Establishment of a sensitive cell line for grass carp reovirus genotype II

Grass carp hemorrhagic disease (GCHD) is an acute, severe and contagious viral disease mainly caused by grass carp reovirus (GCRV)-II. The epidemic outbreaks of GCHD have caused tremendous economic losses and pose a pressing challenge to grass carp aquaculture. Therefore, permissive cell lines for GCRV-II are crucial for elucidating the pathogenesis and vaccine development. In this study, a novel permissive cell line (grass carp brain cell, GCBr) derived from grass carp (Ctenopharyngodon idella) brain tissue was established and characterized. This fibroblast-like cell line grew well in L-15 medium containing 10 % FBS at 28 °C. Of note, the successive and efficient propagation of GCRV-II in GCBr cells was confirmed by viral infection, PCR assay, viral growth curve, and transmission electron microscopy. The GCBr cells showed a non-typical cytopathic effect at 3 days post infection, characterized by more rounded cells. Animal experiments showed that GCRV-II propagated in GCBr cells led to 100 % mortality in grass carp, with the appearance of muscle hemorrhage and viral inclusion bodies in the brain. In addition, host immune responses in the brain, intestine and liver were examined at different time intervals. Taken together, the establishment of this permissive cell line GCBr provides a new and powerful tool for the propagation of GCRV-II, facilitating the elucidation of the pathogenesis of GCRV-II and the prevention and control of GCHD.