Antigenic variation plays a vital role in the pathogenesis of many infectious agents, most notably bacteria and protozoa that cause chronic infections. Borrelia burgdorferi and related organisms cause Lyme disease, a multistage, systemic infection that is transmitted by Ixodes ticks and has dermatologic, neurologic, arthralgic, and constitutional manifestations in humans and other animals. Lyme disease Borrelia have an elaborate antigenic variation system consisting of vlsE, a gene expressing a surface-exposed lipoprotein, and a series of vls silent cassettes, which serve as the source of sequences for random, segmental gene conversion events that change the sequence of the central cassette region of vlsE. It has been established that vlsE expression and variation are required for persistence of infection and immune evasion, yet the mechanisms that govern this biologically important process are poorly understood. In this project, several approaches will be used to address these questions.
In Specific Aim 1, a newly developed tissue explant model system will be optimized and utilized to study vlsE recombination. The effects of environmental conditions on vlsE expression and variation will be analyzed by quantitative polymerase chain reaction (qPCR) and sequence specific PCR.
Specific Aim 2 involves the systematic screening and characterization of trans-acting factors (e.g. proteins) that affect vlsE recombination and expression. A transposon mutant library will be used to screen for genes important in vlsE variation and regulation, and in vitro expression libraries will be employed to screen for factors that regulate vlsE expression and variation.
In Specific Aim 3, the roles of cis-acting elements (vls-associated DNA sequences) in vlsE recombination and functional activities will be examined using a combination of bioinformatic analysis of sequences, comparison of the properties of divergent vls systems, and mutagenic analysis of DNA sequences thought to be important in VlsE sequence variation and function. These studies will define the importance and mechanistic properties of VlsE in the immune evasion, persistent infection, and pathogenesis of Lyme disease Borrelia.

Public Health Relevance

Lyme disease is the most prevalent tick-borne infection in North America and Eurasia and can cause long-term infections that affect the skin, joints, heart, and central nervous system. The bacterium that causes Lyme disease (Borrelia burgdorferi) remains hidden from the immune system by constantly changing a surface protein called VlsE. This project studies the mechanisms Borrelia burgdorferi uses to change VlsE. Understanding these mechanisms will help us to discover ways to prevent Lyme disease and to inhibit the organism's ability to cause persistent infection and debilitating symptoms.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI037277-21
Application #
8269801
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Breen, Joseph J
Project Start
1994-09-01
Project End
2016-05-31
Budget Start
2012-06-01
Budget End
2013-05-31
Support Year
21
Fiscal Year
2012
Total Cost
$375,000
Indirect Cost
$125,000
Name
University of Texas Health Science Center Houston
Department
Pathology
Type
Schools of Medicine
DUNS #
800771594
City
Houston
State
TX
Country
United States
Zip Code
77225
Magnarelli, Louis A; Williams, Scott C; Norris, Steven J et al. (2013) Serum antibodies to Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti in recaptured white-footed mice. J Wildl Dis 49:294-302
Norris, Steven J; Howell, Jerrilyn K; Odeh, Evelyn A et al. (2011) High-throughput plasmid content analysis of Borrelia burgdorferi B31 by using Luminex multiplex technology. Appl Environ Microbiol 77:1483-92
Coutte, Loic; Botkin, Douglas J; Gao, Lihui et al. (2009) Detailed analysis of sequence changes occurring during vlsE antigenic variation in the mouse model of Borrelia burgdorferi infection. PLoS Pathog 5:e1000293
Lin, Tao; Gao, Lihui; Edmondson, Diane G et al. (2009) Central role of the Holliday junction helicase RuvAB in vlsE recombination and infectivity of Borrelia burgdorferi. PLoS Pathog 5:e1000679
Embers, Monica E; Liang, Fang Ting; Howell, Jerrilyn K et al. (2007) Antigenicity and recombination of VlsE, the antigenic variation protein of Borrelia burgdorferi, in rabbits, a host putatively resistant to long-term infection with this spirochete. FEMS Immunol Med Microbiol 50:421-9
Norris, Steven J (2006) Antigenic variation with a twist--the Borrelia story. Mol Microbiol 60:1319-22
Bertin, Patricia B; Lozzi, Silene P; Howell, Jerrilyn K et al. (2005) The thermophilic, homohexameric aminopeptidase of Borrelia burgdorferi is a member of the M29 family of metallopeptidases. Infect Immun 73:2253-61
Lawrenz, Matthew B; Wooten, R Mark; Norris, Steven J (2004) Effects of vlsE complementation on the infectivity of Borrelia burgdorferi lacking the linear plasmid lp28-1. Infect Immun 72:6577-85
Iyer, Radha; Kalu, Ogori; Purser, Joye et al. (2003) Linear and circular plasmid content in Borrelia burgdorferi clinical isolates. Infect Immun 71:3699-706
Purser, Joye E; Lawrenz, Matthew B; Caimano, Melissa J et al. (2003) A plasmid-encoded nicotinamidase (PncA) is essential for infectivity of Borrelia burgdorferi in a mammalian host. Mol Microbiol 48:753-64

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