1. The role of glycosylation in the N-terminus of the hemagglutinin of a unique H4N2 with a natural polybasic cleavage site in virus fitness in vitro and in vivo
- Author
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Melina Vallbracht, Angele Breithaupt, Claudia Blaurock, Jutta Veits, Beate Crossley, Elsayed M. Abdelwhab, Axel Karger, Ola Bagato, Thomas C. Mettenleiter, Marcel Gischke, Eva Böttcher-Friebertshäuser, and David Scheibner
- Subjects
Male ,Glycosylation ,highly pathogenic ,Chick Embryo ,avian influenza virus ,Infectious and parasitic diseases ,RC109-216 ,medicine.disease_cause ,Virus Replication ,Poultry ,Madin Darby Canine Kidney Cells ,chemistry.chemical_compound ,2.2 Factors relating to the physical environment ,Viral ,Aetiology ,h4n2 ,0303 health sciences ,Mutation ,biology ,Virulence ,Monobasic acid ,transmission ,virus diseases ,Brain ,Highly pathogenic ,non-H5/H7 ,Hemagglutinins ,Infectious Diseases ,Influenza A virus ,Medical Microbiology ,Female ,Infection ,Microbiology (medical) ,animal structures ,glycosylation ,Immunology ,Hemagglutinin (influenza) ,Microbiology ,Virus ,03 medical and health sciences ,Dogs ,medicine ,low pathogenic ,Animals ,hemagglutinin ,030304 developmental biology ,030306 microbiology ,Prevention ,Virology ,In vitro ,Influenza A virus subtype H5N1 ,non-h5/h7 ,virulence ,Viral Tropism ,Emerging Infectious Diseases ,chemistry ,Ecological Applications ,proteolytic activation ,biology.protein ,Parasitology ,Genetic Fitness ,Chickens - Abstract
To date, only low pathogenic (LP) H5 and H7 avian influenza viruses (AIV) have been observed to naturally shift to a highly pathogenic (HP) phenotype after mutation of the monobasic hemagglutinin (HA) cleavage site (HACS) to polybasic motifs. The LPAIV monobasic HACS is activated by tissue-restricted trypsin-like enzymes, while the HPAIV polybasic HACS is activated by ubiquitous furin-like enzymes. However, glycosylation near the HACS can affect proteolytic activation and reduced virulence of some HPAIV in chickens. In 2012, a unique H4N2 virus with a polybasic HACS was isolated from quails but was LP in chickens. Whether glycosylation sites (GS) near the HACS hinder the evolution of HPAIV H4N2 remains unclear. Here, we analyzed the prevalence of potential GS in the N-terminus of HA1, 2NYT4 and 18NGT20, in all AIV sequences and studied their impact on H4N2 virus fitness. Although the two motifs are conserved, some non-H5/H7 subtypes lack one or both GS. Both sites were glycosylated in this H4N2 virus. Deglycosylation increased trypsin-independent replication in cell culture, cell-to-cell spread and syncytium formation at low-acidic pH, but negatively affected the thermostability and receptor-binding affinity. Alteration of 2NYT4 with or without 18NGT20 enabled systemic spread of the virus to different organs including the brain of chicken embryos. However, all intranasally inoculated chickens did not show clinical signs. Together, although the conserved GS near the HACS are important for HA stability and receptor binding, deglycosylation increased the H4N2 HA-activation, replication and tissue tropism suggesting a potential role for virus adaptation in poultry.
- Published
- 2021