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Cui X, Ma J, Pang Z, Chi L, Mai C, Liu H, Liao M, Sun H. The evolution, pathogenicity and transmissibility of quadruple reassortant H1N2 swine influenza virus in China: A potential threat to public health. Virol Sin 2024; 39:205-217. [PMID: 38346538 DOI: 10.1016/j.virs.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 02/06/2024] [Indexed: 04/30/2024] Open
Abstract
Swine are regarded as "intermediate hosts" or "mixing vessels" of influenza viruses, capable of generating strains with pandemic potential. From 2020 to 2021, we conducted surveillance on swine H1N2 influenza (swH1N2) viruses in swine farms located in Guangdong, Yunnan, and Guizhou provinces in southern China, as well as Henan and Shandong provinces in northern China. We systematically analyzed the evolution and pathogenicity of swH1N2 isolates, and characterized their replication and transmission abilities. The isolated viruses are quadruple reassortant H1N2 viruses containing genes from pdm/09 H1N1 (PB2, PB1, PA and NP genes), triple-reassortant swine (NS gene), Eurasian Avian-like (HA and M genes), and recent human H3N2 (NA gene) lineages. The NA, PB2, and NP of SW/188/20 and SW/198/20 show high gene similarities to A/Guangdong/Yue Fang277/2017 (H3N2). The HA gene of swH1N2 exhibits a high evolutionary rate. The five swH1N2 isolates replicate efficiently in human, canine, and swine cells, as well as in the turbinate, trachea, and lungs of mice. A/swine/Shandong/198/2020 strain efficiently replicates in the respiratory tract of pigs and effectively transmitted among them. Collectively, these current swH1N2 viruses possess zoonotic potential, highlighting the need for strengthened surveillance of swH1N2 viruses.
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MESH Headings
- Animals
- Swine
- Reassortant Viruses/genetics
- Reassortant Viruses/pathogenicity
- Reassortant Viruses/isolation & purification
- China/epidemiology
- Orthomyxoviridae Infections/virology
- Orthomyxoviridae Infections/transmission
- Orthomyxoviridae Infections/veterinary
- Swine Diseases/virology
- Swine Diseases/transmission
- Influenza A Virus, H1N2 Subtype/genetics
- Influenza A Virus, H1N2 Subtype/pathogenicity
- Influenza A Virus, H1N2 Subtype/isolation & purification
- Humans
- Mice
- Dogs
- Evolution, Molecular
- Phylogeny
- Virus Replication
- Public Health
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/pathogenicity
- Influenza A Virus, H1N1 Subtype/isolation & purification
- Influenza, Human/virology
- Influenza, Human/transmission
- Mice, Inbred BALB C
- Influenza A Virus, H3N2 Subtype/genetics
- Influenza A Virus, H3N2 Subtype/pathogenicity
- Influenza A Virus, H3N2 Subtype/isolation & purification
- Virulence
- Female
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Affiliation(s)
- Xinxin Cui
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China
| | - Jinhuan Ma
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China
| | - Zifeng Pang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China
| | - Lingzhi Chi
- Shandong Vocational Animal Science and Veterinary College, Weifang, 261061, China
| | - Cuishan Mai
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China
| | - Hanlin Liu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China
| | - Ming Liao
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China; Institute of Animal Health, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China.
| | - Hailiang Sun
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China; Key Laboratory of Zoonosis Control and Prevention of Guangdong Province, South China Agricultural University, Guangzhou, 510642, China; National and Regional Joint Engineering Laboratory for Medicament of Zoonosis Prevention and Control, South China Agricultural University, Guangzhou, 510642, China.
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Continued evolution of the Eurasian avian-like H1N1 swine influenza viruses in China. SCIENCE CHINA. LIFE SCIENCES 2023; 66:269-282. [PMID: 36219302 DOI: 10.1007/s11427-022-2208-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 09/26/2022] [Indexed: 12/05/2022]
Abstract
Animal influenza viruses continue to pose a threat to human public health. The Eurasian avian-like H1N1 (EA H1N1) viruses are widespread in pigs throughout Europe and China and have caused human infections in several countries, indicating their pandemic potential. To carefully monitor the evolution of the EA H1N1 viruses in nature, we collected nasal swabs from 103,110 pigs in 22 provinces in China between October 2013 and December 2019, and isolated 855 EA H1N1 viruses. Genomic analysis of 319 representative viruses revealed that these EA H1N1 viruses formed eight different genotypes through reassortment with viruses of other lineages circulating in humans and pigs, and two of these genotypes (G4 and G5) were widely distributed in pigs. Animal studies indicated that some strains have become highly pathogenic in mice and highly transmissible in ferrets via respiratory droplets. Moreover, two-thirds of the EA H1N1 viruses reacted poorly with ferret serum antibodies induced by the currently used H1N1 human influenza vaccine, suggesting that existing immunity may not prevent the transmission of the EA H1N1 viruses in humans. Our study reveals the evolution and pandemic potential of EA H1N1 viruses and provides important insights for future pandemic preparedness.
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Gong L, Chen X, Wang W, Hu X, Zhang G. Different virulence of G4 and G5 Eurasian avian-like H1N1 swine influenza viruses in mice. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2022; 105:105374. [PMID: 36208830 DOI: 10.1016/j.meegid.2022.105374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/30/2022] [Accepted: 10/03/2022] [Indexed: 11/05/2022]
Affiliation(s)
- Lang Gong
- Guangdong Provincial Key Laboratory of Zoonosis Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510462, PR China; Maoming Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Maoming 525000, China
| | - XiongNan Chen
- Guangdong Provincial Key Laboratory of Zoonosis Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510462, PR China; Maoming Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Maoming 525000, China
| | - Wenru Wang
- Guangdong Provincial Key Laboratory of Zoonosis Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510462, PR China; Maoming Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Maoming 525000, China
| | - Xiaokun Hu
- Guangdong Provincial Key Laboratory of Zoonosis Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510462, PR China
| | - Guihong Zhang
- Guangdong Provincial Key Laboratory of Zoonosis Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou 510462, PR China; Maoming Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Maoming 525000, China; Key Laboratory of Animal Vaccine Development, Ministry of Agriculture and Rural Affairs, China.
