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Beach I, Dobrovolny HM. The Effect of Antibodies in the Presence of Syncytia During Viral Infections. Bull Math Biol 2025; 87:76. [PMID: 40382753 DOI: 10.1007/s11538-025-01463-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2025] [Accepted: 05/06/2025] [Indexed: 05/20/2025]
Abstract
Syncytia formation occurs when viruses fuse cells together, creating multinucleated cells. By spreading through fusion, the virus avoids the extracellular environment, protecting it from antibodies that can neutralize the virus. To investigate the effect of this protection, we used a mathematical model to simulate viral infections that spread via both cell-free transmission and syncytia formation and included the effect of antibodies. We compared infections with high, low, and no syncytia fusion, finding that even a low rate of syncytia formation affects infection dynamics and can hinder antibody effectiveness. Specifically, we find that the presence of syncytia increases the viral load, delays the time of peak, and increases the number of cells infected by the virus as compared to infections without syncytia formation. This mathematical model sheds light on how syncytia formation shields viruses from antibodies, aiding in spread of the virus in spite of a robust immune response.
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Affiliation(s)
- Isabelle Beach
- Department of Biology, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX, 75080, USA
- Department of Physics & Astronomy, Texas Christian University, 2800 S. University Drive, Fort Worth, TX, 76129, USA
| | - Hana M Dobrovolny
- Department of Physics & Astronomy, Texas Christian University, 2800 S. University Drive, Fort Worth, TX, 76129, USA.
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2
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Pawłuszkiewicz K, Ryglowski PJ, Idzik N, Błaszczyszyn K, Kucharczyk E, Gaweł-Dąbrowska D, Siczek M, Widelski J, Paluch E. Rotavirus Infections: Pathophysiology, Symptoms, and Vaccination. Pathogens 2025; 14:480. [PMID: 40430800 PMCID: PMC12114175 DOI: 10.3390/pathogens14050480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2025] [Revised: 05/08/2025] [Accepted: 05/13/2025] [Indexed: 05/29/2025] Open
Abstract
Rotavirus (RV) is the most common cause of severe acute gastroenteritis (AGE) in children under five years of age. This review summarizes current knowledge on RV infections, with a particular focus on viral structure, pathophysiological mechanisms, and age-dependent clinical presentation. Special attention is given to systemic manifestations, including central nervous system involvement, autoimmune responses such as type 1 diabetes and celiac disease, and rare associations with biliary atresia. The mechanisms of RV-induced diarrhea and vomiting are discussed in detail. Clinical severity scoring systems-such as the Vesikari and Clark scales-and dehydration assessment tools-the Clinical Dehydration Scale (CDS) and the Dehydration: Assessing Kids Accurately (DHAKA) score-are compared. The review highlights differences in disease course between children under and over five years, emphasizing that RV is not limited to early childhood. A major section addresses the global effectiveness of vaccination programs, their role in reducing disease burden, coverage challenges, and decreased efficacy in low-income countries. Particular focus is placed on high-risk groups, including preterm and immunocompromised infants.
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Affiliation(s)
- Karolina Pawłuszkiewicz
- Faculty of Medicine, Wroclaw Medical University, Wybrzeże L. Pasteura 1, 50-367 Wrocław, Poland; (K.P.); (P.J.R.); (N.I.); (E.K.)
| | - Piotr Józef Ryglowski
- Faculty of Medicine, Wroclaw Medical University, Wybrzeże L. Pasteura 1, 50-367 Wrocław, Poland; (K.P.); (P.J.R.); (N.I.); (E.K.)
| | - Natalia Idzik
- Faculty of Medicine, Wroclaw Medical University, Wybrzeże L. Pasteura 1, 50-367 Wrocław, Poland; (K.P.); (P.J.R.); (N.I.); (E.K.)
| | - Katarzyna Błaszczyszyn
- Jan Mikulicz-Radecki University Hospital in Wroclaw, Borowska 213, 50-556 Wrocław, Poland;
| | - Emilia Kucharczyk
- Faculty of Medicine, Wroclaw Medical University, Wybrzeże L. Pasteura 1, 50-367 Wrocław, Poland; (K.P.); (P.J.R.); (N.I.); (E.K.)
| | - Dagmara Gaweł-Dąbrowska
- Division of Public Health, Faculty of Health Sciences, Wroclaw Medical University, Bujwida 44, 50-345 Wroclaw, Poland;
| | - Marta Siczek
- Department of Forensic Medicine, Wroclaw Medical University, J. Mikulicza-Radeckiego 4, 50-345 Wroclaw, Poland;
| | - Jarosław Widelski
- Department of Pharmacognosy with Medicinal Plant Unit, Medical University of Lublin, Chodźki 1, 20-093 Lublin, Poland
| | - Emil Paluch
- Department of Microbiology, Faculty of Medicine, Wroclaw Medical University, St. T. Chałubińskiego 4, 50-376 Wrocław, Poland
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3
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Voichek M, Bernhard A, Novatchkova M, Handler D, Möseneder P, Rafanel B, Duchek P, Senti KA, Brennecke J. Direct cell-to-cell transmission of retrotransposons. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.03.14.642691. [PMID: 40161635 PMCID: PMC11952523 DOI: 10.1101/2025.03.14.642691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/02/2025]
Abstract
Transposable elements are abundant in host genomes but are generally considered to be confined to the cell in which they are expressed, with the notable exception of endogenous retroviruses. Here, we identify a group of LTR retrotransposons that infect the germline from somatic cells within the Drosophila ovary, despite lacking the fusogenic Envelope protein typically required for retroviral entry. Instead, these elements encode a short transmembrane protein, sORF2, with structural features reminiscent of viral cell-cell fusogens. Through genetics, imaging, and electron microscopy, we show that sORF2 localizes to invasive somatic protrusions, enabling the direct transfer of retrotransposon capsids into the oocyte. Remarkably, sORF2-like proteins are widespread among insect retrotransposons and also occur in piscine nackednaviruses and avian picornaviruses. These findings reveal a noncanonical, Envelope-independent transmission mechanism shared by retrotransposons and non-enveloped viruses, offering important insights into host-pathogen evolution and soma-germline interactions.
