Author ORCID Identifier

https://orcid.org/0000-0002-5913-7314

Defense Date

2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Microbiology & Immunology

First Advisor

Richard Marconi

Second Advisor

Lisa Shock

Third Advisor

Daniel Miller

Fourth Advisor

Paula Bos

Fifth Advisor

Todd Kitten

Abstract

Lyme disease, caused by the spirochete Borreliella burgdorferi, is the most common vector-borne infection in North America. A critical determinant of early mammalian infection is outer surface protein C (OspC), a highly variable lipoprotein that is indispensable for spirochete survival but whose precise function remains unresolved. OspC has been proposed to mediate diverse roles, including complement evasion, adhesion, tissue dissemination, and antiphagocytic activity, supporting the view that it is a multifunctional virulence factor. Structural studies have identified two putative ligand-binding domains (LBD1 and LBD2), with LBD2 forming a solvent-exposed crown at the membrane-distal end of the OspC dimer.

To define the contribution of LBD2, eight site-directed mutants were generated in-cis at the native cp26 ospC locus of B. burgdorferi B31. All mutant strains expressed OspC on the surface and retained its α-helical fold and dimerization, yet none established infection in C3H/HeN mice, as measured by culture or seroconversion. Notably, six of the eight mutants exhibited punctate foci of OspC rather than the continuous circumferential distribution observed in the wild-type strain. Complementation with a wild-type ospC allele restored uniform surface localization and rescued infectivity, demonstrating that the integrity of LBD2 is critical for proper surface organization and in vivo function.

These findings identify LBD2 as an essential functional determinant of OspC and suggest that its contribution to infectivity stems from maintaining correct surface presentation or orientation rather than any single physicochemical property. This work establishes a framework for dissecting the molecular interactions that OspC mediates during early infection, providing new insights to guide the development of diagnostics and vaccines targeting OspC.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

12-15-2025

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