# Defining the Intracellular Growth Niche of Foodborne Listeria monocytogenes

> **NIH NIH R21** · UNIVERSITY OF KENTUCKY · 2021 · $46,056

## Abstract

Ingestion of Listeria monocytogenes (Lm)-contaminated food results in human disease ranging in severity
from mild, self-limiting gastroenteritis to life-threatening septicemia and meningoencephalitis. The specific
factors that influence disease severity are not well understood, and our knowledge of the intestinal phase of
listeriosis, in particular, is severely limited. We recently developed a mouse model of foodborne infection to
study the interaction of Lm with intestinal innate immune cells. In preliminary studies, we found that the
majority of Lm in the gut were extracellular. This was an unexpected result, because intracellular growth
and spread from cell-to-cell without encountering the extracellular milieu are generally regarded as the
primary virulence strategies for these facultative intracellular bacteria. LplA1-deficient Lm that were unable
to replicate intracellularly could readily invade the gut mucosa and establish infection in the underlying
lamina propria, but did not persist as well as wildtype Lm, and by three days post-infection had a severe
defect in spreading to the mesenteric lymph nodes (MLN). This suggests that intracellular growth is not
required for the initial stages of intestinal infection, but replication in some as-yet-unidentified cell type in the
gut becomes increasingly more important as the infection proceeds. Multicolor flow cytometry can
discriminate eight different subsets of myeloid-derived phagocytes that are unique to the gut. Preliminary
data provided here verified that intestinal tissue contained at least one cell type that could support
intracellular growth of Lm, and ruled out Ly6Chi monocytes and all three subsets of conventional dendritic
cells as the intracellular niche. The primary goal of this proposal is to identify the cell type(s) in the gut that
support intracellular growth of Lm and to define the innate immune response of intestinal cell types that that
interact primarily with either intracellular or extracellular Lm. We hypothesize that Lm initially interact
primarily with cell types that that they cannot efficiently invade or survive in, and that later in the course of
infection, the bacteria shift to a cell type that serves as a protected intracellular growth niche.!In Aim 1, four
candidate intestinal myeloid cell types will be sort purified, infected directly ex vivo and assayed for both
intracellular localization and replication. In Aim 2, flow cytometry will be used to identify Lm-associated cells
in the lamina propria and submucosa of the ileum and colon as well as the MLN that drain each of these
tissues (SI-MLN and LI-MLN) to track the fate of Lm that invade the gut mucosa in mice. In Aim 3, we will
define the initial response of all eight subsets of intestinal myeloid cells by measuring the production of
cytokines known to be triggered by either host cell surface bound or cytosolic receptors. These exploratory
studies will fill a key knowledge gap in the field by defining the early e...

## Key facts

- **NIH application ID:** 10356591
- **Project number:** 3R21AI151482-02S1
- **Recipient organization:** UNIVERSITY OF KENTUCKY
- **Principal Investigator:** SARAH E. F. D'ORAZIO
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $46,056
- **Award type:** 3
- **Project period:** 2020-03-01 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10356591

## Citation

> US National Institutes of Health, RePORTER application 10356591, Defining the Intracellular Growth Niche of Foodborne Listeria monocytogenes (3R21AI151482-02S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10356591. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*