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A Eurasian avian-like H1N1 swine influenza reassortant virus became pathogenic and highly transmissible due to mutations in its PA gene. Proc Natl Acad Sci U S A 2022; 119:e2203919119. [PMID: 35969783 PMCID: PMC9407662 DOI: 10.1073/pnas.2203919119] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Previous studies have shown that the Eurasian avian-like H1N1 (EA H1N1) swine influenza viruses circulated widely in pigs around the world and formed multiple genotypes by acquiring non-hemagglutinin and neuraminidase segments derived from other swine influenza viruses. Swine influenza control is not a priority for the pig industry in many countries, and it is worrisome that some strains may become more pathogenic and/or transmissible during their circulation in nature. Our routine surveillance indicated that the EA H1N1 viruses obtained different internal genes from different swine influenza viruses and formed various new genotypes. In this study, we found that a naturally isolated swine influenza reassortant, A/swine/Liaoning/265/2017 (LN265), a representative strain of one of the predominant genotypes in recent years, is lethal in mice and transmissible in ferrets. LN265 contains the hemagglutinin, neuraminidase, and matrix of the EA H1N1 virus; the basic polymerase 2, basic polymerase 1, acidic polymerase (PA), and nucleoprotein of the 2009 H1N1 pandemic virus; and the nonstructural protein of the North American triple-reassortment H1N2 virus. By generating and testing a series of reassortants and mutants, we found that four gradually accumulated mutations in PA are responsible for the increased pathogenicity and transmissibility of LN265. We further revealed that these mutations increase the messenger RNA transcription of viral proteins by enhancing the endonuclease cleavage activity and viral RNA-binding ability of the PA protein. Our study demonstrates that EA H1N1 swine influenza virus became pathogenic and transmissible in ferrets by acquiring key mutations in PA and provides important insights for monitoring field strains with pandemic potential.
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Serological Surveillance of the H1N1 and H3N2 Swine Influenza A Virus in Chinese Swine between 2016 and 2021. BIOMED RESEARCH INTERNATIONAL 2022; 2022:5833769. [PMID: 35528158 PMCID: PMC9071888 DOI: 10.1155/2022/5833769] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 03/27/2022] [Accepted: 04/07/2022] [Indexed: 11/17/2022]
Abstract
Background Swine influenza A virus (IAV-S) is a common cause of respiratory disease in pigs and poses a major public health threat. However, little attention and funding have been given to such studies. The aim of this study was to assess the prevalence of the Eurasian avian-like H1N1 (EA H1N1), 2009 pandemic H1N1 (pdm/09 H1N1), and H3N2 subtype antibodies in unvaccinated swine populations through serological investigations. Such data are helpful in understanding the prevalence of the IAV-S. Methods A total of 40,343 serum samples from 17 regions in China were examined using hemagglutination inhibition (HI) tests against EA H1N1, pdm/09 H1N1, and H3N2 IAV-S from 2016 to 2021. The results were analyzed based on a reginal distribution, seasonal distribution, and in different breeding stages. Results A total of 19,682 serum samples out of the 40,343 were positive for IAV-S (48.79%). The positivity rates to the EA H1N1 subtype, pdm/09 H1N1 subtype, and H3N2 subtype were 24.75% (9,986/40,343), 7.94% (3,205/40,343), and 0.06% (24/40,343), respectively. The occurrences of coinfections from two or more subtypes were also detected. In general, the positivity rates of serum samples were related to the regional distribution and feeding stages. Conclusions The results of this study showed that the anti-EA H1N1 subtype and pdm/09 H1N1 subtype antibodies were readily detected in swine serum samples. The EA H1N1 subtype has become dominant in the pig population. The occurrences of coinfections from two or more subtypes afforded opportunities for their reassortment to produce new viruses. Our findings emphasized the need for continuous surveillance of influenza viruses.
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Cheung JTL, Tsang TK, Yen HL, Perera RAPM, Mok CKP, Lin YP, Cowling BJ, Peiris M. Determining Existing Human Population Immunity as Part of Assessing Influenza Pandemic Risk. Emerg Infect Dis 2022; 28:977-985. [PMID: 35447069 PMCID: PMC9045452 DOI: 10.3201/eid2805.211965] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Zoonotic influenza infections continue to threaten human health. Ongoing surveillance and risk assessment of animal viruses are needed for pandemic preparedness, and population immunity is an important component of risk assessment. We determined age-stratified hemagglutinin inhibition seroprevalence against 5 swine influenza viruses circulating in Hong Kong and Guangzhou in China. Using hemagglutinin inhibition seroprevalence and titers, we modeled the effect of population immunity on the basic reproduction number (R0) if each virus were to become transmissible among humans. Among 353 individual serum samples, we reported low seroprevalence for triple-reassortant H1N2 and Eurasian avian-like H1N1 influenza viruses, which would reduce R0 by only 18%–20%. The smallest R0 needed to cause a pandemic was 1.22–1.24, meaning existing population immunity would be insufficient to block the spread of these H1N1 or H1N2 variants. For human-origin H3N2, existing population immunity could suppress R0 by 47%, thus reducing pandemic risk.
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Das A, Pandita D, Jain GK, Agarwal P, Grewal AS, Khar RK, Lather V. Role of phytoconstituents in the management of COVID-19. Chem Biol Interact 2021; 341:109449. [PMID: 33798507 PMCID: PMC8008820 DOI: 10.1016/j.cbi.2021.109449] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 03/07/2021] [Accepted: 03/21/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND COVID-19, a severe global pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has emerged as one of the most threatening transmissible disease. As a great threat to global public health, the development of treatment options has become vital, and a rush to find a cure has mobilized researchers globally from all areas. SCOPE AND APPROACH This review focuses on deciphering the potential of different secondary metabolites from medicinal plants as therapeutic options either as inhibitors of therapeutic targets of SARS-CoV-2 or as blockers of viral particles entry through host cell receptors. The use of medicinal plants containing specific phytomoieties could be seen in providing a safer and long-term solution for the population with lesser side effects. Key Findings and Conclusions: Considering the high cost and time-consuming drug discovery process, therapeutic repositioning of existing drugs was explored as treatment option in COVID-19, however several molecules have been retracted as therapeutics either due to no positive outcomes or the severe side effects. These effects call for exploring the alternate treatment options which are therapeutically effective as well as safe. Keeping this in mind, phytopharmaceuticals derived from medicinal plants could be explored as important resources in the development of COVID-19 treatment, as their role in the past for treatment of viral diseases like HIV, MERS-CoV, and influenza has been well reported. Considering this fact, different phytoconstituents such as flavonoids, alkaloids, tannins and glycosides etc. Possessing antiviral properties against coronaviruses and possessing potential against SARS-CoV-2 have been reviewed in the present work.
