Entamoeba histolytica: mechanism of decrease of virulence of axenic cultures maintained for prolonged periods.
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.
Olivos
Alfonso
A
Department of Experimental Medicine, National Autonomous University of México Medical School, Mexico. olivosa@yahoo.com
Ramos
Espiridión
E
Nequiz
Mario
M
Barba
Carlos
C
Tello
Eusebio
E
Castañón
Guadalupe
G
González
Augusto
A
Martínez
Rubén D
RD
Montfort
Irmgard
I
Pérez-Tamayo
Ruy
R
D000818:Animals; D006224:Cricetinae; D016572:Cyclosporine / Q000276:immunology; D004748:Entamoeba histolytica / Q000472:pathogenicity*; D005938:Glucocorticoids / Q000494:pharmacology; D007165:Immunosuppression Therapy; D007166:Immunosuppressive Agents / Q000276:immunology; D007970:Leukopenia / Q000276:immunology / Q000469:parasitology; D008099:Liver / Q000469:parasitology / Q000473:pathology; D008101:Liver Abscess, Amebic / Q000276:immunology / Q000469:parasitology* / Q000473:pathology; D008297:Male; D008647:Mesocricetus; D008775:Methylprednisolone / Q000494:pharmacology; D014774:Virulence
D005938:Glucocorticoids; D007166:Immunosuppressive Agents; D016572:Cyclosporine; D008775:Methylprednisolone