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Determination and Therapeutic Exploitation of Ebola Virus Spontaneous Mutation Frequency.

ABSTRACT: Ebola virus (EBOV) is an RNA virus that can cause hemorrhagic fever with high fatality rates, and there are no approved vaccines or therapies. Typically, RNA viruses have high spontaneous mutation rates, which permit rapid adaptation to selection pressures and have other important biological consequences. However, it is unknown if filoviruses exhibit high mutation frequencies. Ultradeep sequencing and a recombinant EBOV that carries the gene encoding green fluorescent protein were used to determine the spontaneous mutation frequency of EBOV. The effects of the guanosine analogue ribavirin during EBOV infections were also assessed. Ultradeep sequencing revealed that the mutation frequency for EBOV was high and similar to those of other RNA viruses. Interestingly, significant genetic diversity was not observed in viable viruses, implying that changes were not well tolerated. We hypothesized that this could be exploited therapeutically. In vitro, the presence of ribavirin increased the error rate, and the 50% inhibitory concentration (IC50) was 27 ?M. In a mouse model of ribavirin therapy given pre-EBOV exposure, ribavirin treatment corresponded with a significant delay in time to death and up to 75% survival. In mouse and monkey models of therapy given post-EBOV exposure, ribavirin treatment also delayed the time to death and increased survival. These results demonstrate that EBOV has a spontaneous mutation frequency similar to those of other RNA viruses. These data also suggest a potential for therapeutic use of ribavirin for human EBOV infections.Ebola virus (EBOV) causes a severe hemorrhagic disease with high case fatality rates; there are no approved vaccines or therapies. We determined the spontaneous mutation frequency of EBOV, which is relevant to understanding the potential for the virus to adapt. The frequency was similar to those of other RNA viruses. Significant genetic diversity was not observed in viable viruses, implying that changes were not well tolerated. We hypothesized that this could be exploited therapeutically. Ribavirin is a viral mutagen approved for treatment of several virus infections; it is also cheap and readily available. In cell culture, we showed that ribavirin was effective at reducing production of infectious EBOV. In mouse and monkey models of therapy given post-EBOV exposure, ribavirin treatment delayed the time to death and increased survival. These data provide a better understanding of EBOV spontaneous mutation and suggest that ribavirin may have great value in the context of human disease.

SUBMITTER: Alfson KJ

PROVIDER: S-EPMC4810732 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature

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Determination and Therapeutic Exploitation of Ebola Virus Spontaneous Mutation Frequency.

Alfson Kendra J KJ Worwa Gabriella G Carrion Ricardo R Griffiths Anthony A

Journal of virology 20151216 5

<h4>Unlabelled</h4>Ebola virus (EBOV) is an RNA virus that can cause hemorrhagic fever with high fatality rates, and there are no approved vaccines or therapies. Typically, RNA viruses have high spontaneous mutation rates, which permit rapid adaptation to selection pressures and have other important biological consequences. However, it is unknown if filoviruses exhibit high mutation frequencies. Ultradeep sequencing and a recombinant EBOV that carries the gene encoding green fluorescent protein ...[more]

PMID: 26676781

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Project description:Ebolaviruses have a surface glycoprotein (GP1,2) that is required for virus attachment and entry into cells. Mutations affecting GP1,2 functions can alter virus growth properties. We generated a recombinant vesicular stomatitis virus encoding Ebola virus Makona variant GP1,2 (rVSV-MAK-GP) and observed emergence of a T544I mutation in the Makona GP1,2 gene during tissue culture passage in certain cell lines. The T544I mutation emerged within two passages when VSV-MAK-GP was grown on Vero E6, Vero, and BS-C-1 cells but not when it was passaged on Huh7 and HepG2 cells. The mutation led to a marked increase in virus growth kinetics and conferred a robust growth advantage over wild-type rVSV-MAK-GP on Vero E6 cells. Analysis of complete viral genomes collected from patients in western Africa indicated that this mutation was not found in Ebola virus clinical samples. However, we observed the emergence of T544I during serial passage of various Ebola Makona isolates on Vero E6 cells. Three independent isolates showed emergence of T544I from undetectable levels in nonpassaged virus or virus passaged once to frequencies of greater than 60% within a single passage, consistent with it being a tissue culture adaptation. Intriguingly, T544I is not found in any Sudan, Bundibugyo, or Tai Forest ebolavirus sequences. Furthermore, T544I did not emerge when we serially passaged recombinant VSV encoding GP1,2 from these ebolaviruses. This report provides experimental evidence that the spontaneous mutation T544I is a tissue culture adaptation in certain cell lines and that it may be unique for the species Zaire ebolavirusIMPORTANCE The Ebola virus (Zaire) species is the most lethal species of all ebolaviruses in terms of mortality rate and number of deaths. Understanding how the Ebola virus surface glycoprotein functions to facilitate entry in cells is an area of intense research. Recently, three groups independently identified a polymorphism in the Ebola glycoprotein (I544) that enhanced virus entry, but they did not agree in their conclusions regarding its impact on pathogenesis. Our findings here address the origins of this polymorphism and provide experimental evidence showing that it is the result of a spontaneous mutation (T544I) specific to tissue culture conditions, suggesting that it has no role in pathogenesis. We further show that this mutation may be unique to the species Zaire ebolavirus, as it does not occur in Sudan, Bundibugyo, and Tai Forest ebolaviruses. Understanding the mechanism behind this mutation can provide insight into functional differences that exist in culture conditions and among ebolavirus glycoproteins.

Dataset Information

Determination and Therapeutic Exploitation of Ebola Virus Spontaneous Mutation Frequency.

Publications

Determination and Therapeutic Exploitation of Ebola Virus Spontaneous Mutation Frequency.

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