Aspartyl proteases from the intestinal brush border of Haemonchus contortus as protective antigens for sheep

• Published in: Parasite immunology 2003-11, Vol.25 (11‐12), p.521-530
• Main Authors: Smith, W. D., Skuce, P. J., Newlands, G. F. J., Smith, S. K., Pettit, D.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; antibodies; Antigens, Helminth - genetics; Antigens, Helminth - isolation & purification; Aspartic Acid Endopeptidases - genetics; Aspartic Acid Endopeptidases - immunology; aspartyl proteases; Base Sequence; DNA, Helminth - genetics; Endopeptidases - genetics; Endopeptidases - immunology; Endopeptidases - isolation & purification; Epitopes - genetics; Epitopes - isolation & purification; glycoprotein complex; Haemonchiasis - immunology; Haemonchiasis - prevention & control; Haemonchiasis - veterinary; Haemonchus - enzymology; Haemonchus - genetics; Haemonchus - immunology; Haemonchus - pathogenicity; Haemonchus contortus; HcPEP1 and HcPEP2; Helminth Proteins - genetics; Helminth Proteins - immunology; Helminth Proteins - isolation & purification; intestinal cell membranes; Intestines - enzymology; Intestines - immunology; Membrane Glycoproteins - genetics; Membrane Glycoproteins - immunology; Membrane Glycoproteins - isolation & purification; Microvilli - enzymology; Microvilli - immunology; Molecular Sequence Data; Molecular Weight; nematode; pepsin‐like; protection; protective antigen; Recombinant Proteins - genetics; Recombinant Proteins - immunology; Recombinant Proteins - isolation & purification; Sequence Homology, Amino Acid; Sheep; Sheep Diseases - immunology; Sheep Diseases - prevention & control
• ISSN: 0141-9838; 1365-3024
• DOI: 10.1111/j.0141-9838.2004.00667.x

SUMMARY A novel pepsin‐like aspartyl protease was identified as a component of Haemonchus galactose‐containing glycoprotein (H‐gal‐GP), which is an integral membrane glycoprotein complex located on the intestinal cells of Haemonchus contortus, and a highly protective antigen for sheep. This molecule, designated HcPEP2, showed 50% sequence identity with a previously described aspartyl protease from H‐gal‐GP known as HcPEP1. Fractions of H‐gal‐GP, either containing both HcPEP1 and 2 or other lower molecular weight components of the complex, were evaluated as protective antigens in immunization – challenge trials in sheep. When separated from the rest of the complex by gel filtration in 8 m urea, the HcPEP1 and 2 fraction significantly reduced H. contortus egg counts by 48% and worm numbers by 36%, but the lower molecular weight components were not significantly protective. However, the HcPEP1 and 2 fraction did not protect if electro‐eluted from SDS‐dissociated H‐gal‐GP, nor did bacterially expressed recombinant HcPEP1, suggesting that conformational epitopes are important for inducing immunity.