Transmission of Borrelia burgdorferi (Bb) via tick-bite leads to the development of Lyme disease, which is the leading vector-borne disease in North America. If not diagnosed and treated appropriately with antibiotics, Bb can produce lasting and debilitating disease in myriad tissues, resulting in significant personal and public health costs. After transmission into a host, the bacteria remain locally in the skin tissues for at least 12-48h before disseminating via the skin to eventually establish persistent infection in multiple tissues throughout the host. The mechanisms by which Bb evades immune clearance are largely unknown. In vitro analyses have been shown to be lacking in their ability to accurately identify host responses to this unique obligate parasite, highlighting the need for better in vivo models. Our group has recently developed novel intravital microscopy techniques that allow for the direct assessment of fluorescent Bb with different immune cell populations directly within the intact skin of living mice and in real-time, providing us for the first time with the tools to accurately assess these critical interactions in the natural host environment. Preliminary data indicates these techniques can accurately delineate depth and distance in skin tissues, identify different extracellular matrix molecules and their co-localization with Bb, and distinguish/measure different diverse motility and interactive characteristics of both Bb and key innate immune cell types, confirming that our techniques are able to perform these analyses. The overall goal is to use these intravital techniques, together with established infection models, to more accurately assess Bb interactions with important immune cell populations and mediators within host skin tissues, and thus more accurately identify virulence mechanisms that are critical for escaping immune clearance and causing Lyme disease. Our preliminary studies have delineated the population kinetics of Bb in skin over >2 years, as well as identified Bb-elicited IL-10 as mediating suppressive effects on overall immune functions and Bb clearance. Based on these findings, fluorescent Bb will be used to provide real-time feedback to determine the relative importance of different immune mechanisms in controlling Bb numbers within skin, different pools of fluorescently-labeled Bb-specific Ab will be used to delineate how Abs interact with Bb during the acute phases of LD, and different IL-10-deficient mouse models utilized to determine how IL-10 suppresses efficient clearance of Bb from mouse tissues.
The specific aims for this proposal are:
Aim 1. Delineate the mechanisms for Bb-elicited IL-10-mediated suppression of innate immune responses to Bb infection within skin tissues.
Aim 2. Delineate the mechanisms that inhibit Ab-mediated clearance of Bb. These studies should provide the first accurate description of the Bb-immune cell interactions that occur during natural infection and dissemination in skin tissues, and may identify targets for potential Lyme therapies.

Public Health Relevance

Transmission of Borrelia burgdorferi (Bb) via tick-bite leads to the development of Lyme disease, which is the leading vector-borne disease in North America. Because current laboratory techniques have proven inadequate, little is known regarding how these bacteria evade immune-mediated clearance, which is crucial for establishing disease. This proposal will utilize novel microscopy-based imaging techniques to directly observe how Bb interacts with a number of critical immune cell types in the presence/absence of important immune mediators, thus allowing identification of key mechanisms that allow these pathogens to escape clearance.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
1R01AI121970-01A1
Application #
9185801
Study Section
Host Interactions with Bacterial Pathogens Study Section (HIBP)
Program Officer
Ilias, Maliha R
Project Start
2016-06-22
Project End
2021-05-31
Budget Start
2016-06-22
Budget End
2017-05-31
Support Year
1
Fiscal Year
2016
Total Cost
$389,683
Indirect Cost
$129,529
Name
University of Toledo
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
807418939
City
Toledo
State
OH
Country
United States
Zip Code
43614