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Guo X, Zhou Y, Yan H, An Q, Liang C, Liu L, Qian J. Molecular Markers and Mechanisms of Influenza A Virus Cross-Species Transmission and New Host Adaptation. Viruses 2024; 16:883. [PMID: 38932174 PMCID: PMC11209369 DOI: 10.3390/v16060883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/25/2024] [Accepted: 05/28/2024] [Indexed: 06/28/2024] Open
Abstract
Influenza A viruses continue to be a serious health risk to people and result in a large-scale socio-economic loss. Avian influenza viruses typically do not replicate efficiently in mammals, but through the accumulation of mutations or genetic reassortment, they can overcome interspecies barriers, adapt to new hosts, and spread among them. Zoonotic influenza A viruses sporadically infect humans and exhibit limited human-to-human transmission. However, further adaptation of these viruses to humans may result in airborne transmissible viruses with pandemic potential. Therefore, we are beginning to understand genetic changes and mechanisms that may influence interspecific adaptation, cross-species transmission, and the pandemic potential of influenza A viruses. We also discuss the genetic and phenotypic traits associated with the airborne transmission of influenza A viruses in order to provide theoretical guidance for the surveillance of new strains with pandemic potential and the prevention of pandemics.
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Affiliation(s)
- Xinyi Guo
- School of Public Health (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China;
| | - Yang Zhou
- Guangzhou Eighth People’s Hospital, Guangzhou Medical University, Guangzhou 510440, China
| | - Huijun Yan
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; (H.Y.); (C.L.)
| | - Qing An
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin 150040, China;
| | - Chudan Liang
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China; (H.Y.); (C.L.)
- Guangdong Provincial Highly Pathogenic Microorganism Science Data Center, Guangzhou 510080, China
| | - Linna Liu
- Guangzhou Eighth People’s Hospital, Guangzhou Medical University, Guangzhou 510440, China
| | - Jun Qian
- School of Public Health (Shenzhen), Shenzhen Campus of Sun Yat-sen University, Shenzhen 518107, China;
- Guangdong Provincial Highly Pathogenic Microorganism Science Data Center, Guangzhou 510080, China
- Shenzhen Key Laboratory of Pathogenic Microbes and Biosafety, Shenzhen 518107, China
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Turkeys possess div6erse Siaα2-3Gal glycans that facilitate their dual susceptibility to avian influenza viruses isolated from ducks and chickens. Virus Res 2022; 315:198771. [DOI: 10.1016/j.virusres.2022.198771] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/03/2022] [Accepted: 04/08/2022] [Indexed: 11/18/2022]
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Russell CJ. Hemagglutinin Stability and Its Impact on Influenza A Virus Infectivity, Pathogenicity, and Transmissibility in Avians, Mice, Swine, Seals, Ferrets, and Humans. Viruses 2021; 13:746. [PMID: 33923198 PMCID: PMC8145662 DOI: 10.3390/v13050746] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 04/21/2021] [Accepted: 04/23/2021] [Indexed: 12/13/2022] Open
Abstract
Genetically diverse influenza A viruses (IAVs) circulate in wild aquatic birds. From this reservoir, IAVs sporadically cause outbreaks, epidemics, and pandemics in wild and domestic avians, wild land and sea mammals, horses, canines, felines, swine, humans, and other species. One molecular trait shown to modulate IAV host range is the stability of the hemagglutinin (HA) surface glycoprotein. The HA protein is the major antigen and during virus entry, this trimeric envelope glycoprotein binds sialic acid-containing receptors before being triggered by endosomal low pH to undergo irreversible structural changes that cause membrane fusion. The HA proteins from different IAV isolates can vary in the pH at which HA protein structural changes are triggered, the protein causes membrane fusion, or outside the cell the virion becomes inactivated. HA activation pH values generally range from pH 4.8 to 6.2. Human-adapted HA proteins tend to have relatively stable HA proteins activated at pH 5.5 or below. Here, studies are reviewed that report HA stability values and investigate the biological impact of variations in HA stability on replication, pathogenicity, and transmissibility in experimental animal models. Overall, a stabilized HA protein appears to be necessary for human pandemic potential and should be considered when assessing human pandemic risk.
