Ability of Antibody Against Coxiella burnetii LPS to Confer Protective Immunity

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The objective of this application is to characterize the role of antibody (Ab)-mediated immunity (AMI against Coxiella burnetii infection. It is based on our observations: 1) formalin-inactivated phase I vaccine (PI-V) generated complete protection against virulent C. burnetii challenge in BALB/c mice, but phase I vaccine (PII-V) did not confer significant protection; 2) PI-V and PII-V elicited different Ab responses, while cytokine responses were similar; 3) phase I lipopolysaccharide (PI-LPS) was able to induce a level o protection similar to PI-V while phase II lipopolysaccharide (PII-LPS) conferred no significant protection; 4 passive transfer of immune serum (IS) from PI-V vaccinated mice induced a level of protection similar to PI-V vaccination in naive mice. The first specific aim is to characterize the role of AMI against C. burnetii infection The working hypothesis is that Abs play a critical role in Pl-V-induced protection against C. burnetii infection We will evaluate the contribution of IS-induced protection against C. burnetii infection in intraperitoneal and aerosol challenged BALB/c mice and aerosol challenged guinea pigs. We will determine whether Abs are the active components of IS-induced protection and define the kinetics of passively transferred antibody protection. The second specific aim will determine the key protective antibody isotypes and epitope targets The working hypothesis is that the target of AMI is LPS core and/or O-side chain polysaccharide. We wil ourify immunoglobulin from serum and establish whether the protective component of IS is antibody. We wil then determine the isotype of protective AMI to develop a hypothesis on the mechanism of AMI. The epitopes recognized by AMI will be defined using highly purified LPS, and LPS components through mmunizations and absorption experiments. As a complimentary approach, a panel of anti-C.burnetii LPS monoclonal antibodies (Mabs) will be generated and tested for the ability to confer immunity by passive transfer. These studies will provide the feasibility, proof of concept research to design a subunit vaccine, which we plan to submit as a product development proposal for the competing continuation application for the WRCE.