Collagenolytic activity related to metalloproteases (and serine proteases) in the fish parasite Hysterothylacium aduncum (Nematoda: Anisakidae).

Proteases have a vital role in both the life cycle of parasites and the parasite-host relationship and are considered important virulence factors. In this study the presence of proteases with collagenolytic activity was investigated in the fish nematode Hysterothylacium aduncum during in vitro development. Collagenolytic activity was found in all studied developmental stages of the nematode (third- (L3), fourth- (L4) larval stages and adults). In L3, the activity was maximum at pH 6.5 and in the other stages, at 7.0. Pepsin is known to favour in vitro development of the worm, but, in this study, collagenolytic activity was shown to be significantly greater when no pepsin was added to the culture medium (at pH 6.5, p = 0.011). At pH 7.0 most activity was observed in the immature adult, after the final moult, suggesting that the collagenolytic activity may be involved in the remodelling of the cuticle and in sexual maturity. On the other hand, at pH 6.5, activity may be related to tissue migration by L3 within the host. Using specific inhibitors, it was demonstrated that most of the collagenolytic activity detected in all the developmental stages was due to metalloproteases (40-100%), although serine proteases were also detected in L4 and adults (10-30%).