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Affiliation(s)
- Charles J Russell
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-3678, USA
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Infection of Human Tracheal Epithelial Cells by H5 Avian Influenza Virus Is Regulated by the Acid Stability of Hemagglutinin and the pH of Target Cell Endosomes. Viruses 2020; 12:v12010082. [PMID: 31936692 PMCID: PMC7019350 DOI: 10.3390/v12010082] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/04/2020] [Accepted: 01/05/2020] [Indexed: 01/04/2023] Open
Abstract
Despite the possible relationships between tracheal infection and concomitant infection of the terminal part of the lower respiratory tract (bronchioles/alveoli), the behavior of avian influenza viruses (AIVs), such as H5N1, in the conducting airways is unclear. To examine the tropism of AIVs for cells lining the conducting airways of humans, we established human tracheal epithelial cell clones (HTEpC-Ts) and examined their susceptibility to infection by AIVs. The HTEpC-Ts showed differing susceptibility to H5N1 and non-zoonotic AIVs. Viral receptors expressed by HTEpC-Ts bound all viruses; however, the endosomal pH was associated with the overall susceptibility to infection by AIVs. Moreover, H5N1 hemagglutinin broadened viral tropism to include HTEpC-Ts, because it had a higher pH threshold for viral-cell membrane fusion. Thus, H5N1 viruses infect human tracheal epithelial cells as a result of their higher pH threshold for membrane fusion which may be one mechanism underlying H5N1 pathogenesis in human airway epithelia. Efficient replication of H5N1 in the conducting airways of humans may facilitate infection of the lower respiratory tract.
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Russell CJ, Hu M, Okda FA. Influenza Hemagglutinin Protein Stability, Activation, and Pandemic Risk. Trends Microbiol 2018; 26:841-853. [PMID: 29681430 PMCID: PMC6150828 DOI: 10.1016/j.tim.2018.03.005] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 03/21/2018] [Accepted: 03/28/2018] [Indexed: 01/09/2023]
Abstract
For decades, hemagglutinin (HA) protein structure and its refolding mechanism have served as a paradigm for understanding protein-mediated membrane fusion. HA trimers are in a high-energy state and are functionally activated by low pH. Over the past decade, HA stability (or the pH at which irreversible conformational changes are triggered) has emerged as an important determinant in influenza virus host range, infectivity, transmissibility, and human pandemic potential. Here, we review HA protein structure, assays to measure its stability, measured HA stability values, residues and mutations that regulate its stability, the effect of HA stability on interspecies adaptation and transmissibility, and mechanistic insights into this process. Most importantly, HA stabilization appears to be necessary for adapting emerging influenza viruses to humans.
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Affiliation(s)
- Charles J Russell
- Department of Infectious Diseases, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-3678, USA; Department of Microbiology, Immunology & Biochemistry, College of Medicine, The University of Tennessee Health Science Center, Memphis, TN 38163, USA.
