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Sun Y, Yuan Y, Mao H, Su L, Ge Q, Gao J, Xu C, Gong L. Molecular Epidemiology of Human Norovirus Variants from Outbreaks in Zhejiang Province, China, during 2021. Adv Virol 2024; 2024:7972494. [PMID: 38846347 PMCID: PMC11156503 DOI: 10.1155/2024/7972494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/01/2024] [Accepted: 05/16/2024] [Indexed: 06/09/2024] Open
Abstract
Background Noroviruses are the most frequent cause of epidemic acute viral gastroenteritis in China. Objectives The aim of this study was to determine the molecular epidemiological characteristics of norovirus outbreaks and the molecular genetic features of norovirus in Zhejiang Province during 2021. Methods First, the local Centers for Disease Control and Prevention in the outbreak area conducted on-site epidemiologic investigations and collected samples from ill patients for initial testing. The general epidemiologic characteristics of the demographic information are presented through descriptive analysis. Positive samples were sent to the Microbiology Laboratory of Zhejiang Provincial Center for Disease Control and Prevention for further verification. The presence of norovirus genogroups I (GI) and II (GII), along with sapovirus, was detected. Subsequently, the specimens positive for norovirus were sequenced for genotyping purposes. Furthermore, the whole genomes of positive samples were sequenced, enabling the characterization of both nucleotide and amino acid differences within the virus. Finally, phylogenetic trees were constructed to further analyze and understand the genetic relationships among the detected viruses. Result 227 norovirus outbreaks were reported in Zhejiang Province, China, during 2021. Schools were the main setting while January was the peak month for outbreaks. A total of 17 diverse genotypes of norovirus were identified in 2021, and GII.P16-GII.2 was the most frequent genotype (30.19%). Seven genomes (five GI.P4-GI.5 and two GII.P16-GII.2) were obtained. Although GI.P4-GI.5 is considered to be a rare genotype of norovirus, the prevalence might have been underestimated. Capsid microvariation of GII.2 displayed histo-blood group antigen binding patterns compared to the GII.2 prototype, although VP1 sequences were considered to have a minimal impact on antigenicity. Conclusion This study revealed the diversity of norovirus strains' genotypes circulating in Zhejiang Province in 2021. Continued molecular surveillance of noroviruses should be strengthened in our further efforts to the development of vaccines.
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Affiliation(s)
- Yi Sun
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
| | - Yongjuan Yuan
- Jia Shan Center for Disease Control and Prevention, Jiaxing, Zhejiang, China
| | - Haiyan Mao
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
| | - Lingxuan Su
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
| | - Qiong Ge
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
| | - Jian Gao
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
| | - Changping Xu
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
| | - Liming Gong
- Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China
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Rouphael N, Beck A, Kirby AE, Liu P, Natrajan MS, Lai L, Phadke V, Winston J, Raabe V, Collins MH, Girmay T, Alvarez A, Beydoun N, Karmali V, Altieri-Rivera J, Lindesmith LC, Anderson EJ, Wang Y, El-Khorazaty J, Petrie C, Baric RS, Baqar S, Moe CL, Mulligan MJ. Dose-Response of a Norovirus GII.2 Controlled Human Challenge Model Inoculum. J Infect Dis 2022; 226:1771-1780. [PMID: 35137154 PMCID: PMC9650503 DOI: 10.1093/infdis/jiac045] [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: 10/02/2021] [Accepted: 02/03/2022] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Genogroup II noroviruses are the most common cause of acute infectious gastroenteritis. We evaluated the use of a new GII.2 inoculum in a human challenge. METHODS Forty-four healthy adults (36 secretor-positive and 8 secretor-negative for histo-blood group antigens) were challenged with ascending doses of a new safety-tested Snow Mountain virus (SMV) GII.2 norovirus inoculum (1.2 × 104 to 1.2 × 107 genome equivalent copies [GEC]; n = 38) or placebo (n = 6). Illness was defined as diarrhea and/or vomiting postchallenge in subjects with evidence of infection (defined as GII.2 norovirus RNA detection in stool and/or anti-SMV immunoglobulin G [IgG] seroconversion). RESULTS The highest dose was associated with SMV infection in 90%, and illness in 70% of subjects with 10 of 12 secretor-positive (83%) and 4 of 8 secretor-negative (50%) becoming ill. There was no association between prechallenge anti-SMV serum IgG concentration, carbohydrate-binding blockade antibody, or salivary immunoglobulin A and infection. The median infectious dose (ID50) was 5.1 × 105 GEC. CONCLUSIONS High rates of infection and illness were observed in both secretor-positive and secretor-negative subjects in this challenge study. However, a high dose will be required to achieve the target of 75% illness to make this an efficient model for evaluating potential norovirus vaccines and therapeutics. CLINICAL TRIALS REGISTRATION NCT02473224.
