Rescue of Senecavirus A to uncover mutation profiles of its progenies during 80 serial passages in vitro.

Senecavirus A (SVA), also known as Seneca Valley virus, belongs to the genus Senecavirus in the family Picornaviridae. In this study, a China SVA isolate (CH-LX-01-2016) was rescued from its cDNA clone, and then identified by RT-PCR, indirect immunofluorescence assay and mass spectrometry. The rescued SVA could separately induce typical plaque formations and cytopathic effects in cell monolayers. In order to uncover its evolutionary dynamics, the SVA was subjected to eighty serial passages in vitro. Its progenies per ten passages were analyzed by next-generation sequencing (NGS). The NGS analyses showed that neither sequence-deleting nor -inserting phenotype was detectable in eight progenies, within which a total of forty-one intra-host single-nucleotide variations (SNVs) arose with passaging. Almost all SNVs were identified as the single-nucleotide polymorphism with mixture of two nucleotides. SNVs led to eighteen nonsynonymous mutations, out of which sixteen could directly reflect their own frequencies of amino acid mutation, due to only one SNV occurring in their individual codons. Compared with its parental virus without passaging, the passage-80 SVA progeny had formed a viral quasispecies, as evidenced by a total of twenty-eight SNVs identified in it.