Effects of a novel OspA Vaccine on Acquisition and Transmission of Borrelia burgdorferi in Ixodes scapularis and Peromyscus maniculatus
Author: Alice Truong
Faculty Supervisor: Andrea Swei
Department: Biology
Ticks are found all over the globe and can spread a variety of diseases that have become a growing health concern, especially in North America. The most well-known tick borne disease is Lyme disease is mainly spread to humans by the arthropod from rodent reservoirs and is caused by the spirochete Borrelia burgdorferi. Although there is not currently a human vaccine for Lyme disease on the market, there are several reservoir-targeted vaccines being developed to break the transmission cycle and indirectly reduce human disease risk. Reservoir-targeted vaccines using the outer surface protein A (ospA) of the spirochete have been shown to both protect Peromyscus mice from disease acquisition as well as eradicate the pathogen from Ixodid spp. ticks. The main methods of vaccine administration in previous studies, however, would be impractical for application to the field and long-term protection. Recent developments have been made to deliver recombinant ospA vaccines to reservoirs through an oral bait. These former studies mainly focus on the East coast Lyme disease system and the East coast strain of Borrelia burgdorferi, B31, but it have not yet been applied to other parts of North America. In laboratory experiments, we investigated the effects the recombinant ospA vaccine would have on disease acquisition and transmission in both Peromyscus maniculatus and Ixodes scapularis to gauge its effectiveness on the West coast. We found that the vaccine appeared to be more effective at protecting the mice from acquiring the CA4 strain, with bacterial loads being significantly lower in mice infected with the CA4 strain. Interestingly, there was a significant decrease in infection prevalence in nymphs infected with CA4, whereas nymphs infected with B31 had an increase in infection prevalence. Although the results of this study did not have strong statistical power due to the small sample size of mice, they suggest that the vaccine will be effective in breaking the Lyme disease transmission cycle on the West coast.