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Affiliation(s)
- Amiya Das
- Amity Institute of Molecular Medicine & Stem Cell Research (AIMMSCR), Amity University Uttar Pradesh, Sector-125, Noida, 201313, India
| | - Deepti Pandita
- Department of Pharmaceutics, Delhi Pharmaceutical Sciences and Research University, Pushp Vihar, New Delhi, 110017, India.
| | - Gaurav Kumar Jain
- Department of Pharmaceutics, Delhi Pharmaceutical Sciences and Research University, Pushp Vihar, New Delhi, 110017, India
| | - Pallavi Agarwal
- Amity Institute of Molecular Medicine & Stem Cell Research (AIMMSCR), Amity University Uttar Pradesh, Sector-125, Noida, 201313, India
| | | | - Roop K Khar
- BS Anangpuria Institute of Pharmacy, Faridabad, Haryana, India
| | - Viney Lather
- Amity Institute of Pharmacy, Amity University Uttar Pradesh, Sector-125, Noida, 201313, India.
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Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection. Proc Natl Acad Sci U S A 2020; 117:17204-17210. [PMID: 32601207 DOI: 10.1073/pnas.1921186117] [Citation(s) in RCA: 165] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pigs are considered as important hosts or "mixing vessels" for the generation of pandemic influenza viruses. Systematic surveillance of influenza viruses in pigs is essential for early warning and preparedness for the next potential pandemic. Here, we report on an influenza virus surveillance of pigs from 2011 to 2018 in China, and identify a recently emerged genotype 4 (G4) reassortant Eurasian avian-like (EA) H1N1 virus, which bears 2009 pandemic (pdm/09) and triple-reassortant (TR)-derived internal genes and has been predominant in swine populations since 2016. Similar to pdm/09 virus, G4 viruses bind to human-type receptors, produce much higher progeny virus in human airway epithelial cells, and show efficient infectivity and aerosol transmission in ferrets. Moreover, low antigenic cross-reactivity of human influenza vaccine strains with G4 reassortant EA H1N1 virus indicates that preexisting population immunity does not provide protection against G4 viruses. Further serological surveillance among occupational exposure population showed that 10.4% (35/338) of swine workers were positive for G4 EA H1N1 virus, especially for participants 18 y to 35 y old, who had 20.5% (9/44) seropositive rates, indicating that the predominant G4 EA H1N1 virus has acquired increased human infectivity. Such infectivity greatly enhances the opportunity for virus adaptation in humans and raises concerns for the possible generation of pandemic viruses.
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Ruan BY, Yao Y, Wang SY, Gong XQ, Liu XM, Wang Q, Yu LX, Zhu SQ, Wang J, Shan TL, Zhou YJ, Tong W, Zheng H, Li GX, Gao F, Kong N, Yu H, Tong GZ. Protective efficacy of a bivalent inactivated reassortant H1N1 influenza virus vaccine against European avian-like and classical swine influenza H1N1 viruses in mice. Vet Microbiol 2020; 246:108724. [PMID: 32605742 DOI: 10.1016/j.vetmic.2020.108724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/06/2020] [Accepted: 05/09/2020] [Indexed: 11/29/2022]
Abstract
The classical swine (CS) H1N1 swine influenza virus (SIVs) emerged in humans as a reassortant virus that caused the H1N1 influenza virus pandemic in 2009, and the European avian-like (EA) H1N1 SIVs has caused several human infections in European and Asian countries. Development of the influenza vaccines that could provide effective protective efficacy against SIVs remains a challenge. In this study, the bivalent reassortant inactivated vaccine comprised of SH1/PR8 and G11/PR8 arboring the hemagglutinin (HA) and neuraminidase (NA) genes from prevalent CS and EA H1N1 SIVs and six internal genes from the A/Puerto Rico/8/34(PR8) virus was developed. The protective efficacy of this bivalent vaccine was evaluated in mice challenged with the lethal doses of CS and EA H1N1 SIVs. The result showed that univalent inactivated vaccine elicited high-level antibody against homologous H1N1 viruses while cross-reactive antibody responses to heterologous H1N1 viruses were not fully effective. In a mouse model, the bivalent inactivated vaccine conferred complete protection against lethal challenge doses of EA SH1 virus or CS G11 virus, whereas the univalent inactivated vaccine only produced insufficient protection against heterologous SIVs. In conclusion, our data demonstrated that the reassortant bivalent inactivated vaccine comprised of SH1/PR8 and G11/PR8 could provide effective protection against the prevalent EA and CS H1N1 subtype SIVs in mice.
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Affiliation(s)
- Bao-Yang Ruan
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Yun Yao
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Shuai-Yong Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Xiao-Qian Gong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Xiao-Min Liu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Qi Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Ling-Xue Yu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Shi-Qiang Zhu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Juan Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Tong-Ling Shan
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Yan-Jun Zhou
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Wu Tong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Hao Zheng
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Guo-Xin Li
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Fei Gao
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China
| | - Ning Kong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China; Shanghai Key Laboratory of Veterinary Biotechnology, Shanghai 200240, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, China
| | - Hai Yu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China; Shanghai Key Laboratory of Veterinary Biotechnology, Shanghai 200240, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, China.
| | - Guang-Zhi Tong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, China
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Li X, Guo L, Liu C, Cheng Y, Kong M, Yang L, Zhuang Z, Liu J, Zou M, Dong X, Su X, Gu Q. Human infection with a novel reassortant Eurasian-avian lineage swine H1N1 virus in northern China. Emerg Microbes Infect 2020; 8:1535-1545. [PMID: 31661383 PMCID: PMC6830285 DOI: 10.1080/22221751.2019.1679611] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Influenza A virus infections occur in different species, causing mild to severe respiratory symptoms that lead to a heavy disease burden. Eurasian avian-like swine influenza A(H1N1) viruses (EAS-H1N1) are predominant in pigs and occasionally infect humans. An influenza A(H1N1) virus was isolated from a boy who was suffering from fever and headache and designated as A/Tianjin-baodi/1606/2018(H1N1). Full-genome sequencing and phylogenetic analysis revealed that A/Tianjin-baodi/1606/2018(H1N1) is a novel reassortant EAS-H1N1 containing gene segments from EAS-H1N1 (HA and NA), classical swine H1N1(NS) and A(H1N1)pdm09(PB2, PB2, PA, NP and M) viruses. The isolation and analysis of A/Tianjin-baodi/1606/2018(H1) provide further evidence that EAS-H1N1 poses a threat to human health and greater attention should be paid to surveillance of influenza virus infection in pigs and humans.
