Development of a sequence-basedin silicoOspA typing method forBorrelia burgdorferisensu lato

Abstract

Lyme disease (LD), caused by spirochete bacteria of the genusBorrelia burgdorferisensu lato, remains the most common vector-borne disease in the northern hemisphere.Borreliaouter surface protein A (OspA) is an integral surface protein expressed during the tick cycle, and a validated vaccine target. There are at least 20 recognizedBorreliagenospecies, that vary in OspA serotype. Traditional serotyping ofBorreliaisolates using OspA-specific monoclonal antibodies is technically challenging and reagent-constrained. This study presents a newin silicosequence-based method for OspA typing using next-generation sequence data. Using a compiled database of over 400Borreliagenomes encompassing all major genospecies, we characterized OspA diversity in a manner that can accommodate existing and new OspA types and then defined boundaries for classification and assignment of OspA types based on the sequence similarity. To accommodate potential novel OspA types, we have developed a new nomenclature: OspAin silicotype (IST). Beyond the ISTs which corresponded to existing OspA serotypes (ST1-8), we identified nine additional ISTs which cover new OspA variants inB. bavariensis(IST9-10),B. garinii(IST11-12), and otherBorreliagenospecies (IST13-17). Compared to traditional OspA serotyping methods, this new computational pipeline provides a more comprehensive and broadly applicable approach for characterization of OspA type andBorreliagenospecies to support vaccine development.Impact StatementAs the incidence of LD continues to rise, so does the need to maintain genomic surveillance of disease-causingBorrelia spp.and support clinical development of new vaccines. Towards this goal, introducing the OspAin silicotype (IST) nomenclature scheme, as well as the open-source release of this OspA analysis pipeline, will enable characterization of novelBorreliaOspA types using NGS data without the need for traditional, antibody-based serotyping systems.