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Hu Y, Chen X, Ling Y, Zhou K, Han M, Wang X, Yue M, Li Y. Influenza A virus inhibits TET2 expression by endoribonuclease PA-X to attenuate type I interferon signaling and promote viral replication. PLoS Pathog 2023; 19:e1011550. [PMID: 37498975 PMCID: PMC10409264 DOI: 10.1371/journal.ppat.1011550] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 08/08/2023] [Accepted: 07/10/2023] [Indexed: 07/29/2023] Open
Abstract
Influenza A virus (IAV) expresses several accessory proteins to limit host anti-viral restriction factors to facilitate viral replication. The Ten-Eleven Translocation 2 (TET2) is a methylcytosine dioxygenase that promotes DNA demethylation by catalyzing the oxidation of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC), which plays a vital role in hematopoiesis and immunity. Here we report that TET2 is a host restriction factor that limits IAV replication. But IAV endoribonuclease PA-X is able to remove the replication restriction by binding to TET2 mRNA and driving TET2 mRNA degradation to reduce TET2 expression during infection. Genetic inactivation of TET2 markedly enhances IAV replication in vitro and in vivo. Mechanistically, we found that TET2 regulates demethylation and transcription of STAT1 and some interferon-stimulated genes (ISGs), including ISG15, ISG20, and IFIT5, so the loss of TET2 greatly impairs type I Interferon signaling. Furthermore, we confirmed that TET2-mediated demethylation of the STAT1 gene is critical for interferon anti-viral activity. Our study demonstrates that the host TET2 is essential to the innate immune response against IAV infection.
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Affiliation(s)
- Yixiang Hu
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Xinru Chen
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Yuehuan Ling
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Kun Zhou
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Meiqing Han
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
| | - Xingbo Wang
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
| | - Min Yue
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, National Medical Center for Infectious Diseases, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Yan Li
- Department of Veterinary Medicine & Institute of Preventive Veterinary Sciences, Zhejiang University College of Animal Sciences, Hangzhou, Zhejiang, China
- Hainan Institute of Zhejiang University, Sanya, Hainan, China
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Hangzhou, Zhejiang, China
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2
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Ghorbani A, Ngunjiri JM, Edward C Abundo M, Pantin-Jackwood M, Kenney SP, Lee CW. Development of in ovo-compatible NS1-truncated live attenuated influenza vaccines by modulation of hemagglutinin cleavage and polymerase acidic X frameshifting sites. Vaccine 2023; 41:1848-1858. [PMID: 36669965 DOI: 10.1016/j.vaccine.2023.01.018] [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: 09/27/2022] [Revised: 01/08/2023] [Accepted: 01/10/2023] [Indexed: 01/20/2023]
Abstract
Emerging avian influenza viruses pose a high risk to poultry production, necessitating the need for more broadly protective vaccines. Live attenuated influenza vaccines offer excellent protective efficacies but their use in poultry farms is discouraged due to safety concerns related to emergence of reassortant viruses. Vaccination of chicken embryos inside eggs (in ovo) induces early immunity in young chicks while reduces the safety concerns related to the use of live vaccines on farms. However, in ovo vaccination using influenza viruses severely affects the egg hatchability. We previously engineered a high interferon-inducing live attenuated influenza vaccine candidate with an enhanced protective efficacy in chickens. Here, we asked whether we could further modify this high interferon-inducing vaccine candidate to develop an in ovo-compatible live attenuated influenza vaccine. We first showed that the enhanced interferon responses induced by the vaccine is not enough to attenuate the virus in ovo. To reduce the pathogenicity of the virus for chicken embryos, we replaced the hemagglutinin cleavage site of the H7 vaccine virus (PENPKTR/GL) with that of the H6-subtype viruses (PQIETR/GL) and disrupted the ribosomal frameshifting site responsible for viral polymerase acidic X protein expression. In ovo vaccination of chickens with up to 105 median egg infectious dose of the modified vaccine had minimal effects on hatchability while protecting the chickens against a heterologous challenge virus at two weeks of age. This study demonstrates that targeted genetic mutations can be applied to further attenuate and enhance the safety of live attenuated influenza vaccines to develop future in ovo vaccines for poultry.
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Affiliation(s)
- Amir Ghorbani
- Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA; Center for Food Animal Health, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, USA
| | - John M Ngunjiri
- Center for Food Animal Health, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, USA
| | - Michael Edward C Abundo
- Center for Food Animal Health, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, USA
| | - Mary Pantin-Jackwood
- Southeast Poultry Research Laboratory, US National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA
| | - Scott P Kenney
- Department of Veterinary Preventive Medicine, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA; Center for Food Animal Health, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH, USA.
| | - Chang-Won Lee
- Southeast Poultry Research Laboratory, US National Poultry Research Center, Agricultural Research Service, U.S. Department of Agriculture, Athens, GA, USA.
