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Wijburg SR, Montizaan MGE, Kik MJL, Joeres M, Cardron G, Luttermann C, Maas M, Maksimov P, Opsteegh M, Schares G. Drivers of infection with Toxoplasma gondii genotype type II in Eurasian red squirrels (Sciurus vulgaris). Parasit Vectors 2024; 17:30. [PMID: 38263195 PMCID: PMC10804655 DOI: 10.1186/s13071-023-06068-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 11/26/2023] [Indexed: 01/25/2024] Open
Abstract
BACKGROUND In September 2014, there was sudden upsurge in the number of Eurasian red squirrels (Sciurus vulgaris) found dead in the Netherlands. High infection levels with the parasite Toxoplasma gondii were demonstrated, but it was unclear what had caused this increase in cases of fatal toxoplasmosis. In the present study, we aimed to gain more knowledge on the pathology and prevalence of T. gondii infections in Eurasian red squirrels in the Netherlands, on the T. gondii genotypes present, and on the determinants of the spatiotemporal variability in these T. gondii infections. The presence of the closely related parasite Hammondia hammondi was also determined. METHODS Eurasian red squirrels that were found dead in the wild or that had died in wildlife rescue centres in the Netherlands over a period of seven years (2014-2020) were examined. Quantitative real-time polymerase chain reaction was conducted to analyse tissue samples for the presence of T. gondii and H. hammondi DNA. Toxoplasma gondii-positive samples were subjected to microsatellite typing and cluster analysis. A mixed logistic regression was used to identify climatic and other environmental predictors of T. gondii infection in the squirrels. RESULTS A total of 178 squirrels were examined (49/178 T. gondii positive, 5/178 H. hammondi positive). Inflammation of multiple organs was the cause of death in 29 squirrels, of which 24 were also T. gondii polymerase chain reaction positive. Toxoplasma gondii infection was positively associated with pneumonia and hepatitis. Microsatellite typing revealed only T. gondii type II alleles. Toxoplasma gondii infection rates showed a positive correlation with the number of days of heavy rainfall in the previous 12 months. Conversely, they showed a negative association with the number of hot days within the 2-week period preceding the sampling date, as well as with the percentage of deciduous forest cover at the sampling site. CONCLUSIONS Toxoplasma gondii infection in the squirrels appeared to pose a significant risk of acute mortality. The T. gondii genotype detected in this study is commonly found across Europe. The reasons for the unusually high infection rates and severe symptoms of these squirrels from the Netherlands remain unclear. The prevalence of T. gondii in the deceased squirrels was linked to specific environmental factors. However, whether the increase in the number of dead squirrels indicated a higher environmental contamination with T. gondii oocysts has yet to be established.
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Affiliation(s)
- Sara R Wijburg
- Centre for Infectious Disease Control, Centre for Zoonoses and Environmental Microbiology, National Institute for Public Health and the Environment (RIVM), Antonie Van Leeuwenhoeklaan 9, 1, 3720 BA, Bilthoven, The Netherlands
- Dutch Wildlife Health Centre, Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
| | - Margriet G E Montizaan
- Dutch Wildlife Health Centre, Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
| | - Marja J L Kik
- Dutch Wildlife Health Centre, Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
- Department Biomolecular Health Sciences, Pathology, Veterinair Pathologisch Diagnostisch Centrum, Yalelaan 1, 3584 CL, Utrecht, The Netherlands
| | - Maike Joeres
- Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald - Insel Riems, Germany
| | - Garance Cardron
- Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald - Insel Riems, Germany
| | - Christine Luttermann
- Institute of Immunology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald - Insel Riems, Germany
| | - Miriam Maas
- Centre for Infectious Disease Control, Centre for Zoonoses and Environmental Microbiology, National Institute for Public Health and the Environment (RIVM), Antonie Van Leeuwenhoeklaan 9, 1, 3720 BA, Bilthoven, The Netherlands
| | - Pavlo Maksimov
- Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald - Insel Riems, Germany
| | - Marieke Opsteegh
- Centre for Infectious Disease Control, Centre for Zoonoses and Environmental Microbiology, National Institute for Public Health and the Environment (RIVM), Antonie Van Leeuwenhoeklaan 9, 1, 3720 BA, Bilthoven, The Netherlands
| | - Gereon Schares
- Institute of Epidemiology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Südufer 10, 17493, Greifswald - Insel Riems, Germany.