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Affiliation(s)
- Xiaoyan Li
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Liru Guo
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Caixia Liu
- Jizhou District Center for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Yanhui Cheng
- Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Mei Kong
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Lei Yang
- Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Zhichao Zhuang
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Jia Liu
- Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People's Republic of China
| | - Ming Zou
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Xiaochun Dong
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Xu Su
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
| | - Qing Gu
- Tianjin Centers for Disease Control and Prevention, Tianjin, People's Republic of China
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The R251K Substitution in Viral Protein PB2 Increases Viral Replication and Pathogenicity of Eurasian Avian-like H1N1 Swine Influenza Viruses. Viruses 2020; 12:v12010052. [PMID: 31906472 PMCID: PMC7019279 DOI: 10.3390/v12010052] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 12/29/2019] [Accepted: 12/31/2019] [Indexed: 12/21/2022] Open
Abstract
The Eurasian avian-like swine (EA) H1N1 virus has affected the Chinese swine industry, and human infection cases have been reported occasionally. However, little is known about the pathogenic mechanism of EA H1N1 virus. In this study, we compared the mouse pathogenicity of A/swine/Guangdong/YJ4/2014 (YJ4) and A/swine/Guangdong/MS285/2017 (MS285) viruses, which had similar genotype to A/Hunan/42443/2015 (HuN-like). None of the mice inoculated with 106 TCID50 of YJ4 survived at 7 days post infection, while the survival rate of the MS285 group was 100%. Therefore, a series of single fragment reassortants in MS285 background and two rescued wild-type viruses were generated by using the reverse genetics method, and the pathogenicity analysis revealed that the PB2 gene contributed to the high virulence of YJ4 virus. Furthermore, there were 11 amino acid differences in PB2 between MS285 and YJ4 identified by sequence alignment, and 11 single amino acid mutant viruses were generated in the MS285 background. We found that the R251K mutation significantly increased the virulence of MS285 in mice, contributed to high polymerase activity and enhanced viral genome transcription and replication. These results indicate that PB2-R251K contributes to the virulence of the EA H1N1 virus and provide new insight into future molecular epidemiological surveillance strategies.
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Zhu W, Feng Z, Chen Y, Yang L, Liu J, Li X, Liu S, Zhou L, Wei H, Gao R, Wang D, Shu Y. Mammalian-adaptive mutation NP-Q357K in Eurasian H1N1 Swine Influenza viruses determines the virulence phenotype in mice. Emerg Microbes Infect 2019; 8:989-999. [PMID: 31267843 PMCID: PMC6609330 DOI: 10.1080/22221751.2019.1635873] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
It has recently been proposed that the Eurasian avian-like H1N1 (EA H1N1) swine influenza virus (SIV) is one of the most likely zoonotic viruses to cause the next influenza pandemic. Two main genotypes EA H1N1 viruses have been recognized to be infected humans in China. Our study finds that one of the genotypes JS1-like viruses are avirulent in mice. However, the other are HuN-like viruses and are virulent in mice. The molecular mechanism underlying this difference shows that the NP gene determines the virulence of the EA H1N1 viruses in mice. In addition, a single substitution, Q357K, in the NP protein of the EA H1N1 viruses alters the virulence phenotype. This substitution is a typical human signature marker, which is prevalent in human viruses but rarely detected in avian influenza viruses. The NP-Q357K substitution is readily to be occurred when avian influenza viruses circulate in pigs, and may facilitate their infection of humans and allow viruses also carrying NP-357K to circulate in humans. Our study demonstrates that the substitution Q357K in the NP protein plays a key role in the virulence phenotype of EA H1N1 SIVs, and provides important information for evaluating the pandemic risk of field influenza strains.
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Affiliation(s)
- Wenfei Zhu
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Zhaomin Feng
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Yongkun Chen
- c School of Public Health (Shenzhen) , Sun Yat-sen University , Guangdong , People's Republic of China
| | - Lei Yang
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Jia Liu
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Xiyan Li
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Suli Liu
- c School of Public Health (Shenzhen) , Sun Yat-sen University , Guangdong , People's Republic of China
| | - Lijuan Zhou
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Hejiang Wei
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Rongbao Gao
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Dayan Wang
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China
| | - Yuelong Shu
- a National Institute for Viral Disease Control and Prevention, Collaboration Innovation Center for Diagnosis and Treatment of Infectious Diseases , Chinese Center for Disease Control and Prevention , Beijing , People's Republic of China.,b Key Laboratory for Medical Virology , National Health and Family Planning Commission , Beijing , People's Republic of China.,c School of Public Health (Shenzhen) , Sun Yat-sen University , Guangdong , People's Republic of China
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13
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Pulit-Penaloza JA, Belser JA, Tumpey TM, Maines TR. Mammalian pathogenicity and transmissibility of a reassortant Eurasian avian-like A(H1N1v) influenza virus associated with human infection in China (2015). Virology 2019; 537:31-35. [PMID: 31430632 PMCID: PMC9608380 DOI: 10.1016/j.virol.2019.08.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 08/06/2019] [Accepted: 08/09/2019] [Indexed: 11/29/2022]
Abstract
Swine-origin (variant) H1 influenza A viruses associated with numerous human infections in North America in recent years have been extensively studied in vitro and in mammalian models to determine their pandemic potential. However, limited information is available on Eurasian avian-like lineage variant H1 influenza viruses. In 2015, A/Hunan/42443/2015 virus was isolated from a child in China with a severe infection. Molecular analysis revealed that this virus possessed several key virulence and human adaptation markers. Similar to what was previously observed in C57BL/6J mice, we report here that in the BALB/c mouse model, A/Hunan/42443/2015 virus caused more severe morbidity and higher mortality than did North American variant H1 virus isolates. Furthermore, the virus efficiently replicated throughout the respiratory tract of ferrets and exhibited a capacity for transmission in this model, underscoring the need to monitor zoonotic viruses that cross the species barrier as they continue to pose a pandemic threat.
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Affiliation(s)
- Joanna A Pulit-Penaloza
- Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Jessica A Belser
- Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Terrence M Tumpey
- Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Taronna R Maines
- Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.
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14
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Cui JA, Chen F. Effects of isolation and slaughter strategies in different species on emerging zoonoses. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2018; 14:1119-1140. [PMID: 29161853 DOI: 10.3934/mbe.2017058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Zoonosis is the kind of infectious disease transmitting among different species by zoonotic pathogens. Different species play different roles in zoonoses. In this paper, we established a basic model to describe the zoonotic pathogen transmission from wildlife, to domestic animals, to humans. Then we put three strategies into the basic model to control the emerging zoonoses. Three strategies are corresponding to control measures of isolation, slaughter or similar in wildlife, domestic animals and humans respectively. We analyzed the effects of these three strategies on control reproductive numbers and equilibriums and we took avian influenza epidemic in China as an example to show the impacts of the strategies on emerging zoonoses in different areas at beginning.
