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Microbial invasion: a covert activity?
G L Gorby1, E N Robinson, L R Barley
1Center for Infectious Diseases, Diagnostic Microbiology and Immunology, University of Utah School of Medicine, Salt Lake City 84132.
Abstract:
In contrast to nonpathogenic microorganisms that exist happily in biofilms on various organic and inorganic surfaces, many pathogenic microbes have the additional ability to invade host tissues by inducing their own endocytosis and transport across normally protective barriers. This phenomenon, designated "parasite-directed endocytosis," has been observed with a variety of surfaces (intestinal, genital, nasopharyngeal, and tracheal epithelium) as well as in endothelial cells. The mechanisms involved in invasion may involve a single factor as described for some species of Yersinia, or may require multiple factors as observed in Shigellae. For the majority of pathogens, the molecular mechanisms of invasion are not well understood (e.g., Neisseria gonorrhoeae). Because parasite-directed endocytosis is reminiscent of receptor-mediated endocytosis, it is quite possible that some pathogens engage in biologic mimicry by producing a molecule that resembles a natural host ligand, for which there is a host cell receptor. Such a masquerade may allow some microbes to enter the host's inner sanctum covertly in a manner analogous to the Trojan horse, rather than overtly by destroying the mucosa and entering host tissues directly. Whereas this hypothesis is speculative at present, bacteria that produce molecules resembling insulin, calmodulin, and chorionic gonadotropin have been described.
Insights
Pathogenic microbes invade host tissues using parasite-directed endocytosis, a process where they induce their own entry. Some pathogens may mimic host molecules to enter cells covertly.
Area of Science:
- Microbiology
- Cell Biology
- Pathogenesis
Background:
- Nonpathogenic microbes form biofilms on surfaces.
- Pathogenic microbes can invade host tissues by inducing endocytosis.
- This invasion occurs across various epithelial and endothelial barriers.
Purpose of the Study:
- To explore the phenomenon of parasite-directed endocytosis.
- To understand the mechanisms and molecular basis of microbial invasion.
- To investigate the hypothesis of biologic mimicry in pathogen entry.
Main Methods:
- Observational studies of microbial invasion across different cell types.
- Analysis of known invasion mechanisms (e.g., Yersinia, Shigella).
- Hypothetical modeling based on similarities to receptor-mediated endocytosis.
Main Results:
- Parasite-directed endocytosis is observed in various pathogens and cell types.
- Invasion mechanisms can involve single or multiple factors.
- The molecular mechanisms for many pathogens remain poorly understood.
Conclusions:
- Parasite-directed endocytosis is a key virulence strategy for many pathogens.
- Biologic mimicry, where pathogens resemble host ligands, is a plausible invasion mechanism.
- Further research is needed to elucidate the specific molecular mechanisms involved.