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Affiliation(s)
- Maya Voichek
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Andreas Bernhard
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Maria Novatchkova
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Dominik Handler
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Paul Möseneder
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Baptiste Rafanel
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
- Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Peter Duchek
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Kirsten-André Senti
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Julius Brennecke
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC); Dr. Bohr-Gasse 3, 1030 Vienna, Austria
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Yu F, Song S, Xu J, Hao K, Wang Y, Zhao Z. Recognition of novel proteins encoded by an aquareovirus using mass spectrometry. Virology 2025; 601:110281. [PMID: 39499964 DOI: 10.1016/j.virol.2024.110281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2024] [Revised: 10/24/2024] [Accepted: 10/28/2024] [Indexed: 12/07/2024]
Abstract
AQUAREOVIRUS: a genus of within the family Spinareoviridae, order Reovirales, infects aquatic animals. Their genomes comprise 11 segments of double-stranded RNA, which function directly as mRNAs upon release into the cytoplasm of infected cells. Here, liquid chromatography-tandem mass spectrometry was employed to annotate small coding ORFs in the Aquareovirus-C genome. Its plus-strand RNA of segment 8 (S8) contains a novel protein-coding frame (NS15), and S5 seems to has an additional reading frame (NS18) with a putative non-AUG initiation codon. Among them, NS15 polypeptide has been proved by immunoblotting assay. Remarkably, the S4 and S11 minus-strand mRNAs may encode polypeptides, suggesting ambisense polarity of the two segmented RNAs. And the newly discovered NS12 ORF in 2019, from viral tricistronic S7 mRNA, was also confirmed by this mass-spectrometry data. Taken together, these identified new ORFs reveal the genome-coding complexity of Aquareovirus-C.
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Affiliation(s)
- Fei Yu
- Jiangsu Province Engineering Research Center for Marine Bio-resources Sustainable Utilization, College of Oceanography, Hohai University, Nanjing, PR China.
| | - Siyang Song
- Jiangsu Province Engineering Research Center for Marine Bio-resources Sustainable Utilization, College of Oceanography, Hohai University, Nanjing, PR China
| | - Jiehua Xu
- Jiangsu Province Engineering Research Center for Marine Bio-resources Sustainable Utilization, College of Oceanography, Hohai University, Nanjing, PR China
| | - Kai Hao
- Jiangsu Province Engineering Research Center for Marine Bio-resources Sustainable Utilization, College of Oceanography, Hohai University, Nanjing, PR China
| | - Yu Wang
- Jiangsu Province Engineering Research Center for Marine Bio-resources Sustainable Utilization, College of Oceanography, Hohai University, Nanjing, PR China
| | - Zhe Zhao
- Jiangsu Province Engineering Research Center for Marine Bio-resources Sustainable Utilization, College of Oceanography, Hohai University, Nanjing, PR China.
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Sartalamacchia K, Porter MS, Veletanlic V, Ogden KM. Avian deltacoronaviruses encode fusion-associated small transmembrane proteins that can induce syncytia formation. Virology 2024; 600:110258. [PMID: 39406032 PMCID: PMC11737098 DOI: 10.1016/j.virol.2024.110258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2024] [Revised: 09/25/2024] [Accepted: 10/07/2024] [Indexed: 10/19/2024]
Abstract
Fusion-associated small transmembrane (FAST) proteins are nonstructural viral proteins that induce cell-cell fusion. FAST proteins, which previously were identified in the genomes of double-stranded RNA viruses, typically contain an acylated N-terminal ectodomain, central transmembrane domain, and C-terminal endodomain with a polybasic region. Using sequence homology and protein motif prediction, we identified accessory proteins in a subset of avian deltacoronaviruses as putative FAST proteins. Transient expression of thrush coronavirus NS7b or common moorhen coronavirus NS7a, but not night heron coronavirus NS7b, induced cell-cell fusion. Syncytia were detected in primate kidney epithelial cells or fibroblasts but not chicken embryo fibroblasts, and addition of an N-terminal FLAG peptide to the proteins ablated fusion activity. These findings suggest that multiple avian deltacoronaviruses, positive-sense RNA viruses, encode nonstructural proteins that can mediate cell-cell fusion and share features with known FAST proteins. Additional studies are needed to understand contributions of these proteins to deltacoronavirus biology.
