201
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Kim HM, Kang YM, Ku KB, Park EH, Yum J, Kim JC, Jin SY, Lee JS, Kim HS, Seo SH. The severe pathogenicity of alveolar macrophage-depleted ferrets infected with 2009 pandemic H1N1 influenza virus. Virology 2013; 444:394-403. [PMID: 23890814 DOI: 10.1016/j.virol.2013.07.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Revised: 06/20/2013] [Accepted: 07/07/2013] [Indexed: 01/24/2023]
Abstract
The in vivo role of alveolar macrophages in the infections with 2009 pandemic H1N1 influenza virus is not as yet known. Ferret study shows that alveolar macrophages are critical for lowering the risk of severe outcomes in 2009 pandemic H1N1 influenza virus infections. Up to 40% of the infected ferrets depleted of alveolar macrophages died, with elevated body temperature and major loss of body weight in contrast to infected ferrets not depleted of alveolar macrophages. The higher viral titers in the lungs were detected in infected ferrets depleted of alveolar macrophages than infected ferrets not depleted of alveolar macrophages 5 days after infection. The inflammatory chemokines were induced at greater levels in the lungs of infected ferrets depleted of alveolar macrophages than in those of infected ferrets not depleted of alveolar macrophages. Our study implies that alveolar macrophages are important for controlling the infections of 2009 pandemic H1N1 influenza virus.
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Affiliation(s)
- Heui Man Kim
- Laboratory of Influenza Research, College of Veterinary Medicine, Chungnam National University, Daejeon, South Korea
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202
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Abstract
Influenza A viruses (IAV) are significant pathogens able to repeatedly switch hosts to infect multiple avian and mammalian species, including humans. The unpredictability of IAV evolution and interspecies movement creates continual public health challenges, such as the emergence of the 2009 pandemic H1N1 virus from swine, as well as pandemic threats from the ongoing H5N1 and the recent H7N9 epizootics. In the last decade there has been increased concern about the “dual use” nature of microbiology, and a set of guidelines covering “dual use research of concern” includes seven categories of potentially problematic scientific experiments. In this Perspective, we consider how in nature IAV continually undergo “dual use experiments” as a matter of evolution and selection, and we conclude that studying these properties of IAV is critical for mitigating and preventing future epidemics and pandemics.
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203
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Poovorawan Y, Pyungporn S, Prachayangprecha S, Makkoch J. Global alert to avian influenza virus infection: from H5N1 to H7N9. Pathog Glob Health 2013; 107:217-23. [PMID: 23916331 PMCID: PMC4001451 DOI: 10.1179/2047773213y.0000000103] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Outbreak of a novel influenza virus is usually triggered by mutational change due to the process known as 'antigenic shift' or re-assortment process that allows animal-to-human or avian-to-human transmission. Birds are a natural reservoir for the influenza virus, and subtypes H5, H7, and H9 have all caused outbreaks of avian influenza in human populations. An especially notorious strain is the HPAI influenza virus H5N1, which has a mortality rate of approximately 60% and which has resulted in numerous hospitalizations, deaths, and significant economic loss. In March 2013, in Eastern China, there was an outbreak of the novel H7N9 influenza virus, which although less pathogenic in avian species, resulted in 131 confirmed cases and 36 deaths in humans over a two-month span. The rapid outbreak of this virus caused global concern but resulted in international cooperation to control the outbreak. Furthermore, cooperation led to valuable research-sharing including genome sequencing of the virus, the development of rapid and specific diagnosis, specimen sharing for future studies, and vaccine development. Although a H7N9 pandemic in the human population is possible due to its rapid transmissibility and extensive surveillance, the closure of the live-bird market will help mitigate the possibility of another H7N9 outbreak. In addition, further research into the source of the outbreak, pathogenicity of the virus, and the development of specific and sensitive detection assays will be essential for controlling and preparing for future H7N9 outbreaks.
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Affiliation(s)
- Yong Poovorawan
- Center of Excellence in Clinical Virology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
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204
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Ngai KLK, Chan MCW, Chan PKS. Replication and transcription activities of ribonucleoprotein complexes reconstituted from avian H5N1, H1N1pdm09 and H3N2 influenza A viruses. PLoS One 2013; 8:e65038. [PMID: 23750226 PMCID: PMC3672204 DOI: 10.1371/journal.pone.0065038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 04/22/2013] [Indexed: 01/14/2023] Open
Abstract
Avian influenza viruses pose a serious pandemic threat to humans. Better knowledge on cross-species adaptation is important. This study examined the replication and transcription efficiency of ribonucleoprotein complexes reconstituted by plasmid co-transfection between H5N1, H1N1pdm09 and H3N2 influenza A viruses, and to identify mutations in the RNA polymerase subunit that affect human adaptation. Viral RNA polymerase subunits PB1, PB2, PA and NP derived from influenza viruses were co-expressed with pPolI-vNP-Luc in human cells, and with its function evaluated by luciferase reporter assay. A quantitative RT-PCR was used to measure vRNA, cRNA, and mRNA levels for assessing the replication and transcription efficiency. Mutations in polymerase subunit were created to identify signature of increased human adaptability. H5N1 ribonucleoprotein complexes incorporated with PB2 derived from H1N1pdm09 and H3N2 viruses increased the polymerase activity in human cells. Furthermore, single amino acid substitutions at PB2 of H5N1 could affect polymerase activity in a temperature-dependent manner. By using a highly sensitive quantitative reverse transcription-polymerase chain reaction, an obvious enhancement in replication and transcription activities of ribonucleoproteins was observed by the introduction of lysine at residue 627 in the H5N1 PB2 subunit. Although less strongly in polymerase activity, E158G mutation appeared to alter the accumulation of H5N1 RNA levels in a temperature-dependent manner, suggesting a temperature-dependent mechanism in regulating transcription and replication exists. H5N1 viruses can adapt to humans either by acquisition of PB2 from circulating human-adapted viruses through reassortment, or by mutations at critical sites in PB2. This information may help to predict the pandemic potential of newly emerged influenza strains, and provide a scientific basis for stepping up surveillance measures and vaccine production.
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MESH Headings
- Animals
- HEK293 Cells
- Humans
- Influenza A Virus, H1N1 Subtype/enzymology
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/physiology
- Influenza A Virus, H3N2 Subtype/enzymology
- Influenza A Virus, H3N2 Subtype/genetics
- Influenza A Virus, H3N2 Subtype/physiology
- Influenza A Virus, H5N1 Subtype/enzymology
- Influenza A Virus, H5N1 Subtype/genetics
- Influenza A Virus, H5N1 Subtype/physiology
- Influenza A virus/enzymology
- Influenza A virus/genetics
- Influenza A virus/physiology
- Mutation
- Pandemics
- RNA-Dependent RNA Polymerase/genetics
- Ribonucleoproteins/genetics
- Temperature
- Transcription, Genetic
- Viral Proteins/genetics
- Virus Replication
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Affiliation(s)
- Karry L. K. Ngai
- Department of Microbiology, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong Special Administration Region, People’s Republic of China
| | - Martin C. W. Chan
- Department of Microbiology, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong Special Administration Region, People’s Republic of China
| | - Paul K. S. Chan
- Department of Microbiology and Stanley Ho Centre for Emerging Infectious Diseases, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong Special Administration Region, People’s Republic of China
- * E-mail:
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205
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Baz M, Paskel M, Matsuoka Y, Zengel J, Cheng X, Jin H, Subbarao K. Replication and immunogenicity of swine, equine, and avian h3 subtype influenza viruses in mice and ferrets. J Virol 2013; 87:6901-10. [PMID: 23576512 PMCID: PMC3676140 DOI: 10.1128/jvi.03520-12] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 04/04/2013] [Indexed: 01/11/2023] Open
Abstract
Since it is difficult to predict which influenza virus subtype will cause an influenza pandemic, it is important to prepare influenza virus vaccines against different subtypes and evaluate the safety and immunogenicity of candidate vaccines in preclinical and clinical studies prior to a pandemic. In addition to infecting humans, H3 influenza viruses commonly infect pigs, horses, and avian species. We selected 11 swine, equine, and avian H3 influenza viruses and evaluated their kinetics of replication and ability to induce a broadly cross-reactive antibody response in mice and ferrets. The swine and equine viruses replicated well in the upper respiratory tract of mice. With the exception of one avian virus that replicated poorly in the lower respiratory tract, all of the viruses replicated in mouse lungs. In ferrets, all of the viruses replicated well in the upper respiratory tract, but the equine viruses replicated poorly in the lungs. Extrapulmonary spread was not observed in either mice or ferrets. No single virus elicited antibodies that cross-reacted with viruses from all three animal sources. Avian and equine H3 viruses elicited broadly cross-reactive antibodies against heterologous viruses isolated from the same or other species, but the swine viruses did not. We selected an equine and an avian H3 influenza virus for further development as vaccines.
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Affiliation(s)
- Mariana Baz
- Laboratory of Infectious Diseases, NIAID, NIH, Bethesda, Maryland, USA
| | - Myeisha Paskel
- Laboratory of Infectious Diseases, NIAID, NIH, Bethesda, Maryland, USA
| | - Yumiko Matsuoka
- Laboratory of Infectious Diseases, NIAID, NIH, Bethesda, Maryland, USA
| | | | - Xing Cheng
- MedImmune LLC, Mountain View, California, USA
| | - Hong Jin
- MedImmune LLC, Mountain View, California, USA
| | - Kanta Subbarao
- Laboratory of Infectious Diseases, NIAID, NIH, Bethesda, Maryland, USA
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206
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An insight into the PB1F2 protein and its multifunctional role in enhancing the pathogenicity of the influenza A viruses. Virology 2013; 440:97-104. [DOI: 10.1016/j.virol.2013.02.025] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 01/18/2013] [Accepted: 02/27/2013] [Indexed: 02/01/2023]
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207
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Chin AWH, Greenbaum BD, Li OTW, Webby RJ, Poon LLM. A statistical strategy to identify recombinant viral ribonucleoprotein of avian, human, and swine influenza A viruses with elevated polymerase activity. Influenza Other Respir Viruses 2013; 7:969-78. [PMID: 23634764 PMCID: PMC3823691 DOI: 10.1111/irv.12117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2013] [Indexed: 12/29/2022] Open
Abstract
Objectives Reassortment of influenza A viruses can give rise to viral ribonucleoproteins (vRNPs) with elevated polymerase activity and the previous three pandemic influenza viruses contained reassorted vRNPs of different origins. These suggest that reassorted vRNP may be one of the factors leading to a pandemic virus. In this study, we reconstituted chimeric vRNPs with three different viral strains isolated from avian, human and swine hosts. We applied a statistical strategy to identify the effect that the origin of a single vRNP protein subunit or the interactions between these subunits on polymerase activity. Design Eighty one chimeric vRNPs were reconstituted in 293T cells at different temperatures. Polymerase activity was determined by luciferase reporter assay and the results were analysed by multiway anova and other statistical methods. Results It was found that PB2, PB1, NP, PB2‐PB1 interaction, PB2‐PA interaction and PB1‐NP interaction had significant effect on polymerase activity at 37°C and several single subunits and interactions were identified to lead to elevation of polymerase activity. Furthermore, we studied 27 out of these 81 different chimieric vRNPs in different combinations via fractional factorial design approach. Our results suggested that the approach can identify the major single subunit or interaction factors that affect the polymerase activity without the need to experimentally reproduce all possible vRNP combinations. Conclusions Statistical approach and fractional factorial design are useful to identify the major single subunit or interaction factors that can modulate viral polymerase activity.