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Abstract
Many viruses induce shutoff of host gene expression (host shutoff) as a strategy to take over cellular machinery and evade host immunity. Without host shutoff activity, these viruses generally replicate poorly in vivo, attesting to the importance of this antiviral strategy. In this review, we discuss one particularly advantageous way for viruses to induce host shutoff: triggering widespread host messenger RNA (mRNA) decay. Viruses can trigger increased mRNA destruction either directly, by encoding RNA cleaving or decapping enzymes, or indirectly, by activating cellular RNA degradation pathways. We review what is known about the mechanism of action of several viral RNA degradation factors. We then discuss the consequences of widespread RNA degradation on host gene expression and on the mechanisms of immune evasion, highlighting open questions. Answering these questions is critical to understanding how viral RNA degradation factors regulate host gene expression and how this process helps viruses evade host responses and replicate.
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Affiliation(s)
- Léa Gaucherand
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, and Graduate Program in Molecular Microbiology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, USA;
| | - Marta Maria Gaglia
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, and Graduate Program in Molecular Microbiology, Tufts Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, USA;
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4
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Nogales A, Villamayor L, Utrilla-Trigo S, Ortego J, Martinez-Sobrido L, DeDiego ML. Natural Selection of H5N1 Avian Influenza A Viruses with Increased PA-X and NS1 Shutoff Activity. Viruses 2021; 13:v13091760. [PMID: 34578340 PMCID: PMC8472985 DOI: 10.3390/v13091760] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/28/2021] [Accepted: 08/31/2021] [Indexed: 12/01/2022] Open
Abstract
Influenza A viruses (IAV) can infect a broad range of mammalian and avian species. However, the host innate immune system provides defenses that restrict IAV replication and infection. Likewise, IAV have evolved to develop efficient mechanisms to counteract host antiviral responses to efficiently replicate in their hosts. The IAV PA-X and NS1 non-structural proteins are key virulence factors that modulate innate immune responses and virus pathogenicity during infection. To study the determinants of IAV pathogenicity and their functional co-evolution, we evaluated amino acid differences in the PA-X and NS1 proteins of early (1996–1997) and more recent (since 2016) H5N1 IAV. H5N1 IAV have zoonotic and pandemic potential and represent an important challenge both in poultry farming and human health. The results indicate that amino acid changes occurred over time, affecting the ability of these two non-structural H5N1 IAV proteins to inhibit gene expression and affecting virus pathogenicity. These results highlight the importance to monitor the evolution of these two virulence factors of IAV, which could result in enhanced viral replication and virulence.
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Affiliation(s)
- Aitor Nogales
- Center for Animal Health Research, CISA-INIA-CSIC, Valdeolmos, 28130 Madrid, Spain; (S.U.-T.); (J.O.)
- Correspondence: (A.N.); (M.L.D.)
| | - Laura Villamayor
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
| | - Sergio Utrilla-Trigo
- Center for Animal Health Research, CISA-INIA-CSIC, Valdeolmos, 28130 Madrid, Spain; (S.U.-T.); (J.O.)
| | - Javier Ortego
- Center for Animal Health Research, CISA-INIA-CSIC, Valdeolmos, 28130 Madrid, Spain; (S.U.-T.); (J.O.)
| | - Luis Martinez-Sobrido
- Department of Disease Intervention and Prevention, Texas Biomedical Research Institute, San Antonio, TX 78227, USA;
| | - Marta L. DeDiego
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain;
- Correspondence: (A.N.); (M.L.D.)
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Amino Acid Residues Involved in Inhibition of Host Gene Expression by Influenza A/Brevig Mission/1/1918 PA-X. Microorganisms 2021; 9:microorganisms9051109. [PMID: 34065592 PMCID: PMC8160905 DOI: 10.3390/microorganisms9051109] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/19/2021] [Accepted: 05/19/2021] [Indexed: 12/12/2022] Open
Abstract
The influenza A virus (IAV) PA-X protein is a virulence factor that selectively degrades host mRNAs leading to protein shutoff. This function modulates host inflammation, antiviral responses, cell apoptosis, and pathogenesis. In this work we describe a novel approach based on the use of bacteria and plasmid encoding of the PA-X gene under the control of the bacteriophage T7 promoter to identify amino acid residues important for A/Brevig Mission/1/1918 H1N1 PA-X’s shutoff activity. Using this system, we have identified PA-X mutants encoding single or double amino acid changes, which diminish its host shutoff activity, as well as its ability to counteract interferon responses upon viral infection. This novel bacteria-based approach could be used for the identification of viral proteins that inhibit host gene expression as well as the amino acid residues responsible for inhibition of host gene expression.
