The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence

Gad Frankel, Gunnar N Schroeder

Research output: Chapter in Book/Report/Conference proceedingChapter (peer-reviewed)

Abstract

Legionella species evolved virulence factors to exploit protozoa as replicative niches in the environment. Cell culture infection models demonstrated that many of these factors also enable the bacteria to thrive in human macrophages; however, these models do not recapitulate the complex interactions between macrophages, lung epithelial, and additional immune cells, which are crucial to control bacterial infections. Thus, suitable infection models are required to understand which bacterial factors are important to trigger disease. Guinea pigs and, most frequently, mice have been successfully used as mammalian model hosts; however, ethical and economic considerations impede their use in high-throughput screening studies of Legionella isolates or small molecule inhibitors.Here, we describe the larvae of the lepidopteran Galleria mellonella as insect model of Legionella pathogenesis. Larvae can be obtained from commercial suppliers in large numbers, maintained without the need of specialized equipment, and infected by injection. Although lacking the complexity of a mammalian immune system, the larvae mount humoral and cellular immune responses to infection. L. pneumophila strain 130b and other prototype isolates withstand these responses and use the Defective in organelle trafficking/Intracellular multiplication (Dot/Icm) type IV secretion system (T4SS ) to inject effectors enabling survival and replication in hemocytes, insect phagocytes, ultimately leading to the death of the larvae. Differences in virulence between L. pneumophila isolates or gene deletion mutants can be analyzed using indicators of larval health and immune induction, such as pigmentation, mobility, histopathology, and survival. Bacterial replication can be measured by plating hemolymph or by immunofluorescence microscopy of isolated circulating hemocytes from infected larvae. Combined, these straightforward experimental readouts make G. mellonella larvae a versatile model host to rapidly assess the virulence of different Legionella isolates and investigate the role of specific virulence factors in overcoming innate host defense mechanisms.

Original languageEnglish
Title of host publicationMethods in Molecular Biology
Subtitle of host publicationLegionella
PublisherSpringer
Pages333-346
Number of pages14
Volume1921
DOIs
Publication statusPublished - 30 Jan 2019

Publication series

NameMethods in Molecular Biology
PublisherHumana Press
ISSN (Print)1064-3745

Fingerprint

Legionella
Molecular Models
Larva
Virulence
Infection
Hemocytes
Virulence Factors
Insects
Macrophages
Survival
Hemolymph
Gene Deletion
Pigmentation
Phagocytes
Humoral Immunity
Fluorescence Microscopy
Bacterial Infections
Cellular Immunity
Organelles
Immune System

Cite this

Frankel, G., & Schroeder, G. N. (2019). The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence. In Methods in Molecular Biology : Legionella (Vol. 1921, pp. 333-346). (Methods in Molecular Biology ). Springer. https://doi.org/10.1007/978-1-4939-9048-1_22
Frankel, Gad ; Schroeder, Gunnar N. / The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence. Methods in Molecular Biology : Legionella . Vol. 1921 Springer, 2019. pp. 333-346 (Methods in Molecular Biology ).
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Frankel, G & Schroeder, GN 2019, The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence. in Methods in Molecular Biology : Legionella . vol. 1921, Methods in Molecular Biology , Springer, pp. 333-346. https://doi.org/10.1007/978-1-4939-9048-1_22

The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence. / Frankel, Gad; Schroeder, Gunnar N.

Methods in Molecular Biology : Legionella . Vol. 1921 Springer, 2019. p. 333-346 (Methods in Molecular Biology ).

Research output: Chapter in Book/Report/Conference proceedingChapter (peer-reviewed)

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AB - Legionella species evolved virulence factors to exploit protozoa as replicative niches in the environment. Cell culture infection models demonstrated that many of these factors also enable the bacteria to thrive in human macrophages; however, these models do not recapitulate the complex interactions between macrophages, lung epithelial, and additional immune cells, which are crucial to control bacterial infections. Thus, suitable infection models are required to understand which bacterial factors are important to trigger disease. Guinea pigs and, most frequently, mice have been successfully used as mammalian model hosts; however, ethical and economic considerations impede their use in high-throughput screening studies of Legionella isolates or small molecule inhibitors.Here, we describe the larvae of the lepidopteran Galleria mellonella as insect model of Legionella pathogenesis. Larvae can be obtained from commercial suppliers in large numbers, maintained without the need of specialized equipment, and infected by injection. Although lacking the complexity of a mammalian immune system, the larvae mount humoral and cellular immune responses to infection. L. pneumophila strain 130b and other prototype isolates withstand these responses and use the Defective in organelle trafficking/Intracellular multiplication (Dot/Icm) type IV secretion system (T4SS ) to inject effectors enabling survival and replication in hemocytes, insect phagocytes, ultimately leading to the death of the larvae. Differences in virulence between L. pneumophila isolates or gene deletion mutants can be analyzed using indicators of larval health and immune induction, such as pigmentation, mobility, histopathology, and survival. Bacterial replication can be measured by plating hemolymph or by immunofluorescence microscopy of isolated circulating hemocytes from infected larvae. Combined, these straightforward experimental readouts make G. mellonella larvae a versatile model host to rapidly assess the virulence of different Legionella isolates and investigate the role of specific virulence factors in overcoming innate host defense mechanisms.

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M3 - Chapter (peer-reviewed)

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Frankel G, Schroeder GN. The Galleria mellonella Infection Model for Investigating the Molecular Mechanisms of Legionella Virulence. In Methods in Molecular Biology : Legionella . Vol. 1921. Springer. 2019. p. 333-346. (Methods in Molecular Biology ). https://doi.org/10.1007/978-1-4939-9048-1_22