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Updated: Jul 3, 2026
Dissecting Innate Immune Signaling in Viral Evasion of Cytokine Production
Published on: March 2, 2014
Expression of frog virus 3 genes is impaired in mammalian cell lines
Heather E Eaton1, Julie Metcalf, Craig R Brunetti
1Department of Biology, Trent University, Peterborough, ON, Canada. heathereaton@trentu.ca
Abstract:
Frog virus 3 (FV3) is a large DNA virus that is the prototypic member of the family Iridoviridae. To examine levels of FV3 gene expression we generated a polyclonal antibody against the FV3 protein 75L. Following a FV3 infection in fathead minnow (FHM) cells 75L was found in vesicles throughout the cytoplasm as early as 3 hours post-infection. While 75L expressed strongly in FHM cells, our findings revealed no 75L expression in mammalian cells lines despite evidence of a FV3 infection. One explanation for the lack of gene expression in mammalian cell lines may be inefficient codon usage. As a result, 75L was codon optimized and transfection of the codon optimized construct resulted in detectable expression in mammalian cells. Therefore, although FV3 can infect and replicate in mammalian cell lines, the virus may not express its full complement of genes due to inefficient codon usage in mammalian species.
Insights
Frog virus 3 (FV3) gene expression in mammalian cells is hindered by inefficient codon usage. Codon optimization of the 75L protein enabled expression in mammalian cells, suggesting a mechanism for limited viral gene function.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Frog virus 3 (FV3) is the prototypic member of the Iridoviridae family.
- Understanding FV3 gene expression is crucial for studying viral pathogenesis.
Purpose of the Study:
- To investigate the expression of FV3 protein 75L in different cell types.
- To explore the reasons for differential gene expression in fish versus mammalian cells.
Main Methods:
- Generated a polyclonal antibody against FV3 protein 75L.
- Infected fathead minnow (FHM) cells and mammalian cell lines with FV3.
- Analyzed 75L expression using the antibody.
- Codon optimized the 75L gene for mammalian expression.
Main Results:
- FV3 protein 75L was detected in FHM cells as early as 3 hours post-infection.
- No 75L expression was observed in mammalian cell lines despite FV3 infection.
- Codon optimization of 75L led to detectable expression in mammalian cells.
Conclusions:
- Inefficient codon usage in mammalian cells limits FV3 75L protein expression.
- FV3 may not express its full gene repertoire in mammalian hosts due to codon bias.
- Codon optimization strategies can overcome expression barriers for viral genes in heterologous hosts.
