Antibody responses of experimentally infected lambs to antigens collected during in vitro maintenance of the adult, metacestode or oncosphere stages ofTaenia hydatigena andTaenia ovis with further observations on anti-oncospheral antibodies

Abstract

The antigenicity and specificity of crude antigens collected during the in vitro maintenance ofTaenia hydatigena andT. ovis, excretory/secretory (ES) antigens, were assessed in a peroxidase microenzyme-linked immunosorbent assay (ELISA), using sera from lambs given experimental monospecific infections withT. hydatigena, T. ovis, Echinococcus granulosus orFasciola hepatica. ES antigens of larval cysts ofT. ovis andT. hydatigena were less reactive than those of adult or oncosphere stages. Strong interspecific cross-reactions occurred between all antigen preparations, and these antigens offered no better specificity than crude somatic extracts. IgG₁ was the major immunoglobulin detected in sera from lambs experimentally infected withT. ovis orT. hydatigena using antigens prepared from sonicated oncospheres. Discrete peaks of anti-oncospheral antibodies were detected following initial and challenge infections with eggs (whether the homologous or heterologous species), when sera were assayed with a PBS sonicate or an ES antigen from oncospheres. However, when oncospheres solubilised with sodium deoxycholate were used, the antibody response was prolonged and resembled that reported previously when somatic extracts of adult and metacestode stages were used as antigen. The results showed that oncospheres share antigens in common with other life-cycle stages, but also support the notion that they may possess some unique stage-specific antigenic determinants.