| | - Meng Hu
- Department of Infectious Diseases, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-3678, USA
| | - Faten A Okda
- Department of Infectious Diseases, St Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105-3678, USA
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A Dual Motif in the Hemagglutinin of H5N1 Goose/Guangdong-Like Highly Pathogenic Avian Influenza Virus Strains Is Conserved from Their Early Evolution and Increases both Membrane Fusion pH and Virulence. J Virol 2018; 92:JVI.00778-18. [PMID: 29899102 DOI: 10.1128/jvi.00778-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 06/02/2018] [Indexed: 12/27/2022] Open
Abstract
Zoonotic highly pathogenic avian influenza viruses (HPAIV) have raised serious public health concerns of a novel pandemic. These strains emerge from low-pathogenic precursors by the acquisition of a polybasic hemagglutinin (HA) cleavage site, the prime virulence determinant. However, required coadaptations of the HA early in HPAIV evolution remained uncertain. To address this question, we generated several HA1/HA2 chimeras and point mutants of an H5N1 clade 2.2.2 HPAIV and an H5N1 low-pathogenic strain. Initial surveys of 3,385 HPAIV H5 HA sequences revealed frequencies of 0.5% for the single amino acids 123R and 124I but a frequency of 97.5% for the dual combination. This highly conserved dual motif is still retained in contemporary H5 HPAIV, including the novel H5NX reassortants carrying neuraminidases of different subtypes, like the H5N8 and the zoonotic H5N6 strains. Remarkably, the earliest Asian H5N1 HPAIV, the Goose/Guangdong strains from 1996/1997, carried 123R only, whereas 124I appeared later in 1997. Experimental reversion in the HPAIV HA to the two residues 123S and124T, characteristic of low-pathogenic strains, prevented virus rescue, while the single substitutions attenuated the virus in both chicken and mice considerably, accompanied by a decreased HA fusion pH. This increased pH sensitivity of H5 HPAIV enables HA-mediated membrane fusion at a higher endosomal pH. Therefore, this HA adaptation may permit infection of cells with less-acidic endosomes, e.g., within the respiratory tract, resulting in an extended organ tropism. Taken together, HA coadaptation to increased acid sensitivity promoted the early evolution of H5 Goose/Guangdong-like HPAIV strains and is still required for their zoonotic potential.IMPORTANCE Zoonotic highly pathogenic avian influenza viruses (HPAIV) have raised serious public health concerns of a novel pandemic. Their prime virulence determinant is the polybasic hemagglutinin (HA) cleavage site. However, required coadaptations in the HA (and other genes) remained uncertain. Here, we identified the dual motif 123R/124I in the HA head that increases the activation pH of HA-mediated membrane fusion, essential for virus genome release into the cytoplasm. This motif is extremely predominant in H5 HPAIV and emerged already in the earliest 1997 H5N1 HPAIV. Reversion to 123S or 124T, characteristic of low-pathogenic strains, attenuated the virus in chicken and mice, accompanied by a decreased HA activation pH. This increased pH sensitivity of H5 HPAIV extends the viral tropism to cells with less-acidic endosomes, e.g., within the respiratory tract. Therefore, early HA adaptation to increased acid sensitivity promoted the emergence of H5 Goose/Guangdong-like HPAIV strains and is required for their zoonotic potential.
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Daidoji T, Watanabe Y, Arai Y, Kajikawa J, Hirose R, Nakaya T. Unique Infectious Strategy of H5N1 Avian Influenza Virus Is Governed by the Acid-Destabilized Property of Hemagglutinin. Viral Immunol 2017; 30:398-407. [PMID: 28654310 DOI: 10.1089/vim.2017.0020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Highly pathogenic avian influenza (HPAI) H5N1 virus emerged in 1997 as a zoonotic disease in Hong Kong. It has since spread to Asia and Europe and is a serious threat to both the poultry industry and human health. For effective surveillance and possible prevention/control of HPAI H5N1 viruses, it is necessary to understand the molecular mechanism underlying HPAI H5N1 pathogenesis. The hemagglutinin (HA) protein of influenza A viruses (IAVs) is one of the major determinants of host adaptation, transmissibility, and viral virulence. The main function of the HA protein is to facilitate viral entry and viral genome release within host cells before infection. To achieve viral infection, IAVs belonging to different subtypes or strains induce viral-cell membrane fusion at different endosomal pH levels after internalization through endocytosis. However, host-specific endosomal pH also affects induction of membrane fusion followed by infection. The HA protein of HPAI H5N1 has a higher pH threshold for membrane fusion than the HA protein of classical avian influenza viruses. Although this particular property of HA (which governs viral infection) is prone to deactivation in the avian intestine or in an ambient environment, it facilitates efficient infection of host cells, resulting in a broad host tropism, regardless of the pH in the host endosome. Accumulated knowledge, together with further research, about the HA-governed mechanism underlying HPAI H5N1 virulence (i.e., receptor tropism and pH-dependent viral-cell membrane fusion) will be helpful for developing effective surveillance strategies and for prevention/control of HPAI H5N1 infection.
