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[Biology and pathogenicity of fungi]
1Service de parasitologie-mycologie Groupe hospitalier La Pitié-La Salpêtrière 75651 Paris.
Abstract:
Men live with a multitude of fungal species and few species can become parasites. Some species are obligatory pathogenic (dermatophytes, dimorphic fungi...) and the majority is opportunistic pathogen. Host-parasite complex is indissociable. For example, Candida albicans is a commensal of the gastrointestinal tract and can dramatically proliferate when host defences are alterated. Passage from the commensal status to pathogenicity is accompanied by modifications of the fungus, which then act as virulence factors (development of filamentous forms, changes in surface hydrophobicity...). Biologic, genetic and antigenic modifications are also observed. Colonisation and adhesion, penetration, multiplication and survival are necessary for infectiosity in a host. Host defence mechanisms are described with non-specific mechanisms by humoral and cellular factors and more specific immune mechanisms involving antibodies, T lymphocytes and the role of cytokines.
Insights
Fungi commonly coexist with humans, but some opportunistic pathogens like Candida albicans can cause infections by altering virulence factors when host defenses weaken. Understanding this host-parasite relationship is key to combating fungal diseases.
Area of Science:
- Medical Mycology
- Immunology
- Microbial Pathogenesis
Background:
- Humans host numerous fungal species, most benign, but some are opportunistic pathogens.
- Obligate pathogenic fungi (e.g., dermatophytes) and opportunistic fungi (e.g., Candida albicans) pose risks.
- The host-parasite relationship is dynamic, with commensal fungi becoming pathogenic under altered host defenses.
Purpose of the Study:
- To explore the complex interactions between fungal species and the human host.
- To elucidate the mechanisms by which commensal fungi transition to pathogenic states.
- To detail the host defense mechanisms against fungal infections.
Main Methods:
- Review of existing literature on fungal-human interactions.
- Analysis of fungal virulence factors and host immune responses.
- Examination of the host-parasite complex dynamics.
Main Results:
- Fungal pathogenicity involves modifications such as filamentous growth and altered surface hydrophobicity.
- Successful infection requires fungal colonization, adhesion, penetration, multiplication, and survival.
- Host defenses include non-specific (humoral, cellular) and specific (antibody, T lymphocyte, cytokine-mediated) immune responses.
Conclusions:
- Fungal infections arise from a complex interplay between fungal virulence and host immune status.
- Understanding fungal adaptation and host immunity is crucial for managing opportunistic fungal infections.
- The transition from commensalism to pathogenicity highlights fungal adaptability and the importance of host immune surveillance.