A vaccine for humans against Lyme disease caused by B. burgdorferi is currently not available due to poor market acceptance and safety concerns of an injectable vaccine based on outer surface protein A (OspA). An alternative approach to protecting humans from Lyme disease is to vaccinate the disease reservoirs to reduce or eliminate B. burgdorferi from vector ticks, thereby suppressing enzootic transmission and preventing them from passing the disease to humans. A number of lab studies have shown that orally administered OspA vaccines successfully vaccinate rodents, and reduce prevalence of infection in ticks. Our objective is to develop a novel approach for preventing human exposure to Lyme disease spirochetes by significantly reducing infection prevalence in the tick vector, Ixodes scapularis, using reservoir targeted vaccines (RTVs) derived from rice grain. In phase I SBIR, we demonstrate that we can produce immunogenic rOspA in rice grain and mice were protected from B. burgdoferi challenge after immunization with rOspA via needle injection. In the present Phase II SBIR proposal, we will develop stable rice lines via field selection in multiple generations to establish seed stock for animal study and for future commercialization. We will test the effectiveness of rOspA in laboratory animals via oral administration on clearance of B. burgdorferi in tick's gut. Finally, we will conduct a field test to determine the reduction of infected tick population in endemic area. Since rice grain is naturally a food of many of the animals expected to serve as B. burgdorferi reservoirs, producing rOspA in rice provides a distinct advantage over other expression systems and more importantly, rice-based rOspA will offer an excellent safety profile to humans, animals and the environment.
Lyme disease, caused by a bite from ticks carrying B. burgdorferi, is a major threat to human health in many areas of the United States. Previous studies show that the prevalence of B. burgdorferi in ticks can be dramatically reduced by vaccinating rodent reservoirs with outer surface protein A from B. burgdorferi. Development of an affordable oral vaccine would enable large scale vaccination of animal reservoirs, and decrease the risk of transmitting Lyme disease to humans.