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6
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Identification of amino acid residues required for inhibition of host gene expression by influenza A/Viet Nam/1203/2004 H5N1 PA-X. J Virol 2021; 96:e0040821. [PMID: 33853954 DOI: 10.1128/jvi.00408-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PA-X is a non-structural protein of influenza A virus (IAV), which is encoded by the polymerase acidic (PA) N-terminal region that contains a C-terminal +1 frameshifted sequence. IAV PA-X protein modulates virus-induced host innate immune responses and viral pathogenicity via suppression of host gene expression or cellular shutoff, through cellular mRNA cleavage. Highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype naturally infect different avian species, they have an enormous economic impact in the poultry farming, and they also have zoonotic and pandemic potential, representing a risk to human public health. In the present study, we describe a novel bacteria-based approach to identify amino acid residues in the PA-X protein of the HPAIV A/Viet Nam/1203/2004 H5N1 that are important for its ability to inhibit host protein expression or cellular shutoff activity. Identified PA-X mutants displayed a reduced shutoff activity as compared to that of the wild-type (WT) A/Viet Nam/1203/2004 H5N1 PA-X protein. Notably, this new bacteria-based screening allowed us to identify amino acid residues widely distributed over the entire N-terminal region of PA-X. Furthermore, we found that some of the residues affecting A/Viet Nam/1203/2004 H5N1 PA-X host shutoff activity also affect PA polymerase activity in a minigenome assay. This information could be used for the rational design of new and more effective compounds with antiviral activity against IAV. Moreover, our results demonstrate the feasibility of using this bacteria-based approach to identify amino acid residues important for the activity of viral proteins to inhibit host gene expression. IMPORTANCE Highly pathogenic avian influenza viruses (HPAIV) continue to pose a huge threat to global animal and human health. Despite of the limited genome size of Influenza A virus (IAV), the virus encodes eight main viral structural proteins and multiple accessory non-structural proteins, depending on the IAV type, subtype or strain. One of the IAV accessory proteins, PA-X, is encoded by the polymerase acidic (PA) protein and is involved in pathogenicity through the modulation of IAV-induced host inflammatory and innate immune responses. However, the molecular mechanism(s) of IAV PA-X regulation of the host immune response is not well understood. In this work, we used, for the first time, a bacteria-based approach for the identification of amino acids important for the ability of IAV PA-X to induce host shutoff activity and describe novel residues relevant for its ability to inhibit host gene expression, and their contribution in PA polymerase activity.
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7
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The influenza A virus host shutoff factor PA-X is rapidly turned over in a strain-specific manner. J Virol 2021; 95:JVI.02312-20. [PMID: 33504608 PMCID: PMC8103685 DOI: 10.1128/jvi.02312-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The influenza A endoribonuclease PA-X regulates virulence and transmission of the virus by reducing host gene expression and thus regulating immune responses to influenza A virus. Despite this key function in viral biology, the levels of PA-X protein remain markedly low during infection, and previous results suggest that these low levels are not solely the result of regulation of the level of translation and RNA stability. How PA-X is regulated post-translationally remains unknown. We now report that the PA-X protein is rapidly turned over. PA-X from multiple viral strains are short-lived, although the half-life of PA-X ranges from ∼30 minutes to ∼3.5 hours depending on the strain. Moreover, sequences in the variable PA-X C-terminal domain are primarily responsible for regulating PA-X half-life, although the N-terminal domain also accounts for some differences among strains. Interestingly, we find that the PA-X from the 2009 pandemic H1N1 strain has a longer half-life compared to the other variants we tested. This PA-X isoform has been reported to have a higher host shutoff activity, suggesting a role for protein turnover in regulating PA-X activity. Collectively, this study reveals a novel regulatory mechanism of PA-X protein levels that may impact host shutoff activity during influenza A virus infection.IMPORTANCE The PA-X protein from influenza A virus reduces host immune responses to infection through suppressing host gene expression, including genes encoding the antiviral response. Thus, it plays a central role in influenza A virus biology. Despite its key function, PA-X was only discovered in 2012 and much remains to be learned including how PA-X activity is regulated to promote optimal levels of viral infection. In this study, we reveal that PA-X protein levels are very low likely because of rapid turnover. We show that instability is a conserved property among PA-X variants from different strains of influenza A virus, but that the half-lives of PA-X variants differ. Moreover, the longer half-life of PA-X from the 2009 pandemic H1N1 strain correlates with its reported higher activity. Therefore, PA-X stability may be a way to regulate its activity and may contribute to the differential virulence of influenza A virus strains.
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8
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Topham DJ, DeDiego ML, Nogales A, Sangster MY, Sant A. Immunity to Influenza Infection in Humans. Cold Spring Harb Perspect Med 2021; 11:a038729. [PMID: 31871226 PMCID: PMC7919402 DOI: 10.1101/cshperspect.a038729] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review discusses the human immune responses to influenza infection with some insights from studies using animal models, such as experimental infection of mice. Recent technological advances in the study of human immune responses have greatly added to our knowledge of the infection and immune responses, and therefore much of the focus is on recent studies that have moved the field forward. We consider the complexity of the adaptive response generated by many sequential encounters through infection and vaccination.
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Affiliation(s)
- David J Topham
- David H. Smith Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA
| | - Marta L DeDiego
- Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, 28049 Madrid, Spain
| | - Aitor Nogales
- Instituto Nacional de Investigación y Tecnologia Agraria y Ailmentaria, 28040 Madrid, Spain
| | - Mark Y Sangster
- David H. Smith Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA
| | - Andrea Sant
- David H. Smith Center for Vaccine Biology and Immunology, Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York 14642, USA
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9
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Li M, Qi W, Chang Q, Chen R, Zhen D, Liao M, Wen J, Deng Y. Influenza A virus protein PA-X suppresses host Ankrd17-mediated immune responses. Microbiol Immunol 2021; 65:48-59. [PMID: 33241870 DOI: 10.1111/1348-0421.12863] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 11/16/2020] [Accepted: 11/19/2020] [Indexed: 11/30/2022]
Abstract
Influenza A virus (IAV) PA-X is a critical ribonuclease protein involved in host cell shutoff but its role in modulating the host immune response to IAV infection remains to be addressed. In this study, host cellular proteins that directly interact with PA-X were screened to investigate the biological function of PA-X in the pathogenesis of IAV infection. The protein ankyrin repeat domain 17 (Ankrd17), a positive regulator of inflammatory responses via the retinoic acid-inducible gene-I (RIG-I)-like receptor (RLR) signaling pathway, was identified as a specific PA-X binding partner that preferred PA-X to the PA protein. The N-terminal ankyrin repeats of Ankrd17 are the key domain for the interaction with PA-X rather than PA, which is required for the function of Ankrd17 in elevating the host immune response. Using Ankrd17 knockout and overexpression, we confirmed that PA-X significantly affected the Ankrd17-mediated response to infection in host cells. Our data therefore reveal a novel function for PA-X in the regulation of innate immune pathways via the interaction between PA-X and Ankrd17.