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Affiliation(s)
- Jing-An Cui
- School of Science, Beijing University of Civil Engineering and Architecture, No. 1, Zhanlanguan Road, Xicheng District, Beijing 100044, China
| | - Fangyuan Chen
- School of Science, Beijing University of Civil Engineering and Architecture, No. 1, Zhanlanguan Road, Xicheng District, Beijing 100044, China
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15
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Ruan BY, Wen F, Gong XQ, Liu XM, Wang Q, Yu LX, Wang SY, Zhang P, Yang HM, Shan TL, Zheng H, Zhou YJ, Tong W, Gao F, Tong GZ, Yu H. Protective efficacy of a high-growth reassortant H1N1 influenza virus vaccine against the European Avian-like H1N1 swine influenza virus in mice and pigs. Vet Microbiol 2018; 222:75-84. [PMID: 30080677 DOI: 10.1016/j.vetmic.2018.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 07/04/2018] [Accepted: 07/05/2018] [Indexed: 11/30/2022]
Abstract
Swine influenza A viruses (SIVs) causing outbreaks of acute, highly contagious respiratory disease in pigs also pose a potential threat to public health. European avian-like H1N1 (EA H1N1) SIVs are the predominant circulating viruses in pigs in China and also occasionally cause human infection. In this study, a high-growth reassortant virus (SH1/PR8), with HA and NA genes from a representative EA H1N1 isolate A/Swine/Shanghai/1/2014 (SH1) in China and six internal genes from the high-growth A/Puerto Rico/8/34 (PR8) virus, was generated by plasmid-based reverse genetics and tested as a candidate seed virus for the preparation of inactivated vaccine. The protective efficacy of inactivated SH1/PR8 was evaluated in mice and pigs challenged with wild-type SH1 virus. After primer and boost vaccination, the SH1/PR8 vaccine induced high-level hemagglutination inhibiting (HI) antibodies, IgG antibodies, and neutralization antibodies in mice and pigs. Mice and pigs in the vaccinated group showed less clinical phenomena and pathological changes than those in the unvaccinated group. In conclusion, the inactivated high-growth reassortant vaccine SH1/PR8 could induce high antibody levels and complete protection is expected against SH1 wild type SIV, and protection against heterologous EA H1N1 SIV needs further evaluation.
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Affiliation(s)
- Bao-Yang Ruan
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Feng Wen
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA
| | - Xiao-Qian Gong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Xiao-Min Liu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Qi Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Ling-Xue Yu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Shuai-Yong Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Peng Zhang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Hai-Ming Yang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Tong-Ling Shan
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Hao Zheng
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Yan-Jun Zhou
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Wu Tong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Fei Gao
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China
| | - Guang-Zhi Tong
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, PR China.
| | - Hai Yu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai 200241, PR China; Shanghai Key Laboratory of Veterinary Biotechnology, Shanghai 200240, PR China; Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, PR China.
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16
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Substitution of D701N in the PB2 protein could enhance the viral replication and pathogenicity of Eurasian avian-like H1N1 swine influenza viruses. Emerg Microbes Infect 2018; 7:75. [PMID: 29717109 PMCID: PMC5931605 DOI: 10.1038/s41426-018-0073-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2017] [Revised: 03/03/2018] [Accepted: 03/21/2018] [Indexed: 12/12/2022]
Abstract
Eurasian avian-like H1N1 (EA H1N1) swine influenza viruses (SIVs) have become predominant in pig populations in China and have recently been reported to have the most potential to raise the next pandemic in humans. The mutation D701N in the PB2 protein, which accounts for 31% of H1N1 SIVs, has previously been shown to contribute to the adaptation of the highly pathogenic H5N1 or H7N7 avian influenza viruses in mammals. However, little is known of the effects of this substitution on the EA H1N1 viruses. Herein, we investigated the contributions of 701N in the PB2 protein to an EA H1N1 SIV (A/Hunan/42443/2015(H1N1), HuN EA-H1N1), which had 701D in the PB2 protein. Our results found that viral polymerase activity, viral replication, and pathogenicity in mice were indeed enhanced due to the introduction of 701N into the PB2 protein, and the increased viral growth was partly mediated by the host factor importin-α7. Thus, substantial attention should be paid to the D701N mutation in pig populations.
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17
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Cai M, Huang J, Bu D, Yu Z, Fu X, Ji C, Zhou P, Zhang G. Molecular evolution of H1N1 swine influenza in Guangdong, China, 2016-2017. INFECTION GENETICS AND EVOLUTION 2018; 60:103-108. [PMID: 29477550 DOI: 10.1016/j.meegid.2018.02.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Revised: 01/30/2018] [Accepted: 02/21/2018] [Indexed: 12/09/2022]
Abstract
Swine are the main host of the H1N1 swine influenza virus (SIV), however, H1N1 can also infect humans and occasionally cause serious respiratory disease. To trace the evolution of the SIV in Guangdong, China, we performed an epidemic investigation during the period of 2016-2017. Nine H1N1 influenza viruses were isolated from swine nasal swabs. Antigenic analysis revealed that these viruses belonged to two distinct antigenic groups, represented by A/Swine/Guangdong/101/2016 and A/Swine/Guangdong/52/2017. Additionally, three genotypes, known as GD52/17-like, GD493/17-like and GD101/16-like, were identified by phylogenetic analysis. Importantly, the genotypes including a minimum of 4 pdm/09-origin internal genes have become prevalent in China in recent years. A total of 2966 swine serum samples were used to perform hemagglutination inhibition (HI) tests, and the results showed that the seroprevalence values of SW/GD/101/16 (32.2% in 2016, 32.1% in 2017) were significantly higher than the seroprevalence values of SW/GD/52/17 (18.0% in 2016, 16.7% in 2017). Our study showed that the three reassortant genotypes of H1N1 SIV currently circulating in China are stable, but H1N1pdm09 poses challenges to human health by the introduction of internal genes into these reassortant genotypes. Strengthening SIV surveillance is therefore critical for SIV control and minimizing its potential threat to public health.
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Affiliation(s)
- Mengkai Cai
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Junming Huang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Dexin Bu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Zhiqing Yu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Xinliang Fu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Chihai Ji
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Pei Zhou
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Comprehensive Prevention and Control for Severe Clinical Animal Diseases of Guangdong Province, Guangzhou, China.
| | - Guihong Zhang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China; Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China.
