{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,14]],"date-time":"2026-10-14T00:59:47Z","timestamp":1791939587740,"version":"4.3.4"},"reference-count":45,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2018,11,19]],"date-time":"2018-11-19T00:00:00Z","timestamp":1542585600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["Scientific Research (A) 26252048, 18H03971"],"award-info":[{"award-number":["Scientific Research (A) 26252048, 18H03971"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>H9N2 avian influenza viruses are present in poultry worldwide. These viruses are considered to have pandemic potential, because recent isolates can recognize human-type receptor and several sporadic human infections have been reported. In this study, we aimed to identify mutations related to mammalian adaptation of H9N2 influenza virus. We found that mouse-adapted viruses had several mutations in hemagglutinin (HA), PB2, PA, and PB1. Among the detected mutations, PB1-K577E was a novel mutation that had not been previously reported to involve mammalian adaptation. A recombinant H9N2 virus bearing only the PB1-K577E mutation showed enhanced pathogenicity in mice, with increased virus titers in nasal turbinates compared to that in mice infected with the wild-type virus. In addition, the PB1-K577E mutation increased virus polymerase activity in human cell culture at a lower temperature. These data suggest that the PB1-K577E mutation is a novel pathogenicity determinant of H9N2 virus in mice and could be a signature for mammalian adaptation.<\/jats:p>","DOI":"10.3390\/v10110653","type":"journal-article","created":{"date-parts":[[2018,11,23]],"date-time":"2018-11-23T03:41:31Z","timestamp":1542944491000},"page":"653","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":43,"title":["A PB1-K577E Mutation in H9N2 Influenza Virus Increases Polymerase Activity and Pathogenicity in Mice"],"prefix":"10.3390","volume":"10","author":[{"given":"Haruhiko","family":"Kamiki","sequence":"first","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hiromichi","family":"Matsugo","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tomoya","family":"Kobayashi","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hiroho","family":"Ishida","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Akiko","family":"Takenaka-Uema","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shin","family":"Murakami","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taisuke","family":"Horimoto","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,11,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"916","DOI":"10.1016\/S0140-6736(99)03311-5","article-title":"Human infection with influenza H9N2","volume":"354","author":"Peiris","year":"1999","journal-title":"Lancet"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"977","DOI":"10.1016\/S0264-410X(98)00005-X","article-title":"Human influenza virus A\/HongKong\/156\/97 (H5N1) infection","volume":"16","author":"Claas","year":"1998","journal-title":"Vaccine"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"859","DOI":"10.3201\/eid1506.090072","article-title":"Past, present, and possible future human infection with influenza virus A subtype H7","volume":"15","author":"Belser","year":"2009","journal-title":"Emerg. Infect. Dis."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"771","DOI":"10.1016\/S2213-2600(13)70221-2","article-title":"Human infection with avian influenza A H6N1 virus: An epidemiological analysis","volume":"1","author":"Wei","year":"2013","journal-title":"Lancet Respir. Med."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"3238","DOI":"10.1097\/00029330-201409200-00009","article-title":"Clinical characteristics of human infection with a novel avian-origin influenza A(H10N8) virus","volume":"127","author":"Zhang","year":"2014","journal-title":"Chin. Med. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"7200","DOI":"10.1128\/JVI.00980-13","article-title":"Adaptation of avian influenza A virus polymerase in mammals to overcome the host species barrier","volume":"87","author":"Manz","year":"2013","journal-title":"J. Virol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"420","DOI":"10.1038\/nature10831","article-title":"Experimental adaptation of an influenza H5 HA confers respiratory droplet transmission to a reassortant H5 HA\/H1N1 virus in ferrets","volume":"486","author":"Imai","year":"2012","journal-title":"Nature"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"277","DOI":"10.2307\/1588472","article-title":"Avian influenza virus infections. III. Antibody response by turkeys to influenza A\/turkey\/Wisconsin\/1966 virus","volume":"14","author":"Homme","year":"1970","journal-title":"Avian Dis."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"279","DOI":"10.1006\/viro.1999.0115","article-title":"Characterization of the pathogenicity of members of the newly established H9N2 influenza virus lineages in Asia","volume":"267","author":"Guo","year":"2000","journal-title":"Virology"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2635","DOI":"10.1128\/JVI.02316-06","article-title":"Evolution and molecular epidemiology of H9N2 influenza A viruses from quail in Southern China, 2000 to 2005","volume":"81","author":"Xu","year":"2007","journal-title":"J. Virol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"9363","DOI":"10.1073\/pnas.96.16.9363","article-title":"Molecular characterization of H9N2 influenza viruses: Were they the donors of the \u201cinternal\u201d genes of H5N1 viruses in Hong Kong?","volume":"96","author":"Guan","year":"1999","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1888","DOI":"10.1056\/NEJMoa1304459","article-title":"Human infection with a novel avian-origin influenza A (H7N9) virus","volume":"368","author":"Gao","year":"2013","journal-title":"N. Engl. J. Med."