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Affiliation(s)
- Alex W H Chin
- Centre of Influenza Research & School of Public Health, The University of Hong Kong, Hong Kong
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208
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Zhang Y, Zhang Q, Kong H, Jiang Y, Gao Y, Deng G, Shi J, Tian G, Liu L, Liu J, Guan Y, Bu Z, Chen H. H5N1 hybrid viruses bearing 2009/H1N1 virus genes transmit in guinea pigs by respiratory droplet. Science 2013; 340:1459-63. [PMID: 23641061 DOI: 10.1126/science.1229455] [Citation(s) in RCA: 177] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In the past, avian influenza viruses have crossed species barriers to trigger human pandemics by reassorting with mammal-infective viruses in intermediate livestock hosts. H5N1 viruses are able to infect pigs, and some of them have affinity for the mammalian type α-2,6-linked sialic acid airway receptor. Using reverse genetics, we systematically created 127 reassortant viruses between a duck isolate of H5N1, specifically retaining its hemagglutinin (HA) gene throughout, and a highly transmissible, human-infective H1N1 virus. We tested the virulence of the reassortants in mice as a correlate for virulence in humans and tested transmissibility in guinea pigs, which have both avian and mammalian types of airway receptor. Transmission studies showed that the H1N1 virus genes encoding acidic polymerase and nonstructural protein made the H5N1 virus transmissible by respiratory droplet between guinea pigs without killing them. Further experiments implicated other H1N1 genes in the enhancement of mammal-to-mammal transmission, including those that encode nucleoprotein, neuraminidase, and matrix, as well as mutations in H5 HA that improve affinity for humanlike airway receptors. Hence, avian H5N1 subtype viruses do have the potential to acquire mammalian transmissibility by reassortment in current agricultural scenarios.
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Affiliation(s)
- Ying Zhang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
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209
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Tønnessen R, Hauge AG, Hansen EF, Rimstad E, Jonassen CM. Host restrictions of avian influenza viruses: in silico analysis of H13 and H16 specific signatures in the internal proteins. PLoS One 2013; 8:e63270. [PMID: 23646204 PMCID: PMC3639990 DOI: 10.1371/journal.pone.0063270] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Accepted: 04/02/2013] [Indexed: 12/01/2022] Open
Abstract
Gulls are the primary hosts of H13 and H16 avian influenza viruses (AIVs). The molecular basis for this host restriction is only partially understood. In this study, amino acid sequences from Eurasian gull H13 and H16 AIVs and Eurasian AIVs (non H13 and H16) were compared to determine if specific signatures are present only in the internal proteins of H13 and H16 AIVs, using a bioinformatics approach. Amino acids identified in an initial analysis performed on 15 selected sequences were checked against a comprehensive set of AIV sequences retrieved from Genbank to verify them as H13 and H16 specific signatures. Analysis of protein similarities and prediction of subcellular localization signals were performed to search for possible functions associated with the confirmed signatures. H13 and H16 AIV specific signatures were found in all the internal proteins examined, but most were found in the non-structural protein 1 (NS1) and in the nucleoprotein. A putative functional signature was predicted to be present in the nuclear export protein. Moreover, it was predicted that the NS1 of H13 and H16 AIVs lack one of the nuclear localization signals present in NS1 of other AIV subtypes. These findings suggest that the signatures found in the internal proteins of H13 and H16 viruses are possibly related to host restriction.
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Affiliation(s)
- Ragnhild Tønnessen
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway.
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210
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Abstract
ABSTRACTNew and reemerging infectious diseases, such as pandemic viruses and resistant bacteria, pose a serious threat in the 21st century. Some of these agents represent global security threats. This review provides an overview of diagnostic challenges presented by pandemic influenza and biothreat agents. The article summarizes recent pandemics and disease outbreaks, point-of-care influenza diagnostic tests, biothreat agents, biothreat instrument systems, and technologies in development. It highlights how medical innovation and health care initiatives can help prepare health care professionals and public health personnel to handle future crises. Based on gap analysis for current point-of-care testing deficiencies, it concludes with policy recommendations that will enhance preparedness. (Disaster Med Public Health Preparedness. 2009;3(Suppl 2):S193–S202)
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211
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Fries AC, Nolting JM, Danner A, Webster RG, Bowman AS, Krauss S, Slemons RD. Evidence for the circulation and inter-hemispheric movement of the H14 subtype influenza A virus. PLoS One 2013; 8:e59216. [PMID: 23555632 PMCID: PMC3610705 DOI: 10.1371/journal.pone.0059216] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 02/12/2013] [Indexed: 11/18/2022] Open
Abstract
Three H14 influenza A virus (IAV) isolates recovered in 2010 during routine virus surveillance along the Mississippi Migratory Bird Flyway in Wisconsin, U.S.A. raised questions about the natural history of these rare viruses. These were the first H14 IAV isolates recovered in the Western Hemisphere and the only H14 IAV isolates recovered since the original four isolates in 1982 in Asia. Full length genomic sequencing of the 2010 H14 isolates demonstrated the hemagglutinin (HA) gene from the 1982 and 2010 H14 isolates showed 89.6% nucleotide and 95.6% amino acid similarity and phylogenetic analysis of these viruses placed them with strong support within the H14 subtype lineage. The level of genomic divergence observed between the 1982 and 2010 viruses provides evidence that the H14 HA segment was circulating undetected in hosts and was not maintained in environmental stasis. Further, the evolutionary relationship observed between 1982 H14 and the closely related H4 subtype HA segments were similar to contemporary comparisons suggesting limited adaptive divergence between these sister subtypes. The nonstructural (NS) segment of one 2010 isolate was placed in a NS clade isolated infrequently over the last several decades that includes the NS segment from a previously reported 1982 H14 isolate indicating the existence of an unidentified pool of genomic diversity. An additional neuraminidase reassortment event indicated a recent inter-hemispheric gene flow from Asia into the center of North America. These results demonstrate temporal and spatial gaps in the understanding of IAV natural history. Additionally, the reassortment history of these viruses raises concern for the inter-continental spread of IAVs and the efficacy of current IAV surveillance efforts in detecting genomic diversity of viruses circulating in wild birds.
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Affiliation(s)
- Anthony C Fries
- The Ohio State University, Department of Veterinary Preventive Medicine, Columbus, OH, USA.
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212
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Belser JA, Tumpey TM. H5N1 pathogenesis studies in mammalian models. Virus Res 2013; 178:168-85. [PMID: 23458998 DOI: 10.1016/j.virusres.2013.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 12/14/2012] [Accepted: 02/06/2013] [Indexed: 12/21/2022]
Abstract
H5N1 influenza viruses are capable of causing severe disease and death in humans, and represent a potential pandemic subtype should they acquire a transmissible phenotype. Due to the expanding host and geographic range of this virus subtype, there is an urgent need to better understand the contribution of both virus and host responses following H5N1 virus infection to prevent and control human disease. The use of mammalian models, notably the mouse and ferret, has enabled the detailed study of both complex virus-host interactions as well as the contribution of individual viral proteins and point mutations which influence virulence. In this review, we describe the behavior of H5N1 viruses which exhibit high and low virulence in numerous mammalian species, and highlight the contribution of inoculation route to virus pathogenicity. The involvement of host responses as studied in both inbred and outbred mammalian models is discussed. The roles of individual viral gene products and molecular determinants which modulate the severity of H5N1 disease in vivo are presented. This research contributes not only to our understanding of influenza virus pathogenesis, but also identifies novel preventative and therapeutic targets to mitigate the disease burden caused by avian influenza viruses.
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Affiliation(s)
- Jessica A Belser
- Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, United States
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213
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Matthaei M, Budt M, Wolff T. Highly pathogenic H5N1 influenza A virus strains provoke heterogeneous IFN-α/β responses that distinctively affect viral propagation in human cells. PLoS One 2013; 8:e56659. [PMID: 23451066 PMCID: PMC3581526 DOI: 10.1371/journal.pone.0056659] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 01/14/2013] [Indexed: 12/24/2022] Open
Abstract
The fatal transmissions of highly pathogenic avian influenza A viruses (IAV) of the H5N1 subtype to humans and high titer replication in the respiratory tract indicate that these pathogens can overcome the bird-to-human species barrier. While type I interferons (IFN-α/β) are well described to contribute to the species barrier of many zoonotic viruses, current data to the role of these antiviral cytokines during human H5N1 IAV infections is limited and contradictory. We hypothesized an important role for the IFN system in limiting productive infection of avian H5N1 strains in human cells. Hence, we examined IFN-α/β gene activation by different avian and human H5N1 isolates, if the IFN-α/β response restricts H5N1 growth and whether the different strains were equally capable to regulate the IFN-α/β system via their IFN-antagonistic NS1 proteins. Two human H5N1 isolates and a seasonal H3N2 strain propagated efficiently in human respiratory cells and induced little IFN-β, whereas three purely avian H5N1 strains were attenuated for replication and provoked higher IFN secretion. Replication of avian viruses was significantly enhanced on interferon-deficient cells, and exogenous IFN potently limited the growth of all strains in human cells. Moreover, IFN-α/β activation by all strains depended on retinoic acid-inducible gene I excluding principal differences in receptor activation between the different viruses. Interestingly, all H5N1 NS1 proteins suppressed IFN-α/β induction comparably well to the NS1 of seasonal IAV. Thus, our study shows that H5N1 strains are heterogeneous in their capacity to activate human cells in an NS1-independent manner. Our findings also suggest that H5N1 viruses need to acquire adaptive changes to circumvent strong IFN-α/β activation in human host cells. Since no single amino acid polymorphism could be associated with a respective high- or low induction phenotype we propose that the necessary adaptations to overcome the human IFN-α/β barrier involve mutations in multiple H5N1 genes.
