MOLECULAR-CLONING AND CHARACTERIZATION OF A PUTATIVE ASPARTATE PROTEINASE ASSOCIATED WITH A GUT MEMBRANE-PROTEIN COMPLEX FROM ADULT HAEMONCHUS-CONTORTUS

A cDNA was isolated from an adult Haemonchus contortus cDNA expression library the deduced amino acid sequence of which showed significant h omology to mammalian pepsinogen sequences. The library was screened wi th antisera raised against Haemonchus galactose-containing glycoprotei n complex, a gut membrane protein complex with aspartyl proteinase act ivity which has shown considerable potential as a protective antigen. The amino acid sequence obtained corresponded very closely in part to the N-terminal amino acid sequences of two polypetides within the comp lex. The enzyme was shown to be almost exclusively expressed by the bl ood-feeding parasite stages. The cDNA was expressed in E. coli, and an tibody produced to the recombinant protein bound to the luminal surfac e of the gut in the adult parasite. The proteinase may play a central role in digesting the blood meal and is considered a potential sub-uni t vaccine candidate. (C) 1997 Elsevier Science B.V.