Warmbrod, KL, Patterson, EI, Kautz, TF, Stanton, A, Rockx-Brouwer, D, Kalveram, BK, Khanipov, K, Thangamani, S, Fofanov, Y and Forrester, NL (2019) Viral RNA-dependent RNA polymerase mutants display an altered mutation spectrum resulting in attenuation in both mosquito and vertebrate hosts. PLoS Pathogens, 15 (4). e1007610 - ?. ISSN 1553-7374

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The presence of bottlenecks in the transmission cycle of many RNA viruses leads to a severe reduction of number of virus particles and this occurs multiple times throughout the viral transmission cycle. Viral replication is then necessary for regeneration of a diverse mutant swarm. It is now understood that any perturbation of the mutation frequency either by increasing or decreasing the accumulation of mutations in an RNA virus results in attenuation of the virus. To determine if altering the rate at which a virus accumulates mutations decreases the probability of a successful virus infection due to issues traversing host bottlenecks, a series of mutations in the RNA-dependent RNA polymerase of Venezuelan equine encephalitis virus (VEEV), strain 68U201, were tested for mutation rate changes. All RdRp mutants were attenuated in both the mosquito and vertebrate hosts, while showing no attenuation during in vitro infections. The rescued viruses containing these mutations showed some evidence of change in fidelity, but the phenotype was not sustained following passaging. However, these mutants did exhibit changes in the frequency of specific types of mutations. Using a model of mutation production, these changes were shown to decrease the number of stop codons generated during virus replication. This suggests that the observed mutant attenuation in vivo may be due to an increase in the number of unfit genomes, which may be normally selected against by the accumulation of stop codons. Lastly, the ability of these attenuated viruses to transition through a bottleneck in vivo was measured using marked virus clones. The attenuated viruses showed an overall reduction in the number of marked clones for both the mosquito and vertebrate hosts, as well as a reduced ability to overcome the known bottlenecks in the mosquito. This study demonstrates that any perturbation of the optimal mutation frequency whether through changes in fidelity or by alterations in the mutation frequency of specific nucleotides, has significant deleterious effects on the virus, especially in the presence of host bottlenecks.

Item Type: Article
Additional Information: © 2019 Warmbrod et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Uncontrolled Keywords: microbial mutation; mosquitoes; cloning; insertion mutation; RNA viruses; vertebrates; viral replication; viral genomics
Subjects: Q Science > QH Natural history
Divisions: Faculty of Natural Sciences > School of Life Sciences
Related URLs:
Depositing User: Symplectic
Date Deposited: 29 Apr 2019 12:39
Last Modified: 29 Apr 2019 12:39
URI: https://eprints.keele.ac.uk/id/eprint/6231

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