scholarly journals Phenotypic Effects of Substitutions within the Receptor Binding Site of Highly Pathogenic Avian Influenza H5N1 Virus Observed during Human Infection

2020 ◽  
Vol 94 (13) ◽  
Author(s):  
Dirk Eggink ◽  
Monique Spronken ◽  
Roosmarijn van der Woude ◽  
Jocynthe Buzink ◽  
Frederik Broszeit ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Binding Site ◽  
Receptor Binding ◽  
Human Infection ◽  
Influenza Viruses ◽  
Receptor Specificity ◽  
Receptor Binding Site ◽  
Human Type ◽  
Human Infections

ABSTRACT Highly pathogenic avian influenza (HPAI) viruses are enzootic in wild birds and poultry and continue to cause human infections with high mortality. To date, more than 850 confirmed human cases of H5N1 virus infection have been reported, of which ∼60% were fatal. Global concern persists that these or similar avian influenza viruses will evolve into viruses that can transmit efficiently between humans, causing a severe influenza pandemic. It was shown previously that a change in receptor specificity is a hallmark for adaptation to humans and evolution toward a transmittable virus. Substantial genetic diversity was detected within the receptor binding site of hemagglutinin of HPAI A/H5N1 viruses, evolved during human infection, as detected by next-generation sequencing. Here, we investigated the functional impact of substitutions that were detected during these human infections. Upon rescue of 21 mutant viruses, most substitutions in the receptor binding site (RBS) resulted in viable virus, but virus replication, entry, and stability were often impeded. None of the tested substitutions individually resulted in a clear switch in receptor preference as measured with modified red blood cells and glycan arrays. Although several combinations of the substitutions can lead to human-type receptor specificity, accumulation of multiple amino acid substitutions within a single hemagglutinin during human infection is rare, thus reducing the risk of virus adaptation to humans. IMPORTANCE H5 viruses continue to be a threat for public health. Because these viruses are immunologically novel to humans, they could spark a pandemic when adapted to transmit between humans. Avian influenza viruses need several adaptive mutations to bind to human-type receptors, increase hemagglutinin (HA) stability, and replicate in human cells. However, knowledge on adaptive mutations during human infections is limited. A previous study showed substantial diversity within the receptor binding site of H5N1 during human infection. We therefore analyzed the observed amino acid changes phenotypically in a diverse set of assays, including virus replication, stability, and receptor specificity. None of the tested substitutions resulted in a clear step toward a human-adapted virus capable of aerosol transmission. It is notable that acquiring human-type receptor specificity needs multiple amino acid mutations, and that variability at key position 226 is not tolerated, reducing the risk of them being acquired naturally.

scholarly journals Substitution Arg140Gly in Hemagglutinin Reduced the Virulence of Highly Pathogenic Avian Influenza Virus H7N1

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1584
Author(s):  
Anastasia Treshchalina ◽  
Yulia Postnikova ◽  
Elizaveta Boravleva ◽  
Alexandra Gambaryan ◽  
Alla Belyakova ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Receptor Binding ◽  
Genome Stability ◽  
Laboratory Strain ◽  
Influenza Viruses ◽  
Single Amino Acid ◽  
Head Part ◽  
Receptor Binding Site ◽  
Highly Pathogenic

The H7 subtype of avian influenza viruses (AIV) stands out among other AIV. The H7 viruses circulate in ducks, poultry and equines and have repeatedly caused outbreaks of disease in humans. The laboratory strain A/chicken/Rostock/R0p/1934 (H7N1) (R0p), which was previously derived from the highly pathogenic strain A/FPV/Rostock/1934 (H7N1), was studied in this work to ascertain its biological property, genome stability and virulent changing mechanism. Several virus variants were obtained by serial passages in the chicken lungs. After 10 passages of this virus through the chicken lungs we obtained a much more pathogenic variant than the starting R0p. The study of intermediate passages showed a sharp increase in pathogenicity between the fifth and sixth passage. By cloning these variants, a pair of strains (R5p and R6p) was obtained, and the complete genomes of these strains were sequenced. Single amino acid substitution was revealed, namely reversion Gly140Arg in HA1. This amino acid is located at the head part of the hemagglutinin, adjacent to the receptor-binding site. In addition to the increased pathogenicity in chicken and mice, R6p differs from R5p in the shape of foci in cell culture and an increased affinity for a negatively charged receptor analogue, while maintaining a pattern of receptor-binding specificity and the pH of conformational change of HA.

