Grass carp reovirus (GCRV) is a causative agent of haemorrhagic disease in grass carp that drastically affects grass carp aquaculture. Here we report a novel GCRV isolate isolated from sick grass carp that induces obvious cytopathic effect in CIK cells and name it as GCRV096. A large number of GCRV 096 viral particles were found in the infected CIK cells by electron microscope. The shape, size and the arrangement of this virus were similar to those of grass carp reovirus. With the primers designed according to GCRV 873 genome sequences, specific bands were amplified from sick grass carp and the infected CIK cells. The homology rates among vp4, vp6 and vp7 gene in GCRV 096 and those of some GCRV isolates were over 89%. In this study, the sequences of vp4, vp6 and vp7 were used to analyse sequence variation, phylogenetic relationships and genotypes in twenty five GCRV isolates. The results indicated these twenty five GCRV isolates should be attributed to four genotypes. And there were no obvious characteristics in the geographical distribution of GCRV genotype. The study should provide the exact foundation for developing more effective prevention strategies of grass carp haemorrhagic disease.

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Grass carp reovirus (GCRV) seriously affects the grass carp farming, as the causative agent of grass carp hemorrhagic disease. In this study, we found the GCRV 096 NS38 protein contained one conservative PXXP motif similar to σNS of avian reovirus, with very low similarity rates with its homologous GCRV proteins of different genotypes. Furthermore, the soluble GCRV 096 NS38 protein was expressed in Escherichia coli, antiserum was raised and characterised. Addition of purified NS38 protein to culture media of Ctenopharyngodon idella kidney (CIK) cells clearly inhibited replication of GCRV 096 (genotype I); however, replication of GCRV GD108 (genotype Ш) was not significantly affected in CIK cells under the same conditions. It was not possible to induce cross-protection among GCRVs of different genotypes. GCRV multi-genotype should be considered and the NS38 protein was a promising candidate for developing therapies against grass carp hemorrhagic disease. Additionally, bioinformatics analysis suggested that the NS38 protein may be involved in viral genome replication.