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Affiliation(s)
- Nadine Rouphael
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Allison Beck
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Amy E Kirby
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Pengbo Liu
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Muktha S Natrajan
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Lilin Lai
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Varun Phadke
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Juton Winston
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Vanessa Raabe
- New York University Grossman School of Medicine and New York University Vaccine Center, New York, New York, USA
| | - Matthew H Collins
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Tigisty Girmay
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Alicarmen Alvarez
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Nour Beydoun
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Vinit Karmali
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Joanne Altieri-Rivera
- Hope Clinic of the Emory Vaccine Center, Division of Infectious Diseases, Department of Medicine, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Lisa C Lindesmith
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Evan J Anderson
- Division of Infectious Diseases, Department of Pediatrics, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Yuke Wang
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | | | - Carey Petrie
- The Emmes Company, LLC, Rockville, Maryland, USA
| | - Ralph S Baric
- Department of Epidemiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Shahida Baqar
- Division of Microbiology and Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Christine L Moe
- Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
| | - Mark J Mulligan
- New York University Grossman School of Medicine and New York University Vaccine Center, New York, New York, USA
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Lindesmith LC, Boshier FAT, Brewer-Jensen PD, Roy S, Costantini V, Mallory ML, Zweigart M, May SR, Conrad H, O’Reilly KM, Kelly D, Celma CC, Beard S, Williams R, Tutill HJ, Becker Dreps S, Bucardo F, Allen DJ, Vinjé J, Goldstein RA, Breuer J, Baric RS. Immune Imprinting Drives Human Norovirus Potential for Global Spread. mBio 2022; 13:e0186122. [PMID: 36102514 PMCID: PMC9600701 DOI: 10.1128/mbio.01861-22] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/25/2022] [Indexed: 01/11/2023] Open
Abstract
Understanding the complex interactions between virus and host that drive new strain evolution is key to predicting the emergence potential of variants and informing vaccine development. Under our hypothesis, future dominant human norovirus GII.4 variants with critical antigenic properties that allow them to spread are currently circulating undetected, having diverged years earlier. Through large-scale sequencing of GII.4 surveillance samples, we identified two variants with extensive divergence within domains that mediate neutralizing antibody binding. Subsequent serological characterization of these strains using temporally resolved adult and child sera suggests that neither candidate could spread globally in adults with multiple GII.4 exposures, yet young children with minimal GII.4 exposure appear susceptible. Antigenic cartography of surveillance and outbreak sera indicates that continued population exposure to GII.4 Sydney 2012 and antigenically related variants over a 6-year period resulted in a broadening of immunity to heterogeneous GII.4 variants, including those identified here. We show that the strongest antibody responses in adults exposed to GII.4 Sydney 2012 are directed to previously circulating GII.4 viruses. Our data suggest that the broadening of antibody responses compromises establishment of strong GII.4 Sydney 2012 immunity, thereby allowing the continued persistence of GII.4 Sydney 2012 and modulating the cycle of norovirus GII.4 variant replacement. Our results indicate a cycle of norovirus GII.4 variant replacement dependent upon population immunity. Young children are susceptible to divergent variants; therefore, emergence of these strains worldwide is driven proximally by changes in adult serological immunity and distally by viral evolution that confers fitness in the context of immunity. IMPORTANCE In our model, preepidemic human norovirus variants harbor genetic diversification that translates into novel antigenic features without compromising viral fitness. Through surveillance, we identified two viruses fitting this profile, forming long branches on a phylogenetic tree. Neither evades current adult immunity, yet young children are likely susceptible. By comparing serological responses, we demonstrate that population immunity varies by age/exposure, impacting predicted susceptibility to variants. Repeat exposure to antigenically similar variants broadens antibody responses, providing immunological coverage of diverse variants but compromising response to the infecting variant, allowing continued circulation. These data indicate norovirus GII.4 variant replacement is driven distally by virus evolution and proximally by immunity in adults.