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18
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Zhu W, Zhang H, Xiang X, Zhong L, Yang L, Guo J, Xie Y, Li F, Deng Z, Feng H, Huang Y, Hu S, Xu X, Zou X, Li X, Bai T, Chen Y, Li Z, Li J, Shu Y. Reassortant Eurasian Avian-Like Influenza A(H1N1) Virus from a Severely Ill Child, Hunan Province, China, 2015. Emerg Infect Dis 2018; 22:1930-1936. [PMID: 27767007 PMCID: PMC5088044 DOI: 10.3201/eid2211.160181] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Infectivity and virulence of this virus in mice are higher than for previous human-origin Eurasian avian–like viruses. In 2015, a novel influenza A(H1N1) virus was isolated from a boy in China who had severe pneumonia. The virus was a genetic reassortant of Eurasian avian-like influenza A(H1N1) (EA-H1N1) virus. The hemagglutinin, neuraminidase, and matrix genes of the reassortant virus were highly similar to genes in EA-H1N1 swine influenza viruses, the polybasic 1 and 2, polymerase acidic, and nucleoprotein genes originated from influenza A(H1N1)pdm09 virus, and the nonstructural protein gene derived from classical swine influenza A(H1N1) (CS H1N1) virus. In a mouse model, the reassortant virus, termed influenza A/Hunan/42443/2015(H1N1) virus, showed higher infectivity and virulence than another human EA-H1N1 isolate, influenza A/Jiangsu/1/2011(H1N1) virus. In the respiratory tract of mice, virus replication by influenza A/Hunan/42443/2015(H1N1) virus was substantially higher than that by influenza A/Jiangsu/1/2011(H1N1) virus. Human-to-human transmission of influenza A/Hunan/42443/2015(H1N1) virus has not been detected; however, given the circulation of novel EA-H1N1 viruses in pigs, enhanced surveillance should be instituted among swine and humans.
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MESH Headings
- Animals
- Cell Line
- China/epidemiology
- Genes, Viral
- History, 21st Century
- Humans
- Infant
- Influenza A Virus, H1N1 Subtype/classification
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/isolation & purification
- Influenza A Virus, H1N1 Subtype/pathogenicity
- Influenza, Human/diagnosis
- Influenza, Human/epidemiology
- Influenza, Human/history
- Influenza, Human/virology
- Multilocus Sequence Typing
- Phylogeny
- RNA, Viral
- Reassortant Viruses
- Serologic Tests
- Severity of Illness Index
- Virulence
- Virus Replication
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19
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Construction and comparison of different source neuraminidase candidate vaccine strains for human infection with Eurasian avian-like influenza H1N1 virus. Microbes Infect 2017; 19:635-640. [DOI: 10.1016/j.micinf.2017.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/10/2017] [Accepted: 08/22/2017] [Indexed: 11/21/2022]
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20
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Wu Y, Yang D, Xu B, Liang W, Sui J, Chen Y, Yang H, Chen H, Wei P, Qiao C. Immune efficacy of an adenoviral vector-based swine influenza vaccine against antigenically distinct H1N1 strains in mice. Antiviral Res 2017; 147:29-36. [PMID: 28941982 DOI: 10.1016/j.antiviral.2017.09.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 09/14/2017] [Accepted: 09/18/2017] [Indexed: 01/24/2023]
Abstract
Avian-like H1N1 swine influenza viruses are prevalent in pigs and have occasionally crossed the species barrier and infected humans, which highlights the importance of preventing swine influenza. Human adenovirus serotype 5 (Ad5) has been tested in human influenza vaccine clinical trials and has exhibited a reliable safety profile. Here, we generated a replication-defective, recombinant adenovirus (designated as rAd5-avH1HA) expressing the hemagglutinin gene of an avian-like H1N1 virus (A/swine/Zhejiang/199/2013, ZJ/199/13). Using a BALB/c mouse model, we showed that a two-dose intramuscular administration of recombinant rAd5-avH1HA induced high levels of hemagglutination inhibition antibodies and prevented homologous and heterologous H1N1 virus-induced weight loss, as well as viral replication in the nasal turbinates and lungs of mice. Furthermore, a prime-boost immunization strategy trial with a recombinant plasmid (designated as pCAGGS-HA) followed by rAd5-avH1HA vaccine provided effective protection against homologous and heterologous H1N1 virus infection in mice. These results indicate that rAd5-avH1HA is an efficacious genetically engineered vaccine candidate against H1N1 swine influenza. Future studies should examine its immune efficacy in pigs.
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MESH Headings
- Adenoviridae/genetics
- Animals
- Antibodies, Viral/blood
- Antigens, Viral/immunology
- Cross Protection
- Hemagglutination Inhibition Tests
- Hemagglutinin Glycoproteins, Influenza Virus/genetics
- Hemagglutinin Glycoproteins, Influenza Virus/immunology
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/immunology
- Influenza Vaccines/administration & dosage
- Influenza Vaccines/genetics
- Influenza Vaccines/immunology
- Influenza Vaccines/standards
- Lung/virology
- Mice
- Mice, Inbred BALB C
- Orthomyxoviridae Infections/prevention & control
- Swine
- Swine Diseases/prevention & control
- Turbinates/virology
- Vaccines, Synthetic/administration & dosage
- Vaccines, Synthetic/genetics
- Vaccines, Synthetic/immunology
- Virus Shedding
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Affiliation(s)
- Yunpu Wu
- College of Veterinary Medicine, Northeast Agricultural University, Harbin 150030, China; State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Dawei Yang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Bangfeng Xu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Wenhua Liang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Jinyu Sui
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Yan Chen
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Huanliang Yang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Hualan Chen
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China
| | - Ping Wei
- College of Veterinary Medicine, Northeast Agricultural University, Harbin 150030, China.
| | - Chuanling Qiao
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150069, China.
