Isolation, Molecular and Phylogenetic Analysis of Porcine Encephalomyocarditis Virus Strain HLJ in China

Encephalomyocarditis virus （EMCV） is a positive single-stranded small RNA virus without envelope,which can infect a variety of mammals.Swines are the most susceptible animals,which can cause acute myocarditis and respiratory failure in piglets and reproductive failure in pregnant sows.Diseases caused by EMCV have a wide range of effects on the global swine industry.In this study,a strain of EMCV was isolated from a swine aborted fetus in northeast China.It was identified by reverse transcriptase polymerase chain reaction （RT-PCR）,electron microscopic observation and indirect immunofluorescence assay.The subsequent results showed that the virus titer of HLJ strain grew to 8.3 lgTCID₅₀ on baby hamster kidney 21 （BHK-21） cells.And HLJ strain caused the specific cytopathic effect （CPE） on BHK-21 cells and severe pathological changes in mice.Complete genome sequencing and multiple sequence alignment showed that the homology between HLJ strain and other isolates worldwide was 71.5%-99.7%.Phylogenetic analysis showed that EMCV isolates fell into five clusters:lineage Ⅰ,Ⅱ,Ⅲ,Ⅳ and Ⅴ,based on the nucleotide sequences of the entire open reading frame （ORF） and VP1 gene.HLJ isolate was grouped into lineage I.The analyses of amino acid mutation sites of VP1 protein showed that the amino acids at positions 20 and 54 in VP1 junction were unique to HLJ strain.The isolation of HLJ strain enriched the epidemiological database of EMCV.