Combinatorial Approaches to Viral Attenuation

ABSTRACT Attenuated viruses have numerous applications, in particular in the context of live viral vaccines. However, purposefully designing attenuated viruses remains challenging, in particular if the attenuation is meant to be resistant to rapid evolutionary recovery. Here we develop and analyze a...

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Autores principales: Matthew L. Paff, Benjamin R. Jack, Bartram L. Smith, James J. Bull, Claus O. Wilke
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Publicado: American Society for Microbiology 2018
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spelling oai:doaj.org-article:291200245dde4ac385767d4c89da75c52021-12-02T19:45:30ZCombinatorial Approaches to Viral Attenuation10.1128/mSystems.00046-182379-5077https://doaj.org/article/291200245dde4ac385767d4c89da75c52018-08-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mSystems.00046-18https://doaj.org/toc/2379-5077ABSTRACT Attenuated viruses have numerous applications, in particular in the context of live viral vaccines. However, purposefully designing attenuated viruses remains challenging, in particular if the attenuation is meant to be resistant to rapid evolutionary recovery. Here we develop and analyze a new attenuation method, promoter ablation, using an established viral model, bacteriophage T7. Ablation of promoters of the two most highly expressed T7 proteins (scaffold and capsid) led to major reductions in transcript abundance of the affected genes, with the effect of the double knockout approximately additive of the effects of single knockouts. Fitness reduction was moderate and also approximately additive; fitness recovery on extended adaptation was partial and did not restore the promoters. The fitness effect of promoter knockouts combined with a previously tested codon deoptimization of the capsid gene was less than additive, as anticipated from their competing mechanisms of action. In one design, the engineering created an unintended consequence that led to further attenuation, the effect of which was studied and understood in hindsight. Overall, the mechanisms and effects of genome engineering on attenuation behaved in a predictable manner. Therefore, this work suggests that the rational design of viral attenuation methods is becoming feasible. IMPORTANCE Live viral vaccines rely on attenuated viruses that can successfully infect their host but have reduced fitness or virulence. Such attenuated viruses were originally developed through trial and error, typically by adaptation of the wild-type virus to novel conditions. That method was haphazard, with no way of controlling the degree of attenuation or the number of attenuating mutations or preventing evolutionary reversion. Synthetic biology now enables rational design and engineering of viral attenuation, but rational design must be informed by biological principles to achieve stable, quantitative attenuation. This work shows that in a model system for viral attenuation, bacteriophage T7, attenuation can be obtained from rational design principles, and multiple different attenuation approaches can be combined for enhanced overall effect.Matthew L. PaffBenjamin R. JackBartram L. SmithJames J. BullClaus O. WilkeAmerican Society for Microbiologyarticlebacteriophagescodon deoptimizationpromoter knockoutviral attenuationMicrobiologyQR1-502ENmSystems, Vol 3, Iss 4 (2018)
institution DOAJ
collection DOAJ
language EN
topic bacteriophages
codon deoptimization
promoter knockout
viral attenuation
Microbiology
QR1-502
spellingShingle bacteriophages
codon deoptimization
promoter knockout
viral attenuation
Microbiology
QR1-502
Matthew L. Paff
Benjamin R. Jack
Bartram L. Smith
James J. Bull
Claus O. Wilke
Combinatorial Approaches to Viral Attenuation
description ABSTRACT Attenuated viruses have numerous applications, in particular in the context of live viral vaccines. However, purposefully designing attenuated viruses remains challenging, in particular if the attenuation is meant to be resistant to rapid evolutionary recovery. Here we develop and analyze a new attenuation method, promoter ablation, using an established viral model, bacteriophage T7. Ablation of promoters of the two most highly expressed T7 proteins (scaffold and capsid) led to major reductions in transcript abundance of the affected genes, with the effect of the double knockout approximately additive of the effects of single knockouts. Fitness reduction was moderate and also approximately additive; fitness recovery on extended adaptation was partial and did not restore the promoters. The fitness effect of promoter knockouts combined with a previously tested codon deoptimization of the capsid gene was less than additive, as anticipated from their competing mechanisms of action. In one design, the engineering created an unintended consequence that led to further attenuation, the effect of which was studied and understood in hindsight. Overall, the mechanisms and effects of genome engineering on attenuation behaved in a predictable manner. Therefore, this work suggests that the rational design of viral attenuation methods is becoming feasible. IMPORTANCE Live viral vaccines rely on attenuated viruses that can successfully infect their host but have reduced fitness or virulence. Such attenuated viruses were originally developed through trial and error, typically by adaptation of the wild-type virus to novel conditions. That method was haphazard, with no way of controlling the degree of attenuation or the number of attenuating mutations or preventing evolutionary reversion. Synthetic biology now enables rational design and engineering of viral attenuation, but rational design must be informed by biological principles to achieve stable, quantitative attenuation. This work shows that in a model system for viral attenuation, bacteriophage T7, attenuation can be obtained from rational design principles, and multiple different attenuation approaches can be combined for enhanced overall effect.
format article
author Matthew L. Paff
Benjamin R. Jack
Bartram L. Smith
James J. Bull
Claus O. Wilke
author_facet Matthew L. Paff
Benjamin R. Jack
Bartram L. Smith
James J. Bull
Claus O. Wilke
author_sort Matthew L. Paff
title Combinatorial Approaches to Viral Attenuation
title_short Combinatorial Approaches to Viral Attenuation
title_full Combinatorial Approaches to Viral Attenuation
title_fullStr Combinatorial Approaches to Viral Attenuation
title_full_unstemmed Combinatorial Approaches to Viral Attenuation
title_sort combinatorial approaches to viral attenuation
publisher American Society for Microbiology
publishDate 2018
url https://doaj.org/article/291200245dde4ac385767d4c89da75c5
work_keys_str_mv AT matthewlpaff combinatorialapproachestoviralattenuation
AT benjaminrjack combinatorialapproachestoviralattenuation
AT bartramlsmith combinatorialapproachestoviralattenuation
AT jamesjbull combinatorialapproachestoviralattenuation
AT clausowilke combinatorialapproachestoviralattenuation
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