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Affiliation(s)
- Kylie Sartalamacchia
- Department of Pediatrics, Vanderbilt University Medical Center, 2200 Children's Way, Suite 2404, Nashville, TN, 37232, USA.
| | - Monique S Porter
- Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Medical Center North, 1161 21st Ave. South, Suite D-2220, Nashville, TN, 37232, USA
| | - Vanesa Veletanlic
- Department of Pediatrics, Vanderbilt University Medical Center, 2200 Children's Way, Suite 2404, Nashville, TN, 37232, USA
| | - Kristen M Ogden
- Department of Pediatrics, Vanderbilt University Medical Center, 2200 Children's Way, Suite 2404, Nashville, TN, 37232, USA; Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Medical Center North, 1161 21st Ave. South, Suite D-2220, Nashville, TN, 37232, USA.
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Sreenivasan CC, Naveed A, Uprety T, Soni S, Jacob O, Adam E, Wang D, Li F. Epidemiological investigation of equine rotavirus B outbreaks in horses in central Kentucky. Vet Microbiol 2024; 298:110278. [PMID: 39437661 DOI: 10.1016/j.vetmic.2024.110278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2024] [Revised: 10/05/2024] [Accepted: 10/12/2024] [Indexed: 10/25/2024]
Abstract
Using metagenomic sequencing we identified equine rotavirus group B (ERVB) of ruminant origin in foal diarrhea outbreaks in the 2021 foaling season. To further investigate ERVB occurrence and determine its environmental stability, we collected mare and foal fecal samples from different farms in Central Kentucky during the 2022 foaling season. The RT-qPCR-based analyses showed that ERVB genome was detected in 16.67 % (42/252) of surveyed mare samples and 26.56 % (34/128) of foal samples. Furthermore, 94.12 % (16/17) of collected soil samples and 100 % (13/13) of water samples obtained from the ERVB-positive farm premises also tested weakly positive. In addition, ERVB genome fragments were detected in 58.33 % (7/12) of indoor samples collected from the equipment/barn/hospital wards during the outbreak period. Finally, the seroprevalence study showed 87 % (113/130) of surveyed horse serum samples were positive for ERVB antibodies. Despite unsuccessful attempts in ERVB cultivation, phylogenetic analyses showed that fecal ERVB strains representing 2022 and 2023 foal diarrhea outbreaks, like 2021 strains, were more closely related to ruminant rotavirus B than other viruses. Further sequence analyses revealed that none of the three viral capsid proteins, the primary targets of virus-neutralizing antibodies, exhibited notable mutations among ERVB strains circulated over the past three years. Our data demonstrated that ERVB was widespread in horses on affected farms with extreme stability in the farm environment. These findings continue to support the need for future surveillance of ERVB in horses and the surrounding environment, and the development of effective countermeasures to protect horses against this new viral disease.
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Affiliation(s)
- Chithra C Sreenivasan
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
| | - Ahsan Naveed
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
| | - Tirth Uprety
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
| | - Shalini Soni
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
| | - Olivia Jacob
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
| | - Emma Adam
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA
| | - Dan Wang
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA.
| | - Feng Li
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA.
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Chamera S, Wycisk K, Czarnocki-Cieciura M, Nowotny M. Cryo-EM structure of rotavirus B NSP2 reveals its unique tertiary architecture. J Virol 2024; 98:e0166023. [PMID: 38421167 PMCID: PMC10949507 DOI: 10.1128/jvi.01660-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 01/23/2024] [Indexed: 03/02/2024] Open
Abstract
Rotavirus (RV) NSP2 is a multifunctional RNA chaperone that exhibits numerous activities that are essential for replication and viral genome packaging. We performed an in silico analysis that highlighted a distant relationship of NSP2 from rotavirus B (RVB) to proteins from other human RVs. We solved a cryo-electron microscopy structure of RVB NSP2 that shows structural differences with corresponding proteins from other human RVs. Based on the structure, we identified amino acid residues that are involved in RNA interactions. Anisotropy titration experiments showed that these residues are important for nucleic acid binding. We also identified structural motifs that are conserved in all RV species. Collectively, our data complete the structural characterization of rotaviral NSP2 protein and demonstrate its structural diversity among RV species.IMPORTANCERotavirus B (RVB), also known as adult diarrhea rotavirus, has caused epidemics of severe diarrhea in China, India, and Bangladesh. Thousands of people are infected in a single RVB epidemic. However, information on this group of rotaviruses remains limited. As NSP2 is an essential protein in the viral life cycle, including its role in the formation of replication factories, it may be a target for future antiviral strategy against viruses with similar mechanisms.
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Affiliation(s)
- Sebastian Chamera
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Krzysztof Wycisk
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Marcin Nowotny
- Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland
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Dobrovolny HM. Mathematical Modeling of Virus-Mediated Syncytia Formation: Past Successes and Future Directions. Results Probl Cell Differ 2024; 71:345-370. [PMID: 37996686 DOI: 10.1007/978-3-031-37936-9_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
Many viruses have the ability to cause cells to fuse into large multi-nucleated cells, known as syncytia. While the existence of syncytia has long been known and its importance in helping spread viral infection within a host has been understood, few mathematical models have incorporated syncytia formation or examined its role in viral dynamics. This review examines mathematical models that have incorporated virus-mediated cell fusion and the insights they have provided on how syncytia can change the time course of an infection. While the modeling efforts are limited, they show promise in helping us understand the consequences of syncytia formation if future modeling efforts can be coupled with appropriate experimental efforts to help validate the models.
