Pergamon Developmental and Comparative Immunology, Vol. 19, No. 2, pp. 135-142, 1995 Copyright 6 1995 Elsevier Science Ltd Printedin the USA. All rights reserved 0145-305x/95 $9.50 + .oo SUPPRESSION OF CHEMILUMINESCENCE OF EASTERN OYSTER (Crassostrea wirginica) HEMOCYTES BY THE PROTOZOAN PARASITE Perkhsus marinus Aswani K. Volety and Fu-Lin E. Chu School of Marine Science, Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062 (Submitted May 1994; Accepted December 1994) q lAbstract-Experiments were conducted to determine the ability of the protistan parasite, zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO Perkinsus marinus, to inhibit chemilumines- cence of hemocytes from the eastern oyster, Crassostrea virginica. Luminol-enhanced chemllutininescence (CL) was used to measure the production of reactive oxygen intermedi- atea (ROI) generated by oyster hemocytes using tymosan as a stimulant. To determine whether P. marinus supptesses ROI evoked from zymo- San-stimulated hemocytes, live or heat killed P. marinus in filtered estuarlne water (YRW) (sa- linity = 20 ppt) were added to (1) zymosan- stimulated hemodytes after CL reached its peak, or (2) hemocytes at the same time as zymosan, and reduction of CL responses were recorded. In both teats, controls received only estutie water. Live P. marinus meronts sig nificantly suppressed ROI production by zymo- san-stimulated hemocytes. The suppression of ROI production was dose dependent. Suppres- sion of ROI production from zymosan- stimulated hemocytes by heat killed P. marinus was significantly less than by live P. marinus. Similarly, CL of hemocytes was reduced, though not significantly when hemocytes were exposed to YRW prelncubated with P. mari- nus. When P. marinus meronts were used as a stimulant, no CL response was elicited. Results of this study suggest that P. marinus cells are able to suppress ROI release from oyster hemo- cytes, thus evading this component of the host’s defense. EiKeywordsXmssostrea virginica; Perkinsus marinus; Hemocytes; Chemilumlnescence; Address correspondence to Fu-Lin E. Chu. Reactive oxygen intermediates; Acid phosphatase; Suppression; Defense. Nomenclature CL chemiluminescence HKP heat killed P. marinus LP live P. marinus PMYRW P. marinus incubated York River water RLO Rickettsiales-like organisms ROI reactive oxygen intermediates YRW filtered estuarine water (York River wa- ZYM ter) zymosan Introduction Heavy mortalities of oysters in Chesa- peake Bay and on the east coast of the United States caused by the protozoan parasite, Perkinsus marinus, have been well documented (1,2) in recent years. Although the physiopathologic effects of the disease organism on the oysters have been studied extensively (3-9, very lit- tle is known about the evasive mecha- nisms of the parasite in escaping the host’s defense mechanisms. Defense mechanisms in vertebrate phagocytes involve complex processes including the production of toxic free ox- ygen radicals by the respiratory burst (6), and other enzymatic processes (7). When vertebrate macrophage mem- branes are stimulated by foreign parti-