Vaccination against the gastrointestinal nematode, Haemonchus contortus, using a purified larval surface antigen

Sheep were immunized with a purified antigen (Hc-sL3) expressed on the surf ace of L3 larvae of the gastro-intestinal parasite, Haemonchus contortus, u sing different adjuvant and immunization routes. In the first experiment, i ntradermal immunization of sheep with Hc-sL3 and QuilA did not result in re ductions in faecal egg counts after subsequent challenge infection while si gnificant reductions were obtained when aluminium hydroxide (AH) was used a s the adjuvant. Significant protection with Hc-sL3 absorbed on AH was confi rmed in a second experiment and this protection was maintained when dextran sulphate was added to the Hc-sL3/AH mixture while the addition of pertussi s toxin abrogated the protective effect. Significant levels of protection, as determined by reductions in both faecal egg counts and worm burdens, wer e also obtained when the Hc-sL3/AH mixture was injected into the rectal muc osa or the Hc-sL3 antigen was deposited on the surface of the rectal mucosa with cholera toxin. No correlations with antibody levels or isotype and pr otection were observed. (C) 1998 Elsevier Science Ltd. All rights reserved.