Potential role of protease-antiprotease interactions in Perkinsus marinus infection in Crassostrea spp.

Perkinsus marinus causes devastating losses in populations of the eastern o yster (Crassostrea virginica). Our studies have demonstrated that P. marinu s secretes extracellular serine proteases which enhance parasite propagatio n and compromise host defences. Crassostrea virginica. however, possesses s everal inhibitors of these proteases. The Pacific oyster (C. gigas) is resi stant to P. marinus and possesses protease inhibitors with significantly hi gher specific activities than those in C. virginica. Interestingly, Crassos trea spp. themselves, elaborate metalloprotease activities which can be det ected in their plasma, and are increased during P. marinus infections. Toge ther our work suggests that there may be a broad spectrum of humoral host d efences that is brought to bear on P. marinus infections by these two Crass ostrea species.