EXTRACELLULAR AND CYTOPLASMIC CU ZN SUPEROXIDE DISMUTASES FROM HAEMONCHUS-CONTORTUS/

Full-length cDNAs encoding cytosolic (SODc) and putative extracelluar (SODe) Cu/Zn superoxide dismutases (SODs) from the ovine gastrointesti nal parasitic nematode Haemonchus contortus have been isolated and cha racterized. The predicted sequences of the H. contortus SODs showed st rong homology to other helminth SODs, the highest level of sequence si milarity was with those of the free-living nematode Caenorhabditis ele gans double dagger. The predicted amino acid sequence of the putative extracellular form contained an N-terminal extension with the characte ristics of a signal sequence including a potential signal peptidase cl eavage site. Transcripts of both classes of Cu/Zn SOD were detected in all life-cycle stages examined. The cytosolic SOD mRNA was approximat ely 6-fold more abundant than that of the extracellular enzyme in adul t parasites. Immunoblotting with antisera raised to in vitro-expressed parasite SODs revealed the presence of 2 proteins in extracts of adul t H. contortus, with molecular masses of approximately 19.8 and 18 kDa . An additional protein of approximately 16.8 kDa was detected in adul t ES material. Immunofluorescent staining showed Cu/Zn SOD was localiz ed in the body wall musculature and the pharynx in adult worms and in the uterine tract of adult females. The immunogenic properties of reco mbinant H. contortus Cu/Zn SODs was assessed in a challenge infection experiment in lambs.