Abstract
Immunogenicity of Schistosoma mansoni egg surface was examined to determine whether intact eggshells have lower antigenicity than ruptured eggs. Swiss Webster mice were inoculated with intact or ultrasonicated S. mansoni eggs isolated from infected human feces. Mice were separated into four groups of six animals each and immunizations were performed approximately every 20 days during a 60-day period. Groups 1-4 were administered with saline solution, sonicated eggs with Freund's adjuvant, sonicated eggs without Freund's adjuvant, and intact eggs, respectively. IgG humoral immune response was assessed by ELISA using Soluble Egg Antigen produced from eggs isolated from the livers of infected mice. Sonicated eggs co-administered with adjuvant induced the highest humoral response at 58 days, which was 11.9-fold (95% CI 6.2-17.5) greater than the response induced by saline solution. Sonicated eggs without adjuvant induced a 4.3-fold stronger response (95% CI 2.4-6.2) than normal saline. Intact eggs induced humoral response that was nominally twice stronger (95% CI 0.8-3.2) than that induced by normal saline but the effect did not reach statistical significance. Soluble antigens are not abundant on the surface of S. mansoni eggs and/or are not secreted in sufficient quantities to induce a significant immune response to intact eggs. Assuming that isolation procedures had not damaged the eggs used for inoculation, our observations suggest that intact eggs either do not induce a significant immune response or, if they do, the mechanism involves insoluble antigens from the egg surface.
Highlights
Immunogenicity of Schistosoma mansoni egg surface was examined to determine whether intact eggshells have lower antigenicity than ruptured eggs
Assuming that isolation procedures had not damaged the eggs used for inoculation, our observations suggest that intact eggs either do not induce a significant immune response or, if they do, the mechanism involves insoluble antigens from the egg surface
Eggs from S. mansoni were isolated from the livers of experimentally infected mice[25] for the production of the soluble egg antigen (SEA) and from a 300g sample of human stool obtained through collaboration with the Regional Management of the Control Program of Schistosomiasis in Minas Gerais, Brazil for the immunization of the mice used in this study
Summary
Immunogenicity of Schistosoma mansoni egg surface was examined to determine whether intact eggshells have lower antigenicity than ruptured eggs. IgG humoral immune response was assessed by ELISA using Soluble Egg Antigen produced from eggs isolated from the livers of infected mice. Conclusions: Soluble antigens are not abundant on the surface of S. mansoni eggs and/or are not secreted in sufficient quantities to induce a significant immune response to intact eggs. Assuming that isolation procedures had not damaged the eggs used for inoculation, our observations suggest that intact eggs either do not induce a significant immune response or, if they do, the mechanism involves insoluble antigens from the egg surface. Schistosomiasis is an endemic chronic infection that occurs in Africa, South America, Caribbean islands, and Eastern Mediterranean[1,2] It remains one of the most prevalent parasitic infections and has significant economic and public health consequences[3].
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