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Joeres M, Cardron G, Passebosc-Faure K, Plault N, Fernández-Escobar M, Hamilton CM, O'Brien-Anderson L, Calero-Bernal R, Galal L, Luttermann C, Maksimov P, Conraths FJ, Dardé ML, Ortega-Mora LM, Jokelainen P, Mercier A, Schares G. A ring trial to harmonize Toxoplasma gondii microsatellite typing: comparative analysis of results and recommendations for optimization. Eur J Clin Microbiol Infect Dis 2023:10.1007/s10096-023-04597-7. [PMID: 37093325 DOI: 10.1007/s10096-023-04597-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 04/10/2023] [Indexed: 04/25/2023]
Abstract
A ring trial among five European laboratories was organized to reach consistency in microsatellite (MS) typing of the zoonotic parasite Toxoplasma gondii. Three sample sets were circulated and analyzed by each laboratory following a previously published method that is based on fragment length polymorphism of 15 MS markers. The first sample set compared typing results in general and focused on effects of DNA concentration; the second sample set focused on the polymorphic fingerprinting markers that can differentiate T. gondii strains within the same archetypal lineage; and the third set focused on non-archetypal genotypes. Methodological variations between laboratories, including the software programs used to determine MS fragment length, were collated using a questionnaire. Overall, lineage-level typing results reached a high level of agreement, especially in samples with the highest DNA concentrations. However, laboratory-specific differences were observed for particular markers. Major median differences in fragment length, of up to 6 base pairs, were related to the fluorophore used to label fragment-specific primers. In addition, primer pairs with identical sequences obtained from different suppliers resulted in fragments of differing length. Furthermore, differences in the way the sequencing profiles were assessed and interpreted may have led to deviating results in fragment length determination. Harmonization of MS typing, for example, by using the same fluorophores or by numerical adjustments applied to the fragment-lengths determined, could improve the uniformity of the results across laboratories. This is the first interlaboratory comparison, providing guidelines (added as a supplement) for the optimization of this technique.
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Affiliation(s)
- M Joeres
- Institute of Epidemiology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - G Cardron
- Institute of Epidemiology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - K Passebosc-Faure
- Centre National de Référence (CNR) Toxoplasmose Centre Hospitalier-Universitaire Dupuytren, Limoges, France
| | - N Plault
- Inserm U1094, IRD U270, Univ. Limoges, CHU Limoges, EpiMaCT - Epidemiology of Chronic Diseases in Tropical Zone, Institute of Epidemiology and Tropical Neurology, OmegaHealth, Limoges, France
| | - M Fernández-Escobar
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Madrid, Spain
| | - C M Hamilton
- The Moredun Research Institute, Penicuik, Midlothian, UK
| | - L O'Brien-Anderson
- Infectious Disease Preparedness, Statens Serum Institut, Copenhagen, Denmark
| | - R Calero-Bernal
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Madrid, Spain
| | - L Galal
- Inserm U1094, IRD U270, Univ. Limoges, CHU Limoges, EpiMaCT - Epidemiology of Chronic Diseases in Tropical Zone, Institute of Epidemiology and Tropical Neurology, OmegaHealth, Limoges, France
| | - C Luttermann
- Institute of Immunology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institut, -Insel Riems, Greifswald, Germany
| | - P Maksimov
- Institute of Epidemiology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - F J Conraths
- Institute of Epidemiology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - M L Dardé
- Centre National de Référence (CNR) Toxoplasmose Centre Hospitalier-Universitaire Dupuytren, Limoges, France
- Inserm U1094, IRD U270, Univ. Limoges, CHU Limoges, EpiMaCT - Epidemiology of Chronic Diseases in Tropical Zone, Institute of Epidemiology and Tropical Neurology, OmegaHealth, Limoges, France
| | - L M Ortega-Mora
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Madrid, Spain
| | - P Jokelainen
- Infectious Disease Preparedness, Statens Serum Institut, Copenhagen, Denmark
| | - A Mercier
- Centre National de Référence (CNR) Toxoplasmose Centre Hospitalier-Universitaire Dupuytren, Limoges, France
- Inserm U1094, IRD U270, Univ. Limoges, CHU Limoges, EpiMaCT - Epidemiology of Chronic Diseases in Tropical Zone, Institute of Epidemiology and Tropical Neurology, OmegaHealth, Limoges, France
| | - G Schares
- Institute of Epidemiology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institut, Südufer 10, 17493, Greifswald-Insel Riems, Germany.
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Blaurock C, Blohm U, Luttermann C, Holzerland J, Scheibner D, Schäfer A, Groseth A, Mettenleiter TC, Abdelwhab EM. The C-terminus of non-structural protein 1 (NS1) in H5N8 clade 2.3.4.4 avian influenza virus affects virus fitness in human cells and virulence in mice. Emerg Microbes Infect 2021; 10:1760-1776. [PMID: 34420477 PMCID: PMC8432360 DOI: 10.1080/22221751.2021.1971568] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Avian influenza viruses (AIV) H5N8 clade 2.3.4.4 pose a public health threat but the viral factors relevant for its potential adaptation to mammals are largely unknown. The non-structural protein 1 (NS1) of influenza viruses is an essential interferon antagonist. It commonly consists of 230 amino acids, but variations in the disordered C-terminus resulted in truncation or extension of NS1 with a possible impact on virus fitness in mammals. Here, we analysed NS1 sequences from 1902 to 2020 representing human influenza viruses (hIAV) as well as AIV in birds, humans and other mammals and with an emphasis on the panzootic AIV subtype H5N8 clade 2.3.4.4A (H5N8-A) from 2013 to 2015 and clade 2.3.4.4B (H5N8-B) since 2016. We found a high degree of prevalence for short NS1 sequences among hIAV, zoonotic AIV and H5N8-B, while AIV and H5N8-A had longer NS1 sequences. We assessed the fitness of recombinant H5N8-A and H5N8-B viruses carrying NS1 proteins with different lengths in human cells and in mice. H5N8-B with a short NS1, similar to hIAV or AIV from a human or other mammal-origins, was more efficient at blocking apoptosis and interferon-induction without a significant impact on virus replication in human cells. In mice, shortening of the NS1 of H5N8-A increased virus virulence, while the extension of NS1 of H5N8-B reduced virus virulence and replication. Taken together, we have described the biological impact of variation in the NS1 C-terminus in hIAV and AIV and shown that this affects virus fitness in vitro and in vivo.