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21
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Cui JA, Chen F, Fan S. Effect of Intermediate Hosts on Emerging Zoonoses. Vector Borne Zoonotic Dis 2017; 17:599-609. [PMID: 28678630 DOI: 10.1089/vbz.2016.2059] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Most emerging zoonotic pathogens originate from animals. They can directly infect humans through natural reservoirs or indirectly through intermediate hosts. As a bridge, an intermediate host plays different roles in the transmission of zoonotic pathogens. In this study, we present three types of pathogen transmission to evaluate the effect of intermediate hosts on emerging zoonotic diseases in human epidemics. These types are identified as follows: TYPE 1, pathogen transmission without an intermediate host for comparison; TYPE 2, pathogen transmission with an intermediate host as an amplifier; and TYPE 3, pathogen transmission with an intermediate host as a vessel for genetic variation. In addition, we established three mathematical models to elucidate the mechanisms underlying zoonotic disease transmission according to these three types. Stability analysis indicated that the existence of intermediate hosts increased the difficulty of controlling zoonotic diseases because of more difficult conditions to satisfy for the disease to die out. The human epidemic would die out under the following conditions: TYPE 1: [Formula: see text] and [Formula: see text]; TYPE 2: [Formula: see text], [Formula: see text], and [Formula: see text]; and TYPE 3: [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] Simulation with similar parameters demonstrated that intermediate hosts could change the peak time and number of infected humans during a human epidemic; intermediate hosts also exerted different effects on controlling the prevalence of a human epidemic with natural reservoirs in different periods, which is important in addressing problems in public health. Monitoring and controlling the number of natural reservoirs and intermediate hosts at the right time would successfully manage and prevent the prevalence of emerging zoonoses in humans.
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Affiliation(s)
- Jing-An Cui
- School of Science, Beijing University of Civil Engineering and Architecture , Beijing, China
| | - Fangyuan Chen
- School of Science, Beijing University of Civil Engineering and Architecture , Beijing, China
| | - Shengjie Fan
- School of Science, Beijing University of Civil Engineering and Architecture , Beijing, China
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22
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Nieto A, Pozo F, Vidal-García M, Omeñaca M, Casas I, Falcón A. Identification of Rare PB2-D701N Mutation from a Patient with Severe Influenza: Contribution of the PB2-D701N Mutation to the Pathogenicity of Human Influenza. Front Microbiol 2017; 8:575. [PMID: 28421062 PMCID: PMC5376584 DOI: 10.3389/fmicb.2017.00575] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 03/20/2017] [Indexed: 11/13/2022] Open
Abstract
Several amino acid changes have been previously implicated in adaptation of avian influenza viruses to human hosts, among them the D701N change in the PB2 polymerase subunit that also is the main determinant of avian virus pathogenesis in animal models. However, previous studies using recombinant viruses did not provide conclusive information of the contribution of this PB2 residue to pathogenicity in human influenza virus strains. We identified this mutation in an A(H1N1)pdm09-like human influenza virus isolated from an infected patient with pneumonia and acute respiratory failure, admitted to the intensive care unit. An exhaustive search has revealed PB2-D701 as a highly conserved position in all available H1N1 human virus sequences in NCBI database, showing a very low prevalence of PB2-D701N change. Presence of PB2-701N amino acid correlates with severe or fatal outcome in those scarce cases with known disease outcome of the infection. In these patients, the residue PB2-701N may contribute to pathogenicity as it was previously reported in humans infected with avian viruses. This study helps to clarify a debate that has arisen regarding the role of PB2-D701N in human influenza virus pathogenicity.
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Affiliation(s)
- Amelia Nieto
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones CientíficasMadrid, Spain.,Ciber de Enfermedades Respiratorias (CIBERES), MadridSpain
| | - Francisco Pozo
- National Influenza Center, Centro Nacional de Microbiología, Instituto de Salud Carlos IIIMadrid, Spain
| | | | - Manuel Omeñaca
- Servicio de Microbiología, Hospital Universitario Miguel ServetZaragoza, Spain
| | - Inmaculada Casas
- National Influenza Center, Centro Nacional de Microbiología, Instituto de Salud Carlos IIIMadrid, Spain
| | - Ana Falcón
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones CientíficasMadrid, Spain.,Ciber de Enfermedades Respiratorias (CIBERES), MadridSpain
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23
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Li Y, Xu J, Shi W, Chen C, Shao Y, Zhu L, Lu W, Han X. Mesenchymal stromal cell treatment prevents H9N2 avian influenza virus-induced acute lung injury in mice. Stem Cell Res Ther 2016; 7:159. [PMID: 27793190 PMCID: PMC5084318 DOI: 10.1186/s13287-016-0395-z] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 08/03/2016] [Accepted: 08/24/2016] [Indexed: 12/25/2022] Open
Abstract
Background The avian influenza virus (AIV) can cross species barriers and expand its host range from birds to mammals, even humans. Avian influenza is characterized by pronounced activation of the proinflammatory cytokine cascade, which perpetuates the inflammatory response, leading to persistent systemic inflammatory response syndrome and pulmonary infection in animals and humans. There are currently no specific treatment strategies for avian influenza. Methods We hypothesized that mesenchymal stromal cells (MSCs) would have beneficial effects in the treatment of H9N2 AIV-induced acute lung injury in mice. Six- to 8-week-old C57BL/6 mice were infected intranasally with 1 × 104 MID50 of A/HONG KONG/2108/2003 [H9N2 (HK)] H9N2 virus to induce acute lung injury. After 30 min, syngeneic MSCs were delivered through the caudal vein. Three days after infection, we measured the survival rate, lung weight, arterial blood gas, and cytokines in both bronchoalveolar lavage fluid (BALF) and serum, and assessed pathological changes to the lungs. Results MSC administration significantly palliated H9N2 AIV-induced pulmonary inflammation by reducing chemokines and proinflammatory cytokines levels, as well as reducing inflammatory cell recruit into the lungs. Thus, H9N2 AIV-induced lung injury was markedly alleviated in mice treated with MSCs. Lung histopathology and arterial blood gas analysis were improved in mice with H9N2 AIV-induced lung injury following MSC treatment. Conclusions MSC treatment significantly reduces H9N2 AIV-induced acute lung injury in mice and is associated with reduced pulmonary inflammation. These results indicate a potential role for MSC therapy in the treatment of clinical avian influenza.
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Affiliation(s)
- Yan Li
- Department of Chronic Communicable Disease, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China.,Medical School, Nanjing University, Nanjing, Jiangsu, 210093, People's Republic of China
| | - Jun Xu
- Institute of Toxicology & Functional Assessment, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China
| | - Weiqing Shi
- Institute of Toxicology & Functional Assessment, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China
| | - Cheng Chen
- Department of Chronic Communicable Disease, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China
| | - Yan Shao
- Department of Chronic Communicable Disease, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China
| | - Limei Zhu
- Department of Chronic Communicable Disease, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China
| | - Wei Lu
- Department of Chronic Communicable Disease, Jiangsu Provincial Center for Disease Prevention and Control, Nanjing, 210009, People's Republic of China.
| | - XiaoDong Han
- Medical School, Nanjing University, Nanjing, Jiangsu, 210093, People's Republic of China.