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Affiliation(s)
- Markus Matthaei
- Division of Influenza/Respiratory Viruses, Robert Koch-Institut, Berlin, Germany
| | - Matthias Budt
- Division of Influenza/Respiratory Viruses, Robert Koch-Institut, Berlin, Germany
| | - Thorsten Wolff
- Division of Influenza/Respiratory Viruses, Robert Koch-Institut, Berlin, Germany
- * E-mail:
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214
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Influenza a virus entry: implications in virulence and future therapeutics. Adv Virol 2013; 2013:121924. [PMID: 23365574 PMCID: PMC3556402 DOI: 10.1155/2013/121924] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 12/09/2012] [Accepted: 12/23/2012] [Indexed: 12/15/2022] Open
Abstract
Influenza A viruses have broad host tropism, being able to infect a range of hosts from wild fowl to swine to humans. This broad tropism makes highly pathogenic influenza A strains, such as H5N1, potentially dangerous to humans if they gain the ability to jump from an animal reservoir to humans. How influenza A viruses are able to jump the species barrier is incompletely understood due to the complex genetic nature of the viral surface glycoprotein, hemagglutinin, which mediates entry, combined with the virus's ability to use various receptor linkages. Current therapeutics against influenza A include those that target the uncoating process after entry as well as those that prevent viral budding. While there are therapeutics in development that target entry, currently there are none clinically available. We review here the genetics of influenza A viruses that contribute to entry tropism, how these genetic alterations may contribute to receptor usage and species tropism, as well as how novel therapeutics can be developed that target the major surface glycoprotein, hemagglutinin.
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215
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Abstract
Although the ferret model has been extensively used to study pathogenesis and transmission of influenza viruses, little has been done to determine whether ferrets are a good surrogate animal model to study influenza virus reassortment. It has been previously shown that the pandemic 2009 H1N1 (H1N1pdm) virus was able to transmit efficiently in ferrets. In coinfection studies with either seasonal H1N1 or H3N2 strains (H1N1s or H3N2s, respectively), the H1N1pdm virus was able to outcompete these strains and become the dominant transmissible virus. However, lack of reassortment could have been the result of differences in the cell or tissue tropism of these viruses in the ferret. To address this issue, we performed coinfection studies with recombinant influenza viruses carrying the surface genes of a seasonal H3N2 strain in the background of an H1N1pdm strain and vice versa. After serial passages in ferrets, a dominant H1N2 virus population was obtained with a constellation of gene segments, most of which, except for the neuraminidase (NA) and PB1 segments, were from the H1N1pdm strain. Our studies suggest that ferrets recapitulate influenza virus reassortment events. The H1N2 virus generated through this process resembles similar viruses that are emerging in nature, particularly in pigs.
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216
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Abstract
Although outbreaks of highly pathogenic avian influenza in wild and domestic birds have been posing the threat of a new influenza pandemic for the past decade, the first pandemic of the twenty-first century came from swine viruses. This fact emphasizes the complexity of influenza viral ecology and the difficulty of predicting influenza viral dynamics. Complete control of influenza viruses seems impossible. However, we must minimize the impact of animal and human influenza outbreaks by learning lessons from past experiences and recognizing the current status. Here, we review the most recent influenza virology data in the veterinary field, including aspects of zoonotic agents and recent studies that assess the pandemic potential of H5N1 highly pathogenic avian influenza viruses.
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217
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Moncorgé O, Long JS, Cauldwell AV, Zhou H, Lycett SJ, Barclay WS. Investigation of influenza virus polymerase activity in pig cells. J Virol 2013; 87:384-94. [PMID: 23077313 PMCID: PMC3536367 DOI: 10.1128/jvi.01633-12] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 10/12/2012] [Indexed: 02/04/2023] Open
Abstract
Reassortant influenza viruses with combinations of avian, human, and/or swine genomic segments have been detected frequently in pigs. As a consequence, pigs have been accused of being a "mixing vessel" for influenza viruses. This implies that pig cells support transcription and replication of avian influenza viruses, in contrast to human cells, in which most avian influenza virus polymerases display limited activity. Although influenza virus polymerase activity has been studied in human and avian cells for many years by use of a minigenome assay, similar investigations in pig cells have not been reported. We developed the first minigenome assay for pig cells and compared the activities of polymerases of avian or human influenza virus origin in pig, human, and avian cells. We also investigated in pig cells the consequences of some known mammalian host range determinants that enhance influenza virus polymerase activity in human cells, such as PB2 mutations E627K, D701N, G590S/Q591R, and T271A. The two typical avian influenza virus polymerases used in this study were poorly active in pig cells, similar to what is seen in human cells, and mutations that adapt the avian influenza virus polymerase for human cells also increased activity in pig cells. In contrast, a different pattern was observed in avian cells. Finally, highly pathogenic avian influenza virus H5N1 polymerase activity was tested because this subtype has been reported to replicate only poorly in pigs. H5N1 polymerase was active in swine cells, suggesting that other barriers restrict these viruses from becoming endemic in pigs.
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Affiliation(s)
- Olivier Moncorgé
- Section of Virology, Department of Medicine, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - Jason S. Long
- Section of Virology, Department of Medicine, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - Anna V. Cauldwell
- Section of Virology, Department of Medicine, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - Hongbo Zhou
- Section of Virology, Department of Medicine, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - Samantha J. Lycett
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, Edinburgh, United Kingdom
| | - Wendy S. Barclay
- Section of Virology, Department of Medicine, Imperial College London, St. Mary's Campus, London, United Kingdom
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Genetic Analysis of Avian Influenza Viruses: Cocirculation of Avian Influenza Viruses with Allele A and B Nonstructural Gene in Northern Pintail (Anas acuta) Ducks Wintering in Japan. INFLUENZA RESEARCH AND TREATMENT 2012; 2012:847505. [PMID: 23320157 PMCID: PMC3540751 DOI: 10.1155/2012/847505] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 12/02/2012] [Accepted: 12/06/2012] [Indexed: 11/18/2022]
Abstract
The pandemic influenza virus strains of 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), and 2009 (H1N1) have genes related to avian influenza viruses (AIVs). The nonstructural (NS) gene of AIVs plays a significant role in host-viral interaction. However, little is known about the degree of diversity of this gene in Northern pintail (Anas acuta) ducks wintering in Japan. This study describes characteristics of pintail-originated H1N1, H1N2, H1N3, H5N2, H5N3, H5N9, and H7N7 viruses. Most of the viruses were revealed to be avian strains and not related to pandemic and seasonal flu strains. Nevertheless, the NP genes of 62.5% (5/8) viruses were found closely related to a A/swine/Korea/C12/08, indicating exchange of genetic material and ongoing mammalian-linked evolution of AIVs. Besides, all the viruses, except Aomori/422/07 H1N1, contain PSIQSR∗GLF motif usually found in avian, porcine, and human H1 strains. The Aomori/422/07 H1N1 has a PSVQSR∗GLF motif identical to a North American strain. This findings linked to an important intercontinental, Asian-American biogeographical interface. Phylogenetically all the viruses were clustered in Eurasian lineage. Cocirculation of allele A and B (NS gene) viruses was evident in the study implying the existence of a wide reservoir of influenza A viruses in pintail wintering in Japan.
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219
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The PA-gene-mediated lethal dissemination and excessive innate immune response contribute to the high virulence of H5N1 avian influenza virus in mice. J Virol 2012; 87:2660-72. [PMID: 23255810 DOI: 10.1128/jvi.02891-12] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Highly pathogenic H5N1 influenza A virus remains a substantial threat to public health. To understand the molecular basis and host mechanism for the high virulence of H5N1 viruses in mammals, we compared two H5N1 isolates which have similar genetic backgrounds but greatly differ in their virulence in mice. A/Chicken/Jiangsu/k0402/2010 (CK10) is highly pathogenic, whereas A/Goose/Jiangsu/k0403/2010 (GS10) is nonpathogenic. We first showed that CK10 elicited a more potent innate immune response than did GS10 in mouse lungs by increasing the number and expression levels of activated genes. We then generated a series of reassortants between the two viruses and evaluated their virulence in mice. Inclusion of the CK10 PA gene in the GS10 background resulted in a dramatic increase in virulence. Conversely, expression of the GS10 PA gene in the CK10 background significantly attenuated the virulence. These results demonstrated that the PA gene mainly determines the pathogenicity discrepancy between CK10 and GS10 in mice. We further determined that arginine (R) at position 353 of the PA gene contributes to the high virulence of CK10 in mice. The reciprocal substitution at position 353 in PA or the exchange of the entire PA gene largely caused the transfer of viral phenotypes, including virus replication, polymerase activity, and manipulation of the innate response, between CK10 and GS10. We therefore defined a novel molecular marker associated with the high virulence of H5N1 influenza viruses, providing further insights into the pathogenesis of H5N1 viruses in mammals.
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220
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Capuano AW, Dawson JD. The trend odds model for ordinal data. Stat Med 2012; 32:2250-61. [PMID: 23225520 DOI: 10.1002/sim.5689] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Accepted: 11/02/2012] [Indexed: 11/10/2022]
Abstract
Ordinal data appear in a wide variety of scientific fields. These data are often analyzed using ordinal logistic regression models that assume proportional odds. When this assumption is not met, it may be possible to capture the lack of proportionality using a constrained structural relationship between the odds and the cut-points of the ordinal values. We consider a trend odds version of this constrained model, wherein the odds parameter increases or decreases in a monotonic manner across the cut-points. We demonstrate algebraically and graphically how this model is related to latent logistic, normal, and exponential distributions. In particular, we find that scale changes in these potential latent distributions are consistent with the trend odds assumption, with the logistic and exponential distributions having odds that increase in a linear or nearly linear fashion. We show how to fit this model using SAS Proc NLMIXED and perform simulations under proportional odds and trend odds processes. We find that the added complexity of the trend odds model gives improved power over the proportional odds model when there are moderate to severe departures from proportionality. A hypothetical data set is used to illustrate the interpretation of the trend odds model, and we apply this model to a swine influenza example wherein the proportional odds assumption appears to be violated.
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Affiliation(s)
- Ana W Capuano
- Department of Biostatistics, University of Iowa College of Public Health, Iowa City, IA 52240, USA.
