Identification and preliminary characterization of cuticular surface proteins of Haemonchus contortus

Cuticular surface antigens of the XL3 and L4 stages of Haemonchus contortus have been studied by surface labeling and immunological techniques. Live worms were labeled with 125I and extracted with sodium dodecyl sulfate (SDS) followed by SDS + 2-mercaptoethanol. The SDS-soluble surface proteins of XL3s and L4s were found to consist of relatively few major species. The pattern of labeled polypeptides was distinctive for each developmental stage. These proteins are refractory to digestion by bacterial collagenase. Several of the proteins are glycosylated. Further extraction of labeled worms with SDS + 2-mercaptoethanol solubilized additional labeled proteins that appeared to be primarily collagens. Rabbit antisera prepared against native XL3 and L4-cuticles reacted strongly with the surfaces of live worms in immunofluorescence assays. In contrast, antisera prepared against SDS-extracted cuticles reacted weakly or not at all with live worms in similar experiments. Rabbit antisera prepared against adult cuticles failed to react with live XL3s or L4s. These studies suggest that the major surface antigens of XL3s and L4s are solubilized by SDS and that there are different antigens present on the cuticular surfaces of XL3s, L4s and adults. Stage-specificity in cuticular surface proteins may contribute to the successful parasitic lifestyle of this nematode.