Understanding Barriers to Borrelia burgdorferi Dissemination during Infection Using Massively Parallel Sequencing

Abstract

dBorrelia burgdorferi is an invasive spirochete that can cause acute and chronic infections in the skin, heart, joints, and central nervous system of infected mammalian hosts. Little is understood about where the bacteria encounter the strongest barriers to infection and how different components of the host immune system influence the population as the infection progresses. To identify population bottlenecks in a murine host, we utilized Tn-seq to monitor the composition of mixed populations of B. burgdorferi during infection. Both wild-type mice and mice lacking the Toll-like receptor adapter molecule MyD88 were infected with a pool of infectious B. burgdorferi transposon mutants with insertions in the same gene. At multiple time points postinfection, bacteria were isolated from the mice and the compositions of the B. burgdorferi populations at the injection site and in distal tissues determined. We identified a population bottleneck at the site of infection that significantly altered the composition of the population. The magnitude of this bottleneck was reduced in MyD88 ؊/؊ mice, indicating a role for innate immunity in limiting early establishment of B. burgdorferi infection. There is not a significant bottleneck during the colonization of distal tissues, suggesting that founder effects are limited and there is not a strict limitation on the number of organisms able to initiate populations at distal sites. These findings further our understanding of the interactions between B. burgdorferi and its murine host in the establishment of infection and dissemination of the organism.

Bacterial Heterogeneity Is a Requirement for Host Superinfection by the Lyme Disease Spirochete

“…A recent study involving mixed populations of B. burgdorferi found a significant role for the host innate response in controlling the early stage of B. burgdorferi infection (39). Additionally, the alternative pathway of the complement system has been shown to have a role in mediating B. burgdorferi host specificity (13,38,40).…”

Use of in vivo Expression Technology for the Identification of Putative Host Adaptation Factors of the Lyme Disease Spirochete

“…coinfection with strains B31 and 297) or by challenging severely immunodeficient mice lacking both antibody and complement, and it was proposed to serve as a biological driver of bacterial heterogeneity in nature [Rogovskyy and Bankhead, 2014]. Recent studies have begun to uncover the dynamics of this infection bottleneck using isogenic clones containing genetic tags [Rego et al, 2014;Troy et al, 2013]. These studies using a smaller number of unique challenge clones have seen similar effects, however to a lesser extent.…”

Gene bb0318 Is Critical for the Oxidative Stress Response and Infectivity of Borrelia burgdorferi

“…burgdorferi has been shown to undergo a population bottleneck upon inoculation into the mammalian host (53,54). The innate immune response is critical for controlling B. burgdorferi infection (55)(56)(57)(58).…”

“…The innate immune response is critical for controlling B. burgdorferi infection (55)(56)(57)(58). The magnitude of the spirochete population bottleneck has been shown to be reduced in mice with an impaired innate immune system (54). The oxidative stress that the spirochete encounters during the initial stages of mammalian infection may be due to H 2 O 2 production by innate immune cells, such as macrophages and neutrophils, during the host inflammatory response (9).…”