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221
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Diagnostic Testing Strategies for Health Care Delivery During the Great Bangkok Flood and Other Weather Disasters. POINT OF CARE 2012. [DOI: 10.1097/poc.0b013e318265f255] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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222
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Zhao J, Wang X, Ragupathy V, Zhang P, Tang W, Ye Z, Eichelberger M, Hewlett I. Rapid detection and differentiation of swine-origin influenza A virus (H1N1/2009) from other seasonal influenza A viruses. Viruses 2012. [PMID: 23202513 PMCID: PMC3509681 DOI: 10.3390/v4113012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We previously developed a rapid and simple gold nanoparticle(NP)-based genomic microarray assay for identification of the avian H5N1 virus and its discrimination from other influenza A virus strains (H1N1, H3N2). In this study, we expanded the platform to detect the 2009 swine-origin influenza A virus (H1N1/2009). Multiple specific capture and intermediate oligonucleotides were designed for the matrix (M), hemagglutinin (HA), and neuraminidase (NA) genes of the H1N1/2009 virus. The H1N1/2009 microarrays were printed in the same format as those of the seasonal influenza H1N1 and H3N2 for the HA, NA, and M genes. Viral RNA was tested using capture-target-intermediate oligonucleotide hybridization and gold NP-mediated silver staining. The signal from the 4 capture-target-intermediates of the HA and NA genes was specific for H1N1/2009 virus and showed no cross hybridization with viral RNA from other influenza strains H1N1, H3N2, and H5N1. All of the 3 M gene captures showed strong affinity with H1N1/2009 viral RNA, with 2 out of the 3 M gene captures showing cross hybridization with the H1N1, H3N2, and H5N1 samples tested. The current assay was able to detect H1N1/2009 and distinguish it from other influenza A viruses. This new method may be useful for simultaneous detection and subtyping of influenza A viruses and can be rapidly modified to detect other emerging influenza strains in public health settings.
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Affiliation(s)
- Jiangqin Zhao
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA; (X.W.); (V.R.); (P.Z.); (W.T.)
- Authors to whom correspondence should be addressed; (J.Z.); (I.H.); Tel.: +1-301-827-0795; Fax: +1-301-480-7928
| | - Xue Wang
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA; (X.W.); (V.R.); (P.Z.); (W.T.)
| | - Viswanath Ragupathy
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA; (X.W.); (V.R.); (P.Z.); (W.T.)
| | - Panhe Zhang
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA; (X.W.); (V.R.); (P.Z.); (W.T.)
| | - Wei Tang
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA; (X.W.); (V.R.); (P.Z.); (W.T.)
| | - Zhiping Ye
- Division of Viral Products, Office of Vaccines Research and Review, CBER, Food and Drug Administration, Bethesda, MD 20892, USA; (Z.Y.); (M.E.)
| | - Maryna Eichelberger
- Division of Viral Products, Office of Vaccines Research and Review, CBER, Food and Drug Administration, Bethesda, MD 20892, USA; (Z.Y.); (M.E.)
| | - Indira Hewlett
- Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA; (X.W.); (V.R.); (P.Z.); (W.T.)
- Authors to whom correspondence should be addressed; (J.Z.); (I.H.); Tel.: +1-301-827-0795; Fax: +1-301-480-7928
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223
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La Gruta N, Kelso A, Brown LE, Chen W, Jackson DC, Turner SJ. Role of CD8(+) T-cell immunity in influenza infection: potential use in future vaccine development. Expert Rev Respir Med 2012; 3:523-37. [PMID: 20477341 DOI: 10.1586/ers.09.44] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Continued circulation of the highly pathogenic avian H5N1 influenza A virus has many people worried that an influenza pandemic is imminent. Compounding this is the realization that H5N1 vaccines based on current influenza vaccine technology (designed to generate protective antibody responses) may be suboptimal at providing protection. As a consequence, there is recent interest in vaccine strategies that elicit cellular immunity, particularly the cytotoxic T lymphocyte response, in an effort to provide protection against a potential pandemic. A major issue is the lack of information about the precise role that these 'hitmen' of the immune system have in protecting against both pandemic and seasonal influenza. We need to know more about how the induction and maintenance of cytotoxic T lymphocytes after influenza infection can impact protection from further infection. The challenge is then to use this information in the design of vaccines that will protect against pandemic influenza and will help optimize CD8(+) killer T-cell responses in other infections.
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Affiliation(s)
- Nicole La Gruta
- Department of Microbiology and Immunology, The University of Melbourne, Royal Parade, Parkville, Victoria 3010, Australia
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224
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Geeraedts F, ter Veer W, Wilschut J, Huckriede A, de Haan A. Effect of viral membrane fusion activity on antibody induction by influenza H5N1 whole inactivated virus vaccine. Vaccine 2012; 30:6501-7. [DOI: 10.1016/j.vaccine.2012.07.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 07/09/2012] [Accepted: 07/16/2012] [Indexed: 01/11/2023]
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225
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Manríquez MEV, Makino A, Tanaka M, Abe Y, Yoshida H, Morioka I, Arakawa S, Takeshima Y, Iwata K, Takasaki J, Manabe T, Nakaya T, Nakamura S, Iglesias ALH, Rossales RMR, Mirabal EP, Ito T, Kitazawa T, Oka T, Yamashita M, Kudo K, Shinya K. Emergence of HA mutants during influenza virus pneumonia. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2012; 5:787-795. [PMID: 23071861 PMCID: PMC3466977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Accepted: 09/05/2012] [Indexed: 06/01/2023]
Abstract
During the influenza pandemic of 2009, the number of viral pneumonia cases showed a marked increase in comparison with seasonal influenza viruses. Mutations at amino acid 222 (D222G mutations) in the virus hemagglutinin (HA) molecule, known to alter the receptor-recognition properties of the virus, were detected in a number of the more severely-affected patients in the early phases of the pandemic. To understand the background for the emergence of the mutant amino acid D222G in human lungs, we conducted histological examinations on lung specimens of patients from Mexico who had succumbed in the pandemic. Prominent regenerative and hyperplastic changes in the alveolar type II pneumocytes, which express avian-type sialoglycan receptors in the respiratory tract of severely affected individuals, were observed in the Mexican patients. An infection model utilizing guinea pigs, which was chosen in order to best simulate the sialic acid distribution of severe pneumonia in human patients, demonstrated an increase of D222G mutants and a delay in the diminution of mutants in the lower respiratory tract in comparison to the upper respiratory tract. Our data suggests that the predominance of avian-type sialoglycan receptors in the pneumonic lungs may contribute to the emergence of viral HA mutants. This data comprehensively illustrates the mechanisms for the emergence of mutants in the clinical samples.
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MESH Headings
- Alveolar Epithelial Cells/virology
- Animals
- Disease Models, Animal
- Disease Outbreaks
- Female
- Genes, Viral
- Guinea Pigs
- Hemagglutinins, Viral/genetics
- Host-Pathogen Interactions
- Humans
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/pathogenicity
- Influenza, Human/pathology
- Influenza, Human/virology
- Madin Darby Canine Kidney Cells
- Mutation
- Orthomyxoviridae Infections/virology
- Pneumonia, Viral/pathology
- Pneumonia, Viral/virology
- RNA, Viral/genetics
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Virus/genetics
- Receptors, Virus/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
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Affiliation(s)
| | | | | | - Yasuhisa Abe
- Department of Infection Control and Prevention, Kobe University HospitalJapan
| | - Hiroyuki Yoshida
- Department of Infection Control and Prevention, Kobe University HospitalJapan
| | - Ichiro Morioka
- Department of Infection Control and Prevention, Kobe University HospitalJapan
| | - Soichi Arakawa
- Department of Infection Control and Prevention, Kobe University HospitalJapan
| | | | - Kentaro Iwata
- Division of Infectious Diseases, Kobe University HospitalJapan
| | - Jin Takasaki
- National Center for Global Health and MedicineTokyo, Japan
| | - Toshie Manabe
- National Center for Global Health and MedicineTokyo, Japan
| | - Takaaki Nakaya
- Research Institute for Microbial Diseases, Osaka UniversityJapan
| | - Shota Nakamura
- Research Institute for Microbial Diseases, Osaka UniversityJapan
| | | | | | | | - Tateki Ito
- National Center for Global Health and MedicineTokyo, Japan
| | | | | | - Makoto Yamashita
- Biological Research Laboratories, Daiichi Sankyo Co., LtdTokyo, Japan
| | - Koichiro Kudo
- National Center for Global Health and MedicineTokyo, Japan
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226
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Lee SMY, Yen HL. Targeting the host or the virus: current and novel concepts for antiviral approaches against influenza virus infection. Antiviral Res 2012; 96:391-404. [PMID: 23022351 PMCID: PMC7132421 DOI: 10.1016/j.antiviral.2012.09.013] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 09/11/2012] [Accepted: 09/17/2012] [Indexed: 12/22/2022]
Abstract
Influenza epidemics and pandemics are constant threats to human health. The application of antiviral drugs provides an immediate and direct control of influenza virus infection. At present, the major strategy for managing patients with influenza is through targeting conserved viral proteins critical for viral replication. Two classes of conventional antiviral drugs, the M2 ion channel blockers and the neuraminidase inhibitors, are frequently used. In recent years, increasing levels of resistance to both drug classes has become a major public health concern, highlighting the urgent need for the development of alternative treatments. Novel classes of antiviral compounds or biomolecules targeting viral replication mechanism are under development, using approaches including high-throughput small-molecule screening platforms and structure-based designs. In response to influenza virus infection, host cellular mechanisms are triggered to defend against the invaders. At the same time, viruses as obligate intracellular pathogens have evolved to exploit cellular responses in support of their efficient replication, including antagonizing the host type I interferon response as well as activation of specific cellular pathways at different stages of the replication cycle. Numerous studies have highlighted the possibility of targeting virus-host interactions and host cellular mechanisms to develop new treatment regimens. This review aims to give an overview of current and novel concepts targeting the virus and the host for managing influenza.
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Affiliation(s)
- Suki Man-Yan Lee
- Centre of Influenza Research, School of Public Health, The University of Hong Kong, Hong Kong
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227
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Kim HM, Kang YM, Song BM, Kim HS, Seo SH. The 2009 pandemic H1N1 influenza virus is more pathogenic in pregnant mice than seasonal H1N1 influenza virus. Viral Immunol 2012; 25:402-10. [PMID: 22985287 DOI: 10.1089/vim.2012.0007] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Pregnant women can experience high mortality, high rates of abortion, and severe pneumonia when infected with pandemic influenza viruses. In this context, the severity of the 2009 pandemic H1N1 influenza virus compared with seasonal H1N1 influenza virus is not clear. Presently, in a mouse model of pregnancy, the 2009 pandemic H1N1 influenza virus killed up to 60% of pregnant mice and caused abortion in up to 40%, whereas a circulating seasonal H1N1 influenza virus did not cause any deaths or abortions. Higher viral titers and levels of inflammatory cytokines and chemokines such as interleukin (IL)-1α, IL-6, granulocyte colony-stimulating factor, RANTES, monocyte chemotactic protein, and KC (CXCL1), were detected in the lungs of pregnant mice infected with the 2009 pandemic H1N1 influenza virus, compared with the seasonal H1N1 influenza virus. The results of our study with pregnant mice suggest that the observed higher pathogenesis in pregnant women infected with the 2009 pandemic H1N1 influenza virus than the seasonal H1N1 influenza virus may be due to higher viral replication, elevated induction of inflammatory chemokines, and reduced progesterone.
