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Lei H, Lu X, Li S, Ren Y. High immune efficacy against different avian influenza H5N1 viruses due to oral administration of a Saccharomyces cerevisiae-based vaccine in chickens. Sci Rep 2021; 11:8977. [PMID: 33903693 PMCID: PMC8076243 DOI: 10.1038/s41598-021-88413-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 04/12/2021] [Indexed: 01/18/2023] Open
Abstract
A safe and effective vaccine is the best way to control large-scale highly pathogenic avian influenza virus (HPAI) A (H5N1) outbreaks. Saccharomyces cerevisiae (S. cerevisiae) is an ideal mucosal delivery vector for vaccine development, and we have previously shown that conventional administration of a S. cerevisiae-based vaccine (EBY100/pYD1-HA) via injection led to protection against the homologous H5N1 virus in a mouse model. Because the diameter of S. cerevisiae is approximately 10 μm, which results in a severe inflammation by injection route, therefore, oral administration is a more suitable approach for EBY100/pYD1-HA conferring protection in poultry. We extended our work by evaluating the immunogenicity and protective efficacy of oral vaccination with EBY100/pYD1-HA in the chicken model. Oral immunization with EBY100/pYD1-HA could induce robust serum IgG, mucosal IgA and cellular immune responses. Importantly, EBY100/pYD1-HA provided protection against challenges with a homologous and a heterologous H5N1 viruses. These findings suggest that EBY100/pYD1-HA, a promising H5N1 oral vaccine candidate, can avoid potential reassortment of other avian influenza viruses in oral administration of live virus vaccines and overcome the limitations of conventional injection routes. Importantly, this platform will be able to provide opportunities for broader applications in poultry during HPAI A (H5N1) outbreaks.
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Affiliation(s)
- Han Lei
- College of Medicine, Southwest Jiaotong University, Chengdu, Sichuan, China.
| | - Xin Lu
- College of Medicine, Southwest Jiaotong University, Chengdu, Sichuan, China
| | - Shuangqin Li
- College of Medicine, Southwest Jiaotong University, Chengdu, Sichuan, China
| | - Yi Ren
- College of Medicine, Southwest Jiaotong University, Chengdu, Sichuan, China
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2
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Naguib MM, Verhagen JH, Mostafa A, Wille M, Li R, Graaf A, Järhult JD, Ellström P, Zohari S, Lundkvist Å, Olsen B. Global patterns of avian influenza A (H7): virus evolution and zoonotic threats. FEMS Microbiol Rev 2019; 43:608-621. [PMID: 31381759 PMCID: PMC8038931 DOI: 10.1093/femsre/fuz019] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 07/31/2019] [Indexed: 01/16/2023] Open
Abstract
Avian influenza viruses (AIVs) continue to impose a negative impact on animal and human health worldwide. In particular, the emergence of highly pathogenic AIV H5 and, more recently, the emergence of low pathogenic AIV H7N9 have led to enormous socioeconomical losses in the poultry industry and resulted in fatal human infections. While H5N1 remains infamous, the number of zoonotic infections with H7N9 has far surpassed those attributed to H5. Despite the clear public health concerns posed by AIV H7, it is unclear why specifically this virus subtype became endemic in poultry and emerged in humans. In this review, we bring together data on global patterns of H7 circulation, evolution and emergence in humans. Specifically, we discuss data from the wild bird reservoir, expansion and epidemiology in poultry, significant increase in their zoonotic potential since 2013 and genesis of highly pathogenic H7. In addition, we analysed available sequence data from an evolutionary perspective, demonstrating patterns of introductions into distinct geographic regions and reassortment dynamics. The integration of all aspects is crucial in the optimisation of surveillance efforts in wild birds, poultry and humans, and we emphasise the need for a One Health approach in controlling emerging viruses such as AIV H7.
