Development of a sequence-based OspA typing method for .

Lyme disease (LD), caused by spirochete bacteria of the genus , remains the most common vector-borne disease in the northern hemisphere. outer surface protein A (OspA) is an integral surface protein expressed during the tick cycle, and a validated vaccine target. There are at least 20 recognized genospecies, that vary in OspA serotype. This study presents a new sequence-based method for OspA typing using next-generation sequence data. Using a compiled database of over 400 genomes encompassing the 4 most common disease-causing 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: OspA type (IST). Beyond the ISTs that corresponded to existing OspA serotypes 1-8, we identified nine additional ISTs that cover new OspA variants in (IST9-10), (IST11-12), and other genospecies (IST13-17). The IST typing scheme and associated OspA variants are available as part of the PubMLST spp. database. Compared to traditional OspA serotyping methods, this new computational pipeline provides a more comprehensive and broadly applicable approach for characterization of OspA type and genospecies to support vaccine development.