Chapter 162 - Immunological prophylaxes for Echinococcus granulosus infection

Abstract

Echinococcus granulosus is a small zoonotic tapeworm that commonly affects dogs (definitive hosts) and ruminants (intermediate hosts). Humans may acquire cystic echinococcosis after accidental ingestion of E. granulosus eggs discharged by dogs. As current treatment options for E. granulosus infections are costly and increasingly ineffective, there is a need to develop vaccines for improved control and prevention of this parasite. Past research has uncovered key aspects of host innate and adaptive immune responses to E. granulosus, including the observation of a mixed Th1/Th2 response (IFN-γ, IL-4 and IL-10 cytokines) in the early stage and subsequent polarization toward a dominant Th2 cytokine profile (IL-4, IL-5, and IL-10 cytokines; IgG4 and IgE antibodies) after formation of adventitial fibrous layer around the laminated cystic layer of hydatid cyst. Since host-protective immunity to E. granulosus infection appears to correlate to Th1 response (IFN-γ), ideal vaccine candidates should aim to induce and maintain a Th1 response against E. granulosus. Given that recombinant EG95 protein derived from E. granulosus oncospheres confers strong protection (85%–95%) against larval infection in intermediate hosts (sheep and cattle), the glaring absence of such a protective antigen against adult worm infection in definitive hosts (dogs) demands additional research efforts.