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Isolation of Fidelity Variants of RNA Viruses and Characterization of Virus Mutation Frequency
Published on: June 16, 2011
Increased fidelity reduces poliovirus fitness and virulence under selective pressure in mice
Julie K Pfeiffer1, Karla Kirkegaard
1Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California, USA.
Abstract:
RNA viruses have high error rates, and the resulting quasispecies may aid survival of the virus population in the presence of selective pressure. Therefore, it has been theorized that RNA viruses require high error rates for survival, and that a virus with high fidelity would be less able to cope in complex environments. We previously isolated and characterized poliovirus with a mutation in the viral polymerase, 3D-G64S, which confers resistance to mutagenic nucleotide analogs via increased fidelity. The 3D-G64S virus was less pathogenic than wild-type virus in poliovirus-receptor transgenic mice, even though only slight growth defects were observed in tissue culture. To determine whether the high-fidelity phenotype of the 3D-G64S virus could decrease its fitness under a defined selective pressure, we compared growth of the 3D-G64S virus and 3D wild-type virus in the context of a revertible attenuating point mutation, 2C-F28S. Even with a 10-fold input advantage, the 3D-G64S virus was unable to compete with 3D wild-type virus in the context of the revertible attenuating mutation; however, in the context of a non-revertible version of the 2C-F28S attenuating mutation, 3D-G64S virus matched the replication of 3D wild-type virus. Therefore, the 3D-G64S high-fidelity phenotype reduced viral fitness under a defined selective pressure, making it likely that the reduced spread in murine tissue could be caused by the increased fidelity of the viral polymerase.
Insights
High-fidelity RNA viruses, like the poliovirus 3D-G64S mutant, may struggle with survival under selective pressures. This study shows increased polymerase fidelity can reduce viral fitness in complex environments.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- RNA viruses possess high error rates, generating quasispecies that can enhance survival under selective pressure.
- It is hypothesized that high error rates are essential for RNA virus survival, while high fidelity may impair adaptation.
- A poliovirus mutant (3D-G64S) with increased polymerase fidelity and resistance to mutagenic analogs was previously identified.
Purpose of the Study:
- To investigate if the high-fidelity phenotype of the 3D-G64S poliovirus mutant impacts its fitness under specific selective pressures.
- To compare the competitive growth of the 3D-G64S mutant against wild-type poliovirus in the presence of an attenuating mutation.
Main Methods:
- Comparative growth analysis of 3D-G64S poliovirus and wild-type poliovirus.
- Utilized a revertible attenuating point mutation (2C-F28S) to introduce selective pressure.
- Assessed viral replication and competition in cell culture.
Main Results:
- The 3D-G64S high-fidelity virus demonstrated significantly reduced fitness compared to wild-type virus when competing under the selective pressure of a revertible attenuating mutation, even with a 10-fold input advantage.
- In contrast, the 3D-G64S virus replicated comparably to wild-type virus when the attenuating mutation was non-revertible.
- These findings suggest that increased fidelity of the viral polymerase can impair viral fitness under certain selective conditions.
Conclusions:
- The high-fidelity phenotype of the 3D-G64S poliovirus mutant reduces its fitness under defined selective pressure.
- Increased viral polymerase fidelity is likely responsible for the observed reduced spread in murine models.
- This research supports the theory that high error rates are crucial for RNA virus adaptation and survival in complex environments.
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