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Affiliation(s)
- Heui Man Kim
- Laboratory of Influenza Research, College of Veterinary Medicine, Chungnam National University, Daejeon, South Korea
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228
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Huang JW, Lin WF, Yang JM. Antigenic sites of H1N1 influenza virus hemagglutinin revealed by natural isolates and inhibition assays. Vaccine 2012; 30:6327-37. [PMID: 22885274 DOI: 10.1016/j.vaccine.2012.07.079] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Revised: 05/16/2012] [Accepted: 07/30/2012] [Indexed: 11/19/2022]
Abstract
The antigenic sites of hemagglutinin (HA) are crucial for understanding antigenic drift and vaccine strain selection for influenza viruses. In 1982, 32 epitope residues (called laboratory epitope residues) were proposed for antigenic sites of H1N1 HA based on the monoclonal antibody-selected variants. Interestingly, these laboratory epitope residues only cover 28% (23/83) mutation positions for 9 H1N1 vaccine strain comparisons (from 1977 to 2009). Here, we propose the entropy and likelihood ratio to model amino acid diversity and antigenic variant score for inferring 41 H1N1 HA epitope residues (called natural epitope residues) with statistically significant scores according to 1572 HA sequences and 197 pairs of HA sequences with hemagglutination inhibition (HI) assays of natural isolates. By combining both natural and laboratory epitope residues, we identified 62 (11 overlapped) residues clustered into five antigenic sites (i.e., A-E) which are highly correlated to the antigenic sites of H3N2 HA. Our method recognizes sites A, B and C as critical sites for escaping from neutralizing antibodies in H1N1 virus. Experimental results show that the accuracies of our models are 81.2% and 82.2% using 41 and 62 epitope residues, respectively, for predicting antigenic variants on 197 paring HA sequences. In addition, our model can detect the emergence of epidemic strains and reflect the genetic diversity and antigenic variant between the vaccine and circulating strains. Finally, our model is theoretically consistent with the evolution rates of H3N2 and H1N1 viruses and is often consistent to WHO vaccine strain selections. We believe that our models and the inferred antigenic sites of HA are useful for understanding the antigenic drift and evolution of influenza A H1N1 virus.
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Affiliation(s)
- Jhang-Wei Huang
- Institute of Bioinformatics and Systems Biology, National Chiao Tung University, Hsinchu, 30050, Taiwan
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229
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Priyadarzini TRK, Selvin JFA, Gromiha MM, Fukui K, Veluraja K. Theoretical investigation on the binding specificity of sialyldisaccharides with hemagglutinins of influenza A virus by molecular dynamics simulations. J Biol Chem 2012; 287:34547-57. [PMID: 22846994 DOI: 10.1074/jbc.m112.357061] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recognition of cell-surface sialyldisaccharides by influenza A hemagglutinin (HA) triggers the infection process of influenza. The changes in glycosidic torsional linkage and the receptor conformations may alter the binding specificity of HAs to the sialylglycans. In this study, 10-ns molecular dynamics simulations were carried out to examine the structural and dynamic behavior of the HAs bound with sialyldisaccharides Neu5Acα(2-3)Gal (N23G) and Neu5Acα(2-6)Gal (N26G). The analysis of the glycosidic torsional angles and the pair interaction energy between the receptor and the interacting residues of the binding site reveal that N23G has two binding modes for H1 and H5 and a single binding mode for H3 and H9. For N26G, H1 and H3 has two binding modes, and H5 and H9 has a single binding mode. The direct and water-mediated hydrogen bonding interactions between the receptors and HAs play dominant roles in the structural stabilization of the complexes. It is concluded from pair interaction energy and Molecular Mechanic-Poisson-Boltzmann Surface Area calculations that N26G is a better receptor for H1 when compared with N23G. N23G is a better receptor for H5 when compared with N26G. However, H3 and H9 can recognize N23G and N26G in equal binding specificity due to the marginal energy difference (≈2.5 kcal/mol). The order of binding specificity of N23G is H3 > H5 > H9 > H1 and N26G is H1 > H3 > H5 > H9, respectively. The proposed conformational models will be helpful in designing inhibitors for influenza virus.
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Affiliation(s)
- Thanu R K Priyadarzini
- Department of Physics, Manonmaniam Sundaranar University, Tirunelveli, Tamilnadu 627 012, India
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230
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Pasricha G, Mishra AC, Chakrabarti AK. Comprehensive global amino acid sequence analysis of PB1F2 protein of influenza A H5N1 viruses and the influenza A virus subtypes responsible for the 20th-century pandemics. Influenza Other Respir Viruses 2012; 7:497-505. [PMID: 22788742 PMCID: PMC5780999 DOI: 10.1111/j.1750-2659.2012.00400.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
BACKGROUND PB1F2 is the 11th protein of influenza A virus translated from +1 alternate reading frame of PB1 gene. Since the discovery, varying sizes and functions of the PB1F2 protein of influenza A viruses have been reported. Selection of PB1 gene segment in the pandemics, variable size and pleiotropic effect of PB1F2 intrigued us to analyze amino acid sequences of this protein in various influenza A viruses. METHODS Amino acid sequences for PB1F2 protein of influenza A H5N1, H1N1, H2N2, and H3N2 subtypes were obtained from Influenza Research Database. Multiple sequence alignments of the PB1F2 protein sequences of the aforementioned subtypes were used to determine the size, variable and conserved domains and to perform mutational analysis. RESULTS Analysis showed that 96·4% of the H5N1 influenza viruses harbored full-length PB1F2 protein. Except for the 2009 pandemic H1N1 virus, all the subtypes of the 20th-century pandemic influenza viruses contained full-length PB1F2 protein. Through the years, PB1F2 protein of the H1N1 and H3N2 viruses has undergone much variation. PB1F2 protein sequences of H5N1 viruses showed both human- and avian host-specific conserved domains. Global database of PB1F2 protein revealed that N66S mutation was present only in 3·8% of the H5N1 strains. We found a novel mutation, N84S in the PB1F2 protein of 9·35% of the highly pathogenic avian influenza H5N1 influenza viruses. CONCLUSIONS Varying sizes and mutations of the PB1F2 protein in different influenza A virus subtypes with pandemic potential were obtained. There was genetic divergence of the protein in various hosts which highlighted the host-specific evolution of the virus. However, studies are required to correlate this sequence variability with the virulence and pathogenicity.
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Affiliation(s)
- Gunisha Pasricha
- Microbial Containment Complex, National Institute of Virology, Pashan, Pune, India
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231
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Recently emerged swine influenza A virus (H2N3) causes severe pneumonia in Cynomolgus macaques. PLoS One 2012; 7:e39990. [PMID: 22808082 PMCID: PMC3394781 DOI: 10.1371/journal.pone.0039990] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 05/30/2012] [Indexed: 12/03/2022] Open
Abstract
The triple reassortant H2N3 virus isolated from diseased pigs in the United States in 2006 is pathogenic for certain mammals without prior adaptation and transmits among swine and ferrets. Adaptation, in the H2 hemagglutinin derived from an avian virus, includes the ability to bind to the mammalian receptor, a significant prerequisite for infection of mammals, in particular humans, which poses a big concern for public health. Here we investigated the pathogenic potential of swine H2N3 in Cynomolgus macaques, a surrogate model for human influenza infection. In contrast to human H2N2 virus, which served as a control and largely caused mild pneumonia similar to seasonal influenza A viruses, the swine H2N3 virus was more pathogenic causing severe pneumonia in nonhuman primates. Both viruses replicated in the entire respiratory tract, but only swine H2N3 could be isolated from lung tissue on day 6 post infection. All animals cleared the infection whereas swine H2N3 infected macaques still presented with pathologic changes indicative of chronic pneumonia at day 14 post infection. Swine H2N3 virus was also detected to significantly higher titers in nasal and oral swabs indicating the potential for animal-to-animal transmission. Plasma levels of IL-6, IL-8, MCP-1 and IFNγ were significantly increased in swine H2N3 compared to human H2N2 infected animals supporting the previously published notion of increased IL-6 levels being a potential marker for severe influenza infections. In conclusion, the swine H2N3 virus represents a threat to humans with the potential for causing a larger outbreak in a non-immune or partially immune population. Furthermore, surveillance efforts in farmed pig populations need to become an integral part of any epidemic and pandemic influenza preparedness.
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232
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Wang Q, Zhang S, Jiang H, Wang J, Weng L, Mao Y, Sekiguchi S, Yasui F, Kohara M, Buchy P, Deubel V, Xu K, Sun B, Toyoda T. PA from an H5N1 highly pathogenic avian influenza virus activates viral transcription and replication and induces apoptosis and interferon expression at an early stage of infection. Virol J 2012; 9:106. [PMID: 22681768 PMCID: PMC3507744 DOI: 10.1186/1743-422x-9-106] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 05/21/2012] [Indexed: 12/28/2022] Open
Abstract
Background Although gene exchange is not likely to occur freely, reassortment between the H5N1 highly pathogenic avian influenza virus (HPAIV) and currently circulating human viruses is a serious concern. The PA polymerase subunit of H5N1 HPAIV was recently reported to activate the influenza replicon activity. Methods The replicon activities of PR8 and WSN strains (H1N1) of influenza containing PA from HPAIV A/Cambodia/P0322095/2005 (H5N1) and the activity of the chimeric RNA polymerase were analyzed. A reassortant WSN virus containing the H5N1 Cambodia PA (C-PA) was then reconstituted and its growth in cells and pathogenicity in mice examined. The interferon promoter, TUNEL, and caspase 3, 8, and 9 activities of C-PA-infected cells were compared with those of WSN-infected cells. Results The activity of the chimeric RNA polymerase was slightly higher than that of WSN, and C-PA replicated better than WSN in cells. However, the multi-step growth of C-PA and its pathogenicity in mice were lower than those of WSN. The interferon promoter, TUNEL, and caspase 3, 8, and 9 activities were strongly induced in early infection in C-PA-infected cells but not in WSN-infected cells. Conclusions Apoptosis and interferon were strongly induced early in C-PA infection, which protected the uninfected cells from expansion of viral infection. In this case, these classical host-virus interactions contributed to the attenuation of this strongly replicating virus.
