Humoral and cytokine response during protection of mice against secondary hydatidosis caused by Echinococcus granulosus

Infection of BALB/c mouse with protoscoleces of Echinococcus granulosus constitutes a model for the study of secondary hydatidosis and the associated immune response in immunization and infection trials. The aims of this study were to induce a protective immunity against secondary hydatidosis using conventional vaccination approaches and to analyse the immune responses that accompany this protection. Mice immunized with antigen B (AgB), a component of crude sheep hydatid fluid (CSHF), showed a significant level of protection as indicated by a 98.3% reduction in cyst load. This reduction in cyst development was accompanied by a high concentration of interferon gamma secreted by antigen-stimulated spleen cells, as compared with those secreted by cells of mice immunized with CSHF or protoscoleces homogenate (PSH) antigens. In contrast, interleukin-4 was significantly higher in the supernatants of cells stimulated with CSHF or PSH compared with AgB (191.5, 195.7 and 127.5 pg, respectively). Kinetic analysis of immunoglobulin subclasses showed persistently high levels of IgG1 and IgG2a subclasses in immunized infected animals until 6 months of infection, whereas IgG3 showed a significant decline after 1 month of infection. In infected non-immunized control mice, all IgG subclasses showed a gradual increase after the first month of infection until the experiment termination (8 months after infection).