scholarly journals Amino acid substitutions in the H5N1 avian influenza haemagglutinin alter pH of fusion and receptor binding to promote a highly pathogenic phenotype in chickens

2021 ◽  
Vol 102 (11) ◽  
Author(s):  
Joshua E. Sealy ◽  
Wendy A. Howard ◽  
Eleonora Molesti ◽  
Munir Iqbal ◽  
Nigel J. Temperton ◽  
...  
Keyword(s):  
Amino Acid ◽  
Avian Influenza ◽  
Binding Site ◽  
Receptor Binding ◽  
Viral Fitness ◽  
Amino Acid Substitutions ◽  
Receptor Binding Site ◽  
Highly Pathogenic ◽  
Ha Gene ◽  
H5n1 Avian Influenza

Highly pathogenic H5N1 avian influenza viruses cause devastating outbreaks in farmed poultry with serious consequences for animal welfare and economic losses. Zoonotic infection of humans through close contact with H5N1 infected birds is often severe and fatal. England experienced an outbreak of H5N1 in turkeys in 1991 that led to thousands of farmed bird mortalities. Isolation of clonal populations of one such virus from this outbreak uncovered amino acid differences in the virus haemagglutinin (HA) gene whereby the different genotypes could be associated with distinct pathogenic outcomes in chickens; both low pathogenic (LP) and high pathogenic (HP) phenotypes could be observed despite all containing a multi-basic cleavage site (MBCS) in the HA gene. Using reverse genetics, three amino acid substitutions in HA were examined for their ability to affect pathogenesis in the chicken. Restoration of amino acid polymorphisms close to the receptor binding site that are commonly found in H5 viruses only partially improved viral fitness in vitro and in vivo. A third novel substitution in the fusion peptide, HA2G4R, enabled the HP phenotype. HA2G4R decreased the pH stability of HA and increased the pH of HA fusion. The substitutions close to the receptor binding site optimised receptor binding while modulating the pH of HA fusion. Importantly, this study revealed pathogenic determinants beyond the MBCS.

Nicotinic receptor binding site probed with unnatural amino acid incorporation in intact cells

Science ◽  
1995 ◽  
Vol 268 (5209) ◽  
pp. 439-442 ◽  
Author(s):  
M. Nowak ◽  
P. Kearney ◽  
Sampson ◽  
M. Saks ◽  
C. Labarca ◽  
...  
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Receptor Binding ◽  
Nicotinic Receptor ◽  
Unnatural Amino Acid ◽  
Amino Acid Incorporation ◽  
Receptor Binding Site ◽  
Intact Cells ◽  
Acid Incorporation

scholarly journals Identification of Stabilizing Mutations in an H5 Hemagglutinin Influenza Virus Protein

2015 ◽  
Vol 90 (6) ◽  
pp. 2981-2992 ◽  
Author(s):  
Anthony Hanson ◽  
Masaki Imai ◽  
Masato Hatta ◽  
Ryan McBride ◽  
Hirotaka Imai ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Avian Influenza ◽  
Conformational Change ◽  
Receptor Binding ◽  
Heat Stability ◽  
Influenza Viruses ◽  
Virus Infectivity ◽  
Highly Pathogenic ◽  
Human Type ◽  
Droplet Transmission

