Variability in H9N2 haemagglutinin receptor-binding preference and the pH of fusion.
H9N2 avian influenza viruses are primarily a disease of poultry; however, they occasionally infect humans and are considered a potential pandemic threat. Little work has been performed to assess the intrinsic biochemical properties related to zoonotic potential of H9N2 viruses. The objective of this study, therefore, was to investigate H9N2 haemagglutinins (HAs) using two well-known correlates for human adaption: receptor-binding avidity and pH of fusion. Receptor binding was characterized using bio-layer interferometry to measure virus binding to human and avian-like receptor analogues and the pH of fusion was assayed by syncytium formation in virus-infected cells at different pHs. We characterized contemporary H9N2 viruses of the zoonotic G1 lineage, as well as representative viruses of the zoonotic BJ94 lineage. We found that most contemporary H9N2 viruses show a preference for sulphated avian-like receptor analogues. However, the 'Eastern' G1 H9N2 viruses displayed a consistent preference in binding to a human-like receptor analogue. We demonstrate that the presence of leucine at position 226 of the HA receptor-binding site correlated poorly with the ability to bind a human-like sialic acid receptor. H9N2 HAs also display variability in their pH of fusion, ranging between pH 5.4 and 5.85 which is similar to that of the first wave of human H1N1pdm09 viruses but lower than the pH of fusion seen in zoonotic H5N1 and H7N9 viruses. Our results suggest possible molecular mechanisms that may underlie the relatively high prevalence of human zoonotic infection by particular H9N2 virus lineages.
Avian Viral Diseases Programme, The Pirbright Institute, Pirbright Woking, GU24 0NF, UK.|Imperial College London, London W2 1NY, UK.
Thomas P
TP
Peacock
The Francis Crick Institute, London NW1 1AT, UK.
Donald J
DJ
Benton
Avian Viral Diseases Programme, The Pirbright Institute, Pirbright Woking, GU24 0NF, UK.
Jean-Remy
JR
Sadeyen
Avian Viral Diseases Programme, The Pirbright Institute, Pirbright Woking, GU24 0NF, UK.
Pengxiang
P
Chang
Avian Viral Diseases Programme, The Pirbright Institute, Pirbright Woking, GU24 0NF, UK.|Royal Veterinary College, University of London, London NW1 0TU, UK.
Joshua E
JE
Sealy
Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme, National Hospital of Tropical Diseases, 78 Giai Phong, Dong Da, Hanoi, Vietnam.
Juliet E
JE
Bryant
The Francis Crick Institute, London NW1 1AT, UK.|Structural Biology Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK.
Stephen R
SR
Martin
Avian Viral Diseases Programme, The Pirbright Institute, Pirbright Woking, GU24 0NF, UK.
Holly
H
Shelton
The Francis Crick Institute, London NW1 1AT, UK.
John W
JW
McCauley
Imperial College London, London W2 1NY, UK.
Wendy S
WS
Barclay
Avian Viral Diseases Programme, The Pirbright Institute, Pirbright Woking, GU24 0NF, UK.
Munir
M
Iqbal
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000502:physiology; D002522:Chlorocebus aethiops; D004285:Dogs; D057809:HEK293 Cells; D006388:Hemagglutinins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053127:Influenza A Virus, H9N2 Subtype / Q000378:metabolism*; D007251:Influenza, Human / Q000378:metabolism*; D007368:Interferometry; D061985:Madin Darby Canine Kidney Cells; D008561:Membrane Fusion; D009976:Orthomyxoviridae Infections / Q000378:metabolism*; D011200:Poultry / Q000821:virology; D011991:Receptors, Virus / Q000737:chemistry / Q000378:metabolism*; D013431:Sulfates / Q000737:chemistry; D014709:Vero Cells; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism; D015047:Zoonoses / Q000378:metabolism
D006388:Hemagglutinins; D011991:Receptors, Virus; D013431:Sulfates; D014764:Viral Proteins