Open AccessNaturally occurring substitution in one amino acid in VHSV phosphoprotein enhances viral virulence in flounder
Author(s) -
Jee Youn Hwang,
Unn Hwa Lee,
Min Jin Heo,
Min Sun Kim,
Ji Min Jeong,
So Yeon Kim,
MunGyeong Kwon,
Bo Young Jee,
Ki Hong Kim,
ChanIl Park,
Jeong Woo Park
Publication year - 2021
Publication title -
plos pathogens
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.719
H-Index - 206
eISSN - 1553-7374
pISSN - 1553-7366
DOI - 10.1371/journal.ppat.1009213
Subject(s) - virulence , biology , flounder , virology , virus , phosphoprotein , microbiology and biotechnology , gene , olive flounder , genetics , fish <actinopterygii> , fishery
Viral hemorrhagic septicemia virus (VHSV) is a rhabdovirus that causes high mortality in cultured flounder. Naturally occurring VHSV strains vary greatly in virulence. Until now, little has been known about genetic alterations that affect the virulence of VHSV in flounder. We recently reported the full-genome sequences of 18 VHSV strains. In this study, we determined the virulence of these 18 VHSV strains in flounder and then the assessed relationships between differences in the amino acid sequences of the 18 VHSV strains and their virulence to flounder. We identified one amino acid substitution in the phosphoprotein (P) (Pro55-to-Leu substitution in the P protein; P P55L ) that is specific to highly virulent strains. This P P55L substitution was maintained stably after 30 cell passages. To investigate the effects of the P P55L substitution on VHSV virulence in flounder, we generated a recombinant VHSV carrying P P55L (rVHSV-P) from rVHSV carrying P55 in the P protein (rVHSV-wild). The rVHSV-P produced high level of viral RNA in cells and showed increased growth in cultured cells and virulence in flounder compared to the rVHSV-wild. In addition, rVHSV-P significantly inhibited the induction of the IFN1 gene in both cells and fish at 6 h post-infection. An RNA-seq analysis confirmed that rVHSV-P infection blocked the induction of several IFN-related genes in virus-infected cells at 6 h post-infection compared to rVHSV-wild. Ectopic expression of P P55L protein resulted in a decrease in IFN induction and an increase in viral RNA synthesis in rVHSV-wild-infected cells. Taken together, our results are the first to identify that the P55L substitution in the P protein enhances VHSV virulence in flounder. The data from this study add to the knowledge of VHSV virulence in flounder and could benefit VHSV surveillance efforts and the generation of a VHSV vaccine.