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Affiliation(s)
- Mahmoud M Naguib
- Zoonosis Science Center, Department of Medical Biochemistry and Microbiology, Husargatan 3, Uppsala University, Uppsala SE-75237, Sweden
- National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, 7 Nadi El-Seid Street, Giza 12618, Egypt
| | - Josanne H Verhagen
- Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, 44008 Hus Vita, Kalmar SE-391 82 , Sweden
| | - Ahmed Mostafa
- Institute of Medical Virology, Justus Liebig University Giessen, Schubertstrasse 81, Giessen 35392, Germany
- Center of Scientific Excellence for Influenza Viruses, National Research Centre (NRC), 33 El-Buhouth street, Giza 12622, Egypt
| | - Michelle Wille
- WHO Collaborating Centre for Reference and Research on Influenza, The Peter Doherty Institute for Infection and Immunity, 792 Elizabeth Street, Melbourne 3000, Victoria, Australia
| | - Ruiyun Li
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, Praed Street, London W2 1PG, United Kingdom
| | - Annika Graaf
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut, Südufer 10, Greifswald-Insel Riems 17493, Germany
| | - Josef D Järhult
- Zoonosis Science Center, Department of Medical Sciences, Uppsala University, Sjukhusvägen 85, Uppsala SE-75185, Sweden
| | - Patrik Ellström
- Zoonosis Science Center, Department of Medical Sciences, Uppsala University, Sjukhusvägen 85, Uppsala SE-75185, Sweden
| | - Siamak Zohari
- Department of Microbiology, National Veterinary Institute, Ulls väg 2B, Uppsala SE-75189, Sweden
| | - Åke Lundkvist
- Zoonosis Science Center, Department of Medical Biochemistry and Microbiology, Husargatan 3, Uppsala University, Uppsala SE-75237, Sweden
| | - Björn Olsen
- Zoonosis Science Center, Department of Medical Sciences, Uppsala University, Sjukhusvägen 85, Uppsala SE-75185, Sweden
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3
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Goossens KE, Ward AC, Lowenthal JW, Bean AGD. Chicken interferons, their receptors and interferon-stimulated genes. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2013; 41:370-376. [PMID: 23751330 DOI: 10.1016/j.dci.2013.05.020] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 05/31/2013] [Accepted: 05/31/2013] [Indexed: 06/02/2023]
Abstract
The prevalence of pathogenic viruses is a serious issue as they pose a constant threat to both the poultry industry and to human health. To prevent these viral infections an understanding of the host-virus response is critical, especially for the development of novel therapeutics. One approach in the control of viral infections would be to boost the immune response through administration of cytokines, such as interferons. However, the innate immune response in chickens is poorly characterised, particularly concerning the interferon pathway. This review will provide an overview of our current understanding of the interferon system of chickens, including their cognate receptors and known interferon-stimulated gene products.
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Affiliation(s)
- Kate E Goossens
- CSIRO Biosecurity Flagship, Australian Animal Health Laboratories, Geelong, VIC, Australia
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4
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Abdelwhab ESM, Veits J, Mettenleiter TC. Genetic changes that accompanied shifts of low pathogenic avian influenza viruses toward higher pathogenicity in poultry. Virulence 2013; 4:441-52. [PMID: 23863606 PMCID: PMC5359749 DOI: 10.4161/viru.25710] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 07/09/2013] [Accepted: 07/10/2013] [Indexed: 11/19/2022] Open
Abstract
Avian influenza viruses (AIV) of H5 and H7 subtypes exhibit two different pathotypes in poultry: infection with low pathogenic (LP) strains results in minimal, if any, health disturbances, whereas highly pathogenic (HP) strains cause severe morbidity and mortality. LPAIV of H5 and H7 subtypes can spontaneously mutate into HPAIV. Ten outbreaks caused by HPAIV are known to have been preceded by circulation of a predecessor LPAIV in poultry. Three of them were caused by H5N2 subtype and seven involved H7 subtype in combination with N1, N3, or N7. Here, we review those outbreaks and summarize the genetic changes which resulted in the transformation of LPAIV to HPAIV under natural conditions. Mutations that were found directly in those outbreaks are more likely to be linked to virulence, pathogenesis, and early adaptation of AIV.
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Affiliation(s)
- El-Sayed M Abdelwhab
- Friedrich-Loeffler-Institut; Federal Research Institute for Animal Health; Institute of Molecular Biology; Greifswald-Insel Riems, Germany
| | - Jutta Veits
- Friedrich-Loeffler-Institut; Federal Research Institute for Animal Health; Institute of Molecular Biology; Greifswald-Insel Riems, Germany
| | - Thomas C Mettenleiter
- Friedrich-Loeffler-Institut; Federal Research Institute for Animal Health; Institute of Molecular Biology; Greifswald-Insel Riems, Germany
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5
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Wang B, Liu B, Chen L, Zhang J, He H, Zhang H. Qualitative and quantitative analyses of influenza virus receptors in trachea and lung tissues of humans, mice, chickens and ducks. SCIENCE CHINA-LIFE SCIENCES 2012; 55:612-7. [PMID: 22864835 DOI: 10.1007/s11427-012-4341-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 04/11/2012] [Indexed: 01/16/2023]
Abstract
To accurately determine the expression and distribution patterns of two influenza virus receptors (SAα2,3-gal and SAα2,6-gal) in trachea and lung tissues of humans, mice, chickens and ducks, we analyzed lectin immunofluorescence stainings of various tissue sections qualitatively and quantitatively. Results from the qualitative analysis showed that both influenza virus receptors were expressed in lung tissues of humans, mice, chickens and ducks as well as trachea tissues of mice and ducks. However, SAα2,6-gal receptor was expressed only in the human trachea tissue and SAα2,3-gal receptor was expressed only in the chicken trachea tissue. Results from the quantitative analysis demonstrated that both receptors were expressed in trachea tissues of human and mouse, as well as in lung tissues of humans, chickens and ducks. Meanwhile, our results also showed that the expression and distribution of influenza virus receptors in the same tissue were not always uniform, indicating that their distribution and expression in various tissues are not simply the distinction between the presence or absence of receptors, but rather the difference in the amount of expressed receptors.
