Gene Diversification of Emerging Fish Virus: A Decade of Mutation in VHSv-IVb

What is it about?

This study analyzes the temporal and spatial mutational patterns of the Viral Hemorrhagic Septicemia virus (VHSv)-IVb across the Great Lakes. The research focuses on the novel non-virion (Nv) gene, which is unique to this group of novirhabdoviruses, in relation to its glycoprotein (G), phosphoprotein (P), and matrix (M) genes. The Nv-gene has been evolving the fastest, with the G-gene evolving at a much slower rate. Most of the 12 unique Nv-haplotypes identified encode different amino acids, with the P-and M-genes evolving at a much slower rate as well. The study also found that new viral variants emerged following the large 2006 outbreak, possibly in response to fish populations developing resistance. Two 2012 variants were isolated from central Lake Erie fish that lacked classic VHSv symptoms, having genetically distinctive Nv-, G-, and M-gene sequences.

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Why is it important?

This research is important because it provides valuable insights into the evolution and dynamics of the Viral Hemorrhagic Septicemia virus (VHSv), a significant fish pathogen that affects over 80 species across the Northern Hemisphere. Understanding the patterns of mutation and evolution in the VHSv-IVb substrain can help predict future outbreaks, inform conservation efforts, and aid in the development of control measures. Key Takeaways: 1. The Nv-gene of VHSv-IVb evolves the fastest among the G-, P-, and M-genes, with the G-gene evolving at a slower rate, while the P- and M-genes are more evolutionarily conserved. 2. Most of the Nv-gene substitutions are non-synonymous, resulting in functional protein changes that may be acted upon by selection. 3. The high substitution rate of the Nv-gene in the VHSv-IVb substrain suggests it has high tolerance of functional substitutions, which may enable the virus to evade fish host recognition and immune response, facilitating endemic maintenance in populations and new colonizations. 4. Rapid evolutionary differentiation may allow VHSv to adapt to changes in fish populations and evade resistance, meriting further investigation.