Amino acid substitutions in antigenic region B of hemagglutinin play a critical role in the antigenic drift of subclade 2.3.4.4 highly pathogenic H5NX influenza viruses

Abstract

As one of the important control strategies for highly pathogenic avian influenza (HPAI) in China, vaccination has been implemented compulsively in poultry flocks since 2004. However, the emergence and dominance of the circulating antigenic variants require the update of vaccines periodically. In order to investigate the key molecular sites responsible for the antigenic drift, a total of 13 amino acid positions divergent between clade 2.3.4 H5 viruses and their descendent subclade 2.3.4.4 variants in or around the recognized antigenic epitopes A–E were initially identified through inspecting a comprehensive HA sequence alignment of the H5 subtype HPAI viruses. Subsequently, a panel of single‐site or multi‐site HA mutants was constructed by reverse genetics with two H5N1 viruses of S (clade 2.3.4) and QD1 (subclade 2.3.4.4) as the HA backbone to study their antigenic variations, respectively. The hemagglutination–inhibition assay revealed an evident impact of mutations at sites 88, 156, 205, 208, 239 and 289 to the HA antigenicity and highlighted that the amino acid substitutions located in the antigenic region B, especially the combined mutations at sites 205 and 208, were the major antigenic determinant which was also consistent with results from flow cytometry and antigenic mapping. Our findings provided more insights into the molecular mechanism of antigenic drift of the H5 subtype HPAI virus, which would be helpful for the selection of vaccine candidates and accordingly for the prevention and control of this devastating viral agent.

Glycosylation deletion of hemagglutinin head in the H5 subtype avian influenza virus enhances its virulence in mammals by inducing endoplasmic reticulum stress

“…Glycosylation on HA stem sites mainly functions on maintaining the HA structure (Wagner, Heuer, Wolff, Herwig, & Klenk, 2002;Zhang et al, 2015) or cleavage (Yin et al, 2017), and glycosylation on the head sites mainly influences virus binding affinity (Wang et al, 2009) or assists in escaping from immune detection of antibody (Liao et al, 2010;Zost et al, 2017). Recently, the H5 subtype AIV has drastically evolved and alterations in its glycosylation sites have become increasingly complex (Gu et al, 2019;Hillman et al, 2019;Li et al, 2019;Qu et al, 2019;Wille et al, 2019).…”

Airborne Transmission of Avian Origin H9N2 Influenza A Viruses in Mammals

“…Antigenic characterization of the HA of H9 subtype IAVs showed that the HA, in particular the globular head, is the immunodominant component, similar to what is described for other IAVs subtypes. Interestingly, the HA of the H9 subtype lacks the 130 lateral loop that forms the antigenic site A, which is an important antigenic region in other subtypes, such as H5 or H3 HAs [38,39]. Such a feature results in two antigenic sites that overlap, designated site I and site II [40].…”

Airborne Transmission of Avian Origin H9N2 Influenza A Viruses

“…Antigenic characterization of the HA of H9 viruses showed that these viruses, like other IAVs, show an immunodominance mediated by the globular head of the HA. Interestingly, the HA of the H9 subtype lack the 130 lateral loop that forms the antigenic site A in other subtypes, such as H5 or H3 HAs (Li et al 2020, Wiley et al 1981). Such feature results in two antigenic sites that overlap, designated site I and site II (Kaverin et al 2004).…”