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Affiliation(s)
- Tomo Daidoji
- 1 Department of Infectious Diseases, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan
| | - Yohei Watanabe
- 1 Department of Infectious Diseases, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan
| | - Yasuha Arai
- 1 Department of Infectious Diseases, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan .,2 Department of Viral Infection, Research Institute for Microbial Diseases, Osaka University , Osaka, Japan
| | - Junichi Kajikawa
- 1 Department of Infectious Diseases, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan
| | - Ryohei Hirose
- 1 Department of Infectious Diseases, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan .,3 Department of Molecular Gastroenterology and Hepatology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan
| | - Takaaki Nakaya
- 1 Department of Infectious Diseases, Graduate School of Medical Science, Kyoto Prefectural University of Medicine , Kyoto, Japan
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pH Optimum of Hemagglutinin-Mediated Membrane Fusion Determines Sensitivity of Influenza A Viruses to the Interferon-Induced Antiviral State and IFITMs. J Virol 2017; 91:JVI.00246-17. [PMID: 28356532 DOI: 10.1128/jvi.00246-17] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 03/20/2017] [Indexed: 12/24/2022] Open
Abstract
The replication and pathogenicity of influenza A viruses (IAVs) critically depend on their ability to tolerate the antiviral interferon (IFN) response. To determine a potential role for the IAV hemagglutinin (HA) in viral sensitivity to IFN, we studied the restriction of IAV infection in IFN-β-treated human epithelial cells by using 2:6 recombinant IAVs that shared six gene segments of A/Puerto Rico/8/1934 virus (PR8) and contained HAs and neuraminidases of representative avian, human, and zoonotic H5N1 and H7N9 viruses. In A549 and Calu-3 cells, viruses displaying a higher pH optimum of HA-mediated membrane fusion, H5N1-PR8 and H7N9-PR8, were less sensitive to the IFN-induced antiviral state than their counterparts with HAs from duck and human viruses, which fused at a lower pH. The association between a high pH optimum of fusion and reduced IFN sensitivity was confirmed by using HA point mutants of A/Hong Kong/1/1968-PR8 that differed solely by their fusion properties. Furthermore, similar effects of the viral fusion pH on IFN sensitivity were observed in experiments with (i) primary human type II alveolar epithelial cells and differentiated cultures of human airway epithelial cells, (ii) nonrecombinant zoonotic and pandemic IAVs, and (iii) preparations of IFN-α and IFN-λ1. A higher pH of membrane fusion and reduced sensitivity to IFN correlated with lower restriction of the viruses in MDCK cells stably expressing the IFN-inducible transmembrane proteins IFITM2 and IFITM3, which are known to inhibit viral fusion. Our results reveal that the pH optimum of HA-driven membrane fusion of IAVs is a determinant of their sensitivity to IFN and IFITM proteins.IMPORTANCE The IFN system constitutes an important innate defense against viral infection. Substantial information is available on how IAVs avoid detection by sensors of the IFN system and disable IFN signaling pathways. Much less is known about the ability of IAVs to tolerate the antiviral activity of IFN-induced cellular proteins. The IFN-induced proteins of the IFITM family block IAV entry into target cells and can restrict viral spread and pathogenicity. Here we show for the first time that the sensitivity of IAVs to the IFN-induced antiviral state and IFITM2 and IFITM3 proteins depends on the pH value at which the viral HA undergoes a conformational transition and mediates membrane fusion. Our data imply that the high pH optimum of membrane fusion typical of zoonotic IAVs of gallinaceous poultry, such as H5N1 and H7N9, may contribute to their enhanced virulence in humans.
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