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Affiliation(s)
- Baolin Wang
- Laboratory of Respiratory Medicine, Department of Respiratory Medicine, Affiliated Hospital of Zunyi Medical College, Zunyi 563003, China
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6
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Lai JM, Hwang YT, Chou CC. Modeling exotic highly pathogenic avian influenza virus entrance risk through air passenger violations. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2012; 32:1093-1103. [PMID: 22150450 DOI: 10.1111/j.1539-6924.2011.01740.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The highly pathogenic avian influenza virus (HPAIV) is able to survive in poultry products and could be carried into a country by air travelers. An assessment model was constructed to estimate the probability of the exotic viable HPAIV entering Taiwan from two neighboring areas through poultry products carried illegally by air passengers at Taiwan's main airports. The entrance risk was evaluated based on HPAIV-related factors (the prevalence and the incubation period of HPAIV; the manufacturing process of poultry products; and the distribution-storage-transportation factor event) and the passenger event. Distribution functions were adopted to simulate the probabilities of each HPAIV factor. The odds of passengers being intercepted with illegal poultry products were estimated by logistic regression. The Monte Carlo simulation established that the risk caused by HPAIV-related factors from area A was lower than area B, whereas the entrance risk by the passenger event from area A was similar to area B. Sensitivity analysis showed that the incubation period of HPAIV and the interception of passenger violations were major determinants. Although the result showed viable HPAIV was unlikely to enter Taiwan through meat illegally carried by air passengers, this low probability could be caused by incomplete animal disease data and modeling uncertainties. Considering the negative socioeconomic impacts of HPAIV outbreaks, strengthening airport quarantine measures is still necessary. This assessment provides a profile of HPAIV entrance risk through air travelers arriving from endemic areas and a feasible direction for quarantine and public health measures.
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Affiliation(s)
- Jyh-Mirn Lai
- Department of Veterinary Medicine, National Chiayi University, Chiayi 600, Taiwan
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7
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Yongolo MG, Christensen H, Handberg K, Minga U, Olsen JE. On the origin and diversity of Newcastle disease virus in Tanzania. ACTA ACUST UNITED AC 2011; 78:312. [PMID: 23327213 DOI: 10.4102/ojvr.v78i1.312] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 05/19/2011] [Accepted: 04/08/2011] [Indexed: 11/01/2022]
Abstract
Free-range rural chickens (FRCs) dominate the poultry industry in developing countries and chickens are exposed to multi-host infections, including Newcastle disease virus (NDV). The knowledge about the characteristics of NDV from FRCs is limited. This study investigated the persistence, spread and risks of NDV from FRCs. NDV isolates (n = 21) from unvaccinated FRCs in Tanzania were characterised by conventional intracerebral pathogenicity index (ICPI) and sequence analysis of a partial region of the deduced fusion protein encompassing the cleavage site. Results showed that five isolates were screened as lentogenic, nine as mesogenic and six as velogenic. Phylogenetic analysis of the 21 isolates compared to reference sequences revealed three, four, nine and five isolates in genotypes 1, 2, 3c and 4a, respectively. Genotype 3c also included published sequences of Tanzanian isolates obtained from exotic birds and chicken isolates from Uganda. The analysis showed that NDV were persistently present among chicken populations and possibly spread through live chicken markets or migration of wild birds. Differences in amino acid sequences detected around the cleavage site separated the isolates in six types. However, cleavage site pattern could not fully differentiate mesogenic isolates from velogenic isolates.
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Affiliation(s)
- Mmeta G Yongolo
- Department of Veterinary Disease Biology, University of Copenhagen.
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8
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Zhang Y, Lin X, Wang G, Zhou J, Lu J, Zhao H, Zhang F, Wu J, Xu C, Du N, Li Z, Zhang Y, Wang X, Bi S, Shu Y, Zhou H, Tan W, Wu X, Chen Z, Wang Y. Neuraminidase and hemagglutinin matching patterns of a highly pathogenic avian and two pandemic H1N1 influenza A viruses. PLoS One 2010; 5:e9167. [PMID: 20161801 PMCID: PMC2820099 DOI: 10.1371/journal.pone.0009167] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Accepted: 01/23/2010] [Indexed: 01/21/2023] Open
Abstract
Background Influenza A virus displays strong reassortment characteristics, which enable it to achieve adaptation in human infection. Surveying the reassortment and virulence of novel viruses is important in the prevention and control of an influenza pandemic. Meanwhile, studying the mechanism of reassortment may accelerate the development of anti-influenza strategies. Methodology/Principal Findings The hemagglutinin (HA) and neuraminidase (NA) matching patterns of two pandemic H1N1 viruses (the 1918 and current 2009 strains) and a highly pathogenic avian influenza A virus (H5N1) were studied using a pseudotyped particle (pp) system. Our data showed that four of the six chimeric HA/NA combinations could produce infectious pps, and that some of the chimeric pps had greater infectivity than did their ancestors, raising the possibility of reassortment among these viruses. The NA of H5N1 (A/Anhui/1/2005) could hardly reassort with the HAs of the two H1N1 viruses. Many biological characteristics of HA and NA, including infectivity, hemagglutinating ability, and NA activity, are dependent on their matching pattern. Conclusions/Significance Our data suggest the existence of an interaction between HA and NA, and the HA NA matching pattern is critical for valid viral reassortment.
