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Sanfaçon H, Alam SB, Ghoshal B, Ghoshal K, Hui E, Jackson AO, Kakani K, Morris TJ, Nagy PD, Simon AE, Sit TL, Smith TJ, White KA, Xiang Y. D'Ann Rochon (1955-2022), a life of passion for plant virology. Virology 2023; 587:109874. [PMID: 37690385 DOI: 10.1016/j.virol.2023.109874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 08/28/2023] [Indexed: 09/12/2023]
Abstract
D'Ann Rochon passed away on November 29th 2022. She is remembered for her outstanding contributions to the field of plant virology, her strong commitment to high quality science and her dedication to the training and mentorship of the next generation of scientists. She was a research scientist for Agriculture and Agri-Food Canada and an Adjunct Professor for the University of British Columbia. Her research program provided new insights on the infection cycle of tombusviruses and related viruses, including ground-breaking research on the structure of virus particles, the mechanisms of virus transmission by fungal zoospores, and the complexity of plant-virus interactions. She also developed diagnostic antibodies for plum pox virus and little cherry virus 2 that have had a significant impact on the management of these viruses.
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Affiliation(s)
- Hélène Sanfaçon
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, 4200 Highway 97, V0H 1Z0, Summerland, BC, Canada.
| | - Syed Benazir Alam
- Nanotechnology Research Center, National Research Council Canada, 11421 Saskatchewan Dr NW, T6G 2M9, Edmonton, AB, Canada.
| | - Basudev Ghoshal
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, 4200 Highway 97, V0H 1Z0, Summerland, BC, Canada.
| | - Kankana Ghoshal
- Canadian Food Inspection Agency, Sidney Laboratory, Center for Plant Health, 8801 East Saanich Road, V8L 1H3, Victoria, BC, Canada.
| | - Elizabeth Hui
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada.
| | | | - Kishore Kakani
- Enzyme/Protein Engineering, Twist Bioscience, 681 Gateway Blvd., South San Francisco, CA 94080, USA.
| | - T Jack Morris
- School of Biological Sciences, University of Nebraska, Lincoln, USA.
| | - Peter D Nagy
- Department of Plant Pathology, University of Kentucky, Lexington, USA.
| | - Anne E Simon
- Department of Cell Biology and Molecular Genetics, University of Maryland - College Park, College Park, MD, USA.
| | - Tim L Sit
- Department of Entomology and Plant Pathology, NC State University, Campus Box 7616, Raleigh, NC 27695-7616, USA.
| | - Thomas J Smith
- University of Texas Medical Branch at Galveston, Department of Biochemistry and Molecular Biology, 301 University Boulevard, Route 0645, Galveston, TX, 77555, USA.
| | - K Andrew White
- Department of Biology, York University, Toronto, ON M3J 1P3, Canada.
| | - Yu Xiang
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, 4200 Highway 97, V0H 1Z0, Summerland, BC, Canada.
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Multiple Signals in the Gut Contract the Mouse Norovirus Capsid To Block Antibody Binding While Enhancing Receptor Affinity. J Virol 2021; 95:e0147121. [PMID: 34468172 DOI: 10.1128/jvi.01471-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human norovirus is the leading cause of gastroenteritis worldwide, with no approved vaccine or antiviral treatment to mitigate infection. These plus-strand RNA viruses have T = 3 icosahedral protein capsids with 90 pronounced protruding (P) domain dimers, to which antibodies and cellular receptors bind. We previously demonstrated that bile binding to the capsid of mouse norovirus (MNV) causes several major conformational changes; the entire P domain rotates by ∼90° and contracts onto the shell, the P domain dimers rotate about each other, and the structural equilibrium of the epitopes at the top of the P domain shifts toward the closed conformation, which favors receptor binding while blocking antibody binding. Here, we demonstrate that MNV undergoes reversible conformational changes at pH 5.0 that are nearly identical to those observed when bile binds. Notably, at low pH or when metals bind, a cluster of acidic resides in the G'-H' loop interact and distort the G'-H' loop, and this may drive C'-D' loop movement toward the closed conformation. Enzyme-linked immunosorbent assays with infectious virus particles at low pH or in the presence of metals demonstrated that all tested antibodies do not bind to this contracted form, akin to what was observed with the MNV-bile complex. Therefore, low pH, cationic metals, and bile salts are physiological triggers in the gut for P domain contraction and structural rearrangement, which synergistically prime the virus for receptor binding while blocking antibody binding. IMPORTANCE The protruding domains on the calicivirus capsids are recognized by cell receptors and antibodies. We demonstrated that MNV P domains are highly mobile, and bile causes contraction onto the shell surface while allosterically blocking antibody binding. We present the near-atomic cryo-electron microscopy structures of infectious MNV at pH 5.0 and pH 7.5. Surprisingly, low pH is sufficient to cause the same conformational changes as when bile binds. A cluster of acidic residues on the G'-H' loop were most likely involved in the pH effects. These residues also bound divalent cations and had the same conformation as observed here at pH 5. Binding assays demonstrated that low pH and metals block antibody binding, and thus the G'-H' loop might be driving the conformational changes. Therefore, low pH, cationic metals, and bile salts in the gut synergistically prime the virus for receptor binding while blocking antibody binding.
