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Serum-inhibited toxicity of Entamoeba histolytica
Abstract:
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.
Insights
Researchers identified a heat-labile glycoprotein toxin from Entamoeba histolytica responsible for cytopathogenic effect (CPD). This toxin
Area of Science:
- Parasitology
- Cell Biology
- Biochemistry
Background:
- Entamoeba histolytica is a protozoan parasite causing amoebiasis.
- The cytopathogenic effect (CPD) is a key virulence factor of E. histolytica.
- Understanding the molecular mechanisms of CPD is crucial for developing treatments.
Purpose of the Study:
- To characterize the soluble antigen responsible for the cytopathogenic effect (CPD) of Entamoeba histolytica.
- To determine the physical and chemical properties of the CPD-inducing toxin.
- To investigate the role of this toxin in parasite-host interactions.
Main Methods:
- Assaying cytopathogenic effect (CPD) on baby hamster kidney (BHK) cell monolayers using various Entamoeba histolytica strains.
- Employing gel chromatography to determine the molecular weight of the active fraction.
- Conducting experiments to assess toxin stability (heat, pH), susceptibility to enzymes (trypsin), and dependence on specific chemical groups (sulphydryl).
- Investigating inhibition by antibodies (IgG) and serum factors.
Main Results:
- A heat-labile glycoprotein toxin with peak activity between 35,000 and 45,000 M.W. was identified.
- The toxin is stable between pH 4 and 10, degraded by trypsin, and requires sulphydryl groups for activity.
- Toxicity was observed in virulent E. histolytica strains and E. invadens, but not in the Huff strain or Acanthamoeba.
- The toxin is excreted by the ameba and its activity is inhibited by anti-E. histolytica IgG and nonimmune serum factors (50,000-100,000 M.W.).
Conclusions:
- A specific, excreted glycoprotein toxin mediates the cytopathogenic effect (CPD) of Entamoeba histolytica.
- The toxin's properties provide insights into its mechanism of action and potential for immune evasion.
- Further research into this toxin could lead to novel diagnostic or therapeutic strategies for amoebiasis.