Mechanisms of central nervous system invasion by the Lyme disease spirochete, Borrelia burgdorferi

PROJECT SUMMARY/ABSTRACT
Lyme disease, which is caused by infection with the tick-borne pathogen Borrelia burgdorferi, can lead to
inflammatory pathologies affecting the joints, heart, and nervous systems. Neurologic disease, referred to as
Lyme neuroborreliosis, can include meningitis, cranial and peripheral neuritis/neuropathy, and encephalopathy.
As there are no vaccines or effective vector controls against the infection, Lyme disease is and will continue to
be a significant public health concern. The overall goal of these studies is to identify key mechanisms of B.
burgdorferi central nervous system invasion and associated host responses.
A critical gap in our understanding of Lyme disease pathology has been the lack of a reproducible small animal
model of neuroborreliosis. Laboratory mice have been instrumental in identifying the mechanisms of Lyme
arthritis and carditis pathology, however the mechanisms of central nervous system invasion and pathology
remain poorly understood as the prevailing view has been that mice do not develop central nervous system
manifestations. Our recent work challenges this paradigm by demonstrating for the first time that B. burgdorferi
colonizes the meninges and cerebrospinal fluid during murine infection, which is accompanied by an influx of
leukocytes and increased inflammatory proteins. Furthermore, the extent of cerebrospinal fluid involvement is
mouse strain dependent and correlates with strain-specific susceptibility to peripheral Lyme
immunopathologies, suggesting a role for host genetics in central nervous system invasion.
Expanding on our recent findings, we hypothesize that the inflammatory response to B. burgdorferi infection
leads to blood-cerebrospinal fluid barrier breakdown, facilitating central nervous system invasion by both
bacteria and immune cells. Using the murine model of B. burgdorferi infection, we will address the following
aims in our studies: (1) Determine the role of the blood-cerebrospinal fluid barrier as a site for B. burgdorferi
and immune cell entry into the central nervous system; and (2) Identify host immune responses associated
with increased central nervous system invasion, with a focus on pathways previously associated with murine
Lyme arthritis severity and/or blood-cerebrospinal fluid barrier permeability.
The tractability of our novel murine model provides a unique opportunity to experimentally investigate the
mechanisms of central nervous system manifestations during B. burgdorferi infection. By performing the
proposed experiments in mouse strains with altered immune responses to B. burgdorferi infection, we expect
to gain insight into host factors important for bacterial invasion into the central nervous system. This work will
provide the foundation for a long-term research program focused on mechanisms of Lyme neuroborreliosis
pathogenesis, with the overall goal of identifying new targets for prophylactic and therapeutic treatments.

Grant Number: 1R21AI190212-01
NIH Institute/Center: NIH
Principal Investigator: Timothy Casselli