Isolation of a novel swine influenza virus from Oklahoma in 2011 which is distantly related to human influenza C viruses

PLoS Pathog. 2013 Feb;9(2):e1003176. doi: 10.1371/journal.ppat.1003176. Epub 2013 Feb 7.

Abstract

Of the Orthomyxoviridae family of viruses, only influenza A viruses are thought to exist as multiple subtypes and has non-human maintenance hosts. In April 2011, nasal swabs were collected for virus isolation from pigs exhibiting influenza-like illness. Subsequent electron microscopic, biochemical, and genetic studies identified an orthomyxovirus with seven RNA segments exhibiting approximately 50% overall amino acid identity to human influenza C virus. Based on its genetic organizational similarities to influenza C viruses this virus has been provisionally designated C/Oklahoma/1334/2011 (C/OK). Phylogenetic analysis of the predicted viral proteins found that the divergence between C/OK and human influenza C viruses was similar to that observed between influenza A and B viruses. No cross reactivity was observed between C/OK and human influenza C viruses using hemagglutination inhibition (HI) assays. Additionally, screening of pig and human serum samples found that 9.5% and 1.3%, respectively, of individuals had measurable HI antibody titers to C/OK virus. C/OK virus was able to infect both ferrets and pigs and transmit to naive animals by direct contact. Cell culture studies showed that C/OK virus displayed a broader cellular tropism than a human influenza C virus. The observed difference in cellular tropism was further supported by structural analysis showing that hemagglutinin esterase (HE) proteins between two viruses have conserved enzymatic but divergent receptor-binding sites. These results suggest that C/OK virus represents a new subtype of influenza C viruses that currently circulates in pigs that has not been recognized previously. The presence of multiple subtypes of co-circulating influenza C viruses raises the possibility of reassortment and antigenic shift as mechanisms of influenza C virus evolution.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Viral / blood*
  • Antigens, Viral / immunology
  • Base Sequence
  • Cell Culture Techniques
  • Ferrets
  • Genome, Viral / genetics*
  • Hemagglutination Inhibition Tests
  • Hemagglutinins, Viral / genetics
  • Hemagglutinins, Viral / metabolism
  • Host Specificity
  • Humans
  • Influenzavirus C / genetics
  • Influenzavirus C / immunology
  • Influenzavirus C / isolation & purification*
  • Influenzavirus C / ultrastructure
  • Male
  • Models, Molecular
  • Molecular Sequence Data
  • Oklahoma
  • Orthomyxoviridae Infections / immunology
  • Orthomyxoviridae Infections / transmission
  • Orthomyxoviridae Infections / virology*
  • Phylogeny
  • Sequence Analysis, DNA
  • Swine
  • Swine Diseases / immunology
  • Swine Diseases / transmission
  • Swine Diseases / virology*
  • Viral Fusion Proteins / genetics
  • Viral Fusion Proteins / metabolism

Substances

  • Antibodies, Viral
  • Antigens, Viral
  • Hemagglutinins, Viral
  • Viral Fusion Proteins
  • hemagglutinin esterase

Associated data

  • GENBANK/JQ922305
  • GENBANK/JQ922306
  • GENBANK/JQ922307
  • GENBANK/JQ922308
  • GENBANK/JQ922309
  • GENBANK/JQ922310
  • GENBANK/JQ922311