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Legionella pneumophila growth in macrophages from susceptible mice is genetically controlled
Y Yamamoto1, T W Klein, H Friedman
1Department of Medical Microbiology and Immunology, University of South Florida College of Medicine, Tampa 33612.
Abstract:
Growth of the intracellular opportunistic bacterium Legionella pneumophila in macrophages from A/J mice is a vigorous as growth in macrophages from susceptible guinea pigs and human monocytes, whereas growth is inhibited in macrophages from other mouse strains, such as nonpermissive BALB/c mice. Permissiveness versus nonpermissiveness of macrophages from A/J versus BALB/c mice appeared to be controlled by a genetic mechanism dependent upon a single gene or a closely clustered family of genes. Susceptibility versus resistance of macrophages from F1 offspring of these two strains of mice and macrophages from backcrossed mice prepared from F1 hybrids and the original parental strain showed a segregation of permissiveness for growth of Legionella in vitro, consistent with genetic control.
Insights
Genetic factors control Legionella pneumophila growth in macrophages. Macrophage permissiveness for this bacterium
Area of Science:
- Immunology
- Microbiology
- Genetics
Background:
- Legionella pneumophila is an intracellular opportunistic bacterium.
- Macrophage susceptibility to L. pneumophila varies between host species and strains.
- Previous studies indicate a genetic component to host resistance.
Purpose of the Study:
- To investigate the genetic basis of differential Legionella pneumophila growth in macrophages from distinct mouse strains.
- To determine if a single gene or gene family controls macrophage permissiveness.
Main Methods:
- Culturing of Legionella pneumophila in macrophages derived from A/J and BALB/c mice.
- Analysis of macrophage permissiveness in F1 offspring and backcrossed mice.
- In vitro growth assays to quantify bacterial replication.
Main Results:
- Macrophage growth of L. pneumophila was vigorous in A/J mice, similar to guinea pigs and human monocytes.
- Growth was inhibited in macrophages from BALB/c mice, indicating non-permissiveness.
- Genetic segregation in F1 and backcrossed mice confirmed a single gene or closely linked gene family controls this trait.
Conclusions:
- Macrophage permissiveness for Legionella pneumophila is controlled by a single gene or a small gene family.
- This genetic mechanism dictates susceptibility or resistance to L. pneumophila infection in mice.
- Understanding these genetic factors can inform strategies for controlling Legionnaires' disease.