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Affiliation(s)
- Mai Li
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Guangdong Food and Drug Vocational College, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
| | - Wenbao Qi
- Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China.,National and Regional Joint Engineering Laboratory for Medicament of Zoonoses Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Qing Chang
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Ruohong Chen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
| | - Danlin Zhen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Ming Liao
- Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China.,National and Regional Joint Engineering Laboratory for Medicament of Zoonoses Prevention and Control, College of Veterinary Medicine, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis Prevention and Control of Guangdong Province, Guangzhou, China
| | - Jikai Wen
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
| | - Yiqun Deng
- Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.,Key Laboratory of Zoonosis of the Ministry of Agriculture and Rural Affairs, South China Agricultural University, Guangzhou, China
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Roles of the Non-Structural Proteins of Influenza A Virus. Pathogens 2020; 9:pathogens9100812. [PMID: 33023047 PMCID: PMC7600879 DOI: 10.3390/pathogens9100812] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 09/29/2020] [Accepted: 10/01/2020] [Indexed: 12/11/2022] Open
Abstract
Influenza A virus (IAV) is a segmented, negative single-stranded RNA virus that causes seasonal epidemics and has a potential for pandemics. Several viral proteins are not packed in the IAV viral particle and only expressed in the infected host cells. These proteins are named non-structural proteins (NSPs), including NS1, PB1-F2 and PA-X. They play a versatile role in the viral life cycle by modulating viral replication and transcription. More importantly, they also play a critical role in the evasion of the surveillance of host defense and viral pathogenicity by inducing apoptosis, perturbing innate immunity, and exacerbating inflammation. Here, we review the recent advances of these NSPs and how the new findings deepen our understanding of IAV–host interactions and viral pathogenesis.
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Truncation of PA-X Contributes to Virulence and Transmission of H3N8 and H3N2 Canine Influenza Viruses in Dogs. J Virol 2020; 94:JVI.00949-20. [PMID: 32461313 DOI: 10.1128/jvi.00949-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 05/20/2020] [Indexed: 12/15/2022] Open
Abstract
Equine-origin H3N8 and avian-origin H3N2 canine influenza viruses (CIVs) prevalent in dogs are thought to pose a public health threat arising from intimate contact between dogs and humans. However, our understanding of CIV virulence is still limited. Influenza A virus PA-X is a fusion protein encoded in part by a +1 frameshifted open reading frame (X-ORF) in segment 3. The X-ORF can be translated in full-length (61-amino-acid) or truncated (41-amino-acid) form. Genetic analysis indicated that the X-ORFs of equine H3N8 and avian H3N2 influenza viruses encoded 61 amino acids but were truncated after introduction into dogs. To determine the effect of PA-X truncation on the biological characteristics of CIVs, we constructed four recombinant viruses on H3N8 and H3N2 CIV backgrounds bearing truncated or full-length PA-Xs. We observed that truncation of PA-X increased growth of both H3N8 and H3N2 CIVs in MDCK cells and suppressed expression from cotransfected plasmids in MDCK cells. Furthermore, truncation of PA-X enhanced viral pathogenicity in dogs, as shown by aggravated clinical symptoms and histopathological changes, increased viral replication in the respiratory system, and prolonged virus shedding. Additionally, CIVs with truncated PA-Xs were transmitted more efficiently in dogs. Global gene expression profiling of the lungs of infected dogs revealed that differentially expressed genes were mainly associated with inflammatory responses, which might contribute to the pathogenicity of PA-X-truncated CIVs. Our findings revealed that truncation of PA-X might be important for the adaptation of influenza viruses to dogs.IMPORTANCE Epidemics of equine-origin H3N8 and avian-origin H3N2 influenza viruses in canine populations are examples of successful cross-species transmission of influenza A viruses. Genetic analysis showed that the PA-X genes of equine H3N8 or avian H3N2 influenza viruses were full-length, with X-ORFs encoding 61 amino acids; however, those of equine-origin H3N8 or avian-origin H3N2 CIVs were truncated, suggesting that PA-X truncation occurred after transmission to dogs. In this study, we extended the PA-X genes of H3N8 and H3N2 CIVs and compared the biological characteristics of CIVs bearing different lengths of PA-X. We demonstrated that for both H3N8 and H3N2 viruses, truncation of PA-X increased virus yields in MDCK cells and enhanced viral replication, pathogenicity, and transmission in dogs. These results might reflect enhanced suppression of host gene expression and upregulation of genes related to inflammatory responses. Collectively, our data partially explain the conservation of truncated PA-X in CIVs.