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Affiliation(s)
- Hana M Dobrovolny
- Department of Physics & Astronomy, Texas Christian University, Fort Worth, TX, USA.
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Carossino M, Balasuriya UBR, Thieulent CJ, Barrandeguy ME, Vissani MA, Parreño V. Quadruplex Real-Time TaqMan ® RT-qPCR Assay for Differentiation of Equine Group A and B Rotaviruses and Identification of Group A G3 and G14 Genotypes. Viruses 2023; 15:1626. [PMID: 37631969 PMCID: PMC10459720 DOI: 10.3390/v15081626] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 07/23/2023] [Accepted: 07/24/2023] [Indexed: 08/27/2023] Open
Abstract
Equine rotavirus A (ERVA) is the leading cause of diarrhea in foals, with G3P[12] and G14P[12] genotypes being the most prevalent. Recently, equine G3-like RVA was recognized as an emerging infection in children, and a group B equine rotavirus (ERVB) was identified as an emergent cause of foal diarrhea in the US. Thus, there is a need to adapt molecular diagnostic tools for improved detection and surveillance to identify emerging strains, understand their molecular epidemiology, and inform future vaccine development. We developed a quadruplex TaqMan® RT-qPCR assay for differentiation of ERVA and ERVB and simultaneous G-typing of ERVA strains, evaluated its analytical and clinical performance, and compared it to (1) a previously established ERVA triplex RT-qPCR assay and (2) standard RT-PCR assay and Sanger sequencing of PCR products. This quadruplex RT-qPCR assay demonstrated high sensitivity (>90%)/specificity (100%) for every target and high overall agreement (>96%). Comparison between the triplex and quadruplex assays revealed only a slightly higher sensitivity for the ERVA NSP3 target using the triplex format (p-value 0.008) while no significant differences were detected for other targets. This quadruplex RT-qPCR assay will significantly enhance rapid surveillance of both ERVA and ERVB circulating and emerging strains with potential for interspecies transmission.
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Affiliation(s)
- Mariano Carossino
- Louisiana Animal Disease Diagnostic Laboratory, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA;
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Udeni B. R. Balasuriya
- Louisiana Animal Disease Diagnostic Laboratory, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA;
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Côme J. Thieulent
- Louisiana Animal Disease Diagnostic Laboratory, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA;
- Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Maria E. Barrandeguy
- Escuela de Veterinaria, Universidad del Salvador, Buenos Aires B1630, Argentina; (M.E.B.); (M.A.V.)
- Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina;
| | - Maria Aldana Vissani
- Escuela de Veterinaria, Universidad del Salvador, Buenos Aires B1630, Argentina; (M.E.B.); (M.A.V.)
- Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina;
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1425, Argentina
| | - Viviana Parreño
- Instituto de Virología, CICVyA, Instituto Nacional de Tecnología Agropecuaria (INTA), Buenos Aires B1686, Argentina;
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1425, Argentina
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Veletanlic V, Sartalamacchia K, Diller JR, Ogden KM. Multiple rotavirus species encode fusion-associated small transmembrane (FAST) proteins with cell type-specific activity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.07.536061. [PMID: 37066280 PMCID: PMC10104117 DOI: 10.1101/2023.04.07.536061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Fusion-associated small transmembrane (FAST) proteins are viral nonstructural proteins that mediate cell-cell fusion to form multinucleated syncytia. We previously reported that human species B rotavirus NSP1-1 is a FAST protein that induces syncytia in primate epithelial cells but not rodent fibroblasts. We hypothesized that the NSP1-1 proteins of other rotavirus species could also mediate cell-cell fusion and that fusion activity might be limited to cell types derived from homologous hosts. To test this hypothesis, we predicted the structure and domain organization of NSP1-1 proteins of species B rotavirus from a human, goat, and pig, species G rotavirus from a pigeon and turkey, and species I rotavirus from a dog and cat. We cloned these sequences into plasmids and transiently expressed the NSP1-1 proteins in avian, canine, hamster, human, porcine, and simian cells. Regardless of host origin of the virus, each NSP1-1 protein induced syncytia in primate cells, while few induced syncytia in other cell types. To identify the domains that determined cell-specific fusion activity for human species B rotavirus NSP1-1, we engineered chimeric proteins containing domain exchanges with the p10 FAST protein from Nelson Bay orthoreovirus. Using the chimeric proteins, we found that the N-terminal and transmembrane domains determined the cell type specificity of fusion activity. Although the species and cell type criteria for fusion activity remain unclear, these findings suggest that rotavirus species B, G, and I NSP1-1 are functional FAST proteins whose N termini play a role in specifying the cells in which they mediate syncytia formation.
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Affiliation(s)
- Vanesa Veletanlic
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Kylie Sartalamacchia
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Julia R. Diller
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Kristen M. Ogden
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Desselberger U. 14th International dsRNA Virus Symposium, Banff, Alberta, Canada, 10-14 October 2022. Virus Res 2023; 324:199032. [PMID: 36584760 PMCID: PMC10242350 DOI: 10.1016/j.virusres.2022.199032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/23/2022] [Accepted: 12/24/2022] [Indexed: 12/29/2022]
Abstract
This triennial International dsRNA Virus Symposium covered original data which have accrued during the most recent five years. In detail, the genomic diversity of these viruses continued to be explored; various structure-function studies were carried out using reverse genetics and biophysical techniques; intestinal organoids proved to be very suitable for special pathogenesis studies; and the potential of next generation rotavirus vaccines including use of rotavirus recombinants as vectored vaccine candidates was explored. 'Non-lytic release of enteric viruses in cloaked vesicles' was the topic of the keynote lecture by Nihal Altan-Bonnet, NIH, Bethesda, USA. The Jean Cohen lecturer of this meeting was Polly Roy, London School of Hygiene and Tropical Medicine, who spoke on aspects of the replication cycle of bluetongue viruses, and how some of the data are similar to details of rotavirus replication.