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"714","DOI":"10.1016\/S0140-6736(14)60111-2","article-title":"Clinical and epidemiological characteristics of a fatal case of avian influenza A H10N8 virus infection: A descriptive study","volume":"383","author":"Chen","year":"2014","journal-title":"Lancet"},{"key":"ref_14","unstructured":"International Centre for Diarrhoeal Disease Research, Bangladesh\/Government of The People\u2019s Republic of Bangladesh (2011). Outbreak of mild respiratory disease caused by H5N1 and H9N2 infections among young children in Dhaka, Bangladesh, 2011. Health Sci. Bull., 9, 5\u201312."},{"key":"ref_15","unstructured":"World Health Organization (WHO) (2018, October 16). Influenza at the Human-Animal Interface. Available online: http:\/\/www.who.int\/influenza\/human_animal_interface\/Influenza_Summary_IRA_HA_interface_3_March_2015.pdf."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"562","DOI":"10.1093\/infdis\/jiv109","article-title":"A systematic review and meta-analysis of the seroprevalence of influenza A(H9N2) infection among humans","volume":"212","author":"Khan","year":"2015","journal-title":"J. Infect. Dis."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"9679","DOI":"10.1128\/JVI.75.20.9679-9686.2001","article-title":"Cocirculation of avian H9N2 and contemporary \u201cHuman\u201d H3N2 influenza A viruses in pigs in Southeastern China: Potential for genetic reassortment?","volume":"75","author":"Peiris","year":"2001","journal-title":"J. Virol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"471","DOI":"10.1016\/j.meegid.2013.10.012","article-title":"Evidence of avian-like H9N2 influenza A virus among dogs in Guangxi, China","volume":"20","author":"Sun","year":"2013","journal-title":"Infect. Genet. Evol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1016\/j.virusres.2013.04.004","article-title":"Domestic cats and dogs are susceptible to H9N2 avian influenza virus","volume":"175","author":"Zhang","year":"2013","journal-title":"Virus Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2127","DOI":"10.1007\/s00705-013-1721-8","article-title":"Experimental infection of non-human primates with avian influenza virus (H9N2)","volume":"158","author":"Zhang","year":"2013","journal-title":"Arch. Virol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"8609","DOI":"10.1128\/JVI.78.16.8609-8614.2004","article-title":"Continuing evolution of H9N2 influenza viruses in Southeastern China","volume":"78","author":"Choi","year":"2004","journal-title":"J. Virol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1006\/viro.2000.0799","article-title":"H9N2 influenza A viruses from poultry in Asia have human virus-like receptor specificity","volume":"281","author":"Matrosovich","year":"2001","journal-title":"Virology"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1006\/viro.1994.1615","article-title":"Receptor specificity in human, avian, and equine H2 and H3 influenza virus isolates","volume":"205","author":"Connor","year":"1994","journal-title":"Virology"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Wan, H., Sorrell, E.M., Song, H., Hossain, M.J., Ramirez-Nieto, G., Monne, I., Stevens, J., Cattoli, G., Capua, I., and Chen, L.-M. (2008). Replication and transmission of H9N2 influenza viruses in ferrets: Evaluation of pandemic potential. PLoS ONE, 3.","DOI":"10.1371\/journal.pone.0002923"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2275","DOI":"10.1007\/s007050170002","article-title":"Universal primer set for the full-length amplification of all influenza A viruses","volume":"146","author":"Hoffmann","year":"2001","journal-title":"Arch. Virol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"9345","DOI":"10.1073\/pnas.96.16.9345","article-title":"Generation of influenza A viruses entirely from cloned cDNAs","volume":"96","author":"Neumann","year":"1999","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1605","DOI":"10.1128\/JVI.01876-07","article-title":"Establishment of canine RNA polymerase I-driven reverse genetics for influenza A virus: Its application for H5N1 vaccine production","volume":"82","author":"Murakami","year":"2008","journal-title":"J. Virol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1284","DOI":"10.1099\/vir.0.018143-0","article-title":"Role of host-specific amino acids in the pathogenicity of avian H5N1 influenza viruses in mice","volume":"91","author":"Kim","year":"2010","journal-title":"J. Gen. Virol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"258","DOI":"10.1086\/518792","article-title":"The molecular basis of the pathogenicity of the Dutch highly pathogenic human influenza A H7N7 viruses","volume":"196","author":"Munster","year":"2007","journal-title":"J. Infect. Dis."