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Affiliation(s)
- Claudia Blaurock
- Institute of Molecular Virology and Cell Biology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Ulrike Blohm
- Institute of Immunology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Christine Luttermann
- Institute of Immunology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Julia Holzerland
- Institute of Molecular Virology and Cell Biology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - David Scheibner
- Institute of Molecular Virology and Cell Biology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Alexander Schäfer
- Institute of Immunology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Allison Groseth
- Institute of Molecular Virology and Cell Biology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Thomas C Mettenleiter
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
| | - Elsayed M Abdelwhab
- Institute of Molecular Virology and Cell Biology, Federal Research Institute for Animal Health Greifswald-Insel Riems, Germany
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Binder F, Gallo G, Bendl E, Eckerle I, Ermonval M, Luttermann C, Ulrich RG. Inhibition of interferon I induction by non-structural protein NSs of Puumala virus and other vole-associated orthohantaviruses: phenotypic plasticity of the protein and potential functional domains. Arch Virol 2021; 166:2999-3012. [PMID: 34389893 PMCID: PMC8362652 DOI: 10.1007/s00705-021-05159-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 05/14/2021] [Indexed: 12/25/2022]
Abstract
The orthohantavirus Puumala virus (PUUV), which is transmitted by bank voles (Clethrionomys glareolus), and other vole-borne hantaviruses contain in their small (S) genome segment two overlapping open reading frames, coding for the nucleocapsid protein and the non-structural protein NSs, a putative type I interferon (IFN-I) antagonist. To investigate the role of NSs of PUUV and other orthohantaviruses, the expression pattern of recombinant NSs constructs and their ability to inhibit human IFN-I promoter activity were investigated. The NSs proteins of PUUV and related cricetid-borne orthohantaviruses showed strong inhibition of IFN-I promoter induction. We identified protein products originating from three and two methionine initiation codons in the NSs ORF of PUUV during transfection and infection, respectively. The three putative start codons are conserved in all PUUV strains analysed. Translation initiation at these start codons influenced the inhibitory activity of the NSs products, with the wild-type (wt) construct expressing two proteins starting at the first and second methionine and showing strong inhibition activity. Analysis of in vitro-generated variants and naturally occurring PUUV NSs proteins indicated that amino acid variation in the NSs protein is well tolerated, suggesting its phenotypic plasticity. The N-terminal 20-amino-acid region of the NSs protein was found to be associated with strong inhibition and to be highly vulnerable to amino acid exchanges and tag fusions. Infection studies using human, bank vole, and Vero E6 cells did not show obvious differences in the replication capacity of PUUV Sotkamo wt and a strain with a truncated NSs protein (NSs21Stop), showing that the lack of a full-length NSs might be compensated by its N-terminal peptide, as seen in transfection experiments. These results contribute to our understanding of virus-host interactions and highlight the importance of future innate immunity studies in reservoir hosts.
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Affiliation(s)
- Florian Binder
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Novel and Emerging Infectious Diseases, Greifswald-Insel Riems, Germany
| | - Giulia Gallo
- Department of Virology, Institut Pasteur, Antiviral Strategies, Paris, France
| | - Elias Bendl
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Novel and Emerging Infectious Diseases, Greifswald-Insel Riems, Germany.,University Hospital Freiburg, Institute of Virology, Freiburg, Germany
| | - Isabella Eckerle
- University of Bonn, Medical Centre, Bonn, Germany.,Geneva Centre for Emerging Viral Diseases, Division of Infectious Diseases, University Hospital of Geneva, Geneva, Switzerland
| | - Myriam Ermonval
- Department of Virology, Institut Pasteur, Antiviral Strategies, Paris, France
| | - Christine Luttermann
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Immunology, Greifswald-Insel Riems, Germany
| | - Rainer G Ulrich
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Novel and Emerging Infectious Diseases, Greifswald-Insel Riems, Germany.
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Mu Y, Tews BA, Luttermann C, Meyers G. Interaction of Pestiviral E1 and E2 Sequences in Dimer Formation and Intracellular Retention. Int J Mol Sci 2021; 22:ijms22147285. [PMID: 34298900 PMCID: PMC8306095 DOI: 10.3390/ijms22147285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 06/29/2021] [Accepted: 07/03/2021] [Indexed: 11/16/2022] Open
Abstract
Pestiviruses contain three envelope proteins: Erns, E1, and E2. Expression of HA-tagged E1 or mutants thereof showed that E1 forms homodimers and -trimers. C123 and, to a lesser extent, C171, affected the oligomerization of E1 with a double mutant C123S/C171S preventing oligomerization completely. E1 also establishes disulfide linked heterodimers with E2, which are crucial for the recovery of infectious viruses. Co-expression analyses with the HA-tagged E1 wt/E1 mutants and E2 wt/E2 mutants demonstrated that C123 in E1 and C295 in E2 are the critical sites for E1/E2 heterodimer formation. Introduction of mutations preventing E1/E2 heterodimer formation into the full-length infectious clone of BVDV CP7 prevented the recovery of infectious viruses, proving that C123 in E1 and C295 in E2 play an essential role in the BVDV life cycle, and further support the conclusion that heterodimer formation is the crucial step. Interestingly, we found that the retention signal of E1 is mandatory for intracellular localization of the heterodimer, so that absence of the E1 retention signal directs the heterodimer to the cell surface even though the E2 retention signal is still present. The covalent linkage between E1 and E2 plays an essential role for this process.
