Location: Infectious Bacterial Diseases Research2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Identify specific factors including tissue or cell tropism, gene regulation, immune evasion mechanisms, and protective antigens through use of transcriptome and proteosome technologies to provide information on the pathophysiology of Brucella species and the host-pathogen interaction. Subobjective 1.1: Characterize transcriptome responses of cattle and pathogen (Brucella abortus) associated with experimental infection. Subobjective 1.2: Engineer site-directed mutants of Brucella spp. to be used as potential live attenuated vaccine candidates. Objective 2: Develop improved diagnostic assays with increased sensitivity and specificity that will differentiate the various Brucella species and allow determination of phylogenetic relationships. Subobjective 2.1: Development of more sensitive and specific B. suis serologic tests for swine. Subobjective 2.2: Improvements in cattle diagnostics to allow serologic differentiation of B. abortus and B. suis infections. Subobjective 2.3: Characterize molecular markers that clarify phylogenetic linkages among isolates with similar DNA fingerprints. Objective 3: Develop improved vaccines using new and novel delivery systems and platforms. Subobjective 3.1: Identify safe and efficacious vaccination strategies to protect targeted hosts against brucellosis caused by Brucella abortus. Subobjective 3.2: Identify safe and efficacious vaccination strategies to protect swine (including feral swine) against infection with Brucella suis.
1b. Approach (from AD-416):
The three objectives of this project include a basic research component (Obj 1), a diagnostic component (Obj 2), and a vaccine efficacy component (Obj 3) as exemplified in Fig 3. The basic research portion is designed to develop basic knowledge of gene expression in the host or pathogen, or modify a Brucella gene which the pathogen may use to subvert immune recognition, in an effort to provide approaches for improved vaccines or diagnostics that could eventually be evaluated in other objectives (Obj 2 & 3). The vaccine efficacy component (Obj 3) builds on previous experiments by expanding RB51 vaccination approaches that directly support the proposed approaches in the Bison Remote Vaccination EIS, and building on previous data using a rough vaccine strain (353-1) and Salmonella RASV strains. Other experiments will use a novel vaccine approach in elk that may modify the non-protective host response to intracellular bacteria. Experiments with B. suis and B. abortus in Obj 1 may also identify targets that may lead to novel approaches for diagnostics in Obj 2. Objectives 1 and 3 will also provide samples to assist in diagnostic development experiments in Obj 2. Scientific advances in diagnostics and vaccines will support National Brucellosis Eradication programs and provide scientific support to other agencies with responsibilities for managing brucellosis in wildlife.
3. Progress Report:
USDA initiated control measures for brucellosis in the 1930’s and established an eradication program in the 1950’s. In support of these regulatory efforts, billions have been invested at the state and federal level to achieve eradication of brucellosis from cattle. However, persistence of Brucella in wildlife reservoirs (bison, elk, and feral swine) pose a risk for reintroduction of disease to domestic livestock. Development of new vaccines and diagnostics that can be applied to domestic livestock and/or wildlife under current field conditions are needed. During the past year, collaborative projects evaluating brucellosis vaccines in elk, bison, and swine have been conducted; including efficacy trials conducted under Biolevel 3 containment. Data collected has suggested that booster vaccination of bison with RB51 (calfhood plus yearling vaccination) induces greater protection against experimental challenge than a single vaccination administered to calves. Data also suggests that administering multiple vaccinations of RB51 to calves may reduce protection when compared to single vaccination. Limited data suggests that pneumatic vaccination with RB51 may be more protective than a single calfhood vaccination. A Brucella suis vaccine being developed by the project demonstrated safety and efficacy when administered to swine orally or by parenteral vaccination. Work on sequencing the bison genome is progressing and will allow development of molecular approaches that molecularly define the interaction between host and pathogen when Brucella abortus infects bison. The project is also evaluating new brucellosis vaccine candidates and exploring new diagnostic strategies for detection of brucellosis in domestic livestock and wildlife. Advances in vaccines and diagnostics will be useful for protecting domestic livestock and managing brucellosis in current wildlife reservoirs within the U.S. Overall, work conducted by the project will facilitate eradication of brucellosis from natural hosts, prevent reintroduction of this disease into livestock in the United States, and help identify the source of new infections.
1. Pneumatic or Multiple vaccination of bison calves with vaccine RB51. There is a high prevalence of brucellosis in free-ranging bison in Yellowstone National Park. As any vaccination program will be difficult and expensive, the most efficacious brucellosis vaccine for bison is needed. ARS researchers in Ames, Iowa, evaluated the safety, immunity, and protection after bison were vaccinated with a single RB51 injection, 4 times by injection, or a single pneumatic vaccination with a needleless system. Measurements of immunity were similar across treatments and did not support the hypothesis that multiple vaccinations would induce greater responses. Experimental protection was similar for the single injection and pneumatic vaccination treatments, but data suggested that bison receiving multiple vaccinations had reduced protection. These data suggests that too frequent vaccination of bison calves with RB51 may actually reduce protection against brucellosis. Results from this study suggests that pneumatic vaccination can be a safe, effective, and needle-less procedure for disease prevention.
2. Bison Genome sequencing. Obtaining and annotating the genomic sequence of a natural host of Brucella will allow detailed understanding of gene expression and regulation in the host and pathogen during natural infections. Greater knowledge of these interactions will allow identification of host and pathogen genes that regulate or modulate infection. ARS researchers in Ames, Iowa, used new generation sequencing technology to obtain the sequence of the bison genome. Currently the genome sequence is being analyzed. Advances in basic molecular knowledge of host and pathogen gene expression will be of benefit in developing new species-specific approaches for advancement of vaccines and diagnostics.
Pires, A.F., Hoar, B.R., Sischo, W.M., Olsen, S.C. 2011. Serological response to administration of Brucella abortus strain RB51 vaccine in beef and dairy heifers, using needle-free and standard needle-based injection systems. Bovine Practitioner Journal. 45(2):1-6.