The secreted and somatic proteinases of the bovine lungwormDictyocaulus viviparusand their inhibition by antibody from infected and vaccinated animals

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Abstract
SUMMARY: Proteinase activities were examined in extracts and excretory–secretory (ES) products of the infective and adult stages of the cattle lungworm,Dictyocaulus viviparus. Multiple enzyme activities were identified from each source, as defined by pH optima, substrate specificities, inhibitor effects and substrate gel electrophoresis. Serine-, cysteine- and metalloproteinases were identified, secreted materials being more active against protein substrates per unit protein than were extracts, and the particular proteinases produced varied with the developmental stage of the parasite. The antigenicity of these parasite proteinases was demonstrated by the inhibition of enzymic activity with Protein G-purified serum IgG antibody from both infected and vaccinated hosts and in the retardation of enzyme migration on electrophoresis of enzyme–antibody complexes. For the adult products, this confirmed that the enzymes concerned were of parasite origin, and not host-derived. These results argue for investigation ofD. viviparusproteinases as targets for the antibody response in the limitation of parasite-mediated tissue damage and as the active principle behind the anti-D. viviparusvaccine.