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

Authors: FERNANDES, LUIS - Oak Ridge Institute For Science And Education (ORISE); Putz, Ellie; Nally, Jarlath

Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2026
Publication Date: 3/19/2026
Citation: Fernandes, L.G., Putz, E.J., Nally, J.E. 2026. The Leptospira immunoglobulin-like protein LigB from Leptospira borgpetersenii serovar Arborea is not required for either acute or chronic infection. Infection and Immunity. https://doi.org/10.1128/iai.00662-25.
DOI: https://doi.org/10.1128/iai.00662-25

Interpretive Summary: Leptospirosis is a widespread disease affecting both humans and animals, caused by various species of the bacterium Leptospira. 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 ligA and ligB in L. interrogans serovar Copenhageni results in attenuation of virulence, whereas single mutagenesis of either ligA or ligB still results in virulent bacteria, most probably due to the overlapping properties displayed by Lig proteins. Interestingly, ligA is absent in L. borgpetersenii species, so we aimed to investigate whether LigB is required for virulence in the absence of ligA. We used a recently described tool called CRISPR-Prime Editing to make a one nucleotide deletion in the ligB gene from a highly infectious strain of L. borgpetersenii serovar Arborea, recently isolated from rodents in the US Virgin Islands. Hamsters and rats were experimentally infected with either normal or LigB-deficient bacteria. Despite 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 ligB alone is dispensable for both acute and chronic infection in the L. borgpetersenii strain LR131 background. This challenges the idea that LigB-based vaccines are universally applicable.

Technical Abstract: Leptospirosis is a globally important zoonotic disease caused by more than 40 pathogenic Leptospira spp. that are responsible for more than one 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 ligA and ligB in L. interrogans 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 Leptospira, we applied the CRISPR-Prime Editing strategy to engineer a one-nucleotide frameshift deletion in ligB, generating a knockout mutant in L. borgpetersenii serogroup Ballum serovar Arborea strain LR131, a pathogenic species that lacks ligA. Despite 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 ligB alone is dispensable for both acute and chronic infection in the L. borgpetersenii strain LR131 background. This work represents the first targeted disruption of ligB in L. borgpetersenii 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.