Development and application of an in vitro tick feeding system to identify Ixodes tick environment-induced genes of the Lyme disease agent, Borrelia burgdorferi

Authors: YAMASAKI, YOUKI - Washington State University; SINGH, PREETI - Washington State University; VIMONISH, RUBIKAH - Washington State University; Ueti, Massaro; BANKHEAD, TROY - Washington State University

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2024
Publication Date: 6/7/2024
Citation: Yamasaki, Y., Singh, P., Vimonish, R., Ueti, M.W., Bankhead, T. 2024. Development and application of an in vitro tick feeding system to identify Ixodes tick environment-induced genes of the Lyme disease agent, Borrelia burgdorferi. Pathogens. 13(6). Article 487. https://doi.org/10.3390/pathogens13060487.
DOI: https://doi.org/10.3390/pathogens13060487

Interpretive Summary: Borrelia burgdorferi is a bacterium responsible for causing Lyme disease, which is capable of infecting mammals and tick vectors. To adapt to these different environments, the bacterium's genes are spread across its genome, which is composed of a linear chromosome as well as circular and linear plasmids. To determine which parts of the bacterium's genome are active during infection of a mammalian host, we have used a technique called In Vivo Expression Technology (IVET). However, studying the behavior of the bacterium in ticks has been difficult because of an "infection bottleneck" in mice. To overcome this challenge, we have developed a new method that uses a membrane-based feeding system to infect ticks with B. burgdorferi without the need for a mice infection model. We utilized IVET to identify the active parts of the bacterium's genome during tick infection. This study demonstrates that this new method could be useful in understanding how B. burgdorferi adapts within ticks.

Technical Abstract: The bacterial agent of Lyme disease, Borrelia burgdorferi, exists in an enzootic cycle by adapting to dissimilar mammalian and tick environments. The genetic elements necessary for host and vector adaptation are spread across a bacterial genome comprised of a linear chromosome and essential linear and circular plasmids. The promoter trap system, In Vivo Expression Technology (IVET), has been used to identify promoters of B. burgdorferi that are transcriptionally active specifically during infection of a murine host. However, an observed infection bottleneck effect in mice prevented the application of this system to study promoters induced in a tick environment. In this study, we adapted a membrane-based in vitro feeding system as a novel method to infect the Ixodes spp. vector with B. burgdorferi. Once adapted, we performed IVET screens as a proof of principle via an infected bloodmeal on the system. The screen yielded B. burgdorferi promoters that are induced during tick infection and verified relative expression levels using qRT-PCR. The results of our study demonstrate the potential of our developed in vitro tick feeding system and IVET systems to gain insight into the adaptive gene expression of the Lyme disease bacteria to the tick vector.