ANTIOXIDANT ACTIVITY AND IMMUNOLOGICAL GENE EXPRESSION INDUCED BY WHITE SPOT SYNDROME VIRUS (WSSV) INFECTION IN Procambarus clarkii

Barcley T. Pace*, Wei Xu, Christopher C. Green
 
 Aquaculture Research Station
 Louisiana State University Agricultural Center
 Baton Rouge, LA 70820
 bpace@agcenter.lsu.edu

The red swamp crayfish, Procambarus clarkii, represents an important aquaculture species responsible for over half of all commercial aquaculture profits in Louisiana. White spot syndrome virus (WSSV) is highly pathogenic and induces mass mortality in aquaculture operations worldwide. Crayfish lack the adaptive ability of the vertebrate immune system, and must depend on primitive, innate immune responses to combat viral infection. WSSV causes oxidative stress and can alter immune system gene expression in crustaceans. The antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) help neutralize the harmful effects of viral-induced oxidative stress on cells, while expression of SOD and the prophenoloxidase (proPO) system play a crucial role in regulating immune response to infection. This study aims to investigate viral-host interaction by examining the biochemical and immunological changes caused by WSSV infection in P. clarkii.

Within a series of three separate trials, crayfish were inoculated with a viral load previously determined to elicit approximately 50% cumulative mortality within 5 days. From each control and WSSV-infected group, the gills and hepatopancreas of six animals were removed at 0, 12, 24, 72 and 120 hours post-inoculation. Commercial assay kits assessed antioxidant activity of SOD, CAT, and GPx in triplicate gill and hepatopancreas samples to determine physiological stress throughout infection (Figure 1). Real-time quantitative PCR will also be performed on gill and hepatopancreas samples to determine gene expression levels of SOD and proPO to examine immunological changes over the time course of infection.

Knowledge of the critical interactions between the innate immune system in crayfish and WSSV can be used to facilitate future investigations towards WSSV prevention and management. By elucidating how and when biochemical and immunological systems respond during viral infection, this research could increase understanding of how these systems are activated in crayfish. The results of this study, as well as previous work on WSSV infectivity in P. clarkii, serve to develop the use of this species as a model organism for investigating immune responses to WSSV infection in other freshwater decapod crustaceans.