# Harnessing iron acquisition to hinder enterobacterial pathogenesis

> **NIH NIH R56** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2022 · $399,521

## Abstract

PROJECT SUMMARY
The primary objective of this renewal application is to investigate siderophore-based immunization and
antibiotic delivery strategies designed to inhibit the growth of Escherichia coli and non-typhoidal Salmonella
(NTS). These Gram-negative facultative anaerobic bacteria are major causes of infections in diverse patient
populations. E. coli includes commensal organisms, pathogens, and pathobionts (organisms that are usually
harmless but are pathogenic in some settings) and cause infections that include urinary tract infections (UTI),
bacteremia, meningitis, and sepsis. Moreover, a pathovar known as adherent-invasive E. coli (AIEC) is
commonly isolated from patients with Crohn’s disease, a form of inflammatory bowel disease. NTS, including
Salmonella enterica serovar Typhimurium (STm), are major causes of inflammatory diarrhea. The primary site
of E. coli and NTS colonization is the gastrointestinal tract, where these organisms thrive during colitis and
disseminate to other body sites. Recent studies, including work from our laboratories, demonstrate that iron (Fe)
availability is a key factor for the progression of E. coli and Salmonella colonization in the gut, motivating the
research proposed in this grant application. Our central hypothesis is that targeting siderophores and their
uptake machineries can limit enteric pathogen growth in vitro and in vivo. Both E. coli and Salmonella deploy the
catecholate siderophores enterobactin (Ent) and salmochelin (DGE, diglucosylated enterobactin) in the gut to
scavenge Fe3+ from the host. We propose that that blocking Ent&DGE-mediated Fe3+ acquisition by bacterial
pathogens or targeting Ent&DGE transport systems to deliver antibiotics will provide a means to inhibit the growth
of STm, AIEC and possibly other enteric pathogens in the inflamed gut. In support of this notion, we developed
a siderophore-based immunization that inhibits STm and AIEC growth in the murine gut, and we synthesized
and evaluated siderophore-antibiotic conjugates (SACs) based on the Ent&DGE scaffold that target E. coli and
STm. In Aim 1, we will produce monoclonal antibodies that capture Ent&DGE, select the antibodies that exhibit
the greatest growth inhibitory activity against STm and AIEC in vitro, and investigate whether these antibodies
inhibit mucosal expansion of STm and AIEC during colitis in vivo as well as their impact on the gut microbiome.
In Aim 2, we will evaluate the antimicrobial activity of three Ent&DGE-based SACs. Studies in vitro will largely
focus on how key environmental variables that characterize diverse host environments affect the antimicrobial
activity of SACs, whereas studies in vivo will evaluate the consequences of SAC administration on the gut
microbiome composition as well as on inhibiting mucosal expansion of STm and AIEC during colitis. This work
may lead to future development of siderophore-binding antibodies and siderophore-antibiotic conjugates as
therapeutics to limit colonizatio...

## Key facts

- **NIH application ID:** 10599510
- **Project number:** 2R56AI114625-07A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** ELIZABETH M NOLAN
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $399,521
- **Award type:** 2
- **Project period:** 2015-06-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10599510

## Citation

> US National Institutes of Health, RePORTER application 10599510, Harnessing iron acquisition to hinder enterobacterial pathogenesis (2R56AI114625-07A1). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10599510. Licensed CC0.

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