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Structural Studies on the Shapeshifting Murine Norovirus. Viruses 2021; 13:v13112162. [PMID: 34834968 PMCID: PMC8621758 DOI: 10.3390/v13112162] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 10/19/2021] [Accepted: 10/22/2021] [Indexed: 12/12/2022] Open
Abstract
Noroviruses are responsible for almost a fifth of all cases of gastroenteritis worldwide. The calicivirus capsid is composed of 180 copies of VP1 with a molecular weight of ~58 kDa. This coat protein is divided into the N-terminus (N), the shell (S) and C-terminal protruding (P) domains. The S domain forms a shell around the viral RNA genome, while the P domains dimerize to form protrusions on the capsid surface. The P domain is subdivided into P1 and P2 subdomains, with the latter containing the binding sites for cellular receptors and neutralizing antibodies. Reviewed here are studies on murine norovirus (MNV) showing that the capsid responds to several physiologically relevant cues; bile, pH, Mg2+, and Ca2+. In the initial site of infection, the intestinal tract, high bile and metal concentrations and low pH cause two significant conformational changes: (1) the P domain contracts onto the shell domain and (2) several conformational changes within the P domain lead to enhanced receptor binding while blocking antibody neutralization. In contrast, the pH is neutral, and the concentrations of bile and metals are low in the serum. Under these conditions, the loops at the tip of the P domain are in the open conformation with the P domain floating on a linker or tether above the shell. This conformational state favors antibody binding but reduces interactions with the receptor. In this way, MNV uses metabolites and environmental cues in the intestine to optimize cellular attachment and escape antibody binding but presents a wholly different structure to the immune system in the serum. To our knowledge, this is the first example of a virus shapeshifting in this manner to escape the immune response.
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Sherman MB, Guenther R, Reade R, Rochon D, Sit T, Smith TJ. Near-Atomic-Resolution Cryo-Electron Microscopy Structures of Cucumber Leaf Spot Virus and Red Clover Necrotic Mosaic Virus: Evolutionary Divergence at the Icosahedral Three-Fold Axes. J Virol 2020; 94:e01439-19. [PMID: 31694952 PMCID: PMC6955255 DOI: 10.1128/jvi.01439-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/28/2019] [Indexed: 12/11/2022] Open
Abstract
Members of the Tombusviridae family have highly similar structures, and yet there are important differences among them in host, transmission, and capsid stabilities. Viruses in the Tombusviridae family have single-stranded RNA (ssRNA) genomes with T=3 icosahedral protein shells with a maximum diameter of ∼340 Å. Each capsid protein is comprised of three domains: R (RNA binding), S (shell), and P (protruding). Between the R domain and S domain is the "arm" region that studies have shown to play a critical role in assembly. To better understand how the details of structural differences and similarities influence the Tombusviridae viral life cycles, the structures of cucumber leaf spot virus (CLSV; genus Aureusvirus) and red clover necrotic mosaic virus (RCNMV; genus Dianthovirus) were determined to resolutions of 3.2 Å and 2.9 Å, respectively, with cryo-electron microscopy and image reconstruction methods. While the shell domains had homologous structures, the stabilizing interactions at the icosahedral 3-fold axes and the R domains differed greatly. The heterogeneity in the R domains among the members of the Tombusviridae family is likely correlated with differences in the sizes and characteristics of the corresponding genomes. We propose that the changes in the R domain/RNA interactions evolved different arm domain interactions at the β-annuli. For example, RCNMV has the largest genome and it appears to have created the necessary space in the capsid by evolving the shortest R domain. The resulting loss in RNA/R domain interactions may have been compensated for by increased intersubunit β-strand interactions at the icosahedral 3-fold axes. Therefore, the R and arm domains may have coevolved to package different genomes within the conserved and rigid shell.IMPORTANCE Members of the Tombusviridae family have nearly identical shells, and yet they package genomes that range from 4.6 kb (monopartite) to 5.3 kb (bipartite) in size. To understand how this genome flexibility occurs within a rigidly conserved shell, we determined the high-resolution cryo-electron microscopy (cryo-EM) structures of cucumber leaf spot virus and red clover necrotic mosaic virus. In response to genomic size differences, it appears that the ssRNA binding (R) domain of the capsid diverged evolutionarily in order to recognize the different genomes. The next region, the "arm," seems to have also coevolved with the R domain to allow particle assembly via interactions at the icosahedral 3-fold axes. In addition, there are differences at the icosahedral 3-fold axes with regard to metal binding that are likely important for transmission and the viral life cycle.