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Affiliation(s)
- Ulrich Desselberger
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, U.K..
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12
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Dittmar T, Hass R. Extracellular Events Involved in Cancer Cell-Cell Fusion. Int J Mol Sci 2022; 23:16071. [PMID: 36555709 PMCID: PMC9784959 DOI: 10.3390/ijms232416071] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/13/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022] Open
Abstract
Fusion among different cell populations represents a rare process that is mediated by both intrinsic and extracellular events. Cellular hybrid formation is relayed by orchestrating tightly regulated signaling pathways that can involve both normal and neoplastic cells. Certain important cell merger processes are often required during distinct organismal and tissue development, including placenta and skeletal muscle. In a neoplastic environment, however, cancer cell fusion can generate new cancer hybrid cells. Following survival during a subsequent post-hybrid selection process (PHSP), the new cancer hybrid cells express different tumorigenic properties. These can include elevated proliferative capacity, increased metastatic potential, resistance to certain therapeutic compounds, and formation of cancer stem-like cells, all of which characterize significantly enhanced tumor plasticity. However, many parts within this multi-step cascade are still poorly understood. Aside from intrinsic factors, cell fusion is particularly affected by extracellular conditions, including an inflammatory microenvironment, viruses, pH and ionic stress, hypoxia, and exosome signaling. Accordingly, the present review article will primarily highlight the influence of extracellular events that contribute to cell fusion in normal and tumorigenic tissues.
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Affiliation(s)
- Thomas Dittmar
- Institute of Immunology, Center for Biomedical Education and Research (ZBAF), Witten/Herdecke University, Stockumer Str. 10, 58448 Witten, Germany
| | - Ralf Hass
- Biochemistry and Tumor Biology Laboratory, Department of Obstetrics and Gynecology, Hannover Medical School, 30625 Hannover, Germany
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Omatola CA, Olaniran AO. Genetic heterogeneity of group A rotaviruses: a review of the evolutionary dynamics and implication on vaccination. Expert Rev Anti Infect Ther 2022; 20:1587-1602. [PMID: 36285575 DOI: 10.1080/14787210.2022.2139239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
INTRODUCTION Human rotavirus remains a major etiology of acute gastroenteritis among under 5-year children worldwide despite the availability of oral vaccines. The genetic instability of rotavirus and the ability to form different combinations from the different G- and P-types reshapes the antigenic landscape of emerging strains which often display limited or no antigen identities with the vaccine strain. As evidence also suggests, the selection of the antigenically distinct novel or rare strains and their successful spread in the human population has raised concerns regarding undermining the effectiveness of vaccination programs. AREAS COVERED We review aspects related to current knowledge about genetic and antigenic heterogeneity of rotavirus, the mechanism of genetic diversity and evolution, and the implication of genetic change on vaccination. EXPERT OPINION Genetic changes in the segmented genome of rotavirus can alter the antigenic landscape on the virion capsid and further promote viral fitness in a fully vaccinated population. Against this background, the potential risk of the appearance of new rotavirus strains over the long term would be better predicted by a continued and increased close monitoring of the variants across the globe to identify any change associated with disease dynamics.
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Affiliation(s)
- Cornelius A Omatola
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Durban, Republic of South Africa
| | - Ademola O Olaniran
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Durban, Republic of South Africa
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14
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Amidei A, Dobrovolny HM. Estimation of virus-mediated cell fusion rate of SARS-CoV-2. Virology 2022; 575:91-100. [PMID: 36088794 PMCID: PMC9449781 DOI: 10.1016/j.virol.2022.08.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/27/2022] [Accepted: 08/28/2022] [Indexed: 12/22/2022]
Abstract
Several viruses have the ability to form large multinucleated cells known as syncytia. Many properties of syncytia and the role they play in the evolution of a viral infection are not well understood. One basic question that has not yet been answered is how quickly syncytia form. We use a novel mathematical model of cell-cell fusion assays and apply it to experimental data from SARS-CoV-2 fusion assays to provide the first estimates of virus-mediated cell fusion rate. We find that for SARS-CoV2, the fusion rate is in the range of 6 × 10-4-12×10-4/h. We also use our model to compare fusion rates when the protease TMPRSS2 is overexpressed (2-4 times larger fusion rate), when the protease furin is removed (one third the original fusion rate), and when the spike protein is altered (1/10th the original fusion rate). The use of mathematical models allows us to provide additional quantitative information about syncytia formation.
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Affiliation(s)
- Ava Amidei
- Department of Chemistry & Biochemistry, Texas Christian University, Fort Worth, TX, USA
| | - Hana M Dobrovolny
- Department of Physics & Astronomy, Texas Christian University, Fort Worth, TX, USA.
