Skip to main content
ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Infectious Bacterial Diseases Research » Research » Research Project #441161

Research Project: Development of Improved Diagnostic and Control Strategies for Brucellosis in Livestock and Wildlife

Location: Infectious Bacterial Diseases Research

2022 Annual Report

Objective 1: Develop rationally-designed vaccines, including recombinants, that prevent disease or mitigate disease spread with an emphasis on platforms that allow for extended antigen release and remote delivery for cattle and elk. Subobjective 1A: Assess the potential of polyanhydride polymers as extended release vaccine platform using killed bacterial preparations to generate cell-mediated immune responses against Brucella in cattle and elk. Subobjective 1B: Evaluate immunogenicity/efficacy of a new recombinant vaccine in elk. Subobjective 1C: Develop new DIVA vaccine strains with targeted mutations using CRISPR. Objective 2: Improve current diagnostic tests for brucellosis that differentiate between Brucella species and can be used in multiple livestock and wildlife species. Subobjective 2A: Characterize sensitivity and specificity of diagnostic tests using synthetic Brucella antigens. Subobjective 2B: Identify new Brucella epitopes recognized by humoral responses of B. suis infected animals using phage library expression. Objective 3: Using transcriptomic approaches, define the immunopathogenesis of brucellosis at the tissue and cellular level by analyzing gene expression of peripheral immune responses and local immune responses to inform vaccine and therapeutic development. Subobjective 3A: Using a transposon generated mutant library of Brucella abortus, characterize how bacterial populations are limited during in vivo infection and identify bacterial genes critical for establishing infection in cattle. Subobjective 3B: Using a transposon-generated mutant library of Brucella abortus, characterize how pregnancy influences diversity of bacterial populations during in vivo infection in cattle. Subobjective 3C: Characterize the gene expression profiles of the peripheral immune response to Brucella in cattle, bison, and elk to determine species-specific differences in response to vaccination.

The long-term goals of this project are to facilitate the completion of brucellosis eradication programs in domestic livestock, and prevent reintroduction of brucellosis into livestock from wildlife reservoirs. Specifically, fundamental knowledge on Brucella pathogenesis will be gained, efficacious vaccination systems will be identified, and sensitive and specific diagnostic tools will be developed to aid eradication programs. Immunogenicity of vaccination strategies in targeted hosts (cattle, bison, elk, and swine), including novel vaccine platforms, will be evaluated in targeted species and efficacy characterized by experimental challenge. In addition, the project will try to improve the standard experimental challenge model for elk to better replicate the clinical effects of brucellosis under field conditions. By simultaneously characterizing the in vivo transcriptome of B. abortus and natural host during infection, we will develop knowledge of molecular mechanisms involved in regulation of host responses to infection, and genes expressed by the pathogen under in vivo conditions. This basic knowledge will identify future targets for development of new vaccines, diagnostics, immunomodulation, and possibly therapeutics. New diagnostics will be developed and analyzed for their ability to detect brucellosis in swine and cattle, and may allow differentiation of which Brucella spp. is associated with infection. The research will help resolve the risk of re-infection of domestic livestock from wildlife reservoirs of brucellosis, protect the financial investment that has been made in the U.S. brucellosis eradication program, and provide public health benefits by reducing the risk of zoonotic infection.

Progress Report
During FY2022, significant progress was made in meeting the objectives of the brucellosis research project. As vaccination is a critical intervention tool for the control of brucellosis, studies on improving existing vaccines and understanding the scientific basis for protective immunity against brucellosis were completed in many species, including bison, elk, and cattle. Work has been initiated to develop new novel vaccines that will be evaluated in subsequent years. Molecular techniques are being incorporated into studies to provide basic knowledge on immune gene expression by natural hosts after infection or vaccination. Work was also initiated to identify new brucellosis antigens that can be incorporated into diagnostic platforms for increased sensitivity in detection of brucellosis infection. The continued use of comparative genomics has identified structural differences between natural hosts of Brucella that may contribute to observed differences in disease pathogenesis. To address Objective 1, immunologic responses and/or efficacy of Brucella vaccines have been evaluated in cattle, bison, and elk in the past year in addition to characterizing immunologic responses associated with clearance of Brucella vaccines. In efforts to improve diagnostic tests for brucellosis (Obj 2) synthetic Brucella antigens and novel brucellosis diagnostics were evaluated for sensitivity and specificity. For Objective 3, RNA was isolated from cattle, elk, and bison to characterize gene expression after vaccination or infection and to compare immune gene expression between species.