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MESH Headings
- Animals
- Birds
- Blotting, Western
- Cell Line
- Cell Line, Tumor
- Disease Outbreaks
- Hemagglutinin Glycoproteins, Influenza Virus/genetics
- Hemagglutinin Glycoproteins, Influenza Virus/metabolism
- Humans
- Influenza A Virus, H5N1 Subtype/genetics
- Influenza A Virus, H5N1 Subtype/metabolism
- Influenza A Virus, H5N1 Subtype/pathogenicity
- Influenza in Birds/epidemiology
- Influenza in Birds/virology
- Influenza, Human/epidemiology
- Influenza, Human/virology
- Neuraminidase/genetics
- Neuraminidase/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Reassortant Viruses/genetics
- Reassortant Viruses/metabolism
- Reassortant Viruses/pathogenicity
- Reverse Transcriptase Polymerase Chain Reaction
- Viral Proteins/genetics
- Viral Proteins/metabolism
- Virion/genetics
- Virion/metabolism
- Virion/pathogenicity
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Affiliation(s)
- Yonghui Zhang
- Institute of Pathogens and Vectors, Dali University, Dali, China
| | - Xiaojing Lin
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Guoqin Wang
- Kitasato Clinical Research Center, School of Medicine, Kitasato University, Sagamihara, Japan
| | - Jianfang Zhou
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jian Lu
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Honglan Zhao
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Fengwei Zhang
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Jia Wu
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Chunqiong Xu
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Ning Du
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Zi Li
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Ye Zhang
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Xiaoyi Wang
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Shengli Bi
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Yuelong Shu
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Hongning Zhou
- Institute of Pathogens and Vectors, Dali University, Dali, China
| | - Wenjie Tan
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Xiaobing Wu
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
| | - Zhihui Chen
- Department of Infectious Disease, Changhai Hospital, Second Military Medical University, Shanghai, China
- * E-mail: (YW); (ZC)
| | - Yue Wang
- State Key Laboratory for Molecular Virology and Genetic Engineering, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China
- * E-mail: (YW); (ZC)
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9
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Avian influenza viral nucleocapsid and hemagglutinin proteins induce chicken CD8+ memory T lymphocytes. Virology 2010; 399:231-8. [PMID: 20116819 PMCID: PMC7111969 DOI: 10.1016/j.virol.2009.12.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 12/09/2009] [Accepted: 12/21/2009] [Indexed: 11/24/2022]
Abstract
The avian influenza viruses (AIVs) can be highly contagious to poultry and a zoonotic threat to humans. Since the memory CD8(+) T lymphocyte responses in chickens to AIV proteins have not been defined, these responses to H5N9 AIV hemagglutinin (HA) and nucleocapsid (NP) proteins were evaluated by ex vivo stimulation with virus infected non-professional antigen presenting cells. Secretion of IFNgamma by activated T lymphocytes was evaluated through macrophage induction of nitric oxide. AIV specific, MHC-I restricted memory CD8(+) T lymphocyte responses to NP and HA were observed 3 to 9 weeks post-inoculation (p.i.). The responses specific to NP were greater than those to HA with maximum responses being observed at 5 weeks p.i. followed by a decline to weakly detectable levels by 9 weeks p.i. The cross-reaction of T lymphocytes to a heterologous H7N2 AIV strain demonstrated their ability to respond to a broader range of AIV.
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10
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Tissue and host tropism of influenza viruses: importance of quantitative analysis. ACTA ACUST UNITED AC 2009; 52:1101-10. [PMID: 20016966 DOI: 10.1007/s11427-009-0161-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Accepted: 11/11/2009] [Indexed: 12/30/2022]
Abstract
It is generally accepted that human influenza viruses preferentially bind to cell-surface glycoproteins/glycolipids containing sialic acids in alpha2,6-linkage; while avian and equine influenza viruses preferentially bind to those containing sialic acids in alpha2,3-linkage. Even though this generalized view is accurate for H3 subtype isolates, it may not be accurate and absolute for all subtypes of influenza A viruses and, therefore, needs to be reevaluated carefully and realistically. Some of the studies published in major scientific journals on the subject of tissue tropism of influenza viruses are inconsistent and caused confusion in the scientific community. One of the reasons for the inconsistency is that most studies were quantitative descriptions of sialic acid receptor distributions based on lectin or influenza virus immunohistochemistry results with limited numbers of stained cells. In addition, recent studies indicate that alpha2,3- and alpha2,6-linked sialic acids are not the sole receptors determining tissue and host tropism of influenza viruses. In fact, determinants for tissue and host tropism of human, avian and animal influenza viruses are more complex than what has been generally accepted. Other factors, such as glycan topology, concentration of invading viruses, local density of receptors, lipid raft microdomains, coreceptors or sialic acid-independent receptors, may also be important. To more efficiently control the global spread of pandemic influenza such as the current circulating influenza A H1N1, it is crucial to clarify the determinants for tissue and host tropism of influenza viruses through quantitative analysis of experimental results. In this review, I will comment on some conflicting issues related to tissue and host tropism of influenza viruses, discuss the importance of quantitative analysis of lectin and influenza virus immunohistochemistry results and point out directions for future studies in this area, which should lead to a better understanding of tissue and host tropism of influenza viruses.