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Affiliation(s)
- Lisa C. Lindesmith
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Florencia A. T. Boshier
- Department of Infection, Immunity and Inflammation, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Paul D. Brewer-Jensen
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Sunando Roy
- Department of Infection, Immunity and Inflammation, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Veronica Costantini
- Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Michael L. Mallory
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Mark Zweigart
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Samantha R. May
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Helen Conrad
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Kathleen M. O’Reilly
- Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Daniel Kelly
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Cristina C. Celma
- Enteric Virus Unit, The Virus Reference Department, UK Health Security Agency, London, United Kingdom
| | - Stuart Beard
- Enteric Virus Unit, The Virus Reference Department, UK Health Security Agency, London, United Kingdom
| | - Rachel Williams
- Department of Infection, Immunity and Inflammation, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
- Department of Genetics & Genomic Medicine, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Helena J. Tutill
- Department of Genetics & Genomic Medicine, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
| | - Sylvia Becker Dreps
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
- Department of Family Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Filemón Bucardo
- Department of Microbiology, National Autonomous University of Nicaragua, León, León, Nicaragua
| | - David J. Allen
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jan Vinjé
- Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Richard A. Goldstein
- Division of Infection and Immunity, University College London, London, United Kingdom
| | - Judith Breuer
- Department of Infection, Immunity and Inflammation, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom
- Department of Microbiology, Great Ormond Street Hospital for Children NHS Foundation Trust, London, United Kingdom
| | - Ralph S. Baric
- Department of Epidemiology, University of North Carolina, Chapel Hill, North Carolina, USA
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Creutznacher R, Maass T, Dülfer J, Feldmann C, Hartmann V, Lane MS, Knickmann J, Westermann LT, Thiede L, Smith TJ, Uetrecht C, Mallagaray A, Waudby CA, Taube S, Peters T. Distinct dissociation rates of murine and human norovirus P-domain dimers suggest a role of dimer stability in virus-host interactions. Commun Biol 2022; 5:563. [PMID: 35680964 PMCID: PMC9184547 DOI: 10.1038/s42003-022-03497-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 05/19/2022] [Indexed: 11/29/2022] Open
Abstract
Norovirus capsids are icosahedral particles composed of 90 dimers of the major capsid protein VP1. The C-terminus of the VP1 proteins forms a protruding (P)-domain, mediating receptor attachment, and providing a target for neutralizing antibodies. NMR and native mass spectrometry directly detect P-domain monomers in solution for murine (MNV) but not for human norovirus (HuNoV). We report that the binding of glycochenodeoxycholic acid (GCDCA) stabilizes MNV-1 P-domain dimers (P-dimers) and induces long-range NMR chemical shift perturbations (CSPs) within loops involved in antibody and receptor binding, likely reflecting corresponding conformational changes. Global line shape analysis of monomer and dimer cross-peaks in concentration-dependent methyl TROSY NMR spectra yields a dissociation rate constant koff of about 1 s−1 for MNV-1 P-dimers. For structurally closely related HuNoV GII.4 Saga P-dimers a value of about 10−6 s−1 is obtained from ion-exchange chromatography, suggesting essential differences in the role of GCDCA as a cofactor for MNV and HuNoV infection. NMR and native mass spectrometry reveal that the major capsid VP1 protein from murine and human norovirus exhibit distinct behaviors and are differentially regulated by the binding of glycochenodeoxycholic acid.
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Zheng GL, Zhu ZX, Cui JL, Yu JM. Evolutionary Analyses of Emerging GII.2[P16] and GII.4 Sydney [P16] Noroviruses. Virus Evol 2022; 8:veac030. [PMID: 35450165 PMCID: PMC9019527 DOI: 10.1093/ve/veac030] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 02/22/2022] [Accepted: 03/30/2022] [Indexed: 11/14/2022] Open
Abstract
GII.2[P16] and GII.4 Sydney [P16] are currently the two predominant norovirus genotypes. This study sought to clarify their evolutionary patterns by analyzing the major capsid VP1 and RNA-dependent RNA polymerase (RdRp) genes. Sequence diversities were analyzed at both nucleotide and amino acid levels. Selective pressures were evaluated with the Hyphy package in different models. Phylogenetic trees were constructed by the maximum likelihood method from full VP1 sequences, and evolutionary rates were estimated by the Bayesian Markov Chain Monte Carlo approach. The results showed that (1) several groups of tightly linked mutations between the RdRp and VP1 genes were detected in the GII.2[P16] and GII.4[P16] noroviruses, and most of these mutations were synonymous, which may lead to a better viral fitness to the host; (2) although the pattern of having new GII.4 variants every 2–4 years has been broken, both the pre- and the post-2015 Sydney VP1 had comparable evolutionary rates to previously epidemic GII.4 variants, and half of the major antigenic sites on GII.4 Sydney had residue substitutions and several caused obvious changes in the carbohydrate-binding surface that may potentially alter the property of the virus; and (3) GII.4 Sydney variants during 2018–21 showed geographical specificity in East Asia, South Asia, and North America; the antigenic sites of GII.2 are strictly conserved, but the GII.2 VP1 chronologically evolved into nine different sublineages over time, with sublineage IX being the most prevalent one since 2018. This study suggested that both VP1 and RdRp of the GII.2[P16] and GII.4 Sydney [P16] noroviruses exhibited different evolutionary directions. GII.4[P16] is likely to generate potential novel epidemic variants by accumulating mutations in the P2 domain, similar to previously epidemic GII.4 variants, while GII.2[P16] has conserved predicted antigenicity and may evolve by changing the properties of nonstructural proteins, such as polymerase replicational fidelity and efficiency. This study expands the understanding of the evolutionary dynamics of GII.2[P16] and GII.4[P16] noroviruses and may predict the emergence of new variants.
