Mitchell, Angela2026-05-282026-05-282026https://hdl.handle.net/1828/23953Syphilis is a major global public health concern with an estimated 8 million new cases each year. The surge in syphilis cases worldwide emphasizes the need for development of a vaccine to complement existing public health measures. Achieving this goal requires a comprehensive understanding of the pathogenic mechanisms used by Treponema pallidum subsp. pallidum, the causative agent of syphilis, including how T. pallidum traverses the blood-brain barrier (BBB) to cause neurosyphilis. Current understanding of T. pallidum’s proteome response to human brain microvascular endothelial cells (BECs), a model for the BBB, is limited. Here, we use liquid chromatography tandem-mass spectrometry (LC-MS/MS)-based label-free quantitative proteomic analyses to investigate T. pallidum protein expression following exposure to BECs. Treponema pallidum was co-incubated for 4 and 24 hours with BECs or rabbit epithelial cells (Sf1Eps; serves as a background control for the in vitro culture conditions used for T. pallidum growth). In this study, a subset of T. pallidum proteins were differentially expressed under conditions where the bacterium was exposed to BECs compared to control Sf1Ep conditions. Notably, these differentially expressed proteins included proteins in the pathogenesis-related categories of outer membrane proteins, predicted pathogenesis-related proteins, and potential human mimic proteins. This study extends our understanding of T. pallidum pathogenesis and informs syphilis vaccine development by identifying T. pallidum proteins that may be important for treponemal BBB traversal. Further, these investigations enhance our understanding of the serious sequelae of neurosyphilis, a life-threatening infection of the central nervous system by T. pallidum that can cause serious neurological issues, including stroke and paralysis.enAvailable to the World Wide WebThesis