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Affiliation(s)
- Yu Mu
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany; (Y.M.); (C.L.)
| | - Birke Andrea Tews
- Institut für Infektionsmedizin, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany;
| | - Christine Luttermann
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany; (Y.M.); (C.L.)
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany; (Y.M.); (C.L.)
- Correspondence: ; Tel.: +49-(0)-3835-171-0
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Villa L, Maksimov P, Luttermann C, Tuschy M, Gazzonis AL, Zanzani SA, Mortarino M, Conraths FJ, Manfredi MT, Schares G. Spatial distance between sites of sampling associated with genetic variation among Neospora caninum in aborted bovine foetuses from northern Italy. Parasit Vectors 2021; 14:47. [PMID: 33441141 PMCID: PMC7805081 DOI: 10.1186/s13071-020-04557-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/16/2020] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND Neospora caninum, a coccidian protozoan, represents an important cause of bovine abortion. Available N. caninum strains show considerable variation in vitro and in vivo, including different virulence in cattle. To which extent sexual recombination, which is possible in the intestines of domestic dogs and closely related carnivores as definitive hosts, contributes to this variation is not clear yet. METHODS Aborted bovine foetuses were collected between 2015 and early 2019 from Italian Holstein Friesian dairy herds suffering from reproductive problems. A total of 198 samples were collected from 165 intensive farms located in Lombardy, northern Italy. N. caninum samples were subjected to multilocus-microsatellite genotyping using ten previously established microsatellite markers. In addition to our own data, those from a recent study providing data on five markers from other northern Italian regions were included and analysed. RESULTS Of the 55 samples finally subjected to genotyping, 35 were typed at all or 9 out of 10 loci and their individual multilocus-microsatellite genotype (MLMG) determined. Linear regression revealed a statistically significant association between the spatial distance of the sampling sites with the genetic distance of N. caninum MLMGs (P < 0.001). Including data from this and a previous North Italian study into eBURST analysis revealed that several of N. caninum MLMGs from northern Italy separate into four groups; most of the samples from Lombardy clustered in one of these groups. Principle component analysis revealed similar clusters and confirmed MLMG groups identified by eBURST. Variations observed between MLMGs were not equally distributed over all loci, but predominantly observed in MS7, MS6A, or MS10. CONCLUSIONS Our findings confirm the concept of local N. caninum subpopulations. The geographic distance of sampling was associated with the genetic distance as determined by microsatellite typing. Results suggest that multi-parental recombination in N. caninum is a rare event, but does not exclude uniparental mating. More comprehensive studies on microsatellites in N. caninum and related species like Toxoplasma gondii should be undertaken, not only to improve genotyping capabilities, but also to understand possible functions of these regions in the genomes of these parasites.
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Affiliation(s)
- Luca Villa
- Department of Veterinary Medicine, Università degli Studi di Milano, Via dell'Università 6, 26900, Lodi, Italy
| | - Pavlo Maksimov
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Christine Luttermann
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute for Immunology, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Mareen Tuschy
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Alessia L Gazzonis
- Department of Veterinary Medicine, Università degli Studi di Milano, Via dell'Università 6, 26900, Lodi, Italy
| | - Sergio A Zanzani
- Department of Veterinary Medicine, Università degli Studi di Milano, Via dell'Università 6, 26900, Lodi, Italy
| | - Michele Mortarino
- Department of Veterinary Medicine, Università degli Studi di Milano, Via dell'Università 6, 26900, Lodi, Italy
| | - Franz J Conraths
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Maria Teresa Manfredi
- Department of Veterinary Medicine, Università degli Studi di Milano, Via dell'Università 6, 26900, Lodi, Italy
| | - Gereon Schares
- Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Epidemiology, Südufer 10, 17493, Greifswald-Insel Riems, Germany.
