RÉSUMÉ
Sera from nine populations in Surinam, South America, were screened for antibodies against Entamoeba histolytica by the enzyme-linked immunosorbent assay (ELISA) technique and a precipitin test (gel diffusion or counterimmunoelectrophoresis). In two small surveys in 1974 and 1978, a high rate of clinically significant ELISA titers was found in a rather isolated group of Amerindians living near the Brazilian border, predominately in the youngest age groups. Amerindians living near the coast showed a low level of seropositivity. Low levels were also found in Bush Negro villages in the interior of Surinam and in Hindustani school children from the savannah area. A high frequency of ELISA titers greater than or equal to 320, indicating a high rate of invasive amebiasis, was detected in persons in a mental institution in Paramaribo. It is concluded that the ELISA, which is much more sensitive than the precipitin tests, is a useful screening test for assessing the prevalence of invasive amebiasis on an epidemiological scale.
Sujet(s)
Amibiase/immunologie , Infection à Entamoeba/immunologie , Test ELISA , Techniques immunoenzymatiques , Études transversales , Infection à Entamoeba/épidémiologie , Humains , SurinameRÉSUMÉ
The cytopathogenic effect (CPD) of soluble antigens prepared from various strains of Entamoeba histolytica, differing in virulence, was assayed on monolayers of baby hamster kidney cells growing in microtiter plates. Serum-inhibited toxicity could be detected in all these strains and in E. invadens, but not in the Huff strain and in an Acanthamoeba species. Gel chromatography demonstrated a peak activity of the toxin in a fraction with M.W. between 35,000 and 45,000. Other experiments learned that the toxin is a heat-labile glycoprotein, stable between pH 4 and 10, degradable by trypsin, dependent in its activity on sulphydryl goups, and inhibited by anti-E. histolytica IgG and nonimmune serum factors with a M.W. between 50,000 and 100,000. It is also excreted by the ameba and this may explain the effect of serum on contact lysis, induced by intact amebae on BHK cells.