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11
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Yoon H, Moon OK, More SJ, Park CK, Park JY, Lee YJ, Lee SD, Ha JK, Jeong SK, Jeong JW, Lee SJ. An outbreak of highly pathogenic avian influenza at a public animal exhibit in seoul, Korea, during 2008. Zoonoses Public Health 2009; 57:142-5. [PMID: 19638167 DOI: 10.1111/j.1863-2378.2009.01235.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This study describes the first recorded outbreak of HPAI in the city of Seoul, in captive birds held in an exhibition for public viewing at a local district office. The index cases were two pheasants, which had been introduced into the exhibit on 24 April, 4 days prior to death, from a store in a local market in Gyeonggi-do. Ducks and chickens from an HPAI outbreak farm, subsequently confirmed on 4 May, had also been held in this store. This outbreak highlights the potential role of local markets in AIV transmission. This outbreak led to considerable public health concern in Korea, however, no human cases were reported. The non-commercial poultry sector needs to be considered in national plans for preparedness and response.
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Affiliation(s)
- H Yoon
- Veterinary Epidemiology Division, National Veterinary Research and Quarantine Service, Anyang, Gyeonggi-do, Republic of Korea.
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12
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Trends of influenza infection in Egypt during two consecutive seasons. J Public Health (Oxf) 2008. [DOI: 10.1007/s10389-008-0236-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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13
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Mohammed SL, Lehmann HP, Kim GR. A proposed taxonomy for characterization and assessment of avian influenza outbreaks. Int J Med Inform 2008; 78:182-92. [PMID: 18805050 DOI: 10.1016/j.ijmedinf.2008.06.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2007] [Revised: 06/28/2008] [Accepted: 06/30/2008] [Indexed: 11/19/2022]
Abstract
PURPOSE The speed and high potential impact of avian influenza's (AI) on local bird populations, poultry economies and human health make timely and coordinated characterization, assessment and response to possible threats essential. To collaborate effectively, stakeholders (public health, medical, veterinary, and agricultural professionals) must be able to communicate and record findings, assessments, and actions in a standard fashion. We seek to discern a taxonomy of concepts and relationships that are important to the stakeholder community when sharing information about the characterization and assessment of an AI outbreak, according to a consistent and common perspective, interpretation, and level of detail. METHODS To derive concepts relevant to AI characterization and assessment, we reviewed selected journal articles, reporting and laboratory forms, and public health websites associated with AI case reporting. We mapped concepts to existing medical terminologies within the Unified Medical Language System when possible, using the National Library of Medicine's MetaMap program. RESULTS From 54 distinct information sources, we extracted 1113 concepts, of which 533 mapped to 15 medical terminologies; 580 did not map to specific terminologies. Using a combination of semantic type-relationship matching and expert consensus, we constructed the proposed taxonomy, with linkages to existing terminologies where pragmatic. CONCLUSION The proposed taxonomy describes core knowledge, data and communication needs for the characterization and assessment of AI outbreaks in the context of existing medical terminologies across different domains. We also describe areas for further work.
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Affiliation(s)
- Sule L Mohammed
- Division of Health Sciences Informatics, School of Medicine, Johns Hopkins University, 2024 East Monument Street, Suite 1-201, Baltimore, MD 21205, USA.
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14
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Furger M, Hoop R, Steinmetz H, Eulenberger U, Hatt JM. Humoral immune response to avian influenza vaccination over a six-month period in different species of captive wild birds. Avian Dis 2008; 52:222-8. [PMID: 18646450 DOI: 10.1637/8111-091707-reg.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In December 2005, the four major Swiss zoos carried out the vaccination of selected zoo birds with the adjuvant inactivated vaccine H5N2 Nobilis influenza. Pre- and post-vaccination antibody titers were determined either by hemagglutination inhibition (HI) test (non-Galliformes) or by enzyme linked immunosorbent assay (ELISA) (Galliformes) at Week 0, 5, 10, and 26 (Day 0-1, 35-36, 70-71, and 182 respectively) to determine the humoral immune response to H5 antigen. After the first vaccination, the overall geometric mean titer of non-Galliformes was 65 (n = 142), which increased to 187 (n = 139) after booster vaccination and dropped to 74 (n = 65) six months after first vaccination. For the Galliformes group, the mean titers were found to be 2.09 at Week 5 (n = 119), 3.24 at Week 10 (n = 113), and 1.20 at Week 26 (n = 39). Within the non-Galliformes, significant differences in geometric mean titers were found among different species representatives. In general, the flamingos (Phoenicopteriformes) showed a strong response to vaccination, reaching a geometric mean titer of 659 at Week 10, while the Sphenisciformes did not show high antibody titers even after booster vaccination, reaching a maximum geometric mean titer of only 65. Based on the antibody titer profiles of all investigated species, we recommend at least annual revaccination for the species that we investigated.
