Insertion of basic amino acids in the hemagglutinin cleavage site of H4N2 avian influenza virus (AIV)—reduced virus fitness in chickens is restored by reassortment with highly pathogenic H5N1 AIV

Marcel Gischke, Reiner Ulrich, Olanrewaju I. Fatola, David Scheibner, Ahmed H. Salaheldin, Beate Crossley, Eva Böttcher-Friebertshäuser, Jutta Veits, Thomas C. Mettenleiter, Elsayed M. Abdelwhab

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Highly pathogenic (HP) avian influenza viruses (AIVs) are naturally restricted to H5 and H7 subtypes with a polybasic cleavage site (CS) in hemagglutinin (HA) and any AIV with an intravenous pathogenicity index (IVPI) ≥ 1.2. Although only a few non-H5/H7 viruses fulfill the criteria of HPAIV; it remains unclear why these viruses did not spread in domestic birds. In 2012, a unique H4N2 virus with a polybasic CS322PEKRRTR/G329 was isolated from quails in California which, however, was avirulent in chickens. This is the only known non-H5/H7 virus with four basic amino acids in the HACS. Here, we investigated the virulence of this virus in chickens after expansion of the polybasic CS by substitution of T327R (322PEKRRRR/G329) or T327K (322PEKRRKR/G329) with or without reassortment with HPAIV H5N1 and H7N7. The impact of single mutations or reassortment on virus fitness in vitro and in vivo was studied. Efficient cell culture replication of T327R/K carrying H4N2 viruses increased by treatment with trypsin, particularly in MDCK cells, and reassortment with HPAIV H5N1. Replication, virus excretion and bird-to-bird transmission of H4N2 was remarkably compromised by the CS mutations, but restored after reassortment with HPAIV H5N1, although not with HPAIV H7N7. Viruses carrying the H4-HA with or without R327 or K327 mutations and the other seven gene segments from HPAIV H5N1 exhibited high virulence and efficient transmission in chickens. Together, increasing the number of basic amino acids in the H4N2 HACS was detrimental for viral fitness particularly in vivo but compensated by reassortment with HPAIV H5N1. This may explain the absence of non-H5/H7 HPAIV in poultry.

Original languageEnglish (US)
Article number2353
JournalInternational journal of molecular sciences
Volume21
Issue number7
DOIs
StatePublished - Apr 1 2020

Keywords

  • Chicken-to-chicken transmission
  • Cleavage site
  • Evolution
  • Highly pathogenic avian influenza virus
  • Low pathogenic avian influenza virus
  • Non-H5/H7
  • Protease
  • Virulence
  • Virulence determinants

ASJC Scopus subject areas

  • Catalysis
  • Molecular Biology
  • Spectroscopy
  • Computer Science Applications
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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