Location: Infectious Bacterial Diseases Research2013 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 of dollars 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 indicated 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 a new B. suis vaccine developed in our laboratory is effective in protecting swine against brucellosis. Limited data suggests that feral swine may be more susceptible to infection with B. suis than domestic swine. The initial assembly of the bison genome is completed and further work is being done to polish and improve the annotated sequence. Initial studies of host and pathogen gene expression when B. abortus infects cattle are being completed. The availability of the bison genomic sequence combined with the studies in cattle will allow comparative analysis of the interaction between natural hosts and Brucella abortus, and may identify genes important for disease pathogenesis. The project is also evaluating new vaccine strategies and exploring new diagnostic approaches for detection and prevention 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 and prevent reintroduction of this disease into livestock in the United States.