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Henritzi D, Petric PP, Lewis NS, Graaf A, Pessia A, Starick E, Breithaupt A, Strebelow G, Luttermann C, Parker LMK, Schröder C, Hammerschmidt B, Herrler G, Beilage EG, Stadlbauer D, Simon V, Krammer F, Wacheck S, Pesch S, Schwemmle M, Beer M, Harder TC. Surveillance of European Domestic Pig Populations Identifies an Emerging Reservoir of Potentially Zoonotic Swine Influenza A Viruses. Cell Host Microbe 2020; 28:614-627.e6. [PMID: 32721380 DOI: 10.1016/j.chom.2020.07.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 06/22/2020] [Accepted: 07/07/2020] [Indexed: 12/31/2022]
Abstract
Swine influenza A viruses (swIAVs) can play a crucial role in the generation of new human pandemic viruses. In this study, in-depth passive surveillance comprising nearly 2,500 European swine holdings and more than 18,000 individual samples identified a year-round presence of up to four major swIAV lineages on more than 50% of farms surveilled. Phylogenetic analyses show that intensive reassortment with human pandemic A(H1N1)/2009 (H1pdm) virus produced an expanding and novel repertoire of at least 31 distinct swIAV genotypes and 12 distinct hemagglutinin/neuraminidase combinations with largely unknown consequences for virulence and host tropism. Several viral isolates were resistant to the human antiviral MxA protein, a prerequisite for zoonotic transmission and stable introduction into human populations. A pronounced antigenic variation was noted in swIAV, and several H1pdm lineages antigenically distinct from current seasonal human H1pdm co-circulate in swine. Thus, European swine populations represent reservoirs for emerging IAV strains with zoonotic and, possibly, pre-pandemic potential.
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Affiliation(s)
- Dinah Henritzi
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Philipp Peter Petric
- Institute of Virology, Medical Center, University of Freiburg, 79104 Freiburg, Germany; Spemann Graduate School of Biology and Medicine, University of Freiburg, 79106 Freiburg, Germany; Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Nicola Sarah Lewis
- Department of Pathobiology and Population Sciences, Royal Veterinary College, Hatfield, Hertfordshire AL9 7TA, UK; OIE/FAO International Reference Laboratory for avian influenza, swine influenza and Newcastle Disease, Animal and Plant Health Agency (APHA) - Weybridge, Addlestone, Surrey KT15 3NB, UK
| | - Annika Graaf
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Alberto Pessia
- Department of Mathematics and Statistics, University of Helsinki, 00014 Helsinki, Finland
| | - Elke Starick
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Angele Breithaupt
- Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Günter Strebelow
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Christine Luttermann
- Institute of Immunology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Larissa Mareike Kristin Parker
- Institute of Virology, Medical Center, University of Freiburg, 79104 Freiburg, Germany; Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Charlotte Schröder
- Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Bärbel Hammerschmidt
- Department of Experimental Animal Facilities and Biorisk Management, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany
| | - Georg Herrler
- Institute of Virology, Department of Infectious Diseases, University of Veterinary Medicine Hannover, Bünteweg 2, 30559 Hannover, Germany
| | - Elisabeth Große Beilage
- Field Station for Epidemiology, University of Veterinary Medicine Hannover, Büscheler Str. 9, 49456 Bakum, Germany
| | - Daniel Stadlbauer
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Viviana Simon
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA; Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Florian Krammer
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Silke Wacheck
- Ceva Santé Animale (former IDT Biologika GmbH), 06861 Dessau-Rosslau, Germany
| | - Stefan Pesch
- Ceva Santé Animale (former IDT Biologika GmbH), 06861 Dessau-Rosslau, Germany
| | - Martin Schwemmle
- Institute of Virology, Medical Center, University of Freiburg, 79104 Freiburg, Germany; Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.
| | - Martin Beer
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany.
| | - Timm Clemens Harder
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institut (FLI), Suedufer 10, 17493 Greifswald-Insel Riems, Germany.
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8
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Parvin R, Schinkoethe J, Grund C, Ulrich R, Bönte F, Behr KP, Voss M, Samad MA, Hassan KE, Luttermann C, Beer M, Harder T. Comparison of pathogenicity of subtype H9 avian influenza wild-type viruses from a wide geographic origin expressing mono-, di-, or tri-basic hemagglutinin cleavage sites. Vet Res 2020; 51:48. [PMID: 32234073 PMCID: PMC7106749 DOI: 10.1186/s13567-020-00771-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 03/11/2020] [Indexed: 01/18/2023] Open
Abstract
An intravenous pathogenicity index (IVPI) of > 1.2 in chickens or, in case of subtypes H5 and H7, expression of a polybasic hemagglutinin cleavage site (HACS), signals high pathogenicity (HP). Viruses of the H9N2-G1 lineage, which spread across Asia and Africa, are classified to be of low pathogenicity although, in the field, they became associated with severe clinical signs and epizootics in chickens. Here we report on a pre-eminent trait of recent H9N2-G1 isolates from Bangladesh and India, which express a tribasic HACS (motif PAKSKR-GLF; reminiscent of an HPAIV-like polybasic HACS) and compare their features to H9Nx viruses with di- and monobasic HACS from other phylogenetic and geographic origins. In an in vitro assay, the tribasic HACS of H9N2 was processed by furin-like proteases similar to bona fide H5 HPAIV while some dibasic sites showed increased cleavability but monobasic HACS none. Yet, all viruses remained trypsin-dependent in cell culture. In ovo, only tribasic H9N2 viruses were found to replicate in a grossly extended spectrum of embryonic organs. In contrast to all subtype H5/H7 HPAI viruses, tribasic H9N2 viruses did not replicate in endothelial cells either in the chorio-allantoic membrane or in other embryonic tissues. By IVPI, all H9Nx isolates proved to be of low pathogenicity. Pathogenicity assessment of tribasic H9N2-G1 viruses remains problematic. It cannot be excluded that the formation of a third basic amino acid in the HACS forms an intermediate step towards a gain in pathogenicity. Continued observation of the evolution of these viruses in the field is recommended.