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Affiliation(s)
- Maria Furger
- Clinic of Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
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Smallman-Raynor M, Cliff AD. The Geographical Spread of Avian Influenza A (H5N1): Panzootic Transmission (December 2003–May 2006), Pandemic Potential, and Implications. ACTA ACUST UNITED AC 2008. [DOI: 10.1080/00045600802098958] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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16
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van den Berg T, Lambrecht B, Marché S, Steensels M, Van Borm S, Bublot M. Influenza vaccines and vaccination strategies in birds. Comp Immunol Microbiol Infect Dis 2008; 31:121-65. [PMID: 17889937 DOI: 10.1016/j.cimid.2007.07.004] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2007] [Indexed: 12/21/2022]
Abstract
Although it is well accepted that the present Asian H5N1 panzootic is predominantly an animal health problem, the human health implications and the risk of human pandemic have highlighted the need for more information and collaboration in the field of veterinary and human health. H5 and H7 avian influenza (AI) viruses have the unique property of becoming highly pathogenic (HPAI) during circulation in poultry. Therefore, the final objective of poultry vaccination against AI must be eradication of the virus and the disease. Actually, important differences exist in the control of avian and human influenza viruses. Firstly, unlike human vaccines that must be adapted to the circulating strain to provide adequate protection, avian influenza vaccination provides broader protection against HPAI viruses. Secondly, although clinical protection is the primary goal of human vaccines, poultry vaccination must also stop transmission to achieve efficient control of the disease. This paper addresses these differences by reviewing the current and future influenza vaccines and vaccination strategies in birds.
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Affiliation(s)
- Thierry van den Berg
- Avian Virology & Immunology, Veterinary & Agrochemical Research Centre, 99 Groeselenberg, 1180 Brussels, Belgium.
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17
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Ong WT, Omar AR, Ideris A, Hassan SS. Development of a multiplex real-time PCR assay using SYBR Green 1 chemistry for simultaneous detection and subtyping of H9N2 influenza virus type A. J Virol Methods 2007; 144:57-64. [PMID: 17512062 DOI: 10.1016/j.jviromet.2007.03.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2006] [Revised: 03/21/2007] [Accepted: 03/28/2007] [Indexed: 11/26/2022]
Abstract
Avian influenza viruses are pathogens of economical and public health concerns. However, infections caused by low pathogenic avian influenza particularly H9N2 subtype are not associated with clear clinical features. Hence, rapid detection and subtyping of the virus will enable immediate measures to be implemented for preventing widespread transmission. This study highlights the development of a multiplex real-time reverse-transcriptase polymerase chain reaction (RRT-PCR) assay using SYBR Green 1 chemistry for universal detection of avian influenza viruses and specific subtyping of H9N2 isolates based on melting temperatures (T(m)) discriminations. Three melting peaks generated simultaneously at temperatures 85.2+/-1.0, 81.9+/-0.9 and 78.7+/-0.9 degrees C represent NP, H9 and N2 gene products, respectively. The RRT-PCR assay was about 10-100-fold more sensitive when compared to the conventional RT-PCR method using reference H9N2 isolate. In addition, the RRT-PCR assay was 100% sensitive as well as 92% specific according to the standard virus isolation method in detecting experimentally infected specific-pathogen-free (SPF) chickens.
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Affiliation(s)
- Wee Theng Ong
- Institute of Biosciences, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia
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18
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Yamamoto Y, Nakamura K, Kitagawa K, Ikenaga N, Yamada M, Mase M, Narita M. Severe nonpurulent encephalitis with mortality and feather lesions in call ducks (Anas platyrhyncha var. domestica) inoculated intravenously with H5N1 highly pathogenic avian influenza virus. Avian Dis 2007; 51:52-7. [PMID: 17461267 DOI: 10.1637/0005-2086(2007)051[0052:snewma]2.0.co;2] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
One-day-old, 2-wk-old, and 4-wk-old call ducks (Anas platyrhyncha var. domestica) inoculated intravenously with the H5N1 highly pathogenic avian influenza virus A/chicken/Yamaguchi/7/2004 isolate (Ck/Yama/7/04) were examined clinically, pathologically, and virologically. Clinically, the birds exhibited mild-to-severe neurologic signs and corneal opacity. All birds in the 1-day-old group and one bird in the 4-wk-old group died within 4 days after the virus inoculation. Histologic changes were characterized by severe nonpurulent encephalitis and necrotic lesions of feather epithelium on day 3 postinoculation (PI) or later. Focal necrosis of myocardial cells, pancreatic acinar cells, skeletal myocytes, and corneal epithelial cells was observed. Viral antigens were detected in association with necrotic changes. Viruses were isolated from all examined organs including the skin with many feathers. Serum antibody against the virus was detected in all surviving birds on day 10 PI by hemagglutination-inhibition tests. These results suggest that Ck/Yama/7/04 has a pathogenicity that causes neurologic sign, nonpurulent encephalitis with mortality, and feather lesions for call ducks. Feather lesions with viral antigens and the virus isolation from the skin suggest that Ck/Yama/ 7/04 has a predilection for feathers in call ducks.
