# Mechanisms of intracellular pathogen dissemination

> **NIH NIH R01** · UNIVERSITY OF VIRGINIA · 2020 · $478,487

## Abstract

Listeria monocytogenes and Shigella flexneri are human intestinal pathogens that replicate in the cytosol of
infected cells and spread directly from primary infected cells to adjacent cells. The dissemination process is a
fundamental aspect of pathogenesis as spreading-defective bacterial mutants are essentially avirulent. The
ability of L. monocytogenes and S. flexneri to spread from cell to cell is related to their ability to display actin-
based motility in the cytosol of infected cells. These bacteria produce virulence factors that lead to the
recruitment at their surface of an essential host cell actin nucleator, the ARP2/3 complex. This results in actin
polymerization at one pole of the bacteria, which propels the rods throughout the cytosol. Seminal electron
microscopy studies revealed that, when bacteria reach the cell cortex, they form plasma membrane extensions
that project into the cytosol of adjacent cells. These protrusions are resolved in adjacent cells into double
membrane vacuoles, from which the pathogens escape by producing virulence factors that disrupt the integrity
of eukaryotic membranes. In contrast to our advanced understanding of the molecular mechanisms supporting
cytosolic actin-based motility, the mechanisms supporting pathogen dissemination through membrane
protrusion formation are unresolved. To address this gap in knowledge, we have developed innovative
procedures for imaging intracellular pathogen dissemination and identified cellular and bacterial factors
supporting bacterial pathogen spread from cell to cell. In previous work, we defined the cellular machinery and
the bacterial factors specifically required for L. monocytogenes spread from cell to cell. Recently, we uncovered
the notion that, although utilizing similar mechanisms of actin-based motility in the cytosol, L. monocytogenes
and S. flexneri have evolved different strategies of cell-to-cell spread. Unlike L. monocytogenes, S. flexneri
hijacks phosphoinositide (PI(3)P) signaling in protrusions in order to facilitate their resolution into vacuoles.
Here, we propose to gain the first mechanistic insight into the bacterial and cellular mechanisms supporting S.
flexneri PI(3)P-dependent dissemination (Aim1 and Aim2); and the role of PI(3)P-dependent dissemination in
pathogenesis (Aim3).

## Key facts

- **NIH application ID:** 9917682
- **Project number:** 5R01AI073904-12
- **Recipient organization:** UNIVERSITY OF VIRGINIA
- **Principal Investigator:** HERVE F AGAISSE
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $478,487
- **Award type:** 5
- **Project period:** 2007-06-01 → 2023-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9917682

## Citation

> US National Institutes of Health, RePORTER application 9917682, Mechanisms of intracellular pathogen dissemination (5R01AI073904-12). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9917682. Licensed CC0.

---

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