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12
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Lutz MM, Dunagan MM, Kurebayashi Y, Takimoto T. Key Role of the Influenza A Virus PA Gene Segment in the Emergence of Pandemic Viruses. Viruses 2020; 12:v12040365. [PMID: 32224899 PMCID: PMC7232137 DOI: 10.3390/v12040365] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 03/24/2020] [Indexed: 12/18/2022] Open
Abstract
Influenza A viruses (IAVs) are a significant human pathogen that cause seasonal epidemics and occasional pandemics. Avian waterfowl are the natural reservoir of IAVs, but a wide range of species can serve as hosts. Most IAV strains are adapted to one host species and avian strains of IAV replicate poorly in most mammalian hosts. Importantly, IAV polymerases from avian strains function poorly in mammalian cells but host adaptive mutations can restore activity. The 2009 pandemic H1N1 (H1N1pdm09) virus acquired multiple mutations in the PA gene that activated polymerase activity in mammalian cells, even in the absence of previously identified host adaptive mutations in other polymerase genes. These mutations in PA localize within different regions of the protein suggesting multiple mechanisms exist to activate polymerase activity. Additionally, an immunomodulatory protein, PA-X, is expressed from the PA gene segment. PA-X expression is conserved amongst many IAV strains but activity varies between viruses specific for different hosts, suggesting that PA-X also plays a role in host adaptation. Here, we review the role of PA in the emergence of currently circulating H1N1pdm09 viruses and the most recent studies of host adaptive mutations in the PA gene that modulate polymerase activity and PA-X function.
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Affiliation(s)
- Michael M. Lutz
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
| | - Megan M. Dunagan
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
| | - Yuki Kurebayashi
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
- Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka-shi 422-8526, Japan
| | - Toru Takimoto
- Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, NY 14642, USA (M.M.D.); (Y.K.)
- Correspondence: ; Tel.: +1-585-273-2856
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N-Terminal Acetylation by NatB Is Required for the Shutoff Activity of Influenza A Virus PA-X. Cell Rep 2020; 24:851-860. [PMID: 30044982 DOI: 10.1016/j.celrep.2018.06.078] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 03/26/2018] [Accepted: 06/18/2018] [Indexed: 12/17/2022] Open
Abstract
N-terminal acetylation is a major posttranslational modification in eukaryotes catalyzed by N-terminal acetyltransferases (NATs), NatA through NatF. Although N-terminal acetylation modulates diverse protein functions, little is known about its roles in virus replication. We found that NatB, which comprises NAA20 and NAA25, is involved in the shutoff activity of influenza virus PA-X. The shutoff activity of PA-X was suppressed in NatB-deficient cells, and PA-X mutants that are not acetylated by NatB showed reduced shutoff activities. We also evaluated the importance of N-terminal acetylation of PA, because PA-X shares its N-terminal sequence with PA. Viral polymerase activity was reduced in NatB-deficient cells. Moreover, mutant PAs that are not acetylated by NatB lost their function in the viral polymerase complex. Taken together, our findings demonstrate that N-terminal acetylation is required for the shutoff activity of PA-X and for viral polymerase activity.
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Galvin HD, Husain M. Influenza A virus-induced host caspase and viral PA-X antagonize the antiviral host factor, histone deacetylase 4. J Biol Chem 2019; 294:20207-20221. [PMID: 31757810 DOI: 10.1074/jbc.ra119.010650] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 11/05/2019] [Indexed: 12/22/2022] Open
Abstract
Influenza A virus (IAV) effectively manipulates host machinery to replicate. There is a growing evidence that an optimal acetylation environment in the host cell is favorable to IAV proliferation and vice versa. The histone deacetylases (HDACs), a family of 18 host enzymes classified into four classes, are central to negatively regulating the acetylation level, hence the HDACs would not be favorable to IAV. Indeed, by using the RNAi and overexpression strategies, we found that human HDAC4, a class II member, possesses anti-IAV properties and is a component of host innate antiviral response. We discovered that IAV multiplication was augmented in HDAC4-depleted cells and abated in HDAC4-supplemented cells. Likewise, the expression of IFITM3, ISG15, and viperin, some of the critical markers of host anti-IAV response was abated in HDAC4-depleted cells and augmented in HDAC4-supplemented cells. In turn, IAV strongly antagonizes the HDAC4, by down-regulating its expression both at the mRNA level via viral RNA endonuclease PA-X and at the polypeptide level by inducing its cleavage via host caspase 3 in infected cells. Such HDAC4 polypeptide cleavage resulted in a ∼30 kDa fragment that is also observed in some heterologous systems and may have a significant role in IAV replication.