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Affiliation(s)
- Qiang Wang
- Key Laboratory of Molecular Virology & Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, 411 Hefei Road, 200025, Shanghai, P. R. China
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233
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Effect of priming with H1N1 influenza viruses of variable antigenic distances on challenge with 2009 pandemic H1N1 virus. J Virol 2012; 86:8625-33. [PMID: 22674976 DOI: 10.1128/jvi.00147-12] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Compared to seasonal influenza viruses, the 2009 pandemic H1N1 (pH1N1) virus caused greater morbidity and mortality in children and young adults. People over 60 years of age showed a higher prevalence of cross-reactive pH1N1 antibodies, suggesting that they were previously exposed to an influenza virus or vaccine that was antigenically related to the pH1N1 virus. To define the basis for this cross-reactivity, ferrets were infected with H1N1 viruses of variable antigenic distance that circulated during different decades from the 1930s (Alaska/35), 1940s (Fort Monmouth/47), 1950s (Fort Warren/50), and 1990s (New Caledonia/99) and challenged with 2009 pH1N1 virus 6 weeks later. Ferrets primed with the homologous CA/09 or New Jersey/76 (NJ/76) virus served as a positive control, while the negative control was an influenza B virus that should not cross-protect against influenza A virus infection. Significant protection against challenge virus replication in the respiratory tract was observed in ferrets primed with AK/35, FM/47, and NJ/76; FW/50-primed ferrets showed reduced protection, and NC/99-primed ferrets were not protected. The hemagglutinins (HAs) of AK/35, FM/47, and FW/50 differ in the presence of glycosylation sites. We found that the loss of protective efficacy observed with FW/50 was associated with the presence of a specific glycosylation site. Our results suggest that changes in the HA occurred between 1947 and 1950, such that prior infection could no longer protect against 2009 pH1N1 infection. This provides a mechanistic understanding of the nature of serological cross-protection observed in people over 60 years of age during the 2009 H1N1 pandemic.
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234
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Li W, Zhang H, Wang G, Zhang C, Zeng X, Liu H, Chen X, Xu Y, Li K. Heterologous interactions between NS1 proteins from different influenza A virus subtypes/strains. SCIENCE CHINA. LIFE SCIENCES 2012; 55:507-15. [PMID: 22744180 DOI: 10.1007/s11427-012-4335-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 05/10/2012] [Indexed: 02/05/2023]
Abstract
Non-structural protein 1 (NS1) of the influenza virus plays a crucial role in modulating the host immune response and facilitating virus replication. The formation of a homodimer or an oligomer is necessary for NS1 to exert its function efficiently. In the present study, the NS1 protein from the A/Shantou/602/06(H3N2) virus (herein abbreviated as NS32) was found to interact with NS1 from A/Shantou/169/06(H1N1), A/Chicken/Guangdong/1/05(H5N1) and A/Quail/Hong Kong/G1/97(H9N2) (abbreviated as NS11, NS51 and NS92, respectively) viruses, although NS32 shares 17.4%-20.9% sequence diversity with NS11, NS51 and NS92. This indicates that the heterologous interactions between NS1 proteins from different influenza A virus subtypes/ strains may be a common event during co-infection.
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MESH Headings
- Amino Acid Sequence
- Animals
- Cell Line, Tumor
- Chickens
- Genetic Variation
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- HeLa Cells
- Humans
- Immunoblotting
- Immunoprecipitation
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/metabolism
- Influenza A Virus, H3N2 Subtype/genetics
- Influenza A Virus, H3N2 Subtype/metabolism
- Influenza A Virus, H5N1 Subtype/genetics
- Influenza A Virus, H5N1 Subtype/metabolism
- Influenza A Virus, H9N2 Subtype/genetics
- Influenza A Virus, H9N2 Subtype/metabolism
- Influenza in Birds/virology
- Influenza, Human/virology
- Microscopy, Fluorescence
- Molecular Sequence Data
- Protein Binding
- Sequence Homology, Amino Acid
- Species Specificity
- Two-Hybrid System Techniques
- Viral Nonstructural Proteins/genetics
- Viral Nonstructural Proteins/metabolism
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Affiliation(s)
- Weizhong Li
- Department of Microbiology and Immunology, Key Immunopathology Laboratory of Guangdong Province, Shantou University Medical College, Shantou 515041, China
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235
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Antibody pressure by a human monoclonal antibody targeting the 2009 pandemic H1N1 virus hemagglutinin drives the emergence of a virus with increased virulence in mice. mBio 2012; 3:mBio.00120-12. [PMID: 22647789 PMCID: PMC3372962 DOI: 10.1128/mbio.00120-12] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In 2009, a novel H1N1 influenza A virus (2009 pH1N1) emerged and caused a pandemic. A human monoclonal antibody (hMAb; EM4C04), highly specific for the 2009 pH1N1 virus hemagglutinin (HA), was isolated from a severely ill 2009 pH1N1 virus-infected patient. We postulated that under immune pressure with EM4C04, the 2009 pH1N1 virus would undergo antigenic drift and mutate at sites that would identify the antibody binding site. To do so, we infected MDCK cells in the presence of EM4C04 and generated 11 escape mutants, displaying 7 distinct amino acid substitutions in the HA. Six substitutions greatly reduced MAb binding (K123N, D131E, K133T, G134S, K157N, and G158E). Residues 131, 133, and 134 are contiguous with residues 157 and 158 in the globular domain structure and contribute to a novel pH1N1 antibody epitope. One mutation near the receptor binding site, S186P, increased the binding affinity of the HA to the receptor. 186P and 131E are present in the highly virulent 1918 virus HA and were recently identified as virulence determinants in a mouse-passaged pH1N1 virus. We found that pH1N1 escape variants expressing these substitutions enhanced replication and lethality in mice compared to wild-type 2009 pH1N1 virus. The increased virulence of these viruses was associated with an increased affinity for α2,3 sialic acid receptors. Our study demonstrates that antibody pressure by an hMAb targeting a novel epitope in the Sa region of 2009 pH1N1 HA is able to inadvertently drive the development of a more virulent virus with altered receptor binding properties. This broadens our understanding of antigenic drift. Influenza viruses accumulate amino acid substitutions to evade the antibody response in a process known as antigenic drift, making it necessary to vaccinate against influenza annually. Mapping human monoclonal antibody (hMAb) epitopes is a necessary step towards understanding antigenic drift in humans. We defined the specificity of an hMAb that specifically targeted the 2009 pH1N1 virus and describe a novel epitope. In addition, we identified a previously unappreciated potential for antibody escape to enhance the pathogenicity of a virus. The escape mutation that we identified with in vitro immune pressure was independently reported by other investigators using in vivo selection in nonimmune mice. Although in vitro generation of escape mutants is unlikely to recapitulate antigenic drift in its entirety, the data demonstrate that pressure by a human monoclonal antibody targeting a novel epitope in the hemagglutinin of the 2009 pandemic H1N1 virus can inadvertently drive the development of escape mutants, of which a subset have increased virulence and altered receptor binding properties.
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236
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Van Borm S, Rosseel T, Vangeluwe D, Vandenbussche F, van den Berg T, Lambrecht B. Phylogeographic analysis of avian influenza viruses isolated from Charadriiformes in Belgium confirms intercontinental reassortment in gulls. Arch Virol 2012; 157:1509-22. [PMID: 22580556 DOI: 10.1007/s00705-012-1323-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 03/22/2012] [Indexed: 11/28/2022]
Abstract
Nine influenza viruses isolated from gulls and shorebirds in Belgium (2008-2010), including H3N8, H5N2, H6N1, H11N9, H13N6, H13N8, and H16N3 subtypes, were targeted using random amplification and next-generation sequencing. The gene segments of these viruses segregated into three phylogeographic lineage types: (1) segments circulating in waterfowl in Eurasia with sporadic introduction in other species and in the Americas ("Eurasian avian"), (2) segments circulating in American waterfowl with sporadic introduction to other species and regions ("American avian"), and (3) segments circulating exclusively in gulls and shorebirds and having increased connectivity between the two hemispheres ("Charadriiformes specific"). Notably, an H6N1 and an H5N2 isolated from L. argentatus had mainly Eurasian avian genes but shared a matrix segment of American avian origin (first documentation in European gulls of transhemispheric reassortment). These data support the growing evidence of an important role of Charadriiformes birds in the dynamic nature of avian influenza ecology.
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Affiliation(s)
- Steven Van Borm
- Department of Virology, Veterinary and Agrochemical Research Center, Groeselenbergstraat 99, 1180 Uccle, Belgium.
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237
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Cheng VCC, To KKW, Tse H, Hung IFN, Yuen KY. Two years after pandemic influenza A/2009/H1N1: what have we learned? Clin Microbiol Rev 2012; 25:223-63. [PMID: 22491771 PMCID: PMC3346300 DOI: 10.1128/cmr.05012-11] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The world had been anticipating another influenza pandemic since the last one in 1968. The pandemic influenza A H1N1 2009 virus (A/2009/H1N1) finally arrived, causing the first pandemic influenza of the new millennium, which has affected over 214 countries and caused over 18,449 deaths. Because of the persistent threat from the A/H5N1 virus since 1997 and the outbreak of the severe acute respiratory syndrome (SARS) coronavirus in 2003, medical and scientific communities have been more prepared in mindset and infrastructure. This preparedness has allowed for rapid and effective research on the epidemiological, clinical, pathological, immunological, virological, and other basic scientific aspects of the disease, with impacts on its control. A PubMed search using the keywords "pandemic influenza virus H1N1 2009" yielded over 2,500 publications, which markedly exceeded the number published on previous pandemics. Only representative works with relevance to clinical microbiology and infectious diseases are reviewed in this article. A significant increase in the understanding of this virus and the disease within such a short amount of time has allowed for the timely development of diagnostic tests, treatments, and preventive measures. These findings could prove useful for future randomized controlled clinical trials and the epidemiological control of future pandemics.
