Development of a baited oral vaccine for use in reservoir-targeted strategies against Lyme disease.

Lyme disease is a major human health problem which continues to increase in incidence and geographic distribution. As a vector-borne zoonotic disease, Lyme disease may be amenable to reservoir targeted strategies for control. We have previously reported that a vaccinia virus (VV) based vaccine expressing outer surface protein A (OspA) of Borrelia burgdorferi, the causative agent of Lyme disease, protects inbred strains of laboratory mice against infection by feeding ticks and clears the ticks of infection when administered by gavage. Here we extend these studies to develop an effective bait formulation for delivery of the VV based vaccine and test its characteristics under simulated environmental conditions. We show that this vaccine is efficacious in decreasing acquisition of B. burgdorferi by uninfected larval ticks as well as in decreasing transmission from infected ticks to its natural reservoir, Peromyscus leucopus, when fed to mice in oral baits. Using live, in vivo imaging techniques, we describe the distribution of vaccinia virus infection after ingestion of the baited vaccines and establish the use of in vivo imaging technology for optimization of bait delivery. In summary, a VV based OspA vaccine is stable in an oral bait preparation and provides protection against infection for both the natural reservoir and the tick vector of Lyme disease.