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Affiliation(s)
- Henry D Galvin
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand
| | - Matloob Husain
- Department of Microbiology and Immunology, University of Otago, Dunedin 9054, New Zealand
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15
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Chua SCJH, Tan HQ, Engelberg D, Lim LHK. Alternative Experimental Models for Studying Influenza Proteins, Host-Virus Interactions and Anti-Influenza Drugs. Pharmaceuticals (Basel) 2019; 12:E147. [PMID: 31575020 PMCID: PMC6958409 DOI: 10.3390/ph12040147] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 09/11/2019] [Accepted: 09/12/2019] [Indexed: 12/14/2022] Open
Abstract
Ninety years after the discovery of the virus causing the influenza disease, this malady remains one of the biggest public health threats to mankind. Currently available drugs and vaccines only partially reduce deaths and hospitalizations. Some of the reasons for this disturbing situation stem from the sophistication of the viral machinery, but another reason is the lack of a complete understanding of the molecular and physiological basis of viral infections and host-pathogen interactions. Even the functions of the influenza proteins, their mechanisms of action and interaction with host proteins have not been fully revealed. These questions have traditionally been studied in mammalian animal models, mainly ferrets and mice (as well as pigs and non-human primates) and in cell lines. Although obviously relevant as models to humans, these experimental systems are very complex and are not conveniently accessible to various genetic, molecular and biochemical approaches. The fact that influenza remains an unsolved problem, in combination with the limitations of the conventional experimental models, motivated increasing attempts to use the power of other models, such as low eukaryotes, including invertebrate, and primary cell cultures. In this review, we summarized the efforts to study influenza in yeast, Drosophila, zebrafish and primary human tissue cultures and the major contributions these studies have made toward a better understanding of the disease. We feel that these models are still under-utilized and we highlight the unique potential each model has for better comprehending virus-host interactions and viral protein function.
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Affiliation(s)
- Sonja C J H Chua
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117593, Singapore.
- NUS Immunology Program, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore.
- CREATE-NUS-HUJ Molecular Mechanisms of Inflammatory Diseases Programme, National University of Singapore, Singapore 138602, Singapore.
| | - Hui Qing Tan
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117593, Singapore.
- NUS Immunology Program, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore.
| | - David Engelberg
- CREATE-NUS-HUJ Molecular Mechanisms of Inflammatory Diseases Programme, National University of Singapore, Singapore 138602, Singapore.
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore.
- Department of Biological Chemistry, The Institute of Life Science, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
| | - Lina H K Lim
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117593, Singapore.
- NUS Immunology Program, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore.
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16
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A Yeast Suppressor Screen Used To Identify Mammalian SIRT1 as a Proviral Factor for Middle East Respiratory Syndrome Coronavirus Replication. J Virol 2019; 93:JVI.00197-19. [PMID: 31142674 PMCID: PMC6675885 DOI: 10.1128/jvi.00197-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/21/2019] [Indexed: 02/08/2023] Open
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) initially emerged in 2012 and has since been responsible for over 2,300 infections, with a case fatality ratio of approximately 35%. We have used the highly characterized model system of Saccharomyces cerevisiae to investigate novel functional interactions between viral proteins and eukaryotic cells that may provide new avenues for antiviral intervention. We identify a functional link between the MERS-CoV ORF4a proteins and the YDL042C/SIR2 yeast gene. The mammalian homologue of SIR2 is SIRT1, an NAD-dependent histone deacetylase. We demonstrate for the first time that SIRT1 is a proviral factor for MERS-CoV replication and that ORF4a has a role in modulating its activity in mammalian cells. Viral proteins must intimately interact with the host cell machinery during virus replication. Here, we used the yeast Saccharomyces cerevisiae as a system to identify novel functional interactions between viral proteins and eukaryotic cells. Our work demonstrates that when the Middle East respiratory syndrome coronavirus (MERS-CoV) ORF4a accessory gene is expressed in yeast it causes a slow-growth phenotype. ORF4a has been characterized as an interferon antagonist in mammalian cells, and yet yeast lack an interferon system, suggesting further interactions between ORF4a and eukaryotic cells. Using the slow-growth phenotype as a reporter of ORF4a function, we utilized the yeast knockout library collection to perform a suppressor screen where we identified the YDL042C/SIR2 yeast gene as a suppressor of ORF4a function. The mammalian homologue of SIR2 is SIRT1, an NAD-dependent histone deacetylase. We found that when SIRT1 was inhibited by either chemical or genetic manipulation, there was reduced MERS-CoV replication, suggesting that SIRT1 is a proviral factor for MERS-CoV. Moreover, ORF4a inhibited SIRT1-mediated modulation of NF-κB signaling, demonstrating a functional link between ORF4a and SIRT1 in mammalian cells. Overall, the data presented here demonstrate the utility of yeast studies for identifying genetic interactions between viral proteins and eukaryotic cells. We also demonstrate for the first time that SIRT1 is a proviral factor for MERS-CoV replication and that ORF4a has a role in modulating its activity in cells. IMPORTANCE Middle East respiratory syndrome coronavirus (MERS-CoV) initially emerged in 2012 and has since been responsible for over 2,300 infections, with a case fatality ratio of approximately 35%. We have used the highly characterized model system of Saccharomyces cerevisiae to investigate novel functional interactions between viral proteins and eukaryotic cells that may provide new avenues for antiviral intervention. We identify a functional link between the MERS-CoV ORF4a proteins and the YDL042C/SIR2 yeast gene. The mammalian homologue of SIR2 is SIRT1, an NAD-dependent histone deacetylase. We demonstrate for the first time that SIRT1 is a proviral factor for MERS-CoV replication and that ORF4a has a role in modulating its activity in mammalian cells.
