title: Emergence of the virulence-associated PB2 E627K substitution in a fatal human case of highly pathogenic avian influenza virus A(H7N7) infection as determined by Illumina ultra-deep sequencing.
abstract: Avian influenza viruses are capable of crossing the species barrier and infecting humans. Although evidence of human-to-human transmission of avian influenza viruses to date is limited, evolution of variants toward more-efficient human-to-human transmission could result in a new influenza virus pandemic. In both the avian influenza A(H5N1) and the recently emerging avian influenza A(H7N9) viruses, the polymerase basic 2 protein (PB2) E627K mutation appears to be of key importance for human adaptation. During a large influenza A(H7N7) virus outbreak in the Netherlands in 2003, the A(H7N7) virus isolated from a fatal human case contained the PB2 E627K mutation as well as a hemagglutinin (HA) K416R mutation. In this study, we aimed to investigate whether these mutations occurred in the avian or the human host by Illumina Ultra-Deep sequencing of three previously uninvestigated clinical samples obtained from the fatal case. In addition, we investigated three chicken samples, two of which were obtained from the source farm. Results showed that the PB2 E627K mutation was not present in any of the chicken samples tested. Surprisingly, the avian samples were characterized by the presence of influenza virus defective RNA segments, suggestive for the synthesis of defective interfering viruses during infection in poultry. In the human samples, the PB2 E627K mutation was identified with increasing frequency during infection. Our results strongly suggest that human adaptation marker PB2 E627K has emerged during virus infection of a single human host, emphasizing the importance of reducing human exposure to avian influenza viruses to reduce the likelihood of viral adaptation to humans.
authors.affiliation: Department of Virology, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Marcel
authors.initials: M
authors.lastname: Jonges
authors.forename: Matthijs R A
authors.initials: MR
authors.lastname: Welkers
authors.forename: Rienk E
authors.initials: RE
authors.lastname: Jeeninga
authors.forename: Adam
authors.initials: A
authors.lastname: Meijer
authors.forename: Peter
authors.initials: P
authors.lastname: Schneeberger
authors.forename: Ron A M
authors.initials: RA
authors.lastname: Fouchier
authors.forename: Menno D
authors.initials: MD
authors.lastname: de Jong
authors.forename: Marion
authors.initials: M
authors.lastname: Koopmans
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002645:Chickens; D017809:Fatal Outcome; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D053126:Influenza A Virus, H7N7 Subtype / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000821:virology*; D007251:Influenza, Human / Q000821:virology*; D008297:Male; D059645:Mutation Rate; D020125:Mutation, Missense; D011201:Poultry Diseases / Q000821:virology*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism; D014774:Virulence
chemical_list: C057027:PB2 protein, Influenzavirus A; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase