Cross-protection studies with gut membrane glycoprolein antigens from Haemonchus contortus and Teladorsagia circumcincta

Gel profiles of the peanut and ConA lectin binding integral membrane glycop roteins of Teladorsagia circumcincta and Haemonchus contortus were compared and found to be considerably different. However some of the Teladorsagia p olypeptides were recognized by antisera specific for Haemonchus amino-, met allo- or aspartyl peptidases, enzymes which are known to be protective anti gens for that parasite. As expected, an experimental vaccine containing the se Haemonchus proteases was extremely effective against homologous challeng e, reducing egg and worm counts by more than 99% and 92%, respectively, but it did not provide any useful cross-protection against either T. circumcin cta, Trichostrongylus axel or Cooperia oncophora A reciprocal experiment wh ere sheep were immunized with the equivalent glycoproteins from T. circumci ncta, showed that, while they were not protected against homologous challen ge, there was some cross-protection against Haemonchus as measured by a sig nificant reduction in worm egg output.