Relative protective properties of three membrane glycoprotein fractions from Haemonchus contortus

Jacalin lectin was used as a ligand to isolate a fraction containing two di stinct protective antigens from detergent extracts of membranes from Haemon chus contortus. The first antigen was identified as a complex which appeare d very similar to Haemonchus galactose-containing glycoprotein (H-gal-GP), which is a previously described protective protease complex, except that it was substantially depleted of one of the main H-gal-GP components, a 230 k Da metallopeptidase-containing band. The new complex was termed Haemonchus sialylated galactose-containing glycoprotein (H-sialgal-GP), because it bou nd to jacalin but not to peanut lectin and only jacalin will bind the sialy lated form of galactosyl (beta-1,3) N-acetylgalactosamine. Two protection t rials with sheep showed that H-sialgal-GP and H-gal-GP were equally efficac ious, reducing numbers of Haemonchus eggs by between 86% and 93% and worms by between 52% and 75%, respectively. The second jacalin-binding protective antigen fraction was separated from H-sialgal-GP by ion exchange and gel f iltration chromatography. It was greatly enriched for two proteins termed p 46 and p52 according to their apparent molecular weights. Immunization of s heep with these proteins gave protection values of 78% for eggs and 33% for worms, which are significantly lower than those obtained with either H-gal -GP or H-sialgal-GP. N-terminal amino acid sequence data from p46 and p52 s howed that both proteins were closely related to a previously described 45 kDa Haemonchus membrane protein, which had conferred protection against Hae monchus in guinea-pigs.