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Affiliation(s)
- Rokshana Parvin
- Institute of Diagnostic Virology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute (FLI), Suedufer 10, 17493, Greifswald-Insel Riems, Germany.,Department of Pathology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, 2202, Bangladesh
| | - Jan Schinkoethe
- Institute of Veterinary Pathology, Faculty of Veterinary Medicine, University of Leipzig, An den Tierkliniken 33, 04103, Leipzig, Germany
| | - Christian Grund
- Institute of Diagnostic Virology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute (FLI), Suedufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Reiner Ulrich
- Institute of Veterinary Pathology, Faculty of Veterinary Medicine, University of Leipzig, An den Tierkliniken 33, 04103, Leipzig, Germany
| | - Franziska Bönte
- University of Applied Sciences Wedel, Feldstraße 143, 22880, Wedel, Germany
| | - Klaus P Behr
- AniCon Labor GmbH, Mühlenstraße, 49685, Höltinghausen, Germany
| | - Matthias Voss
- Lohmann Tierzucht GmbH, Veterinär-Labor, Abschnede 64, 27472, Cuxhaven, Germany
| | - Mohammed A Samad
- NRL-AI, Bangladesh Livestock Research Institute (BLRI), Savar, Dhaka, Bangladesh
| | - Kareem E Hassan
- Institute of Diagnostic Virology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute (FLI), Suedufer 10, 17493, Greifswald-Insel Riems, Germany.,Poultry Diseases Department, Faculty of Veterinary Medicine, Beni-Suef University, Beni Suef, Egypt
| | - Christine Luttermann
- Institute of Immunology, Friedrich-Loeffler-Institute, Greifswald-Riems, Germany
| | - Martin Beer
- Institute of Diagnostic Virology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute (FLI), Suedufer 10, 17493, Greifswald-Insel Riems, Germany
| | - Timm Harder
- Institute of Diagnostic Virology, Federal Research Institute for Animal Health, Friedrich-Loeffler-Institute (FLI), Suedufer 10, 17493, Greifswald-Insel Riems, Germany.
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9
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Wennesz R, Luttermann C, Kreher F, Meyers G. Structure-function relationship in the 'termination upstream ribosomal binding site' of the calicivirus rabbit hemorrhagic disease virus. Nucleic Acids Res 2019; 47:1920-1934. [PMID: 30668745 PMCID: PMC6393290 DOI: 10.1093/nar/gkz021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 01/04/2019] [Accepted: 01/10/2019] [Indexed: 12/12/2022] Open
Abstract
Caliciviruses use a termination/reinitiation mechanism for translation of their minor capsid protein VP2. A sequence element of about 80 nucleotides denoted ‘termination upstream ribosomal binding site’ (TURBS) is crucial for reinitiation. RNA secondary structure probing and computer aided secondary structure prediction revealed a rather low degree of secondary structure determinants for the TURBS of the rabbit hermorrhagic disease virus. Mutation analysis showed that prevention of duplex formation had major impact on the VP2 expression levels. Restoration of complementarity of the respective sequences by reciprocal mutation at least partially restored reinitiating rates. Synthetic TURBS structures preserving only the secondary structure forming sequences and the known short motifs important for TURBS function were found to drive reinitiation when the altered sequence could be predicted to allow establishment of the crucial secondary structures of the TURBS.
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Affiliation(s)
- René Wennesz
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany
| | - Christine Luttermann
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany
| | - Felix Kreher
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-17493 Greifswald-Insel Riems, Germany
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10
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Hassan KE, El-Kady MF, El-Sawah AAA, Luttermann C, Parvin R, Shany S, Beer M, Harder T. Respiratory disease due to mixed viral infections in poultry flocks in Egypt between 2017 and 2018: Upsurge of highly pathogenic avian influenza virus subtype H5N8 since 2018. Transbound Emerg Dis 2019; 68:21-36. [PMID: 31297991 DOI: 10.1111/tbed.13281] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 06/06/2019] [Accepted: 06/11/2019] [Indexed: 02/06/2023]
Abstract
For several years, poultry production in Egypt has been suffering from co-circulation of multiple respiratory viruses including highly pathogenic avian influenza virus (HPAIV) H5N1 (clade 2.2.1.2) and low pathogenic H9N2 (clade G1-B). Incursion of HPAIV H5N8 (clade 2.3.4.4b) to Egypt in November 2016 via wild birds followed by spread into commercial poultry flocks further complicated the situation. Current analyses focussed on 39 poultry farms suffering from respiratory manifestation and high mortality in six Egyptian governorates during 2017-2018. Real-time RT-PCR (RT-qPCR) substantiated the co-presence of at least two respiratory virus species in more than 80% of the investigated flocks. The percentage of HPAIV H5N1-positive holdings was fairly stable in 2017 (12.8%) and 2018 (10.2%), while the percentage of HPAIV H5N8-positive holdings increased from 23% in 2017 to 66.6% during 2018. The proportion of H9N2-positive samples was constantly high (2017:100% and 2018:63%), and H9N2 co-circulated with HPAIV H5N8 in 22 out of 39 (56.8%) flocks. Analyses of 26 H5, 18 H9 and 4 N2 new sequences confirmed continuous genetic diversification. In silico analysis revealed numerous amino acid substitutions in the HA and NA proteins suggestive of increased adaptation to mammalian hosts and putative antigenic variation. For sensitive detection of H9N2 viruses by RT-qPCR, an update of primers and probe sequences was crucial. Reasons for the relative increase of HPAIV H5N8 infections versus H5N1 remained unclear, but lack of suitable vaccines against clade 2.3.4.4b cannot be excluded. A reconsideration of surveillance and control measures should include updating of diagnostic tools and vaccination strategies.
