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Viruses. 2016 Jun 3;8(6). pii: E155. doi: 10.3390/v8060155.

Accurate Measurement of the Effects of All Amino-Acid Mutations on Influenza Hemagglutinin.

Doud MB1,2,3, Bloom JD4,5.

Author information

1
Division of Basic Sciences Basic Sciences and Computational Biology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, WA 98109, USA. mbdoud@gmail.com.
2
Department of Genome Sciences, University of Washington, 3720 15th Ave NE, Seattle, WA 98195-5065, USA. mbdoud@gmail.com.
3
Medical Scientist Training Program, University of Washington, Seattle, WA 98109, USA. mbdoud@gmail.com.
4
Division of Basic Sciences Basic Sciences and Computational Biology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, WA 98109, USA. jbloom@fredhutch.org.
5
Department of Genome Sciences, University of Washington, 3720 15th Ave NE, Seattle, WA 98195-5065, USA. jbloom@fredhutch.org.

Abstract

Influenza genes evolve mostly via point mutations, and so knowing the effect of every amino-acid mutation provides information about evolutionary paths available to the virus. We and others have combined high-throughput mutagenesis with deep sequencing to estimate the effects of large numbers of mutations to influenza genes. However, these measurements have suffered from substantial experimental noise due to a variety of technical problems, the most prominent of which is bottlenecking during the generation of mutant viruses from plasmids. Here we describe advances that ameliorate these problems, enabling us to measure with greatly improved accuracy and reproducibility the effects of all amino-acid mutations to an H1 influenza hemagglutinin on viral replication in cell culture. The largest improvements come from using a helper virus to reduce bottlenecks when generating viruses from plasmids. Our measurements confirm at much higher resolution the results of previous studies suggesting that antigenic sites on the globular head of hemagglutinin are highly tolerant of mutations. We also show that other regions of hemagglutinin-including the stalk epitopes targeted by broadly neutralizing antibodies-have a much lower inherent capacity to tolerate point mutations. The ability to accurately measure the effects of all influenza mutations should enhance efforts to understand and predict viral evolution.

KEYWORDS:

deep mutational scanning; evolution; hemagglutinin; influenza; mutational tolerance

PMID:
27271655
PMCID:
PMC4926175
DOI:
10.3390/v8060155
[Indexed for MEDLINE]
Free PMC Article

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