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Affiliation(s)
- Michael B Sherman
- University of Texas Medical Branch at Galveston, Department of Biochemistry and Molecular Biology, Galveston, Texas, USA
| | - Richard Guenther
- North Carolina State University, Department of Entomology and Plant Pathology, Raleigh, North Carolina, USA
| | - Ron Reade
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada
| | - D'Ann Rochon
- Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada
| | - Tim Sit
- North Carolina State University, Department of Entomology and Plant Pathology, Raleigh, North Carolina, USA
| | - Thomas J Smith
- University of Texas Medical Branch at Galveston, Department of Biochemistry and Molecular Biology, Galveston, Texas, USA
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LaBauve AE, Rinker TE, Noureddine A, Serda RE, Howe JY, Sherman MB, Rasley A, Brinker CJ, Sasaki DY, Negrete OA. Lipid-Coated Mesoporous Silica Nanoparticles for the Delivery of the ML336 Antiviral to Inhibit Encephalitic Alphavirus Infection. Sci Rep 2018; 8:13990. [PMID: 30228359 PMCID: PMC6143628 DOI: 10.1038/s41598-018-32033-w] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 08/29/2018] [Indexed: 11/09/2022] Open
Abstract
Venezuelan equine encephalitis virus (VEEV) poses a major public health risk due to its amenability for use as a bioterrorism agent and its severe health consequences in humans. ML336 is a recently developed chemical inhibitor of VEEV, shown to effectively reduce VEEV infection in vitro and in vivo. However, its limited solubility and stability could hinder its clinical translation. To overcome these limitations, lipid-coated mesoporous silica nanoparticles (LC-MSNs) were employed. The large surface area of the MSN core promotes hydrophobic drug loading while the liposome coating retains the drug and enables enhanced circulation time and biocompatibility, providing an ideal ML336 delivery platform. LC-MSNs loaded 20 ± 3.4 μg ML336/mg LC-MSN and released 6.6 ± 1.3 μg/mg ML336 over 24 hours. ML336-loaded LC-MSNs significantly inhibited VEEV in vitro in a dose-dependent manner as compared to unloaded LC-MSNs controls. Moreover, cell-based studies suggested that additional release of ML336 occurs after endocytosis. In vivo safety studies were conducted in mice, and LC-MSNs were not toxic when dosed at 0.11 g LC-MSNs/kg/day for four days. ML336-loaded LC-MSNs showed significant reduction of brain viral titer in VEEV infected mice compared to PBS controls. Overall, these results highlight the utility of LC-MSNs as drug delivery vehicles to treat VEEV.
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Affiliation(s)
- Annette E LaBauve
- Department of Biotechnology and Bioengineering, Sandia National Laboratories, Livermore, CA, USA
| | - Torri E Rinker
- Department of Biotechnology and Bioengineering, Sandia National Laboratories, Livermore, CA, USA
| | - Achraf Noureddine
- Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, NM, USA.,Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, USA.,Center for Micro-Engineered Materials, Advanced Materials Laboratory, Albuquerque, NM, USA
| | - Rita E Serda
- Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, NM, USA.,Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, USA.,Center for Micro-Engineered Materials, Advanced Materials Laboratory, Albuquerque, NM, USA
| | - Jane Y Howe
- Hitachi High Technologies America Inc., Clarksburg, MD, USA
| | - Michael B Sherman
- Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX, USA
| | - Amy Rasley
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, USA
| | - C Jeffery Brinker
- Advanced Materials Laboratory, Sandia National Laboratories, Albuquerque, NM, USA.,Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, USA.,Center for Micro-Engineered Materials, Advanced Materials Laboratory, Albuquerque, NM, USA
| | - Darryl Y Sasaki
- Department of Biotechnology and Bioengineering, Sandia National Laboratories, Livermore, CA, USA
| | - Oscar A Negrete
- Department of Biotechnology and Bioengineering, Sandia National Laboratories, Livermore, CA, USA.
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