IMMUNE-RESPONSES OF TEXEL SHEEP TO EXCRETORY SECRETORY PRODUCTS OF ADULT HAEMONCHUS-CONTORTUS/

The excretory/secretory (E/S) products of adult Haemonchus contortus c omprise of at least 15 polypeptides with molecular weights ranging fro m 10 to > 100 kDa. These E/S products induce an immune response in inf ected Texel sheep, as demonstrated by specific IgG1 levels and a signi ficant lymphocyte proliferation index. Moreover, immunoblotting analys is revealed that sera of primary H. contortus-infected sheep specifica lly recognize a 24 kDa E/S product. In addition, sera of challenged sh eep react strongly with a 15 kDa E/S product. The other E/S products o f H. contortus showed immunoreactivity with serum samples of Haemonchu s-infected sheep as well as with samples of sheep harbouring other tri chostrongylid infections. These cross-reacting epitopes are the main c ause of the lack of specificity of an E/S material-based ELISA. This E LISA can differentiate Haemonchus infections from Nematodirus battus i nfections, but not from Ostertagia circumcincta or Trichostrongylus co lubriformis infections.