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Affiliation(s)
- Kareem E Hassan
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, Greifswald-Riems, Germany.,Department of Poultry Diseases, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, Egypt
| | - Magdy F El-Kady
- Department of Poultry Diseases, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, Egypt
| | - Azza A A El-Sawah
- Department of Poultry Diseases, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, Egypt
| | - Christine Luttermann
- Institute of Immunology Virology, Friedrich-Loeffler-Institute, Greifswald-Riems, Germany
| | - Rokshana Parvin
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, Greifswald-Riems, Germany.,Department of Pathology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh, Bangladesh
| | - Salama Shany
- Department of Poultry Diseases, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef, Egypt
| | - Martin Beer
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, Greifswald-Riems, Germany
| | - Timm Harder
- Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, Greifswald-Riems, Germany
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11
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Naguib MM, Graaf A, Fortin A, Luttermann C, Wernery U, Amarin N, Hussein HA, Sultan H, Al Adhadh B, Hassan MK, Beer M, Monne I, Harder TC. Novel real-time PCR-based patho- and phylotyping of potentially zoonotic avian influenza A subtype H5 viruses at risk of incursion into Europe in 2017. ACTA ACUST UNITED AC 2017; 22:30435. [PMID: 28084214 PMCID: PMC5388100 DOI: 10.2807/1560-7917.es.2017.22.1.30435] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Accepted: 12/20/2016] [Indexed: 12/20/2022]
Abstract
Since November 2016, Europe witnesses another wave of incursion of highly pathogenic avian influenza (HPAI) A(H5) viruses of the Asian origin goose/Guangdong (gs/GD) lineage. Infections with H5 viruses of clade 2.3.4.4b affect wild bird and poultry populations. H5 viruses of clades 2.2, 2.3.1.2c and 2.3.4.4a were detected previously in Europe in 2006, 2010 and 2014. Clades 2.2.1.2 and 2.3.2.1.c are endemic in Egypt and Western Africa, respectively and have caused human fatalities. Evidence exists of their co-circulation in the Middle East. Subtype H5 viruses of low pathogenicity (LPAI) are endemic in migratory wild bird populations. They potentially mutate into highly pathogenic phenotypes following transmission into poultry holdings. However, to date only the gs/GD H5 lineage had an impact on human health. Rapid and specific diagnosis marks the cornerstone for control and eradication of HPAI virus incursions. We present the development and validation of five real-time RT-PCR assays (RT-qPCR) that allow sequencing-independent pathotype and clade-specific distinction of major gs/GD HPAI H5 virus clades and of Eurasian LPAI viruses currently circulating. Together with an influenza A virus-generic RT-qPCR, the assays significantly speed up time-to-diagnosis and reduce reaction times in a OneHealth approach of curbing the spread of gs/GD HPAI viruses.
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Affiliation(s)
- Mahmoud M Naguib
- Institute of Diagnostic Virology, Friedrich Loeffler Institute, Greifswald-Riems, Germany.,National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Giza, Egypt
| | - Annika Graaf
- Institute of Diagnostic Virology, Friedrich Loeffler Institute, Greifswald-Riems, Germany
| | - Andrea Fortin
- Istituto Zooprofilattico Sperimentale delle Venezie, Padua, Italy
| | - Christine Luttermann
- Institute of Immunology, Friedrich Loeffler Institute, Greifswald-Riems, Germany
| | - Ulrich Wernery
- Central Veterinary Research Laboratory (CVRL), Dubai, United Arab Emirates
| | - Nadim Amarin
- Boehringer Ingelheim, Dubai, United Arab Emirates
| | | | - Hesham Sultan
- Birds and Rabbits Medicine Department, Faculty of Veterinary Medicine, Sadat City University, Egypt
| | - Basem Al Adhadh
- Central Veterinary Laboratory, Ministry of Agriculture, Baghdad, Iraq
| | - Mohamed K Hassan
- National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Giza, Egypt
| | - Martin Beer
- Institute of Diagnostic Virology, Friedrich Loeffler Institute, Greifswald-Riems, Germany
| | - Isabella Monne
- Istituto Zooprofilattico Sperimentale delle Venezie, Padua, Italy
| | - Timm C Harder
- Institute of Diagnostic Virology, Friedrich Loeffler Institute, Greifswald-Riems, Germany
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12
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Arafa AS, Naguib MM, Luttermann C, Selim AA, Kilany WH, Hagag N, Samy A, Abdelhalim A, Hassan MK, Abdelwhab EM, Makonnen Y, Dauphin G, Lubroth J, Mettenleiter TC, Beer M, Grund C, Harder TC. Emergence of a novel cluster of influenza A(H5N1) virus clade 2.2.1.2 with putative human health impact in Egypt, 2014/15. ACTA ACUST UNITED AC 2015; 20:2-8. [PMID: 25860390 DOI: 10.2807/1560-7917.es2015.20.13.21085] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A distinct cluster of highly pathogenic avian influenzaviruses of subtype A(H5N1) has been found to emergewithin clade 2.2.1.2 in poultry in Egypt since summer2014 and appears to have quickly become predominant.Viruses of this cluster may be associated withincreased incidence of human influenza A(H5N1) infectionsin Egypt over the last months.