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Oishi K, Yamayoshi S, Kawaoka Y. Identification of Amino Acid Residues in Influenza A Virus PA-X That Contribute to Enhanced Shutoff Activity. Front Microbiol 2019; 10:432. [PMID: 30894843 PMCID: PMC6414799 DOI: 10.3389/fmicb.2019.00432] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/19/2019] [Indexed: 01/07/2023] Open
Abstract
The influenza virus protein PA-X modulates the host immune responses and viral pathogenicity through suppression of host protein expression. The endonuclease active site in the N-terminal region, the basic amino acid cluster in the C-terminal PA-X-specific region, and N-terminal acetylation of PA-X by NatB are important for the shutoff activity of PA-X. Here, we focused on the shutoff activity of PA-X derived from the A/California/04/2009 and A/WSN/33 viruses because these two PA-X proteins differ in their shutoff activity. Mutagenesis analysis revealed that proline and serine at positions 28 and 65, respectively, play a central role in this difference. Furthermore, we found that P28 and S65 also affect the shutoff activity of PA-X derived from other influenza virus subtypes. These data demonstrate that P28 and S65 contribute to enhanced shutoff activity of PA-X.
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Affiliation(s)
- Kohei Oishi
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
| | - Seiya Yamayoshi
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
| | - Yoshihiro Kawaoka
- Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin–Madison, Madison, WI, United States
- Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo, Japan
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18
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Nogales A, Martinez-Sobrido L, Topham DJ, DeDiego ML. Modulation of Innate Immune Responses by the Influenza A NS1 and PA-X Proteins. Viruses 2018; 10:v10120708. [PMID: 30545063 PMCID: PMC6315843 DOI: 10.3390/v10120708] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 12/06/2018] [Accepted: 12/08/2018] [Indexed: 12/14/2022] Open
Abstract
Influenza A viruses (IAV) can infect a broad range of animal hosts, including humans. In humans, IAV causes seasonal annual epidemics and occasional pandemics, representing a serious public health and economic problem, which is most effectively prevented through vaccination. The defense mechanisms that the host innate immune system provides restrict IAV replication and infection. Consequently, to successfully replicate in interferon (IFN)-competent systems, IAV has to counteract host antiviral activities, mainly the production of IFN and the activities of IFN-induced host proteins that inhibit virus replication. The IAV multifunctional proteins PA-X and NS1 are virulence factors that modulate the innate immune response and virus pathogenicity. Notably, these two viral proteins have synergistic effects in the inhibition of host protein synthesis in infected cells, although using different mechanisms of action. Moreover, the control of innate immune responses by the IAV NS1 and PA-X proteins is subject to a balance that can determine virus pathogenesis and fitness, and recent evidence shows co-evolution of these proteins in seasonal viruses, indicating that they should be monitored for enhanced virulence. Importantly, inhibition of host gene expression by the influenza NS1 and/or PA-X proteins could be explored to develop improved live-attenuated influenza vaccines (LAIV) by modulating the ability of the virus to counteract antiviral host responses. Likewise, both viral proteins represent a reasonable target for the development of new antivirals for the control of IAV infections. In this review, we summarize the role of IAV NS1 and PA-X in controlling the antiviral response during viral infection.
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Affiliation(s)
- Aitor Nogales
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- Centro de Investigación en Sanidad Animal (CISA)-INIA, Valdeolmos, 28130 Madrid, Spain.
| | - Luis Martinez-Sobrido
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
| | - David J Topham
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
| | - Marta L DeDiego
- Department of Microbiology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- David H. Smith Center for Vaccine Biology and Immunology, University of Rochester, Rochester, New York, NY 14642, USA.
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain.
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Singh RK, Dhama K, Karthik K, Khandia R, Munjal A, Khurana SK, Chakraborty S, Malik YS, Virmani N, Singh R, Tripathi BN, Munir M, van der Kolk JH. A Comprehensive Review on Equine Influenza Virus: Etiology, Epidemiology, Pathobiology, Advances in Developing Diagnostics, Vaccines, and Control Strategies. Front Microbiol 2018; 9:1941. [PMID: 30237788 PMCID: PMC6135912 DOI: 10.3389/fmicb.2018.01941] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 07/31/2018] [Indexed: 01/23/2023] Open
Abstract
Among all the emerging and re-emerging animal diseases, influenza group is the prototype member associated with severe respiratory infections in wide host species. Wherein, Equine influenza (EI) is the main cause of respiratory illness in equines across globe and is caused by equine influenza A virus (EIV-A) which has impacted the equine industry internationally due to high morbidity and marginal morality. The virus transmits easily by direct contact and inhalation making its spread global and leaving only limited areas untouched. Hitherto reports confirm that this virus crosses the species barriers and found to affect canines and few other animal species (cat and camel). EIV is continuously evolving with changes at the amino acid level wreaking the control program a tedious task. Until now, no natural EI origin infections have been reported explicitly in humans. Recent advances in the diagnostics have led to efficient surveillance and rapid detection of EIV infections at the onset of outbreaks. Incessant surveillance programs will aid in opting a better control strategy for this virus by updating the circulating vaccine strains. Recurrent vaccination failures against this virus due to antigenic drift and shift have been disappointing, however better understanding of the virus pathogenesis would make it easier to design effective vaccines predominantly targeting the conserved epitopes (HA glycoprotein). Additionally, the cold adapted and canarypox vectored vaccines are proving effective in ceasing the severity of disease. Furthermore, better understanding of its genetics and molecular biology will help in estimating the rate of evolution and occurrence of pandemics in future. Here, we highlight the advances occurred in understanding the etiology, epidemiology and pathobiology of EIV and a special focus is on designing and developing effective diagnostics, vaccines and control strategies for mitigating the emerging menace by EIV.
