{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T17:48:22Z","timestamp":1792086502308,"version":"4.4.0"},"reference-count":33,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T00:00:00Z","timestamp":1760227200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2022YFC2303800"],"award-info":[{"award-number":["2022YFC2303800"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>The antigenic relationship between Eurasian avian-like H1N1 swine influenza viruses (EA H1N1) and human pandemic 2009 H1N1 viruses (2009\/H1N1) remains a critical question for influenza surveillance and vaccine efficacy. This study systematically investigated the antigenic differences between strains A\/swine\/Tianjin\/312\/2016 (TJ312, EA H1N1) and A\/Guangdong-Maonan\/SWL1536\/2019 (GD1536, 2009\/H1N1). Cross-hemagglutination inhibition (HI) assays revealed a significant antigenic disparity, with a 16-fold reduction in heterologous versus homologous HI titers. Comparative sequence analysis identified 22 amino acid differences across the five major antigenic sites (Sa, Sb, Ca1, Ca2, and Cb) of the HA1 subunit. Using reverse genetics, a panel of mutant viruses was generated. This study revealed that a single histidine (H)-to-asparagine (N) substitution at residue 128 (H3 numbering) in the Sa antigenic site acts as a primary determinant of antigenic variation, sufficient to cause a four-fold change in HI titers and a measurable drift in antigenic distance. Structural modeling via AlphaFold3 and PyMOL software suggests that the H128N mutation may alter the local conformation of the antigenic site. It is plausible that H at position 128 could exert electrostatic repulsion with adjacent amino acids, whereas N might facilitate hydrogen bond formation with neighboring residues. These interactions would potentially lead to structural changes in the antigenic site. Our findings confirm that residue 128 is a critical molecular marker for the antigenic differentiation of EA H1N1 and 2009\/H1N1 viruses. The study underscores the necessity of monitoring specific HA mutations that could reduce cross-reactivity and provides valuable insights for refining vaccine strain selection and pandemic preparedness strategies.<\/jats:p>","DOI":"10.3390\/v17101360","type":"journal-article","created":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T08:10:31Z","timestamp":1760343031000},"page":"1360","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["H128N Substitution in the Sa Antigenic Site of HA1 Causes Antigenic Drift Between Eurasian Avian-like H1N1 and 2009 Pandemic H1N1 Influenza Viruses"],"prefix":"10.3390","volume":"17","author":[{"given":"Fei","family":"Meng","sequence":"first","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhang","family":"Cheng","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zijian","family":"Feng","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yijie","family":"Zhang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yali","family":"Zhang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanwen","family":"Wang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yujia","family":"Zhai","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peichun","family":"Kuang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rui","family":"Qu","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yan","family":"Chen","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chuanling","family":"Qiao","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8910-898X","authenticated-orcid":false,"given":"Hualan","family":"Chen","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2049-332X","authenticated-orcid":false,"given":"Huanliang","family":"Yang","sequence":"additional","affiliation":[{"name":"State Key Laboratory for Animal Disease Control and Prevention, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"614","DOI":"10.1016\/j.chom.2020.07.006","article-title":"Surveillance of European Domestic Pig Populations Identifies an Emerging Reservoir of Potentially Zoonotic Swine Influenza A Viruses","volume":"28","author":"Henritzi","year":"2020","journal-title":"Cell Host Microbe"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1007\/s11427-022-2208-0","article-title":"Continued evolution of the Eurasian avian-like H1N1 swine influenza viruses in China","volume":"66","author":"Meng","year":"2023","journal-title":"Sci. China-Life Sci."},{"key":"ref_3","first-page":"75","article-title":"Evidence for the natural transmission of influenza A virus from wild ducts to swine and its potential importance for man","volume":"59","author":"Pensaert","year":"1981","journal-title":"Bull. World Health Organ."