PROTECTIVE IMMUNITY TO A BLOOD-FEEDING NEMATODE (HAEMONCHUS-CONTORTUS) INDUCED BY PARASITE GUT ANTIGENS

To determine the ability of gut antigens to induce a protective immune response against blood-feeding nematodes, isolated gut antigens were used to immunize goats against Haemonchus contortus. Immunization-induced antibody responses recognized parasite gut antigens which were associated predominantly with the microvillous membrane region of the parasite gut. Antibody from immune serum also recognized seven predominant gut proteins on a Western blot (immunoblot). Several of these proteins appeared to be integral membrane proteins on the basis of their solubility in the detergent Triton X-114, indicating that the presentation protocol stimulated an antibody response to microvillous membrane antigens. Three different age groups of goats ranging from < 6 months to > 1 year were immunized for challenge experiments. After infection with 10(4) larvae, an 87 to 95% reduction in fecal egg counts for all age groups of goats was achieved in the immunized compared with the control group. The reduction of worms in immunized goats ranged from 65% (kids) to 89% (yearlings) compared with controls. These results indicate that gut antigens can induce significant protection against blood-feeding nematodes. Antibody to H. contortus gut antigens also cross-reacted with microvilli of other blood-feeding nematodes including Ostertagia ostertagi and small strongyles of horses, which indicates that epitopes associated with the gut are phylogenetically conserved.