PROJECT SUMMARY/ABSTRACT In keeping with the NIH’s stated priority for the development of vaccines to bacterial zoonoses, our goal is to develop an effective and conveniently delivered vaccine to protect against the spirochaete, Borrelia burgdorferi, the causative agent of Lyme disease. The bacterium is vectored by infected Ixodes species ticks between humans and mammalian reservoirs. Our chosen antigen candidate is OspA, a surface protein which presents as the spirochaete transits between the arthropod vector and the mammalian host. Vaccination with this antigen allows protective antibodies to encounter the spirochaete while still inside the tick as it engorges with a blood meal, and has been shown to be effective as a transmission blocking vaccine. In order to develop adequate amounts of antigen for an effective and adequate immune response, we have established a proprietorial expression system using recombinant maize. An additional advantage of maize expression is that vaccine antigens can be directly administered through the oral route rather than purified for injection. In this proposal, our goal is to produce large amounts of OspA antigen candidate in maize, orally administer the antigen to mice in feed formulated from recombinant maize flour, and demonstrate that the antigen elicits a protective immune response against challenge.