The infectious haemorrhagic syndrome virus (IHSV) from rice-field eel (Monopterus albus): Isolation, genome sequence, cross-infection and induced-immune response in Chinese perch (Siniperca chuatsi)

Rhabdoviruses are pathogens threatening aquaculture industry. Although the viruses are reported from a range of fish species, the knowledge on their isolate genome variation and cross-species infection is rather limited. In this study, a new isolate, named as infectious haemorrhagic syndrome virus (IHSV), of siniperhavirus was identified from diseased rice-field eels (Monopterus albus, Synbranchidae, Synbranchiformes) in Hubei Province, China. The IHSV genome has 11,540 bp in size and contains conserved genomic arrangement, 3′-N-P-M-G-L-5′, and belongs to the species, Siniperhavirus chuatsi through genomic and phylogenetic analyses. The infection of IHSV in rice-field eels resulted in haemorrhage in various tissues and on body surface, and this virus was fatal to larvae of Chinese perch (Siniperca chuatsi, Sinipercidae, Centrarchiformes) in immersion infection. A new cell line, designed as Chinese perch stomach (CPS) cells or cell line, was established from the Chinese perch stomach tissue, and can be used for the proliferation of IHSV and for investigating cellular immune response induced by IHSV infection. The transcriptome and gene expression analyses revealed that the IHSV infection induced the expression of 5404 genes in CPS cells, which are involved in immune/metabolism-related pathways, including RIG-I-like receptor signaling, NOD-like receptor signaling, cytosolic DNA-sensing, cytokine-cytokine receptor interaction, Toll-like receptor signaling etc. Interestingly, a new longer transcript of IFNh and IFNc each was identified in Chinese perch in addition to the previously reported transcripts of these two IFN genes, and the promoter of these longer transcripts can be activated by IRF3 and MAVS through ISRE sites. It is thus revealed that IHSV is cross-species infective, and is immune-inductive, providing information for understanding the possible relationship between rhabdoviruses and their potential fish hosts.