The effects of Perkinsus marinus extracellular products and purified proteases on oyster defence parameters in vitro

The effects of extracellular products (ECP) and purified proteases from the protozoan parasite Perkinsus marinus on three host defence parameters (haemocyte motility, lysozyme and haemagglutinin) of the eastern oyster, Crassostrea virginica, were investigated. ECP with high proteolytic activities, as well as purified proteases, significantly decreased the random migration of haemocytes through micro-porous filters in Boyden chambers. Stimulation of haemocyte migration by P. marinus cells or P. marinus cell lysate was also dramatically reduced by ECP and purified proteases. Incubation of oyster plasma with ECP and purified proteases caused a significant decrease in lysozyme activity and also appeared to reduce haemagglutinin titres. These data suggest that P. marinus ECP, as well as the proteolytic fraction of the ECP, can modulate some defence parameters of oysters in vitro. (C) 1996 Academic Press Limited