Effect of white spot syndrome virus on the activity of immune-related enzymes in the red claw crayfish (Cherax quadricarinatus)

Abstract

In this study, we explored the pathogenic effects of white spot syndrome virus\xa0(WSSV) and effects of yeast cell wall\xa0in the red claw crayfish, Cherax quadricarinatus, by investigating the activity of enzymes related to innate immune function following artificial infection of immunized and non-immunized crayfish. Our results reveal that\xa0the activity of four enzymes, phenoloxidase (PO), peroxidase\xa0(POD), superoxide dismutase\xa0(SOD) and lysozyme\xa0(LSZ), increased in the hepatopancreas and antennal\xa0gland of C. quadricarinatus\xa06 – 24 hours after exposure to WSSV. After, activity levels of these enzymes decreased rapidly, such that 72 h post-exposure the activity of the enzymes in WSSV-infected crayfish were significantly\xa0lower than those of the control\xa0individuals (except for LSZ). Interestingly, we found that immunization with yeast cell wall\xa0before challenge with WSSV conferred an immune protection rate of 51.86% at 7 days post-infection, demonstrating that\xa0yeast cell wall\xa0could improve immune-related\xa0enzyme activity in the crayfish and enhance the anti-viral defenses of this species. Morphological examination by transmission electron microscopy revealed significant damage in the hepatopancreas and antennal\xa0glands of infected crayfish. WSSV infection caused damage to the epithelium of the hepatopancreas and antennas\xa0and reduced the number and size of microvilli. In addition, mitochondria morphology changed following infection, with parts of the cristae diminished leaving large vacuoles. Moreover, the dictyosome morphology changed, the lysosome membranes ruptured, and heterochromatinized nuclei could be seen in cells with ruptured nuclear membranes. Despite this no WSSV particles\xa0appeared in the hepatopancreas or in the antennal gland.