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"570","DOI":"10.1007\/s12275-015-5329-4","article-title":"Molecular characterization of mammalian-adapted Korean-type avian H9N2 virus and evaluation of its virulence in mice","volume":"53","author":"Park","year":"2015","journal-title":"J. Microbiol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1840","DOI":"10.1126\/science.1062882","article-title":"Molecular basis for high virulence of Hong Kong H5N1 influenza A viruses","volume":"293","author":"Hatta","year":"2001","journal-title":"Science"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1016\/j.virol.2014.08.010","article-title":"PB2-E627K and PA-T97I substitutions enhance polymerase activity and confer a virulent phenotype to an H6N1 avian influenza virus in mice","volume":"468","author":"Cheng","year":"2014","journal-title":"Virology"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"5278","DOI":"10.1128\/JVI.00063-09","article-title":"Selection of H5N1 influenza virus PB2 during replication in humans","volume":"83","author":"Le","year":"2009","journal-title":"J. Virol."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1146","DOI":"10.1128\/JVI.01698-07","article-title":"A single-amino-acid substitution in the NS1 protein changes the pathogenicity of H5N1 avian influenza viruses in mice","volume":"82","author":"Jiao","year":"2008","journal-title":"J. Virol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1016\/j.virol.2008.11.044","article-title":"Two amino acid residues in the matrix protein M1 contribute to the virulence difference of H5N1 avian influenza viruses in mice","volume":"384","author":"Fan","year":"2009","journal-title":"Virology"},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Ping, J., Keleta, L., Forbes, N.E., Dankar, S., Stecho, W., Tyler, S., Zhou, Y., Babiuk, L., Weingartl, H., and Halpin, R.A. (2011). Genomic and protein structural maps of adaptive evolution of human influenza A virus to increased virulence in the mouse. PLoS ONE, 6.","DOI":"10.1371\/journal.pone.0021740"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"4456","DOI":"10.1093\/nar\/24.22.4456","article-title":"Identification of two separate domains in the influenza virus PB1 protein involved in the interaction with the PB2 and PA subunits: A model for the viral RNA polymerase structure","volume":"24","year":"1996","journal-title":"Nucleic Acids Res."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1038\/nature14009","article-title":"Structural insight into cap-snatching and RNA synthesis by influenza polymerase","volume":"516","author":"Reich","year":"2014","journal-title":"Nature"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1254","DOI":"10.1128\/JVI.01533-09","article-title":"Nuclear import and assembly of influenza A virus RNA polymerase studied in live cells by fluorescence cross-correlation spectroscopy","volume":"84","author":"Huet","year":"2010","journal-title":"J. Virol."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Hatta, M., Hatta, Y., Kim, J.H., Watanabe, S., Shinya, K., Nguyen, T., Lien, P.S., Le, Q.M., and Kawaoka, Y. (2007). Growth of H5N1 influenza A viruses in the upper respiratory tracts of mice. PLoS Pathog., 3.","DOI":"10.1371\/journal.ppat.0030133"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1038\/ncomms1158","article-title":"Differential use of importin-\u03b1 isoforms governs cell tropism and host adaptation of influenza virus","volume":"2","author":"Gabriel","year":"2011","journal-title":"Nat. Commun."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"12325","DOI":"10.1128\/JVI.01373-09","article-title":"The polymerase acidic protein gene of influenza a virus contributes to pathogenicity in a mouse model","volume":"83","author":"Song","year":"2009","journal-title":"J. Virol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1128\/JVI.78.1.240-249.2004","article-title":"Structural differences among hemagglutinins of influenza A virus subtypes are reflected in their antigenic architecture: Analysis of H9 escape mutants","volume":"78","author":"Kaverin","year":"2004","journal-title":"J. Virol."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"107","DOI":"10.1007\/s00705-009-0535-1","article-title":"Readaptation of a low-virulence influenza H9 escape mutant in mice: The role of changes in hemagglutinin as revealed by site-specific mutagenesis","volume":"155","author":"Ilyushina","year":"2010","journal-title":"Arch. Virol."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"11181","DOI":"10.1073\/pnas.201401198","article-title":"X-ray structures of H5 avian and H9 swine influenza virus hemagglutinins bound to avian and human receptor analogs","volume":"98","author":"Ha","year":"2001","journal-title":"Proc. Natl. Acad. Sci. USA"}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/10\/11\/653\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:30:36Z","timestamp":1760196636000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/10\/11\/653"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,11,19]]},"references-count":45,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2018,11]]}},"alternative-id":["v10110653"],"URL":"https:\/\/doi.org\/10.3390\/v10110653","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,11,19]]}}}