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15
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Johne R, Schilling-Loeffler K, Ulrich RG, Tausch SH. Whole Genome Sequence Analysis of a Prototype Strain of the Novel Putative Rotavirus Species L. Viruses 2022; 14:v14030462. [PMID: 35336869 PMCID: PMC8954357 DOI: 10.3390/v14030462] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 02/21/2022] [Accepted: 02/22/2022] [Indexed: 02/05/2023] Open
Abstract
Rotaviruses infect humans and animals and are a main cause of diarrhea. They are non-enveloped viruses with a genome of 11 double-stranded RNA segments. Based on genome analysis and amino acid sequence identities of the capsid protein VP6, the rotavirus species A to J (RVA-RVJ) have been defined so far. In addition, rotaviruses putatively assigned to the novel rotavirus species K (RVK) and L (RVL) have been recently identified in common shrews (Sorex araneus), based on partial genome sequences. Here, the complete genome sequence of strain KS14/0241, a prototype strain of RVL, is presented. The deduced amino acid sequence for VP6 of this strain shows only up to 47% identity to that of RVA to RVJ reference strains. Phylogenetic analyses indicate a clustering separated from the established rotavirus species for all 11 genome segments of RVL, with the closest relationship to RVH and RVJ within the phylogenetic RVB-like clade. The non-coding genome segment termini of RVL showed conserved sequences at the 5′-end (positive-sense RNA strand), which are common to all rotaviruses, and those conserved among the RVB-like clade at the 3′-end. The results are consistent with a classification of the virus into a novel rotavirus species L.
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Affiliation(s)
- Reimar Johne
- Department of Biological Safety, German Federal Institute for Risk Assessment, 10589 Berlin, Germany; (K.S.-L.); (S.H.T.)
- Correspondence:
| | - Katja Schilling-Loeffler
- Department of Biological Safety, German Federal Institute for Risk Assessment, 10589 Berlin, Germany; (K.S.-L.); (S.H.T.)
| | - Rainer G. Ulrich
- Institute of Novel and Emerging Infectious Diseases, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany;
- German Centre for Infection Research (DZIF), 17493 Greifswald-Insel Riems, Germany
| | - Simon H. Tausch
- Department of Biological Safety, German Federal Institute for Risk Assessment, 10589 Berlin, Germany; (K.S.-L.); (S.H.T.)
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16
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Giglione C, Meinnel T. Mapping the myristoylome through a complete understanding of protein myristoylation biochemistry. Prog Lipid Res 2021; 85:101139. [PMID: 34793862 DOI: 10.1016/j.plipres.2021.101139] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 11/04/2021] [Accepted: 11/06/2021] [Indexed: 12/22/2022]
Abstract
Protein myristoylation is a C14 fatty acid modification found in all living organisms. Myristoylation tags either the N-terminal alpha groups of cysteine or glycine residues through amide bonds or lysine and cysteine side chains directly or indirectly via glycerol thioester and ester linkages. Before transfer to proteins, myristate must be activated into myristoyl coenzyme A in eukaryotes or, in bacteria, to derivatives like phosphatidylethanolamine. Myristate originates through de novo biosynthesis (e.g., plants), from external uptake (e.g., human tissues), or from mixed origins (e.g., unicellular organisms). Myristate usually serves as a molecular anchor, allowing tagged proteins to be targeted to membranes and travel across endomembrane networks in eukaryotes. In this review, we describe and discuss the metabolic origins of protein-bound myristate. We review strategies for in vivo protein labeling that take advantage of click-chemistry with reactive analogs, and we discuss new approaches to the proteome-wide discovery of myristate-containing proteins. The machineries of myristoylation are described, along with how protein targets can be generated directly from translating precursors or from processed proteins. Few myristoylation catalysts are currently described, with only N-myristoyltransferase described to date in eukaryotes. Finally, we describe how viruses and bacteria hijack and exploit myristoylation for their pathogenicity.
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Affiliation(s)
- Carmela Giglione
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
| | - Thierry Meinnel
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
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17
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Dittmar T, Weiler J, Luo T, Hass R. Cell-Cell Fusion Mediated by Viruses and HERV-Derived Fusogens in Cancer Initiation and Progression. Cancers (Basel) 2021; 13:5363. [PMID: 34771528 PMCID: PMC8582398 DOI: 10.3390/cancers13215363] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 10/22/2021] [Accepted: 10/24/2021] [Indexed: 12/13/2022] Open
Abstract
Cell fusion is a well-known, but still scarcely understood biological phenomenon, which might play a role in cancer initiation, progression and formation of metastases. Although the merging of two (cancer) cells appears simple, the entire process is highly complex, energy-dependent and tightly regulated. Among cell fusion-inducing and -regulating factors, so-called fusogens have been identified as a specific type of proteins that are indispensable for overcoming fusion-associated energetic barriers and final merging of plasma membranes. About 8% of the human genome is of retroviral origin and some well-known fusogens, such as syncytin-1, are expressed by human (cancer) cells. Likewise, enveloped viruses can enable and facilitate cell fusion due to evolutionarily optimized fusogens, and are also capable to induce bi- and multinucleation underlining their fusion capacity. Moreover, multinucleated giant cancer cells have been found in tumors derived from oncogenic viruses. Accordingly, a potential correlation between viruses and fusogens of human endogenous retroviral origin in cancer cell fusion will be summarized in this review.