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Affiliation(s)
- Vincent C C Cheng
- Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
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238
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Zhu W, Zhu Y, Qin K, Yu Z, Gao R, Yu H, Zhou J, Shu Y. Mutations in polymerase genes enhanced the virulence of 2009 pandemic H1N1 influenza virus in mice. PLoS One 2012; 7:e33383. [PMID: 22438920 PMCID: PMC3305307 DOI: 10.1371/journal.pone.0033383] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 02/13/2012] [Indexed: 11/18/2022] Open
Abstract
Influenza A virus can infect a wide variety of animal species with illness ranging from mild to severe, and is a continual cause for concern. Genetic mutations that occur either naturally or during viral adaptation in a poorly susceptible host are key mechanisms underlying the evolution and virulence of influenza A virus. Here, the variants containing PA-A36T or PB2-H357N observed in the mouse-adapted descendants of 2009 pandemic H1N1 virus (pH1N1), A/Sichuan/1/2009 (SC), were characterized. Both mutations enhanced polymerase activity in mammalian cells. These effects were confirmed using recombinant SC virus containing polymerase genes with wild type (WT) or mutant PA or PB2. The PA-A36T mutant showed enhanced growth property compared to the WT in both human A549 cells and porcine PK15 cells in vitro, without significant effect on viral propagation in murine LA-4 cells and pathogenicity in mice; however, it did enhance the lung virus titer. PB2-H357N variant demonstrated growth ability comparable to the WT in A549 cells, but replicated well in PK15, LA-4 cells and in mice with an enhanced pathogenic phenotype. Despite such mutations are rare in nature, they could be observed in avian H5 and H7 subtype viruses which were currently recognized to pose potential threat to human. Our findings indicated that pH1N1 may adapt well in mammals when acquiring these mutations. Therefore, future molecular epidemiological surveillance should include scrutiny of both markers because of their potential impact on pathogenesis.
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MESH Headings
- Amino Acid Substitution
- Animals
- Cell Line
- Dogs
- Female
- Genes, Viral
- History, 21st Century
- Humans
- Influenza A Virus, H1N1 Subtype/enzymology
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/pathogenicity
- Influenza, Human/epidemiology
- Influenza, Human/history
- Influenza, Human/virology
- Mice
- Mice, Inbred BALB C
- Mutagenesis, Site-Directed
- Mutation
- Orthomyxoviridae Infections/virology
- Pandemics/history
- Polymorphism, Single Nucleotide
- RNA-Dependent RNA Polymerase/genetics
- RNA-Dependent RNA Polymerase/metabolism
- Recombination, Genetic
- Swine
- Viral Proteins/genetics
- Viral Proteins/metabolism
- Virulence/genetics
- Virulence/physiology
- Virus Replication
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Affiliation(s)
| | | | | | | | | | | | - Jianfang Zhou
- Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, China CDC, Beijing, People's Republic of China
- * E-mail: (JFZ); (YLS)
| | - Yuelong Shu
- Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, China CDC, Beijing, People's Republic of China
- * E-mail: (JFZ); (YLS)
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239
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Talaat KR, Karron RA, Liang PH, McMahon BA, Luke CJ, Thumar B, Chen GL, Min JY, Lamirande EW, Jin H, Coelingh KL, Kemble GW, Subbarao K. An open-label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults. Influenza Other Respir Viruses 2012; 7:66-73. [PMID: 22417012 PMCID: PMC3527634 DOI: 10.1111/j.1750-2659.2012.00350.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Please cite this paper as: Talaat et al. (2012) An open‐label phase I trial of a live attenuated H2N2 influenza virus vaccine in healthy adults. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2012.00350.x. Background Live attenuated influenza vaccines (LAIV) against a variety of strains of pandemic potential are being developed and tested. We describe the results of an open‐label phase I trial of a live attenuated H2N2 virus vaccine. Objectives To evaluate the safety, infectivity, and immunogenicity of a live attenuated H2N2 influenza virus vaccine. Participants/methods The A/Ann Arbor/6/60 (H2N2) virus used in this study is the attenuated, cold‐adapted, temperature‐sensitive strain that provides the genetic backbone of seasonal LAIV (MedImmune). We evaluated the safety, infectivity, and immunogenicity of two doses of 107 TCID50 of this vaccine administered by nasal spray 4 weeks apart to normal healthy seronegative adults. Results Twenty‐one participants received a first dose of the vaccine; 18 participants received a second dose. No serious adverse events occurred during the trial. The most common adverse events after vaccination were headache and musculoskeletal pain. The vaccine was restricted in replication: 24% and 17% had virus detectable by culture or rRT‐PCR after the first and second dose, respectively. Antibody responses to the vaccine were also restricted: 24% of participants developed an antibody response as measured by either hemagglutination‐inhibition assay (10%), or ELISA for H2 HA‐specific serum IgG (24%) or IgA (16%) after either one or two doses. None of the participants had a neutralizing antibody response. Vaccine‐specific IgG‐secreting cells as measured by enzyme‐linked immunospot increased from a mean of 0·5 to 2·0/106 peripheral blood mononuclear cells (PBMCs); vaccine‐specific IgA‐secreting cells increased from 0·1 to 0·5/106 PBMCs. Conclusions The live attenuated H2N2 1960 AA ca vaccine demonstrated a safety profile consistent with seasonal trivalent LAIV but was restricted in replication and minimally immunogenic in healthy seronegative adults.
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Affiliation(s)
- Kawsar R Talaat
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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240
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Chen Z, Zhou H, Kim L, Jin H. The receptor binding specificity of the live attenuated influenza H2 and H6 vaccine viruses contributes to vaccine immunogenicity and protection in ferrets. J Virol 2012; 86:2780-6. [PMID: 22190726 PMCID: PMC3302243 DOI: 10.1128/jvi.06219-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Accepted: 12/07/2011] [Indexed: 12/16/2022] Open
Abstract
To prepare for influenza pandemics that may be caused by the H2 and H6 subtype influenza viruses, live attenuated influenza virus (LAIV) H2 and H6 vaccines are being developed and evaluated. The H2 and H6 vaccine candidates with different receptor binding preferences specified by amino acid substitutions at residues 226 and 228 were generated and evaluated for their growth in embryonated chicken eggs and their immunogenicity and protection against wild-type virus challenge in the ferret model. The viruses containing Q226 and G228 in the hemagglutinin (HA) protein bound to the avian-like α2,3-sialic acid (SA) receptor and replicated efficiently in chicken eggs. The viruses with L226 and G228 bound preferentially to the human-like α2,6-SA receptor. The viruses containing L226 and S228 displayed dual binding to both α2,3-SA and α2,6-SA receptors and replicated efficiently in eggs. The strains containing L226/G228 or L226/S228 that preferentially bound to α2,6-SA receptors replicated efficiently in the upper respiratory tract of ferrets, induced high levels of neutralizing antibody, and conferred a high level of protection against wild-type virus challenge infection compared to the strain with the Q226/G228 residues. Our data suggest that pandemic vaccines with receptor binding preference to both avian- and human-like receptors might be desired for efficient viral replication in eggs and for inducing protective immune responses in humans.
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MESH Headings
- Animals
- Antibodies, Viral/immunology
- Female
- Ferrets
- Hemagglutinin Glycoproteins, Influenza Virus/genetics
- Hemagglutinin Glycoproteins, Influenza Virus/immunology
- Hemagglutinin Glycoproteins, Influenza Virus/metabolism
- Humans
- Influenza A virus/genetics
- Influenza A virus/immunology
- Influenza A virus/physiology
- Influenza Vaccines/genetics
- Influenza Vaccines/immunology
- Influenza Vaccines/metabolism
- Influenza, Human/immunology
- Influenza, Human/metabolism
- Influenza, Human/prevention & control
- Influenza, Human/virology
- Male
- N-Acetylneuraminic Acid/metabolism
- Protein Binding
- Receptors, Virus/metabolism
- Vaccines, Attenuated/genetics
- Vaccines, Attenuated/immunology
- Vaccines, Attenuated/metabolism
- Virus Replication
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241
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Nakazono Y, Hara K, Kashiwagi T, Hamada N, Watanabe H. The RNA polymerase PB2 subunit of influenza A/HongKong/156/1997 (H5N1) restricts the replication of reassortant ribonucleoprotein complexes [corrected]. PLoS One 2012; 7:e32634. [PMID: 22389716 PMCID: PMC3289661 DOI: 10.1371/journal.pone.0032634] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 01/28/2012] [Indexed: 11/18/2022] Open
Abstract
Background Genetic reassortment plays a critical role in the generation of pandemic strains of influenza virus. The influenza virus RNA polymerase, composed of PB1, PB2 and PA subunits, has been suggested to influence the efficiency of genetic reassortment. However, the role of the RNA polymerase in the genetic reassortment is not well understood. Methodology/Principal Findings Here, we reconstituted reassortant ribonucleoprotein (RNP) complexes, and demonstrated that the PB2 subunit of A/HongKong/156/1997 (H5N1) [HK PB2] dramatically reduced the synthesis of mRNA, cRNA and vRNA when introduced into the polymerase of other influenza strains of H1N1 or H3N2. The HK PB2 had no significant effect on the assembly of the polymerase trimeric complex, or on promoter binding activity or replication initiation activity in vitro. However, the HK PB2 was found to remarkably impair the accumulation of RNP. This impaired accumulation and activity of RNP was fully restored when four amino acids at position 108, 508, 524 and 627 of the HK PB2 were mutated. Conclusions/Significance Overall, we suggest that the PB2 subunit of influenza polymerase might play an important role for the replication of reassortant ribonucleoprotein complexes.
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Affiliation(s)
- Yoko Nakazono
- Division of Infectious Diseases, Department of Infectious Medicine, Kurume University School of Medicine, Fukuoka, Japan
| | - Koyu Hara
- Division of Infectious Diseases, Department of Infectious Medicine, Kurume University School of Medicine, Fukuoka, Japan
- * E-mail:
| | - Takahito Kashiwagi
- Division of Infectious Diseases, Department of Infectious Medicine, Kurume University School of Medicine, Fukuoka, Japan
| | - Nobuyuki Hamada
- Division of Infectious Diseases, Department of Infectious Medicine, Kurume University School of Medicine, Fukuoka, Japan
| | - Hiroshi Watanabe
- Division of Infectious Diseases, Department of Infectious Medicine, Kurume University School of Medicine, Fukuoka, Japan
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242
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Ocaña-Macchi M, Ricklin ME, Python S, Monika GA, Stech J, Stech O, Summerfield A. Avian influenza A virus PB2 promotes interferon type I inducing properties of a swine strain in porcine dendritic cells. Virology 2012; 427:1-9. [PMID: 22365327 DOI: 10.1016/j.virol.2012.01.037] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 11/23/2011] [Accepted: 01/30/2012] [Indexed: 01/26/2023]
Abstract
The 2009 influenza A virus (IAV) pandemic resulted from reassortment of avian, human and swine strains probably in pigs. To elucidate the role of viral genes in host adaptation regarding innate immune responses, we focussed on the effect of genes from an avian H5N1 and a porcine H1N1 IAV on infectivity and activation of porcine GM-CSF-induced dendritic cells (DC). The highest interferon type I responses were achieved by the porcine virus reassortant containing the avian polymerase gene PB2. This finding was not due to differential tropism since all viruses infected DC equally. All viruses equally induced MHC class II, but porcine H1N1 expressing the avian viral PB2 induced more prominent nuclear NF-κB translocation compared to its parent IAV. The enhanced activation of DC may be detrimental or beneficial. An over-stimulation of innate responses could result in either pronounced tissue damage or increased resistance against IAV reassortants carrying avian PB2.
