The <i>Leptospira</i> immunoglobulin-like protein LigB from <i>Leptospira borgpetersenii</i> serovar Arborea is not required for either acute or chronic infection

Leptospirosis is a globally important zoonotic disease caused by more than 40 pathogenic <i>Leptospira</i> spp. that are responsible for more than 1 million human cases and almost 60,000 deaths annually. The disease also affects many companion, domestic, and wild animal species. Leptospiral immunoglobulin-like proteins (Lig), particularly LigA and LigB, are well-established surface membrane proteins that have been extensively studied due to their interactions with the host immune system. Silencing expression of both <i>ligA</i> and <i>ligB</i> in <i>L. interrogans</i> serovar Copenhageni results in attenuation of virulence, confirming their role as virulence factors. To examine the role of Lig proteins in other pathogenic species of <i>Leptospira</i>, we applied the CRISPR-Prime Editing (CRISPR-PE) strategy to engineer a one-nucleotide frameshift deletion in <i>ligB</i>, generating a knockout mutant in <i>L. borgpetersenii</i> serogroup Ballum serovar Arborea strain LR131, a pathogenic species that lacks <i>ligA</i>. Despite a complete loss of LigB expression, the mutant strain maintained its ability to cause acute lethal infection in hamsters and the ability to establish renal colonization in rats. These findings demonstrate that <i>ligB</i> alone is dispensable for both acute and chronic infection in the <i>L. borgpetersenii</i> strain LR131 background. This work represents the first targeted disruption of <i>ligB</i> in <i>L. borgpetersenii</i> as facilitated by CRISPR-PE and prompts a reevaluation of LigB as a universal virulence determinant in different genetic backgrounds. These insights are critical for advancing our understanding of leptospiral pathogenesis and guiding the design of broadly protective subunit vaccines.