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Affiliation(s)
- Thomas Dittmar
- Institute of Immunology, Center for Biomedical Education and Research (ZBAF), Witten/Herdecke University, 58448 Witten, Germany;
| | - Julian Weiler
- Institute of Immunology, Center for Biomedical Education and Research (ZBAF), Witten/Herdecke University, 58448 Witten, Germany;
| | - Tianjiao Luo
- Biochemistry and Tumor Biology Laboratory, Department of Obstetrics and Gynecology, Hannover Medical School, 30625 Hannover, Germany;
| | - Ralf Hass
- Biochemistry and Tumor Biology Laboratory, Department of Obstetrics and Gynecology, Hannover Medical School, 30625 Hannover, Germany;
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18
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Caddy S, Papa G, Borodavka A, Desselberger U. Rotavirus research: 2014-2020. Virus Res 2021; 304:198499. [PMID: 34224769 DOI: 10.1016/j.virusres.2021.198499] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 02/09/2023]
Abstract
Rotaviruses are major causes of acute gastroenteritis in infants and young children worldwide and also cause disease in the young of many other mammalian and of avian species. During the recent 5-6 years rotavirus research has benefitted in a major way from the establishment of plasmid only-based reverse genetics systems, the creation of human and other mammalian intestinal enteroids, and from the wide application of structural biology (cryo-electron microscopy, cryo-EM tomography) and complementary biophysical approaches. All of these have permitted to gain new insights into structure-function relationships of rotaviruses and their interactions with the host. This review follows different stages of the viral replication cycle and summarizes highlights of structure-function studies of rotavirus-encoded proteins (both structural and non-structural), molecular mechanisms of viral replication including involvement of cellular proteins and lipids, the spectrum of viral genomic and antigenic diversity, progress in understanding of innate and acquired immune responses, and further developments of prevention of rotavirus-associated disease.
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Affiliation(s)
- Sarah Caddy
- Cambridge Institute for Therapeutic Immunology and Infectious Disease Jeffery Cheah Biomedical Centre, Cambridge, CB2 0AW, UK.
| | - Guido Papa
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus Francis Crick Avenue, Cambridge, CB2 0QH, UK.
| | - Alexander Borodavka
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, UK.
| | - Ulrich Desselberger
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
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19
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Kanai Y, Kobayashi T. FAST Proteins: Development and Use of Reverse Genetics Systems for Reoviridae Viruses. Annu Rev Virol 2021; 8:515-536. [PMID: 34586868 DOI: 10.1146/annurev-virology-091919-070225] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Reverse genetics systems for viruses, the technology used to generate gene-engineered recombinant viruses from artificial genes, enable the study of the roles of the individual nucleotides and amino acids of viral genes and proteins in infectivity, replication, and pathogenicity. The successful development of a reverse genetics system for poliovirus in 1981 accelerated the establishment of protocols for other RNA viruses important for human health. Despite multiple efforts, rotavirus (RV), which causes severe gastroenteritis in infants, was refractory to reverse genetics analysis, and the first complete reverse genetics system for RV was established in 2017. This novel technique involves use of the fusogenic protein FAST (fusion-associated small transmembrane) derived from the bat-borne Nelson Bay orthoreovirus, which induces massive syncytium formation. Co-transfection of a FAST-expressing plasmid with complementary DNAs encoding RV genes enables rescue of recombinant RV. This review focuses on methodological insights into the reverse genetics system for RV and discusses applications and potential improvements to this system.
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Affiliation(s)
- Yuta Kanai
- Department of Virology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan; ,
| | - Takeshi Kobayashi
- Department of Virology, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka 565-0871, Japan; ,
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20
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Recent advances in rotavirus reverse genetics and its utilization in basic research and vaccine development. Arch Virol 2021; 166:2369-2386. [PMID: 34216267 PMCID: PMC8254061 DOI: 10.1007/s00705-021-05142-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 04/27/2021] [Indexed: 11/29/2022]
Abstract
Rotaviruses are segmented double-stranded RNA viruses with a high frequency of gene reassortment, and they are a leading cause of global diarrheal deaths in children less than 5 years old. Two-thirds of rotavirus-associated deaths occur in low-income countries. Currently, the available vaccines in developing countries have lower efficacy in children than those in developed countries. Due to added safety concerns and the high cost of current vaccines, there is a need to develop cost-effective next-generation vaccines with improved safety and efficacy. The reverse genetics system (RGS) is a powerful tool for investigating viral protein functions and developing novel vaccines. Recently, an entirely plasmid-based RGS has been developed for several rotaviruses, and this technological advancement has significantly facilitated novel rotavirus research. Here, we review the recently developed RGS platform and discuss its application in studying infection biology, gene reassortment, and development of vaccines against rotavirus disease.
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21
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The role of syncytia during viral infections. J Theor Biol 2021; 525:110749. [PMID: 33964289 DOI: 10.1016/j.jtbi.2021.110749] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 03/25/2021] [Accepted: 04/29/2021] [Indexed: 12/16/2022]
Abstract
Respiratory syncytial virus (RSV) is a common, contagious infection of the lungs and the respiratory tract. RSV is characterized by syncytia, which are multinuclear cells created by cells that have fused together. We use a mathematical model to study how different assumptions about the viral production and lifespan of syncytia change the resulting infection time course. We find that the effect of syncytia on viral titer is only apparent when the basic reproduction number for infection via syncytia formation is similar to the reproduction number for cell free viral transmission. When syncytia fusion rate is high, we find the presence of syncytia can lead to slowly growing infections if viral production is suppressed in syncytia. Our model provides insight into how the presence of syncytia can affect the time course of a viral infection.
