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Imaging InlC Secretion to Investigate Cellular Infection by the Bacterial Pathogen Listeria monocytogenes
Published on: September 19, 2013
Immunogold labelling of Listeria monocytogenes virulence-related factors within Caco-2 cells
1Division of Bacterial and Mycotic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia 30333.
Abstract:
We demonstrated by immunoelectron microscopy that listeriolysin O (LLO), phospholipases and other putative virulence-related proteins produced by Listeria monocytogenes were primarily cell-wall-associated when the bacterium infected Caco-2 tissue culture cell monolayers. Antibodies made to LLO, serogroup 1/2a reacted poorly with serogroup 4b cells and vice-versa, indicating fundamental structural differences in the two proteins. Finally, comet-tail pseudopod structures shown to be involved in cell-to-cell passage of Listeria in Caco-2 cells did not possess detectable Listeria antigens on their anterior surface or within their structure, suggesting that the phagocytic process is primarily host-cell-dependent once it is initiated by the bacterial cell.
Insights
Listeria monocytogenes virulence proteins are cell-wall-associated during Caco-2 cell infection. Comet-tail structures involved in cell passage lack bacterial antigens, indicating host-cell dependence in phagocytosis.
Area of Science:
- Microbiology
- Cell Biology
- Immunology
Background:
- Listeria monocytogenes is an intracellular pathogen that infects host cells.
- Virulence factors, such as listeriolysin O (LLO), play crucial roles in Listeria pathogenesis.
- Understanding the interaction between Listeria and host cells is vital for developing effective treatments.
Purpose of the Study:
- To investigate the location of Listeria monocytogenes virulence proteins during host cell infection.
- To examine the structural differences between LLO in different Listeria serogroups.
- To elucidate the mechanism of Listeria cell-to-cell spread.
Main Methods:
- Immunoelectron microscopy was used to visualize the localization of bacterial proteins.
- Antibody cross-reactivity assays were performed to compare LLO structures.
- Caco-2 tissue culture cell monolayers were infected with Listeria monocytogenes.
Main Results:
- Virulence-related proteins, including LLO and phospholipases, were found to be primarily associated with the Listeria cell wall.
- Antibodies to LLO showed poor cross-reactivity between serogroup 1/2a and 4b, indicating structural variations.
- Comet-tail pseudopod structures, involved in cell-to-cell spread, did not contain detectable Listeria antigens.
Conclusions:
- Listeria virulence factors are predominantly cell-wall-associated during Caco-2 cell infection.
- Structural differences exist in LLO between Listeria serogroups.
- The cell-to-cell passage of Listeria is a host-cell-dependent process, initiated by the bacterium but mediated by host cell machinery.