ABSTRACTHighly pathogenic avian influenza viruses of the H5N1 subtype continue to circulate in poultry in Asia, Africa, and the Middle East. Recently, outbreaks of novel reassortant H5 viruses have also occurred in North America. Although the number of human infections with highly pathogenic H5N1 influenza viruses continues to rise, these viruses remain unable to efficiently transmit between humans. However, we and others have identified H5 viruses capable of respiratory droplet transmission in ferrets. Two experimentally introduced mutations in the viral hemagglutinin (HA) receptor-binding domain conferred binding to human-type receptors but reduced HA stability. Compensatory mutations in HA (acquired during virus replication in ferrets) were essential to restore HA stability. These stabilizing mutations in HA also affected the pH at which HA undergoes an irreversible switch to its fusogenic form in host endosomes, a crucial step for virus infectivity. To identify additional stabilizing mutations in an H5 HA, we subjected a virus library possessing random mutations in the ectodomain of an H5 HA (altered to bind human-type receptors) to three rounds of treatment at 50°C. We isolated several mutants that maintained their human-type receptor-binding preference but acquired an appreciable increase in heat stability and underwent membrane fusion at a lower pH; collectively, these properties may aid H5 virus respiratory droplet transmission in mammals.IMPORTANCEWe have identified mutations in HA that increase its heat stability and affect the pH that triggers an irreversible conformational change (a prerequisite for virus infectivity). These mutations were identified in the genetic background of an H5 HA protein that was mutated to bind to human cells. The ability to bind to human-type receptors, together with physical stability and an altered pH threshold for HA conformational change, may facilitate avian influenza virus transmission via respiratory droplets in mammals.

scholarly journals Avian Influenza A Viruses Differ from Human Viruses by Recognition of Sialyloligosaccharides and Gangliosides and by a Higher Conservation of the HA Receptor-Binding Site

Virology ◽  
1997 ◽  
Vol 233 (1) ◽  
pp. 224-234 ◽  
Author(s):  
M.N. Matrosovich ◽  
A.S. Gambaryan ◽  
S. Teneberg ◽  
V.E. Piskarev ◽  
S.S. Yamnikova ◽  
...  
Keyword(s):  
Avian Influenza ◽  
Binding Site ◽  
Receptor Binding ◽  
Influenza A ◽  
Influenza A Viruses ◽  
Receptor Binding Site ◽  
Human Viruses

scholarly journals Correction for Koel et al., Antigenic Variation of Clade 2.1 H5N1 Virus Is Determined by a Few Amino Acid Substitutions Immediately Adjacent to the Receptor Binding Site

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Björn F. Koel ◽  
Stefan van der Vliet ◽  
David F. Burke ◽  
Theo M. Bestebroer ◽  
Eny E. Bharoto ◽  
...  
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Receptor Binding ◽  
H5n1 Virus ◽  
Antigenic Variation ◽  
Amino Acid Substitutions ◽  
Receptor Binding Site

scholarly journals Zoonotic Potential of Currently Circulating Avian Influenza Viruses

2020 ◽  
Vol 39 (1) ◽  
pp. 8-14
Author(s):  
Vladimir Savić
Keyword(s):  
Avian Influenza ◽  
Influenza A ◽  
Human Infection ◽  
Influenza Viruses ◽  
Influenza A Viruses ◽  
Avian Influenza Viruses ◽  
Influenza Pandemics ◽  
Human Infections ◽  
Virus Adaptation ◽  
Efficient Transmission

Over the past and the current centuries, human influenza pandemics have been attributable to viruses with an avian ancestry. Birds are the main source of influenza A viruses and harbour a variety of antigenic subtypes. Certain avian influenza viruses are capable for cross-species transmission including human infections. Although sustained intrehuman transmission of such viruses has not been documented so far, each human infection with avian influenza viruses provides chances for the virus adaptation towards efficient transmission within human population. Here are reviewed currently circulating avian influenza viruses that are of major significance for public health.

scholarly journals N-Linked Glycans and K147 Residue on Hemagglutinin Synergize To Elicit Broadly Reactive H1N1 Influenza Virus Antibodies

