Location: Animal Disease Research
Project Number: 2090-32000-043-000-D
Project Type: In-House Appropriated
Start Date: Oct 1, 2021
End Date: Sep 30, 2026
Objective 1: Characterize the immune response that correlates with protection from infection and/or disease. Sub-objective 1A: Identify the functional antibody profile that predicts protection against bovine anaplasmosis. Sub-objective 1B: Identify the vaccine candidates against which the protective, functional antibody response is directed. Objective 2: Develop a vaccine platform for A. marginale antigen expression. Sub-objective 2A: Determine if A. marginale vaccine candidates expressed by C. burnetii Nine Mile phase II induce protective immunity. Sub-objective 2B: Develop media that supports A. marginale replication in the absence of host cells.
Goal 1A1: Characterize the functional Fc-mediated antibody response produced by immunization of cattle using A. marginale OMPs. Specifically, we will measure antibody dependent cellular phagocytosis by bovine monocytes and neutrophils, antibody dependent complement activation, antibody dependent activation of NK cells and WC1+ 'd T cells, and antibody dependent platelet activation. Goal 1A2: Identify the functional antibody profile that best predicts protection from disease. Following challenge with A. marginale, nearly all animals immunized with OMPs are protected from severe disease, however, the degree of protection among individual animals tends to be variable. We will leverage this variation to identify the functional antibody profiles that best predict protective immunity. Goal 1B: Use the functional antibody profile predictive of protective immunity to select vaccine candidates for immunization and challenge trials. We will have identified the Fc mediated effector functions that correlate with protective immunity to bovine anaplasmosis. We will then use these correlates of immunity to identify individual proteins against which the antibodies that mediate these protective immune functions are directed. This will allow us to prioritize the existing vaccine candidates for testing in immunization and challenge trials. The vaccine candidates will be expressed as recombinant protein and used as antigen in the functional antibody assays. We will identify the candidates that elicit an antigen-specific antibody profile that mirrors the profile predictive of protection. Hypothesis 2A1: Immunization of cattle with A. marginale Omps expressed in C. burnetii phase II induce antibodies that recognize the corresponding native A. marginale proteins. As a proof of principle, we will immunize animals with proteins expressed in C. burnetii phase II and determine if the resulting antibodies bind native A. marginale proteins. Hypothesis 2A2: The vaccine candidates identified in Sub-objective 1B, when expressed in C. burnetii phase II, induce protection against A. marginale challenge. We will then express the vaccine candidates prioritized in Sub-objective 1B in C. burnetii phase II and determine if they induce protective immunity. Goal 2B: Develop an axenic growth medium for A. marginale. An efficient method to culture A. marginale in the absence of animals or host cells will allow for the use of OMPs in a vaccine and circumvent the need to identify a subset of proteins and the appropriate formulation to produce a recombinant vaccine. Using a step-wise approach we will identify the nutrients and other components required for A. marginale metabolism as measured first by protein synthesis and then by replication. Once axenic replication is achieved, we will verify expression of a full array of outer membrane proteins.