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1073\/pnas.1522643113","article-title":"Prevalence, genetics, and transmissibility in ferrets of Eurasian avian-like H1N1 swine influenza viruses","volume":"113","author":"Yang","year":"2016","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"17204","DOI":"10.1073\/pnas.1921186117","article-title":"Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection","volume":"117","author":"Sun","year":"2020","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_6","first-page":"2001638","article-title":"Zoonotic infection with swine A\/H1(av)N1 influenza virus in a child, Germany, June 2020","volume":"25","author":"Durrwald","year":"2020","journal-title":"Euro Surveill. Bull. Eur. Sur Les Mal. Transm. = Eur. Commun. Dis. Bull."},{"key":"ref_7","first-page":"2400662","article-title":"Human infections with Eurasian avian-like swine influenza virus detected by coincidence via routine respiratory surveillance systems, the Netherlands, 2020 to 2023","volume":"30","author":"Eggink","year":"2025","journal-title":"Euro Surveill. Bull. Eur. Sur Les Mal. Transm. = Eur. Commun. Dis. Bull."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1016\/j.bsheal.2024.11.007","article-title":"Antigenicity and genetic properties of an Eurasian avian-like H1N1 swine influenza virus in Jiangsu Province, China","volume":"6","author":"He","year":"2024","journal-title":"Biosaf. Health"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"He, Y., Song, S., Wu, J., Wu, J., Zhang, L., Sun, L., Li, Z., Wang, X., Kou, Z., and Liu, T. (2024). Emergence of Eurasian Avian-Like Swine Influenza A (H1N1) virus in a child in Shandong Province, China. BMC Infect. Dis., 24.","DOI":"10.1186\/s12879-024-09441-7"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"1535","DOI":"10.1080\/22221751.2019.1679611","article-title":"Human infection with a novel reassortant Eurasian-avian lineage swine H1N1 virus in northern China","volume":"8","author":"Li","year":"2019","journal-title":"Emerg. Microbes Infect."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"939","DOI":"10.3201\/eid2703.201863","article-title":"Human Infection with Eurasian Avian-Like Swine Influenza A(H1N1) Virus, the Netherlands, September 2019","volume":"27","author":"Parys","year":"2021","journal-title":"Emerg. Infect. Dis."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1709","DOI":"10.3201\/eid1910.130420","article-title":"Human infection with Eurasian avian-like influenza A(H1N1) virus, China","volume":"19","author":"Wang","year":"2013","journal-title":"Emerg. Infect. Dis."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1007\/s12250-018-0034-1","article-title":"Emergence of Eurasian Avian-Like Swine Influenza A (H1N1) Virus from an Adult Case in Fujian Province, China","volume":"33","author":"Xie","year":"2018","journal-title":"Virol. Sin."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1930","DOI":"10.3201\/eid2211.160181","article-title":"Reassortant Eurasian Avian-Like Influenza A(H1N1) Virus from a Severely Ill Child, Hunan Province, China, 2015","volume":"22","author":"Zhu","year":"2016","journal-title":"Emerg. Infect. Dis."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"989","DOI":"10.1080\/22221751.2019.1635873","article-title":"Mammalian-adaptive mutation NP-Q357K in Eurasian H1N1 Swine Influenza viruses determines the virulence phenotype in mice","volume":"8","author":"Zhu","year":"2019","journal-title":"Emerg. Microbes Infect."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"931","DOI":"10.1038\/nature08157","article-title":"Emergence and pandemic potential of swine-origin H1N1 influenza virus","volume":"459","author":"Neumann","year":"2009","journal-title":"Nature"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1122","DOI":"10.1038\/nature08182","article-title":"Origins and evolutionary genomics of the 2009 swine-origin H1N1 influenza A epidemic","volume":"459","author":"Smith","year":"2009","journal-title":"Nature"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"e00275-16","DOI":"10.1128\/mSphere.00275-16","article-title":"A Phylogeny-Based Global Nomenclature System and Automated Annotation Tool for H1 Hemagglutinin Genes from Swine Influenza A Viruses","volume":"1","author":"Anderson","year":"2016","journal-title":"mSphere"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"519","DOI":"10.1038\/nature10004","article-title":"Long-term evolution and transmission dynamics of swine influenza A virus","volume":"473","author":"Vijaykrishna","year":"2011","journal-title":"Nature"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"10748","DOI":"10.1073\/pnas.162366899","article-title":"The total influenza vaccine failure of 1947 revisited: Major intrasubtypic antigenic change can explain failure of vaccine in a post-World War II epidemic","volume":"99","author":"Kilbourne","year":"2002","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"982","DOI":"10.1093\/infdis\/jiw183","article-title":"A High-Resolution Look at Influenza Virus Antigenic Drift","volume":"214","author":"Schotsaert","year":"2016","journal-title":"J. Infect. Dis."