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243
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Lee HJ, Lee DH, Lee YN, Kwon JS, Lee YJ, Lee JB, Park SY, Choi IS, Song CS. Generation of reassortant influenza viruses within the non-industrial poultry system. INFECTION GENETICS AND EVOLUTION 2012; 12:933-46. [PMID: 22386854 DOI: 10.1016/j.meegid.2012.02.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 12/31/2011] [Accepted: 02/01/2012] [Indexed: 12/09/2022]
Abstract
We compared the genetic and biologic characteristics of 35 influenza viruses of different epidemiological backgrounds in Korea, including H3N2 canine influenza virus (CIV). Phylogenetic analysis revealed that chicken adapted H9N2 viruses (A/chicken/Korea/96006/96 [CK/Kor/96006-like]) have acquired aquatic avian gene segments through reassortment, and these reassorted H9N2 viruses were more frequently detected from minor poultry species than from industrial poultry. Conversely, gene segments from CK/Kor/96006-like viruses were also detected in most of the viruses from domestic ducks. Interestingly, domestic ducks, rather than wild aquatic birds, harbored close relatives of all eight gene segments of H3N2 CIV, which preferred binding to avian receptors. Therefore, bidirectional virus transmission events are assumed to have occurred between land-based poultry and aquatic poultry, in particular within the non-industrial poultry system. These events have contributed to the generation of a novel reassortant, H3N2 CIV. To prevent generating other reassortants capable of interspecies transmission, gene movements in the non-industrial poultry systems should be clarified and managed.
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Affiliation(s)
- Hyun-Jeong Lee
- College of Veterinary Medicine, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea
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244
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de Silva UC, Tanaka H, Nakamura S, Goto N, Yasunaga T. A comprehensive analysis of reassortment in influenza A virus. Biol Open 2012; 1:385-90. [PMID: 23213428 PMCID: PMC3509451 DOI: 10.1242/bio.2012281] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Genetic reassortment plays a vital role in the evolution of the influenza virus and has historically been linked with the emergence of pandemic strains. Reassortment is believed to occur when a single host - typically swine - is simultaneously infected with multiple influenza strains. The reassorted viral strains with novel gene combinations tend to easily evade the immune system in other host species, satisfying the basic requirements of a virus with pandemic potential. Therefore, it is vital to continuously monitor the genetic content of circulating influenza strains and keep an eye out for new reassortants. We present a new approach to identify reassortants from large data sets of influenza whole genome nucleotide sequences and report the results of the first ever comprehensive search for reassortants of all published influenza A genomic data. 35 of the 52 well supported candidate reassortants we found are reported here for the first time while our analysis method offers new insight that enables us to draw a more detailed picture of the origin of some of the previously reported reassortants. A disproportionately high number (13/52) of the candidate reassortants found were the result of the introduction of novel hemagglutinin and/or neuraminidase genes into a previously circulating virus. The method described in this paper may contribute towards automating the task of routinely searching for reassortants among newly sequenced strains.
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Affiliation(s)
- U Chandimal de Silva
- Department of Genome Informatics ; World Premier International Immunology Frontier Research Centre, Osaka University , Osaka 565-0871 , Japan
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245
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Bui VN, Ogawa H, Xininigen, Karibe K, Matsuo K, Awad SSA, Minoungou GL, Yoden S, Haneda H, Ngo LH, Tamaki S, Yamamoto Y, Nakamura K, Saito K, Watanabe Y, Runstadler J, Huettman F, Happ GM, Imai K. H4N8 subtype avian influenza virus isolated from shorebirds contains a unique PB1 gene and causes severe respiratory disease in mice. Virology 2012; 423:77-88. [PMID: 22192630 PMCID: PMC3253874 DOI: 10.1016/j.virol.2011.11.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 09/16/2011] [Accepted: 11/15/2011] [Indexed: 01/26/2023]
Abstract
H4N8 subtype avian influenza viruses were isolated from shorebirds in eastern Hokkaido. All the isolates shared >99.7% nucleotide homology, and all the viral genes except for PB1 were highly related to those of A/red-necked stint/Australia/1/04. Thus, the isolates were regarded as PB1 reassortants. The most similar PB1 gene was identified in A/mallard/New Zealand/1615-17/04 (H4N6) with nucleotide homology of 90.9%. BALB/c mice intranasally inoculated with the H4N8 isolates developed severe respiratory disease, which eventually led to death in some mice. The virus was isolated from the lungs, and viral antigen was detected in the lungs with pneumonia. Other H4 subtype viruses tested did not cause any symptoms in mice, although these viruses were also isolated from the lungs. The PB2 gene of the H4N8 isolates contains K482R, but not the E627K or D701N substitutions. The PB1-F2 gene of the isolates consists of a 101-amino acid unique sequence, but lacks the N66S mutation.
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Affiliation(s)
- Vuong N. Bui
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Haruko Ogawa
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Xininigen
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Kazuji Karibe
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Kengo Matsuo
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Sanaa S. A. Awad
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Germaine L. Minoungou
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Satoshi Yoden
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Hiroaki Haneda
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Lai H. Ngo
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Shio Tamaki
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Yu Yamamoto
- National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, Japan
| | - Kikuyasu Nakamura
- National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, Japan
| | - Keisuke Saito
- Institute for Raptor Biomedicine, Kushiro, Hokkaido 084-0922, Japan
| | - Yukiko Watanabe
- Institute for Raptor Biomedicine, Kushiro, Hokkaido 084-0922, Japan
| | - Jonathan Runstadler
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775
| | - Falk Huettman
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775
| | - George M. Happ
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775
| | - Kunitoshi Imai
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
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Abstract
INTRODUCTION Influenza virus infections cause significant morbidity, and the unique ability of these viruses to undergo antigenic drift and shift means that it is critical for current laboratory assays to keep pace with these changes for accurate diagnosis. New subtypes have the potential to evolve into pandemics hence accurate virus subtyping is also essential. AREAS COVERED In this article, the authors review the current techniques available to detect influenza virus. EXPERT OPINION The biggest gains in improving on influenza diagnostics may lie in reappraising our current approach and optimizing all existing steps in influenza detection: pre-analytical, analytical, post-analytical. In addition, we must foster close collaboration between governments, surveillance networks and frontline diagnostic laboratories, and utilize advances in information technology to facilitate these interactions and to disseminate crucial information.
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Affiliation(s)
- Matthew C Gray
- Department of Microbiology and Infectious Diseases, Sydney South West Pathology Service -Liverpool , Locked Bag 7090, Liverpool BC, NSW, 1871 , Australia +0061 2 9828 5124 ; +0061 2 9828 5129 ;
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Abstract
We provide a brief introduction into the genome organization, life cycle, pathogenicity, and host range of influenza A viruses. We also briefly summarize influenza pandemics and currently available measures to control influenza virus outbreaks, including vaccines and antiviral compounds to influenza viruses.
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248
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Wong KKY, Bull RA, Rockman S, Scott G, Stelzer-Braid S, Rawlinson W. Correlation of polymerase replication fidelity with genetic evolution of influenza A/Fujian/411/02(H3N2) viruses. J Med Virol 2011; 83:510-6. [PMID: 21264873 DOI: 10.1002/jmv.21991] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Influenza virus evolves continuously through mutations presumed to result from evolutionary pressure driving viral replication. This study examined the relationship between the genetic evolution and replication fidelity of influenza viruses. Analysis of influenza sequences from National Centre for Biotechnology Information (NCBI) database revealed a gradual decrease in the rate of genetic evolution of A/Fujian/411/02(H3N2)-like variants after the emergence and predominance of the A/H3N2 Fujian strain in 2002. This decrease may be related to an increase in replication fidelity, which was investigated by assessing mutation frequencies of reassortant viruses carrying the PB1 segment of Fujian variants isolated between 2003 and 2005 in a sequencing-based plaque assay. The data revealed a threefold decrease in substitution per site of the reassortant viruses carrying the Fujian PB1 segments isolated in 2004-2005 compared with those circulating in 2003. The decrease in mutation frequency paralleled a decrease in genetic evolution of the Fujian variants from the NCBI database. This correlation implicates changes in the polymerase replication fidelity as contributing to altered genetic evolution of influenza viruses.
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Affiliation(s)
- Karen Ka Yin Wong
- Faculty of Medicine, School of Medical Sciences, University of New South Wales, Sydney, Australia
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249
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Van Borm S, Vangeluwe D, Steensels M, Poncin O, van den Berg T, Lambrecht B. Genetic characterization of low pathogenic H5N1 and co-circulating avian influenza viruses in wild mallards (Anas platyrhynchos) in Belgium, 2008. Avian Pathol 2011; 40:613-28. [DOI: 10.1080/03079457.2011.621410] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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250
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Reassortment and mutation of the avian influenza virus polymerase PA subunit overcome species barriers. J Virol 2011; 86:1750-7. [PMID: 22090127 DOI: 10.1128/jvi.06203-11] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The emergence of new pandemic influenza A viruses requires overcoming barriers to cross-species transmission as viruses move from animal reservoirs into humans. This complicated process is driven by both individual gene mutations and genome reassortments. The viral polymerase complex, composed of the proteins PB1, PB2, and PA, is a major factor controlling host adaptation, and reassortment events involving polymerase gene segments occurred with past pandemic viruses. Here we investigate the ability of polymerase reassortment to restore the activity of an avian influenza virus polymerase that is normally impaired in human cells. Our data show that the substitution of human-origin PA subunits into an avian influenza virus polymerase alleviates restriction in human cells and increases polymerase activity in vitro. Reassortants with 2009 pandemic H1N1 PA proteins were the most active. Mutational analyses demonstrated that the majority of the enhancing activity in human PA results from a threonine-to-serine change at residue 552. Reassortant viruses with avian polymerases and human PA subunits, or simply the T552S mutation, displayed faster replication kinetics in culture and increased pathogenicity in mice compared to those containing a wholly avian polymerase complex. Thus, the acquisition of a human PA subunit, or the signature T552S mutation, is a potential mechanism to overcome the species-specific restriction of avian polymerases and increase virus replication. Our data suggest that the human, avian, swine, and 2009 H1N1-like viruses that are currently cocirculating in pig populations set the stage for PA reassortments with the potential to generate novel viruses that could possess expanded tropism and enhanced pathogenicity.
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