No abstract

Surgical treatment of human hydatidsosis involves the use of various scolicidal agents to kill infective Echinococcus granulosus protoscoleces that may disseminate into the peritoneal cavity during surgery and potentially re-infect the patient. Currently, no scolicidal agent is completely effective in killing intracystic protoscoleces in humans. Cyclosporin A (CsA) has previously been found to be lethal for E. granulosus protoscoleces in vitro. In this study, we further assessed the effectiveness of CsA as a scolicidal agent by testing the toxic effect of CsA at higher doses over various time-periods. Experiments were performed on activated and unactivated protoscoleces cultured in nutrient medium or sheep hydatid cyst fluid. All activated protoscoleces were killed following culture in 100 microg/ml of CsA for 3 days and 50 or 20 microg/ml for 5 days. The lethal effect of CsA on unactivated protoscoleces varied but reached 100% over 15 days in culture with 100 or 50 microg/ml of CsA. Pulse treatment of protoscoleces with 50, 20 or 10 microg/ml of CsA for 5 min or 72 h killed all parasites by day 10 and day 5 respectively. Untreated protoscoleces remained greater than 95 % viable for the duration of experiments. Changes in protoscolex ultrastructure induced by treatment with 10 microg/ml of CsA over 10 days in in vitro culture was assessed by TEM. Protoscolex alterations observed in treated parasites included an increase in cellular vacuolization, swelling of mitochondria, rounding of cells, damage to the tegument, decrease in glycogen, a breakdown of the extracellular matrix and an increase in lipid globules. The untreated protoscoleces, by comparison, had few changes during the 10-day culture period with the exception of large amounts of extracellular glycogen observed in the protoscoleces at culture days 7 and 10. From these results, CsA is clearly an effective scolicidal agent in vitro that may have potential application as a new therapeutic agent in the treatment of human hydatid disease.

Heat shock protein 70 (hsp70) was chosen as a model antigen with which to investigate autoantibody production in humans with cystic hydatid disease. Levels of specific serum antibody were assessed in the sera of patients with surgically confirmed infection with E. granulosus and sera from non-infected controls. Antigens used were human hsp70, obtained from K562 cells grown in culture, and E. granulosus hsp70 obtained by expression of the full length protein in Escherichia coli following cloning of the associated mRNA. Antibody reactivity to human hsp70 was detected in the sera of only a small proportion of hydatid patients (10%) as well as a similar proportion of sera from age matched controls. Specific antibodies reactive with E. granulosus hsp70 were detected in 60% of hydatid patients, although some samples (21%) from healthy controls also reacted with E. granulosus hsp70, the level of reactivity was significantly higher in hydatid patients. This report identifies E. granulosus hsp70 as an immunogen during human hydatid infection but, despite its having a predicted 81% protein sequence homology with human hsp70, it does not appear to induce autoimmune reactivity against the homologous human protein.

No abstract

The prolonged survival of Echinococcus granulosus within the human host indicates that some mechanism is operating to permit parasite evasion of the host immune response. Several publications have described autoimmune phenomena in patients infected with hydatid cysts. The aim of this study was to test the postulate that there is a higher prevalence of autoantibodies in serum from patients with hydatid disease than in control samples, and this may provide some evidence of an association between autoimmunity and E. granulosus infection. Sera from 70 patients with hydatid disease and 45 control subjects were assayed for the presence of antinuclear antibodies (ANA), tissue specific autoantibodies and rheumatoid factor. All patients were aged between 20 and 80 years of age with no known history of autoimmune disease. Hydatid patients were surgically confirmed cases. Control subjects were chosen on the basis that they were age and sex matched to the test sera and had no known illness at the time blood samples were obtained. On the basis of an ANA autoantibody titre of > 1:40 being regarded as positive, 19 (27%) of the hydatid patients, 13 (28%) of the controls were positive. Low levels of tissue specific autoantibodies and rheumatoid factor were detected in sera from 5 (7%) and 2 (11%) hydatid patients and 4 (8%) and 3 (16%) of control subjects respectively. No significant differences (P > 0.05) were found between autoantibody levels in the hydatid patient sera and the controls. These findings suggest that there is no association between hydatid infection and the level of autoantibodies to a broad range of self antigens.