# Functions of Leptospira Lig Proteins in the Pathogenesis of Leptospirosis

> **NIH VA I01** · VA GREATER LOS ANGELES HEALTHCARE SYSTEM · 2022 · —

## Abstract

Leptospirosis is a neglected global human health problem caused by transmission from reservoir
hosts that harbor pathogenic Leptospira species in their kidneys and shed them into the environment via
their urine. Our goal is to elucidate the role(s) of the surface-exposed leptospiral immunoglobulin-
like (Lig) proteins in mechanisms of leptospiral pathogenesis and immunity. The LigA and LigB
proteins exhibit high affinity binding to host ligands and inhibit complement activation, trigger plasminogen,
and inhibit fibrin formation. However, initial studies found that ligA and ligB single gene knockout mutants
were competent for infection. A recent study by one of our collaborators showed that knocking down
expression of both ligA and ligB by targeting their identical promoters with the TALE system resulted in the
loss of virulence, indicating that the functions of LigA and LigB are redundant. Despite the large and
growing literature on their structure and function, the roles of the Lig proteins in virulence remain poorly
understood. The in vitro activities of the Lig proteins suggest that their role is to resist host defense
mechanisms. Our overall hypothesis is that discrete segments of the Lig proteins are required at an
early step of infection to evade killing by the host. For this project, we will focus on LigB since ligA is
missing from a majority of pathogenic Leptospira species. We will evaluate the functions of LigB in the
context of the bacterial cell and determine which of its domains are responsible for these functions. We will
also develop a LigB vaccine that provides cross-protective immunity. To accomplish these goals, we will
employ powerful and innovative approaches to track infection including whole animal optical imaging and
high-throughput parallel sequencing. These studies are vital for development of effective approaches for
protection from and treatment of leptospirosis.
 Specific Aim 1. When are the Lig proteins critical for infection? The wild-type and TALE-lig
knockdown strains of L. interrogans will be engineered to express bioluminescence. Hamsters will be
infected with the bioluminescent strains, and infection will be monitored with whole animal in vivo imaging to
determine when and where infection is halted when the Lig proteins are not generated.
 Specific Aim 2. What functions are mediated by LigB expressed on the bacterial cell surface?
We will determine the bacterial cell surface functions mediated by the LigB by employing a “gain-of-function”
strategy. We will transform L. biflexa with a ligB plasmid and test the ability of the “knock-in” strain to adhere
to host plasma proteins, interfere with serum killing, activate plasminogen, and slow fibrin clot formation. We
will also perform these experiments with the L. interrogans TALE-lig knockdown strain and with the
knockdown strain harboring ligB plasmid to determine the contribution of LigB to these pathogenic functions.
 Specific Aim 3. What regions of LigB are respo...

## Key facts

- **NIH application ID:** 10455512
- **Project number:** 5I01BX002003-08
- **Recipient organization:** VA GREATER LOS ANGELES HEALTHCARE SYSTEM
- **Principal Investigator:** James Matsunaga
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2022
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2014-01-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10455512

## Citation

> US National Institutes of Health, RePORTER application 10455512, Functions of Leptospira Lig Proteins in the Pathogenesis of Leptospirosis (5I01BX002003-08). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10455512. Licensed CC0.

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