Abstract:

In order to understand the biological and genome characteristics of mammalian orthoreovirus (MRV) from sheep, a MRV strain named MRV-XJ23 was isolated from sheep suffering diarrhea, and identified by RT-PCR, electron microscopy and indirect immunofluorescence assay (IFA), respectively. The whole genome of the isolated strain was amplified by RT-PCR and the homology and genetic evolution were analyzed further. The results showed that the MRV-XJ23 strain cultured stably in MDBK cells and performed specific cytopathic effect with a virus titer of 10⁶ TCID₅₀·mL^-1. Specific fluorescence was observed in MRV-infected MDBK cells by IFA detection, and electron microscope detection showed that the virus was purified by ultracentrifugation with a diameter of about 70 nm. The whole MRV genome was obtained by RT-PCR, MRV-XJ23 contained 10 segments with the length of 23 534 bp. Nucleotide sequence alignments and genetic evolution analysis showed that the MRV-XJ23 isolate was belonged to MRV-1 serotype. Results of sequence and phylogenetic trees indicate that the novel MRV isolate was a novel reassortant among three MRV strains of BatMRV2/SNU1/Korea/2021, C/bovine/Indiana/MRV00304/2014 strain and Homo sapiens/Osaka2005. In this study, a reassorting strain of MRV-1 type originated from sheep was isolated and identified for the first time, which proved important evidence that sheep could be infected with MRV and broadened the host species. Moreover, the reassortant strain was derived from bat, bovine and homo sapiens-MRV, which indicated that these strains were infected the new host and reassortment was present after possible cross-species infection. This study revealed the risk of MRV transmission circle in various species to public health, and the importance to study the epidemiology, reassortment and pathogenicity of MRV in sheep and even livestock.

Key words: mammalian orthoreovirus, sheep, isolation and identification, reassortment, evolutionary analysis