Protective immunisation of guinea pigs against Dictyocaulus viviparus using excretory/secretory products of adult parasites.

Parasite preparations were examined for their ability to induce protective immunity against Dictyocaulus viviparus in guinea pigs. Dunkin-Hartley strain guinea pigs were immunised with somatic extracts of adult parasites, somatic extracts of third stage larvae or excretory/secretory (ES) products from adult parasites. The groups were immunised twice with Freund's adjuvant four weeks apart and challenged with 6000 infective L3. Significant levels of protective immunity were observed only in the adult ES-immunised animals. The antibody responses of the different groups were compared following analysis by ELISA and immunoprecipitation. To examine the protective role of antibody, guinea pigs were passively immunised with serum from animals immunised with adult ES products or serum from guinea pigs exposed to experimental D. viviparus infection. Following challenge with infective L3, lung-worm burdens of these groups were significantly lower than in guinea pigs which received normal sera. The results suggest that D. viviparus adult ES products contain protective antigens and that antibody-mediated mechanisms contribute to immune protection.