1. Influence of other vaccines on immune responses to brucellosis vaccination. Brucellosis causes reproductive losses in domestic livestock and can also cause human infection. Vaccination with the Brucella abortus RB51 vaccine strain is frequently used to prevent brucellosis infection in domestic livestock. As multiple vaccines are often administered simultaneously to domestic livestock, it was important to determine if common modified-live vaccines (Bovine viral diarrhea, parainfluenza, infectious bovine rhinotracheitis) may influence immune responses to RB51 vaccination in cattle. ARS scientists in Ames, Iowa, co-administered modified-live and RB51 vaccines to cattle and characterized immune responses. Data demonstrated that modified-live vaccines did not reduce immune responses to brucellosis vaccines. This data will be of interest to regulatory officials and producers to affirm that current industry practices will not influence efficacy of brucellosis vaccines.

2. Tuberculosis vaccination reduces immune responses to brucellosis vaccines. Brucellosis causes reproductive losses in domestic livestock and can also cause human infection. Vaccination is an important intervention strategy for brucellosis in domestic livestock. Tuberculosis is an immunosuppressive disease that is re-emerging in the United States and is endemic in many other countries. Using the Mycobacterium bovis strain BCG (BCG) vaccine to mimic tuberculosis infection, ARS scientists in Ames, Iowa, characterized the effects of co-administration of BCG and the Brucella abortus RB51 vaccine in bison and cattle. Data demonstrated that co-infection with BCG dramatically reduced immunologic responses to RB51 vaccination. This data will be of interest to regulatory officials, producers, and other scientists who have interest in the efficacy of brucellosis vaccines.

3. Influence of RB51 vaccination on serologic responses to infection with virulent Brucella. Brucellosis causes reproductive losses in domestic livestock and can also cause human infection. Vaccination is an important intervention strategy to prevent disease in domestic livestock and serologic diagnostics are critical for identifying brucellosis infection. As determination of infection status is frequently based on the magnitude of serologic responses, ARS scientists in Ames, Iowa, conducted a study in cattle to determine if calfhood brucellosis vaccination influenced antibody responses after experimental infection with a virulent Brucella strain. Data demonstrated that cattle vaccinated with the B. abortus strain RB51 vaccine had lower titers on brucellosis diagnostic tests after experimental infection with a virulent Brucella strain when compared to responses of non-vaccinated cattle. This data could suggest that detection of infection may be reduced in RB51-vaccinated cattle in endemic areas. This data has implications for regulatory actions in Brucella-infected herds, setting of cutoff values for diagnostic tests, and will be of interest to regulatory officials and producers.

Review Publications
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.
Martins, M., Boggiatto, P.M., Buckley, A., Cassmann, E.D., Falkenberg, S.M., Caserta, L.C., Fernandes, M.H., Kanipe, C.R., Lager, K.M., Palmer, M.V., Diel, D.G. 2022. From Deer-to-Deer: SARS-CoV-2 is efficiently transmitted and presents broad tissue tropism and replication sites in highly susceptible white-tailed deer. PLoS Pathogens. 18(3). Article e1010197.
Wilson-Welder, J.H., Alt, D.P., Nally, J.E., Olsen, S.C. 2021. Bovine immune response to vaccination and infection with Leptospira borgpetersenii serovar Hardjo. mSphere. 6(2).