2019 ◽  
Vol 94 (6) ◽  
Author(s):  
Ying Huang ◽  
Simon O. Owino ◽  
Corey J. Crevar ◽  
Donald M. Carter ◽  
Ted M. Ross
Keyword(s):  
Amino Acids ◽  
Influenza Virus ◽  
Binding Site ◽  
Receptor Binding ◽  
Hemagglutination Inhibition ◽  
Vaccine Development ◽  
H1n1 Influenza ◽  
Influenza Viruses ◽  
Wild Type ◽  
Receptor Binding Site

ABSTRACT Vaccination is the most effective way to prevent influenza virus infections. However, the diversity of antigenically distinct isolates is a challenge for vaccine development. In order to overcome the antigenic variability and improve the protective efficacy of influenza vaccines, our research group has pioneered the development of computationally optimized broadly reactive antigens (COBRA) for hemagglutinin (HA). Two candidate COBRA HA vaccines, P1 and X6, elicited antibodies with differential patterns of hemagglutination inhibition (HAI) activity against a panel of H1N1 influenza viruses. In order to better understand how these HA antigens elicit broadly reactive immune responses, epitopes in the Cb, Sa, or Sb antigenic sites of seasonal-like and pandemic-like wild-type or COBRA HA antigens were exchanged with homologous regions in the COBRA HA proteins to determine which regions and residues were responsible for the elicited antibody profile. Mice were vaccinated with virus-like particles (VLPs) expressing one of the 12 modified HA antigens (designated V1 to V12), COBRA HA antigens, or wild-type HA antigens. The elicited antisera was assessed for hemagglutination inhibition activity against a panel of historical seasonal-like and pandemic-like H1N1 influenza viruses. Primarily, the pattern of glycosylation sites and residues in the Sa antigenic region, around the receptor binding site (RBS), served as signatures for the elicitation of broadly reactive antibodies by these HA immunogens. Mice were vaccinated with VLPs expressing HA antigens that lacked a glycosylation site at residue 144 and a deleted lysine at position 147 residue were more effective at protecting against morbidity and mortality following infection with pandemic-like and seasonal-like H1N1 influenza viruses. IMPORTANCE There is a great need to develop broadly reactive or universal vaccines against influenza viruses. Advanced, next-generation hemagglutinin (HA) head-based vaccines that elicit protective antibodies against H1N1 influenza viruses have been developed. This study focused on understanding the specific amino acids around the receptor binding site (RBS) that were important in elicitation of these broadly reactive antibodies. Specific glycan sites and amino acids located at the tip of the HA molecule enhanced the elicitation of these broadly reactive antibodies. A better understanding of the HA structures around the RBS will lead to more effective HA immunogens.

scholarly journals Avian influenza viruses in humans: lessons from past outbreaks

2019 ◽  
Vol 132 (1) ◽  
pp. 81-95 ◽  
Author(s):  
Yao-Tsun Li ◽  
Martin Linster ◽  
Ian H Mendenhall ◽  
Yvonne C F Su ◽  
Gavin J D Smith
Keyword(s):  
Risk Factors ◽  
Avian Influenza ◽  
Virus Transmission ◽  
Human Infection ◽  
Influenza Viruses ◽  
Avian Species ◽  
Avian Influenza Viruses ◽  
Virus Surveillance ◽  
Changing Patterns ◽  
Human Infections

Abstract Background Human infections with avian influenza viruses (AIV) represent a persistent public health threat. The principal risk factor governing human infection with AIV is from direct contact with infected poultry and is primarily observed in Asia and Egypt where live-bird markets are common. Areas of agreement Changing patterns of virus transmission and a lack of obvious disease manifestations in avian species hampers early detection and efficient control of potentially zoonotic AIV. Areas of controversy Despite extensive studies on biological and environmental risk factors, the exact conditions required for cross-species transmission from avian species to humans remain largely unknown. Growing points The development of a universal (‘across-subtype’) influenza vaccine and effective antiviral therapeutics are a priority. Areas timely for developing research Sustained virus surveillance and collection of ecological and physiological parameters from birds in different environments is required to better understand influenza virus ecology and identify risk factors for human infection.

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