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Affiliation(s)
- A S Arafa
- National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza, Egypt
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13
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Haß M, Luttermann C, Meyers G. Feline calicivirus can tolerate gross changes of its minor capsid protein expression levels induced by changing translation reinitiation frequency or use of a separate VP2-coding mRNA. PLoS One 2014; 9:e102254. [PMID: 25007260 PMCID: PMC4090194 DOI: 10.1371/journal.pone.0102254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 06/16/2014] [Indexed: 12/31/2022] Open
Abstract
Caliciviruses use reinitiation of translation governed by a ‘termination upstream ribosomal binding site’ (TURBS) for expression of their minor capsid protein VP2. Mutation analysis allowed to identify sequences surrounding the translational start/stop site of the feline calicivirus (FCV) that fine tune reinitiation frequency. A selection of these changes was introduced into the infectious FCV cDNA clone to check the influence of altered VP2 levels on virus replication. In addition, full length constructs were established that displayed a conformation, in which VP2 expression occurred under control of a duplicated subgenomic promoter. Viable viruses recovered from such constructs revealed a rather broad range of VP2 expression levels but comparable growth kinetics showing that caliciviruses can tolerate gross changes of the VP2 expression level.
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Affiliation(s)
- Maria Haß
- Institut für Immunologie, Friedrich-Loeffler-Institut, Tübingen, Germany
| | | | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Tübingen, Germany
- * E-mail:
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14
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Abstract
The calicivirus minor capsid protein VP2 is expressed via termination/reinitiation. This process depends on an upstream sequence element denoted termination upstream ribosomal binding site (TURBS). We have shown for feline calicivirus and rabbit hemorrhagic disease virus that the TURBS contains three sequence motifs essential for reinitiation. Motif 1 is conserved among caliciviruses and is complementary to a sequence in the 18 S rRNA leading to the model that hybridization between motif 1 and 18 S rRNA tethers the post-termination ribosome to the mRNA. Motif 2 and motif 2* are proposed to establish a secondary structure positioning the ribosome relative to the start site of the terminal ORF. Here, we analyzed human norovirus (huNV) sequences for the presence and importance of these motifs. The three motifs were identified by sequence analyses in the region upstream of the VP2 start site, and we showed that these motifs are essential for reinitiation of huNV VP2 translation. More detailed analyses revealed that the site of reinitiation is not fixed to a single codon and does not need to be an AUG, even though this codon is clearly preferred. Interestingly, we were able to show that reinitiation can occur at AUG codons downstream of the canonical start/stop site in huNV and feline calicivirus but not in rabbit hemorrhagic disease virus. Although reinitiation at the original start site is independent of the Kozak context, downstream initiation exhibits requirements for start site sequence context known for linear scanning. These analyses on start codon recognition give a more detailed insight into this fascinating mechanism of gene expression.
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Affiliation(s)
- Christine Luttermann
- Institut für Immunologie, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald, Insel Riems, Germany.
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Südufer 10, 17493 Greifswald, Insel Riems, Germany.
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15
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Abstract
The mechanism leading to reinitiation of translation after termination of protein synthesis in eukaryotes has not yet been resolved in detail. One open question concerns the way the post-termination ribosome is tethered to the mRNA to allow binding of the necessary initiation factors. In caliciviruses, a family of positive strand RNA viruses, the capsid protein VP2 is translated via a termination/reinitiation process. VP2 of the feline calicivirus is encoded in the 3'-terminal open reading frame 3 (ORF3) that overlaps with the preceding ORF2 by four nucleotides. In transient expression studies, the efficiency of VP2 expression was 20 times lower than that of the ORF2 proteins. The close vicinity of the ORF2 termination signal and the ORF3 AUG codon was crucial, whereas the AUG could be replaced by alternative codons. Deletion mapping revealed that the 3'-terminal 69 nucleotides of ORF2 are crucial for VP2 expression. This sequence contains two essential sequence motifs. The first motif is conserved among caliciviruses and complementary to part of the 18 S rRNA. In conclusion, VP2 is expressed in a translation termination/reinitiation process that is special because it requires a sequence element that could prevent dissociation of post-termination ribosomes via hybridization with 18 S rRNA.
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Affiliation(s)
- Christine Luttermann
- Institut für Immunologie, Friedrich-Loeffler-Institut, D-72001 Tübingen, Germany
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