8, 12, 16, and 24 wks after initial vaccination, PBMC from parenteral RB51 vaccines demonstrated greater proliferative responses to RB51 when compared to responses of control animals. In comparison, bison inoculated with the RB51 dry dart had greater (P less than 0.05) proliferative responses only at 8 weeks after inoculation when compared to responses of non-vaccinates. Bison were pasture bred and pregnant animals experimentally challenged in mid-gestation with 107 CFU of B. abortus strain 2308. Bison in parenteral vaccination treatments had reduced (P less than 0.05) abortions and infection in uterine and fetal samples as compared to non-vaccinated bison, with booster vaccinates tending to have the lowest colonization (CFU/gm) in tissues. In comparison, the dry dart formulation did reduced abortion (P less than 0.05) but not infection (P greater than 0.05) when compared to non-vaccinated bison. The results of this study reaffirm the efficacy of boostered parenteral vaccination of bison with RB51 in preventing brucellosis. Our data also suggests that the novel dry dart RB51 formulation does not induce sufficient efficacy in bison after a single inoculation.