Entamoeba histolytica: mechanism of decrease of virulence of axenic cultures maintained for prolonged periods |
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Authors: | Olivos Alfonso Ramos Espiridión Nequiz Mario Barba Carlos Tello Eusebio Castañón Guadalupe González Augusto Martínez Rubén D Montfort Irmgard Pérez-Tamayo Ruy |
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Affiliation: | Department of Experimental Medicine, National Autonomous University of México Medical School, Mexico. olivosa@yahoo.com |
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Abstract: | Intraportal injection of non-virulent E. histolytica (derived from prolonged axenic culture of virulent E. histolytica) strain HM1-IMSS in normal hamsters results in no liver lesions and disappearance of the parasites 48-72 h after injection. Viability of non-virulent E. histolytica after 2 h of in vitro incubation in either fresh or decomplemented hamster serum is the same as control virulent E. histolytica (50-90%). In hamsters made leukopenic, or both leukopenic+hypocomplementemic, or hypocomplementemic+sephadex microspheres (to produce focal liver ischemia) intraportally injected non-virulent E. histolytica cause no lesions and disappear after 24 h. In addition, neither hypocomplementemia nor immunosuppression with cyclosporin A prolonged the survival of non-virulent E. histolytica. Methyl prednisolone treatment of hamsters resulted in survival of large numbers of non-virulent E. histolytica in the liver, with little inflammation and minimal tissue damage, for up to 7 days. Inflammatory cells (macrophages) would appear to be chiefly responsible for elimination of non-virulent E. histolytica. Parallel experiments with E. dispar suggest a different mechanism for its non-pathogenicity. |
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Keywords: | vEh, virulent Entamoeba histolytica nvEh, non-virulent Entamoeba histolytica Ed, Entamoeba dispar Acute experimental amoebic liver abscess Hamster (Mesocricetus auratus) Leukopenia Hypocomplementemia Focal liver ischemia PMN, polymorphonuclear leukocytes Lymphocytes Macrophages Immunosuppression Cyclosporin A Methyl prednisolone |
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