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Affiliation(s)
- Yu Yamamoto
- National Institute of Animal Health, Kannondai, Tsukuba, Ibaraki, 305-0856 Japan
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19
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Legastelois I, Garcia-Sastre A, Palese P, Tumpey TM, Maines TR, Katz JM, Vogel FR, Moste C. Preparation of genetically engineered A/H5N1 and A/H7N1 pandemic vaccine viruses by reverse genetics in a mixture of Vero and chicken embryo cells. Influenza Other Respir Viruses 2007; 1:95-104. [PMID: 19453414 PMCID: PMC4941877 DOI: 10.1111/j.1750-2659.2007.00015.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND In case of influenza pandemic, a robust, easy and clean technique to prepare reassortants would be necessary. OBJECTIVES Using reverse genetics, we prepared two vaccine reassortants (A/H5N1 x PR8 and A/H7N1 x PR8) exhibiting the envelope glycoproteins from non-pathogenic avian viruses, A/Turkey/Wisconsin/68 (A/H5N9) and A/Rhea/New Caledonia/39482/93 (A/H7N1) and the internal proteins of the attenuated human virus A/Puerto Rico/8/34 (H1N1). METHODS The transfection was accomplished using a mixture of Vero and chicken embryo cells both of which are currently being used for vaccine manufacturing. RESULTS This process was reproducible, resulting in consistent recovery of influenza viruses in 6 days. Because it is mainly the A/H5N1 strain that has recently crossed the human barrier, it is the A/PR8 x A/H5N1 reassortant (RG5) that was further amplified, either in embryonated hen eggs or Vero cells, to produce vaccine pre-master seed stocks that met quality control specifications. Safety testing in chickens and ferrets was performed to assess the non-virulence of the reassortant, and finally analysis using chicken and ferret sera immunized with the RG5 virus showed that the vaccine candidate elicited an antibody response cross-reactive with the Hong Kong 1997 and 2003 H5N1 strains but not the Vietnam/2004 viruses. CONCLUSIONS The seeds obtained could be used as part of a pandemic vaccine strain 'library' available in case of propagation in humans of a new highly pathogenic avian strain.
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Affiliation(s)
- Isabelle Legastelois
- Research and Development, sanofi pasteur, 1541 Avenue Marcel Mérieux, Marcy L'Etoile, France.
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Toro H, Tang DCC, Suarez DL, Sylte MJ, Pfeiffer J, Van Kampen KR. Protective avian influenza in ovo vaccination with non-replicating human adenovirus vector. Vaccine 2006; 25:2886-91. [PMID: 17055126 PMCID: PMC2736859 DOI: 10.1016/j.vaccine.2006.09.047] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2006] [Revised: 09/06/2006] [Accepted: 09/12/2006] [Indexed: 11/30/2022]
Abstract
Protective immunity against avian influenza virus was elicited in chickens by single-dose in ovo vaccination with a non-replicating human adenovirus vector encoding an H5N9 avian influenza virus hemagglutinin. Vaccinated chickens were protected against both H5N1 (89% hemagglutinin homology; 68% protection) and H5N2 (94% hemagglutinin homology; 100% protection) highly pathogenic avian influenza virus challenges. This vaccine can be mass-administered using available robotic in ovo injectors which provide a major advantage over current vaccination regimens. In addition, this class of adenovirus-vectored vaccines can be produced rapidly with improved safety since they do not contain any replication-competent adenoviruses. Furthermore, this mode of vaccination is compatible with epidemiological surveys of natural avian influenza virus infections.
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Affiliation(s)
- Haroldo Toro
- Department of Pathobiology, Auburn University, Auburn, AL 36849, USA
| | | | - David L. Suarez
- Southeast Poultry Research Laboratory, Athens, GA 30605, USA
| | - Matt J. Sylte
- Southeast Poultry Research Laboratory, Athens, GA 30605, USA
| | | | - Kent R. Van Kampen
- Vaxin Inc., Birmingham, AL 35211, USA
- Corresponding author. Tel.: +1 205 909 3737; fax: +1 205 943 6656. Email address: (K.R. Van Kampen)
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Hernandez-Divers SM, Villegas P, Prieto F, Unda JC, Stedman N, Ritchie B, Carroll R, Hernandez-Divers SJ. A Survey of Selected Avian Pathogens of Backyard Poultry in Northwestern Ecuador. J Avian Med Surg 2006. [DOI: 10.1647/2005-015r.1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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22
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Kent J, Bailey T, Silvanose CD, McKeown S, Wernery U, Kinne J, Manvell R. An outbreak of low pathogenic avian influenza in a mixed-species aviculture unit in Dubai in 2005. Vet Clin North Am Exot Anim Pract 2006; 9:523-31. [PMID: 16931369 DOI: 10.1016/j.cvex.2006.05.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This case describes an outbreak of low pathogenic hemagglutinin 9 neuraminidase 2 avian influenza virus (AIV) in two white-bellied bustards (Eupodotis senegalensis), one stone curlew (Burhinus oedicnemius), and a blacksmith plover (Antibyx armatus) in a private zoologic collection in Dubai, United Arab Emirates. The four birds showed signs of respiratory disease, and all died as a result of disease or euthanasia. Attention has been paid to the diagnostic process and common differential diagnosis for upper respiratory tract disease in bustards, curlews, and plovers. To the knowledge of the authors, AIV has not been previously described in these species.
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Affiliation(s)
- Jo Kent
- The Dubai Falcon Hospital, Dubai, United Arab Emirates.