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22
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Del Papa J, Clarkin RG, Parks RJ. Use of cell fusion proteins to enhance adenoviral vector efficacy as an anti-cancer therapeutic. Cancer Gene Ther 2020; 28:745-756. [DOI: 10.1038/s41417-020-0192-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/18/2020] [Accepted: 06/23/2020] [Indexed: 01/03/2023]
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23
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Yang Y, Gaspard G, McMullen N, Duncan R. Polycistronic Genome Segment Evolution and Gain and Loss of FAST Protein Function during Fusogenic Orthoreovirus Speciation. Viruses 2020; 12:v12070702. [PMID: 32610593 PMCID: PMC7412057 DOI: 10.3390/v12070702] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 06/03/2020] [Accepted: 06/25/2020] [Indexed: 12/29/2022] Open
Abstract
The Reoviridae family is the only non-enveloped virus family with members that use syncytium formation to promote cell–cell virus transmission. Syncytiogenesis is mediated by a fusion-associated small transmembrane (FAST) protein, a novel family of viral membrane fusion proteins. Previous evidence suggested the fusogenic reoviruses arose from an ancestral non-fusogenic virus, with the preponderance of fusogenic species suggesting positive evolutionary pressure to acquire and maintain the fusion phenotype. New phylogenetic analyses that included the atypical waterfowl subgroup of avian reoviruses and recently identified new orthoreovirus species indicate a more complex relationship between reovirus speciation and fusogenic capacity, with numerous predicted internal indels and 5’-terminal extensions driving the evolution of the orthoreovirus’ polycistronic genome segments and their encoded FAST and fiber proteins. These inferred recombination events generated bi- and tricistronic genome segments with diverse gene constellations, they occurred pre- and post-orthoreovirus speciation, and they directly contributed to the evolution of the four extant orthoreovirus FAST proteins by driving both the gain and loss of fusion capability. We further show that two distinct post-speciation genetic events led to the loss of fusion in the waterfowl isolates of avian reovirus, a recombination event that replaced the p10 FAST protein with a heterologous, non-fusogenic protein and point substitutions in a conserved motif that destroyed the p10 assembly into multimeric fusion platforms.
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Affiliation(s)
- Yiming Yang
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4R2, Canada; (Y.Y.); (G.G.); (N.M.)
| | - Gerard Gaspard
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4R2, Canada; (Y.Y.); (G.G.); (N.M.)
| | - Nichole McMullen
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4R2, Canada; (Y.Y.); (G.G.); (N.M.)
| | - Roy Duncan
- Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4R2, Canada; (Y.Y.); (G.G.); (N.M.)
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
- Correspondence:
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Rotavirus Species B Encodes a Functional Fusion-Associated Small Transmembrane Protein. J Virol 2019; 93:JVI.00813-19. [PMID: 31375572 DOI: 10.1128/jvi.00813-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/19/2019] [Indexed: 02/07/2023] Open
Abstract
Rotavirus is an important cause of diarrheal disease in young mammals. Rotavirus species A (RVA) causes most human rotavirus diarrheal disease and primarily affects infants and young children. Rotavirus species B (RVB) has been associated with sporadic outbreaks of human adult diarrheal disease. RVA and RVB are predicted to encode mostly homologous proteins but differ significantly in the proteins encoded by the NSP1 gene. In the case of RVB, the NSP1 gene encodes two putative protein products of unknown function, NSP1-1 and NSP1-2. We demonstrate that human RVB NSP1-1 mediates syncytium formation in cultured human cells. Based on sequence alignment, NSP1-1 proteins from species B, G, and I contain features consistent with fusion-associated small transmembrane (FAST) proteins, which have previously been identified in other genera of the Reoviridae family. Like some other FAST proteins, RVB NSP1-1 is predicted to have an N-terminal myristoyl modification. Addition of an N-terminal FLAG peptide disrupts NSP1-1-mediated fusion. NSP1-1 from a human RVB mediates fusion of human cells but not hamster cells and, thus, may serve as a species tropism determinant. NSP1-1 also can enhance RVA replication in human cells, both in single-cycle infection studies and during a multicycle time course in the presence of fetal bovine serum, which inhibits rotavirus spread. These findings suggest potential yet untested roles for NSP1-1 in RVB species tropism, immune evasion, and pathogenesis.IMPORTANCE While species A rotavirus is commonly associated with diarrheal disease in young children, species B rotavirus has caused sporadic outbreaks of adult diarrheal disease. A major genetic difference between species A and B rotaviruses is the NSP1 gene, which encodes two proteins for species B rotavirus. We demonstrate that the smaller of these proteins, NSP1-1, can mediate fusion of cultured human cells. Comparison with viral proteins of similar function provides insight into NSP1-1 domain organization and fusion mechanism. These comparisons suggest that there is a fatty acid modification at the amino terminus of the protein, and our results show that an intact amino terminus is required for NSP1-1-mediated fusion. NSP1-1 from a human virus mediates fusion of human cells, but not hamster cells, and enhances species A rotavirus replication in culture. These findings suggest potential, but currently untested, roles for NSP1-1 in RVB host species tropism, immune evasion, and pathogenesis.
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