Evaluation of immunization with gut membrane glycoproteins of Ostertagia ostertagi against homologous challenge in calves and against Haemonchus contortus in sheep

Peanut and ConA lectins were used as ligands to isolate glycoproteins from detergent extracts of adult Ostertagia ostertagi membranes. As judged by th eir profiles following SDS-PAGE, these fractions closely resembled the equi valents from Haemonchus contortus which are derived from the nematode intes tinal cell microvillar membranes and which are highly protective when used as antigens. Groups of calves were immunized with the peanut and ConA bindi ng fractions of Ostertagia, either as separate or pooled antigens mixed wit h QuilA as adjuvant. All calves, including controls immunized with adjuvant only, were challenged with a single dose of infective Ostertagia larvae an d faecal egg counts were monitored for 5 weeks. In two experiments where th e antigen fractions were pooled, moderate (30-50%), but statistically signi ficant reductions in egg output were observed, but the number of worms was not diminished. No significant protection was observed in a third trial whe re groups of calves were immunized with peanut or ConA binding proteins giv en separately. Two further trials were conducted in sheep immunized with th e same Ostertagia fractions but challenged with Haemonchus. Irrespective of whether they were administered separately or together, the Ostertagia anti gens cross protected efficiently against Haemonchus reducing egg counts by between 81% and 97% and worm numbers by between 57% and 84%.