Identifying Determinants of Borrelia burgdorferi and Peromyscus leucopus symbiosis

Project Summary/Abstract: My postdoctoral studies focus on understanding how Borrelia burgdorferi, the causal agent of Lyme disease, survives in nature—which involves studying its relationship with its natural mammalian reservoir host, Peromyscus leucopus. While previous work has demonstrated that Ixodes scapularis ticks disproportionately obtain B. burgdorferi (which can then be passed onto humans) by feeding on asymptomatic P. leucopus mice, it remains unclear (a) why P. leucopus appear better suited than other small rodents to pass on B. burgdorferi, (b) why P. leucopus remain asymptomatic despite chronic, systemic B. burgdorferi infection, and (c) what molecular tools B. burgdorferi uses to successfully infect P. leucopus. Elucidating the natural ecology of B. burgdorferi represents an important public health goal, as, while B. burgdorferi infection is typically treatable, a substantial fraction of patients remains symptomatic for months to decades. Thus, finding mechanisms to prevent B. burgdorferi infection is critical. The long-term goal of this project is to better understand the symbiotic relationship between B. burgdorferi and P. leucopus to reveal targets for disrupting the enzootic cycle and reducing the burden of Lyme disease. This grant seeks to better understand the P. leucopus-B. burgdorferi host-microbe interaction by (a) performing experimental work to monitor the dynamics of B. burgdorferi infection and P. leucopus inflammation change over time, and (b) identify B. burgdorferi genes that are required for P. leucopus infection. For the first goal, I will attempt to understand how bacterial burden in P. leucopus tissues correlates with histopathology, tick infectivity, and changes in gene expression over time. This will involve performing the most comprehensive study of B. burgdorferi infection in these rodents to date and will test a variety of hypotheses that have been postulated but left untested in the field. To accomplish this, I will leverage digital-droplet PCR, RNA-sequencing, microscopic histology analyses, and xenodiagnostic testing. Of note, I will simultaneously perform the same experiments in two Mus musculus inbred lines (C57BL/6J and C3H/HeN, which develop mild and severe Lyme disease-like symptoms, accordingly) to compare my findings against frequently used murine models. For the second aim, I will deploy transposon sequencing screening using a mutant library that my lab has frequently utilized in past publications. In sum, these experiments will dramatically improve our understanding of both the host and pathogen factors that facilitate B. burgdorferi survival in nature. Additionally, this project is well-suited to promote my long-term goal of starting an independent research program at an academic institution, as the datasets generated in this study will serve as the foundation of my future laboratory.