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23
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Zhou J, Law HKW, Cheung CY, Ng IHY, Peiris JSM, Lau YL. Functional tumor necrosis factor-related apoptosis-inducing ligand production by avian influenza virus-infected macrophages. J Infect Dis 2006; 193:945-53. [PMID: 16518756 PMCID: PMC7109654 DOI: 10.1086/500954] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Accepted: 10/31/2005] [Indexed: 11/29/2022] Open
Abstract
Severe human disease associated with influenza A H5N1 virus was first detected in Hong Kong in 1997. Its recent reemergence in Asia and high associated mortality highlight the need to understand its pathogenesis. We investigated the roles of death receptor ligands (DRLs) in H5N1 infection. Significant up-regulation of tumor necrosis factor (TNF)–related apoptosis-inducing ligand (TRAIL) and TNF-α, but not Fas ligand (FasL) mRNA, was detected in human monocyte–derived macrophages (MDMs) infected with avian influenza viruses A/Hong Kong/483/97 (H5N1/97) or its precursor, A/Quail/Hong Kong/G1/97. H5N1/97-infected MDMs exhibited the strongest induction of apoptosis in Jurkat T cells, and it could be reduced by TRAIL–receptor 2 blocking antibody. Furthermore, influenza virus infection enhanced the sensitivity of Jurkat T cells to apoptosis induced by TNF-α, TRAIL, and FasL. Our data suggested that functional TRAIL produced by influenza virus–infected MDMs was related to their cytotoxicity and that the enhanced sensitization to DRL-induced apoptosis detected in avian influenza may contribute to disease pathogenesis
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Affiliation(s)
- Jianfang Zhou
- Paediatrics and Adolescent Medicine and
- Reprints or correspondence: Dr. Yu Lung Lau, Dept. of Paediatrics and Adolescent Medicine, Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam, Hong Kong SAR, China ()
| | | | - Chung Yan Cheung
- Microbiology, Hong Kong Jockey Club Clinical Research Centre, Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - Iris H. Y. Ng
- Microbiology, Hong Kong Jockey Club Clinical Research Centre, Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
| | - J. S. Malik Peiris
- Microbiology, Hong Kong Jockey Club Clinical Research Centre, Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
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Arino J, Jordan R, van den Driessche P. Quarantine in a multi-species epidemic model with spatial dynamics. Math Biosci 2005; 206:46-60. [PMID: 16343557 DOI: 10.1016/j.mbs.2005.09.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Revised: 08/17/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
Motivation is provided for the development of infectious disease models that incorporate the movement of individuals over a range of spatial scales. A general model is formulated for a disease that can be transmitted between different species and multiple patches, and the behavior of the system is investigated in the case in which the spatial component consists of a ring of patches. The influence of various parameters on the spatial and temporal spread of the disease is studied numerically, with particular focus on the role of quarantine in the form of travel restriction.
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Affiliation(s)
- Julien Arino
- Department of Mathematics and Statistics, McMaster University, Hamilton, ON, Canada L8S 4K7.
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25
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Yoon H, Park CK, Nam HM, Wee SH. Virus Spread Pattern within Infected Chicken Farms using Regression Model: the 2003-2004 HPAI Epidemic in the Republic of Korea. ACTA ACUST UNITED AC 2005; 52:428-31. [PMID: 16364017 DOI: 10.1111/j.1439-0450.2005.00891.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
During the 2003-2004 epidemic in Korea, the infection time and within-farm spread pattern of virus were analysed for the highly pathogenic avian influenza (HPAI) outbreak on chicken farms using regression models based on epidemiological data. Mortality observed on a given day had a positive linear association with time after initial infection. HPAI spread more rapidly on farms managed by employees and on farms with larger numbers of chicken houses in use. The disease spread more rapidly among layer chickens than among broilers. Using statistical model, we found that farmers recognize the abnormally high mortality resulting from HPAI approximately 5 days after infection. Without any intervention, entire flocks would die within 12 days of introduction of the HPAI virus to the infected farm.
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Affiliation(s)
- H Yoon
- Veterinary Epidemiology Division, National Veterinary Research and Quarantine Service, 480 Anyang 6-dong, Manan-gu, Anyang 430-824, Republic of Korea
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Abstract
Les virus émergents ont défrayé la chronique durant les années 2003 et 2004. À cette occasion sont réapparues les peurs antiques concernant l’apparition d’un agent infectieux hautement pathogène, pouvant provoquer des épidémies associées à une mortalité élevée. Ces phénomènes sont clairement des menaces à répétition. L’analyse des mécanismes ayant permis l’apparition de ces virus montre que pour chaque virus émergent décrit, il ne s’agit en aucun cas de phénomènes purement aléatoires, mais bien de l’accumulation de facteurs qui permettent à ces agents infectieux de diffuser de l’animal vers l’homme. Différents modes d’infection existent, soit par transmission directe, soit par l’intermédiaire des vecteurs (moustiques, tiques ou autres animaux). La conjonction de facteurs écologiques, économiques et épidémiologiques font que ces épidémies naissent et éventuellement diffusent. Grâce au développement des réseaux de surveillance et à l’amélioration des techniques diagnostiques, les virus responsables de ces épidémies sont mieux identifiés. Les expériences récentes du SRAS et de la grippe aviaire en sont les meilleurs exemples.
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