title: Progressive glycosylation of the haemagglutinin of avian influenza H5N1 modulates virus replication, virulence and chicken-to-chicken transmission without significant impact on antigenic drift.
abstract: Highly pathogenic H5N1 avian influenza virus (A/H5N1) devastated the poultry industry and continues to pose a pandemic threat. Studying the progressive genetic changes in A/H5N1 after long-term circulation in poultry may help us to better understand A/H5N1 biology in birds. A/H5N1 clade 2.2.1.1 antigenic drift viruses have been isolated from vaccinated commercial poultry in Egypt. They exhibit a peculiar stepwise accumulation of glycosylation sites (GS) in the haemagglutinin (HA) with viruses carrying, beyond the conserved 5 GS, additional GS at amino acid residues 72, 154, 236 and 273 resulting in 6, 7, 8 or 9 GS in the HA. Available information about the impact of glycosylation on virus fitness and pathobiology is mostly derived from mammalian models. Here, we generated recombinant viruses imitating the progressive acquisition of GS in HA and investigated their biological relevance in vitro and in vivo. Our in vitro results indicated that the accumulation of GS correlated with increased glycosylation, increased virus replication, neuraminidase activity, cell-to-cell spread and thermostability, however, strikingly, without significant impact on virus escape from neutralizing antibodies. In vivo, glycosylation modulated virus virulence, tissue tropism, replication and chicken-to-chicken transmission. Predominance in the field was towards viruses with hyperglycosylated HA. Together, progressive glycosylation of the HA may foster persistence of A/H5N1 by increasing replication, stability and bird-to-bird transmission without significant impact on antigenic drift.
authors.affiliation: National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza 12618, Egypt.|Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: El-Sayed M
authors.initials: EM
authors.lastname: Abdelwhab
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Veits
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Tauscher
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Ziller
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Grund
authors.affiliation: National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza 12618, Egypt.
authors.forename: Mohamed K
authors.initials: MK
authors.lastname: Hassan
authors.affiliation: National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza 12618, Egypt.
authors.forename: Momtaz
authors.initials: M
authors.lastname: Shaheen
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Timm C
authors.initials: TC
authors.lastname: Harder
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Teifke
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Stech
authors.affiliation: Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493 Greifswald-Insel Riems, Germany.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Mettenleiter
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D000940:Antigenic Variation; D002645:Chickens; D004534:Egypt; D006031:Glycosylation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D053124:Influenza A Virus, H5N1 Subtype / Q000145:classification / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D005585:Influenza in Birds / Q000635:transmission* / Q000821:virology; D010802:Phylogeny; D011201:Poultry Diseases / Q000821:virology*; D014774:Virulence; D014779:Virus Replication
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus