The 14-3-3 protein is secreted by the adult worm of Echinococcus granulosus

The 14-3-3 protein, already described in the metacestode of Echinococcus multilocularis, has been characterized in the Echinococcus granulosus adult worm. Immunolocalization studies show the presence of the 14-3-3 protein in the periphery of testes and externally associated with the apical rostellum and adjacent worm tegument. The alcian blue staining in consecutive parasite sections gave similar reactivity patterns, suggesting that the 14-3-3 protein is produced and secreted by rostellar glands. Immunoblot analysis showed the presence of the 14-3-3 protein in somatic and excretory-secretory worm products with higher and smaller apparent molecular masses, respectively, than those detected in E. multilocularis or E. granulosus metacestode tissues. Conversely, the 14-3-3 protein was not detected in metacestode secretory products. Detection of anti-E. granulosus 14-3-3 reactivity in sera of experimentally infected dogs was achieved at early stages of infection. Specific antibody titres decreased during the course of infection. The possible origin and functions of the 14-3-3 protein produced by the adult worm are discussed.