# Innate immunity and inflammatory response of macrophages to Legionella infection

> **NIH NIH R01** · UNIVERSITY OF LOUISVILLE · 2022 · $382,517

## Abstract

Project Summary
Depending on the signals in vitro, macrophages can undergo transient and reversible differentiation
into two main subsets: pro-inflammatory “M1” (classically activated) or anti-inflammatory “M2”
(alternatively activated) phenotype. Upon exposure of macrophages to high levels of glucose in vitro
or in diabetic patients in vivo, they undergo differentiation and activation into a M1 pro-inflammatory
state, which produces pro-inflammatory cytokines mediated by cellular reprogramming of metabolism
through upregulating aerobic glycolysis. The M1 pro-inflammatory differentiation of macrophages is
an import arm of the innate immune response to control bacterial infections. Our preliminary data
show that when macrophages engulf the intracellular bacterial pathogen Legionella pneumophila
(Lp), they rapidly respond by differentiation into an activated M1-like pro-inflammatory phenotype.
Despite this rapid macrophage pro-inflammatory activation, the Legionella-containing vacuole
(LCV) bypasses macrophage activation by limiting its fusion to lysosomes. We show that the early
M1-like pro-inflammatory differentiation of human monocytes-derived macrophages (hMDMs) to
Lp is an innate immune response to cytosolic hyper-glucose generated through rapid degradation of
glycogen by the injected Legionella amylase (LamA) effector. We discovered that Lp has evolved a
lysosomal degradation bypass pathway within the pro-inflammatory hMDMs by injecting the MavE
effector, which becomes localized in a micro-domain on the cytosolic side of the LCV membrane.
The mavE-deficient mutant is targeted by hMDMs to the lysosomes for degradation, and the mutant
is totally attenuated in vitro and in vivo. We have resolved the novel three dimensional crystal structure
of MavE, which shows a cytosolic surface-exposed domain with an NPxY eukaryotic motif involved
in binding to phosphotyrosine-binding adaptor proteins. Our central hypothesis is: the M1-like pro-
inflammatory activation of hMDMs to Lp infection is an innate immune response to the cytosolic
hyper-glucose elicited by LamA, and the pathogen utilizes MavE to bypass the innate immune
macrophage pathway of lysosomal degradation. To test the hypothesis, our specific aims are:
Specific Aim I: The mechanisms of M1-like pro-inflammatory differentiation of hMDMs in
response to the effect of LamA; and Specific Aim II: The mechanisms of evasion of the innate
macrophage function of lysosomal degradation through utilization of a lysosomes bypass
pathway mediated by MavE. Upon completion of our proposed studies, we will discover the
mechanism of the innate pro-inflammatory response of macrophages to Lp and the lysosomal
degradation bypass pathway maneuvered by the pathogen to avoid a fatal fate.

## Key facts

- **NIH application ID:** 10466923
- **Project number:** 5R01AI140195-05
- **Recipient organization:** UNIVERSITY OF LOUISVILLE
- **Principal Investigator:** Yousef A Abu Kwaik
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $382,517
- **Award type:** 5
- **Project period:** 2018-09-14 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10466923

## Citation

> US National Institutes of Health, RePORTER application 10466923, Innate immunity and inflammatory response of macrophages to Legionella infection (5R01AI140195-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10466923. Licensed CC0.

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