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24
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Transmission and pathogenicity of novel reassortants derived from Eurasian avian-like and 2009 pandemic H1N1 influenza viruses in mice and guinea pigs. Sci Rep 2016; 6:27067. [PMID: 27252023 PMCID: PMC4890009 DOI: 10.1038/srep27067] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 04/20/2016] [Indexed: 11/08/2022] Open
Abstract
Given the present extensive co-circulation in pigs of Eurasian avian-like (EA) swine H1N1 and 2009 pandemic (pdm/09) H1N1 viruses, reassortment between them is highly plausible but largely uncharacterized. Here, experimentally co-infected pigs with a representative EA virus and a pdm/09 virus yielded 55 novel reassortant viruses that could be categorized into 17 genotypes from Gt1 to Gt17 based on segment segregation. Majority of novel reassortants were isolated from the lower respiratory tract. Most of reassortant viruses were more pathogenic and contagious than the parental EA viruses in mice and guinea pigs. The most transmissible reassortant genotypes demonstrated in guinea pigs (Gt2, Gt3, Gt7, Gt10 and Gt13) were also the most lethal in mice. Notably, nearly all these highly virulent reassortants (all except Gt13) were characterized with possession of EA H1 and full complement of pdm/09 ribonucleoprotein genes. Compositionally, we demonstrated that EA H1-222G contributed to virulence by its ability to bind avian-type sialic acid receptors, and that pdm/09 RNP conferred the most robust polymerase activity to reassortants. The present study revealed high reassortment compatibility between EA and pdm/09 viruses in pigs, which could give rise to progeny reassortant viruses with enhanced virulence and transmissibility in mice and guinea pig models.
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25
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Prevalence, genetics, and transmissibility in ferrets of Eurasian avian-like H1N1 swine influenza viruses. Proc Natl Acad Sci U S A 2015; 113:392-7. [PMID: 26711995 DOI: 10.1073/pnas.1522643113] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Pigs are important intermediate hosts for generating novel influenza viruses. The Eurasian avian-like H1N1 (EAH1N1) swine influenza viruses (SIVs) have circulated in pigs since 1979, and human cases associated with EAH1N1 SIVs have been reported in several countries. However, the biologic properties of EAH1N1 SIVs are largely unknown. Here, we performed extensive influenza surveillance in pigs in China and isolated 228 influenza viruses from 36,417 pigs. We found that 139 of the 228 strains from pigs in 10 provinces in China belong to the EAH1N1 lineage. These viruses formed five genotypes, with two distinct antigenic groups, represented by A/swine/Guangxi/18/2011 and A/swine/Guangdong/104/2013, both of which are antigenically and genetically distinct from the current human H1N1 viruses. Importantly, the EAH1N1 SIVs preferentially bound to human-type receptors, and 9 of the 10 tested viruses transmitted in ferrets by respiratory droplet. We found that 3.6% of children (≤10 y old), 0% of adults, and 13.4% of elderly adults (≥60 y old) had neutralization antibodies (titers ≥40 in children and ≥80 in adults) against the EAH1N1 A/swine/Guangxi/18/2011 virus, but none of them had such neutralization antibodies against the EAH1N1 A/swine/Guangdong/104/2013 virus. Our study shows the potential of EAH1N1 SIVs to transmit efficiently in humans and suggests that immediate action is needed to prevent the efficient transmission of EAH1N1 SIVs to humans.
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26
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Krammer F. Emerging influenza viruses and the prospect of a universal influenza virus vaccine. Biotechnol J 2015; 10:690-701. [PMID: 25728134 DOI: 10.1002/biot.201400393] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 01/06/2015] [Accepted: 02/03/2015] [Indexed: 11/07/2022]
Abstract
Influenza viruses cause annual seasonal epidemics and pandemics at irregular intervals. Several cases of human infections with avian and swine influenza viruses have been detected recently, warranting enhanced surveillance and the development of more effective countermeasures to address the pandemic potential of these viruses. The most effective countermeasure against influenza virus infection is the use of prophylactic vaccines. However, vaccines that are currently in use for seasonal influenza viruses have to be re-formulated and re-administered in a cumbersome process every year due to the antigenic drift of the virus. Furthermore, current seasonal vaccines are ineffective against novel pandemic strains. This paper reviews zoonotic influenza viruses with pandemic potential and technological advances towards better vaccines that induce broad and long lasting protection from influenza virus infection. Recent efforts have focused on the development of broadly protective/universal influenza virus vaccines that can provide immunity against drifted seasonal influenza virus strains but also against potential pandemic viruses.
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Affiliation(s)
- Florian Krammer
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
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27
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Wang DY, Qi SX, Li XY, Guo JF, Tan MJ, Han GY, Liu YF, Lan Y, Yang L, Huang WJ, Cheng YH, Zhao X, Bai T, Wang Z, Wei HJ, Xiao N, Shu YL. Human infection with Eurasian avian-like influenza A(H1N1) virus, China. Emerg Infect Dis 2014; 19:1709-11. [PMID: 24050834 PMCID: PMC3810748 DOI: 10.3201/eid1910.130420] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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28
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Prevalence of antibodies to European porcine influenza viruses in humans living in high pig density areas of Germany. Med Microbiol Immunol 2013; 203:13-24. [PMID: 24013183 DOI: 10.1007/s00430-013-0309-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 08/16/2013] [Indexed: 01/29/2023]
Abstract
The risk of zoonotic human infection caused by European porcine influenza virus strains was estimated in German regions with a high pig density. Sera from 622 healthy volunteers were collected between April 2009 and November 2011, mainly in Westphalia and western Lower Saxony. These included 362 subjects with occupational contact to pigs and 260 blood donors without any direct exposition to pigs. Samples were analysed by the haemagglutination inhibition (HI) assay against a panel of six swine viruses of subtypes avian-like H1N1 and human-like H3N2 as well as against human H1N1 and H3N2 viruses including the pandemic H1N1 strain of 2009. Reciprocal HI titres ≥20 were quoted as seroreactive. Compared to the control group, a significantly higher proportion of subjects with direct contact to pigs exhibited seroreactivity against porcine antigens of the avian-like H1N1 (37.0 %/7.7 %), the human-like H3N2 (59.7 %/43.1 %), the pandemic H1N1 strain of 2009 (51.7 %/26.5 %) and against a historic seasonal H3N2 strain that is closely related antigenetically to currently circulating human-like H3N2 viruses of European pigs (57.5 %/36.5 %). This trend was also observed when a reciprocal HI titre ≥40 was chosen as cut-off. Particularly, in younger subjects, the differences in seroreactivity against porcine strains between the exposed and non-exposed group were significant. The data indicate a higher risk of infection in the exposed individuals.
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