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Affiliation(s)
- Raj K. Singh
- ICAR-Indian Veterinary Research Institute, Bareilly, India
| | - Kuldeep Dhama
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Bareilly, India
| | - Kumaragurubaran Karthik
- Central University Laboratory, Tamil Nadu Veterinary and Animal Sciences University, Chennai, India
| | - Rekha Khandia
- Department of Biochemistry and Genetics, Barkatullah University, Bhopal, India
| | - Ashok Munjal
- Department of Biochemistry and Genetics, Barkatullah University, Bhopal, India
| | | | - Sandip Chakraborty
- Department of Veterinary Microbiology, College of Veterinary Sciences and Animal Husbandry, West Tripura, India
| | - Yashpal S. Malik
- Division of Biological Standardization, ICAR-Indian Veterinary Research Institute, Bareilly, India
| | | | - Rajendra Singh
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Bareilly, India
| | | | - Muhammad Munir
- Division of Biomedical and Life Sciences, Lancaster University, Lancaster, United Kingdom
| | - Johannes H. van der Kolk
- Division of Clinical Veterinary Medicine, Swiss Institute for Equine Medicine (ISME), Vetsuisse Faculty, University of Bern and Agroscope, Bern, Switzerland
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20
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Levene RE, Gaglia MM. Host Shutoff in Influenza A Virus: Many Means to an End. Viruses 2018; 10:E475. [PMID: 30189604 PMCID: PMC6165434 DOI: 10.3390/v10090475] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 08/31/2018] [Accepted: 09/01/2018] [Indexed: 12/21/2022] Open
Abstract
Influenza A virus carries few of its own proteins, but uses them effectively to take control of the infected cells and avoid immune responses. Over the years, host shutoff, the widespread down-regulation of host gene expression, has emerged as a key process that contributes to cellular takeover in infected cells. Interestingly, multiple mechanisms of host shutoff have been described in influenza A virus, involving changes in translation, RNA synthesis and stability. Several viral proteins, notably the non-structural protein NS1, the RNA-dependent RNA polymerase and the endoribonuclease PA-X have been implicated in host shutoff. This multitude of host shutoff mechanisms indicates that host shutoff is an important component of the influenza A virus replication cycle. Here we review the various mechanisms of host shutoff in influenza A virus and the evidence that they contribute to immune evasion and/or viral replication. We also discuss what the purpose of having multiple mechanisms may be.
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Affiliation(s)
- Rachel Emily Levene
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA 02111, USA.
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA 02111, USA.
| | - Marta Maria Gaglia
- Graduate Program in Molecular Microbiology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA 02111, USA.
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Ave, Boston, MA 02111, USA.
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Hu J, Ma C, Liu X. PA-X: a key regulator of influenza A virus pathogenicity and host immune responses. Med Microbiol Immunol 2018; 207:255-269. [PMID: 29974232 PMCID: PMC7086933 DOI: 10.1007/s00430-018-0548-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 06/28/2018] [Indexed: 02/07/2023]
Abstract
PA-X, a fusion protein belonging to influenza A viruses (IAVs), integrating the N-terminal 191 amino acids of PA gene and the ribosomal frame-shifting product that lengthens out to 41 or 61 amino acids. Since its discovery in 2012, multiple functions have been attributed to this small protein, including a process, where wide-spread protein synthesis in infected host cells is shut down (called host shutoff), and viral replication, polymerase activity, viral-induced cell apoptosis, PA nuclear localization, and virulence are modulated. However, many of its proposed functions may be specific to strain, subtype, host, or cell line. In this review, we start by describing the well-defined global host-shutoff ability of PA-X and the potential mechanisms underlying it. We move on to the role played by PA-X in modulating innate and acquired immune responses in the host. We then systematically discuss the role played by PA-X in modulating the virulence of influenza viruses of different subtypes and host origins, and finish with a general overview of the research advances made in identifying the host cell partners that interact with PA-X. To uncover possible clues about the differential effects of PA-X in modulating viral virulence, we focus on systemically evaluating polymorphisms in PA-X from various viral subtypes and hosts, including avian and human H5N1, H5N6, H9N2, and H7N9 viruses. Finally, we conclude with a proposition regarding the possible future research directions for this important protein.
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Affiliation(s)
- Jiao Hu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, 48 East Wenhui Road, Yangzhou, 225009, Jiangsu Province, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Chunxi Ma
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, 48 East Wenhui Road, Yangzhou, 225009, Jiangsu Province, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China
| | - Xiufan Liu
- Animal Infectious Disease Laboratory, School of Veterinary Medicine, Yangzhou University, 48 East Wenhui Road, Yangzhou, 225009, Jiangsu Province, China.
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonosis, Yangzhou University, Yangzhou, Jiangsu, China.
- Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agri-food Safety and Quality, Ministry of Agriculture of China (26116120), Yangzhou University, Yangzhou, China.
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