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"14001","DOI":"10.1073\/pnas.96.24.14001","article-title":"Variable efficacy of repeated annual influenza vaccination","volume":"96","author":"Smith","year":"1999","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"e2203919119","DOI":"10.1073\/pnas.2203919119","article-title":"A Eurasian avian-like H1N1 swine influenza reassortant virus became pathogenic and highly transmissible due to mutations in its PA gene","volume":"119","author":"Meng","year":"2022","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"a038778","DOI":"10.1101\/cshperspect.a038778","article-title":"Influenza Hemagglutinin Structures and Antibody Recognition","volume":"10","author":"Wu","year":"2020","journal-title":"Cold Spring Harb. Perspect. Med."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1016\/0092-8674(82)90135-0","article-title":"The antigenic structure of the influenza virus A\/PR\/8\/34 hemagglutinin (H1 subtype)","volume":"31","author":"Caton","year":"1982","journal-title":"Cell"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"713","DOI":"10.1038\/290713a0","article-title":"Antigenic structure of influenza virus haemagglutinin defined by hybridoma antibodies","volume":"290","author":"Gerhard","year":"1981","journal-title":"Nature"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1224","DOI":"10.1099\/jgv.0.000800","article-title":"In vitro and in vivo evidence of a potential A(H1N1)pdm09 antigenic drift mediated by escape mutations in the haemagglutinin Sa antigenic site","volume":"98","author":"Retamal","year":"2017","journal-title":"J. Gen. Virol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1186\/1743-422X-9-91","article-title":"Subtype- and antigenic site-specific differences in biophysical influences on evolution of influenza virus hemagglutinin","volume":"9","author":"Stray","year":"2012","journal-title":"Virol. J."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1126\/science.1186430","article-title":"Structural basis of preexisting immunity to the 2009 H1N1 pandemic influenza virus","volume":"328","author":"Xu","year":"2010","journal-title":"Science"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"6283","DOI":"10.1073\/pnas.0701396104","article-title":"Simultaneous amino acid substitutions at antigenic sites drive influenza A hemagglutinin evolution","volume":"104","author":"Shih","year":"2007","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_31","first-page":"1798","article-title":"Interspecies Transmission of Swine Influenza A Viruses and Human Seasonal Vaccine-Mediated Protection Investigated in Ferret Model","volume":"29","author":"Byrne","year":"2023","journal-title":"Emerg. Infect. Dis."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"e236","DOI":"10.1111\/tbed.14288","article-title":"A single amino acid at position 158 in haemagglutinin affects the antigenic property of Eurasian avian-like H1N1 swine influenza viruses","volume":"69","author":"Wang","year":"2022","journal-title":"Transbound. Emerg. Dis."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"e0097122","DOI":"10.1128\/jvi.00971-22","article-title":"Immune Escape Adaptive Mutations in Hemagglutinin Are Responsible for the Antigenic Drift of Eurasian Avian-Like H1N1 Swine Influenza Viruses","volume":"96","author":"Xu","year":"2022","journal-title":"J. Virol."}],"container-title":["Viruses"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4915\/17\/10\/1360\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T08:12:35Z","timestamp":1760343155000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4915\/17\/10\/1360"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,10,12]]},"references-count":33,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2025,10]]}},"alternative-id":["v17101360"],"URL":"https:\/\/doi.org\/10.3390\/v17101360","relation":{},"ISSN":["1999-4915"],"issn-type":[{"value":"1999-4915","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,10,12]]}}}