Proteomic analysis of the Echinococcus granulosus metacestode during infection of its intermediate host.

Cystic hydatid disease (CHD) is caused by infection with the Echinococcus granulosus metacestode and affects both humans and livestock. In this work, we performed a proteomic analysis of the E. granulosus metacestode during infection of its intermediate bovine host. Parasite proteins were identified in different metacestode components (94 from protoscolex, 25 from germinal layer and 20 from hydatid cyst fluid), along with host proteins (58) that permeate into the hydatid cyst, providing new insights into host-parasite interplay. E. granulosus and platyhelminth EST data allowed successful identification of proteins potentially involved in downregulation of host defenses, highlighting possible evasion mechanisms adopted by the parasite to establish infection. Several intracellular proteins were found in hydatid cyst fluid, revealing a set of newly identified proteins that were previously thought to be inaccessible for inducing or modulating the host immune response. Host proteins identified in association with the hydatid cyst suggest that the parasite may bind/adsorb host molecules with nutritional and/or immune evasion purposes, masking surface antigens or inhibiting important effector molecules of host immunity, such as complement components and calgranulin. Overall, our results provide valuable information on parasite survival strategies in the adverse host environment and on the molecular mechanisms underpinning CHD immunopathology.