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Affiliation(s)
- Guo-li Zheng
- College of Life Sciences and Bioengineering, Beijing Jiaotong University, Beijing 100044, China
| | - Zheng-xi Zhu
- College of Life Sciences and Bioengineering, Beijing Jiaotong University, Beijing 100044, China
| | - Jia-le Cui
- College of Life Sciences and Bioengineering, Beijing Jiaotong University, Beijing 100044, China
| | - Jie-mei Yu
- College of Life Sciences and Bioengineering, Beijing Jiaotong University, Beijing 100044, China
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Tenge VR, Hu L, Prasad BVV, Larson G, Atmar RL, Estes MK, Ramani S. Glycan Recognition in Human Norovirus Infections. Viruses 2021; 13:2066. [PMID: 34696500 PMCID: PMC8537403 DOI: 10.3390/v13102066] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/07/2021] [Accepted: 10/08/2021] [Indexed: 12/11/2022] Open
Abstract
Recognition of cell-surface glycans is an important step in the attachment of several viruses to susceptible host cells. The molecular basis of glycan interactions and their functional consequences are well studied for human norovirus (HuNoV), an important gastrointestinal pathogen. Histo-blood group antigens (HBGAs), a family of fucosylated carbohydrate structures that are present on the cell surface, are utilized by HuNoVs to initially bind to cells. In this review, we describe the discovery of HBGAs as genetic susceptibility factors for HuNoV infection and review biochemical and structural studies investigating HuNoV binding to different HBGA glycans. Recently, human intestinal enteroids (HIEs) were developed as a laboratory cultivation system for HuNoV. We review how the use of this novel culture system has confirmed that fucosylated HBGAs are necessary and sufficient for infection by several HuNoV strains, describe mechanisms of antibody-mediated neutralization of infection that involve blocking of HuNoV binding to HBGAs, and discuss the potential for using the HIE model to answer unresolved questions on viral interactions with HBGAs and other glycans.
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Affiliation(s)
- Victoria R. Tenge
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (V.R.T.); (B.V.V.P.); (R.L.A.); (M.K.E.)
| | - Liya Hu
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA;
| | - B. V. Venkataram Prasad
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (V.R.T.); (B.V.V.P.); (R.L.A.); (M.K.E.)
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA;
| | - Göran Larson
- Department of Laboratory Medicine, University of Gothenburg, SE 413 45 Gothenburg, Sweden;
| | - Robert L. Atmar
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (V.R.T.); (B.V.V.P.); (R.L.A.); (M.K.E.)
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Mary K. Estes
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (V.R.T.); (B.V.V.P.); (R.L.A.); (M.K.E.)
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sasirekha Ramani
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA; (V.R.T.); (B.V.V.P.); (R.L.A.); (M.K.E.)
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A Norovirus Uses Bile Salts To Escape Antibody Recognition While Enhancing Receptor Binding. J Virol 2021; 95:e0017621. [PMID: 33827952 DOI: 10.1128/jvi.00176-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Noroviruses, members of the Caliciviridae family, are the major cause of epidemic gastroenteritis in humans, causing ∼20 million cases annually. 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. In the case of mouse norovirus (MNV), bile salts have been shown to enhance receptor (CD300lf) binding to the P domain. We demonstrated previously that the P domains of several genotypes are markedly flexible and "float" over the shell, but the role of this flexibility was unclear. Recently, we demonstrated that bile causes a 90° rotation and collapse of the P domain onto the shell surface. Since bile binds distally to the P-shell interface, it was not at all clear how it could cause such dramatic changes. Here, we present the near-atomic resolution cryo-electron microscopy (cryo-EM) structure of the MNV protruding domain complexed with a neutralizing Fab. On the basis of previous results, we show here that bile salts cause allosteric conformational changes in the P domain that block antibody recognition of the top of the P domain. In addition, bile causes a major rearrangement of the P domain dimers that is likely responsible for the bile-induced collapse of the P domain onto the shell. In the contracted shell conformation, antibodies to the P1 and shell domains are not expected to bind. Therefore, at the site of infection in the gut, the host's own bile allows the virus to escape antibody-mediated neutralization while enhancing cell attachment. IMPORTANCE The major feature of calicivirus capsids is the 90 protruding domains (P domains) that are the site of cell receptor attachment and antibody epitopes. We demonstrated previously that these P domains are highly mobile and that bile causes these "floating" P domains in mouse norovirus (MNV) to contract onto the shell surface. Here, we present the near-atomic cryo-EM structure of the isolated MNV P domain complexed with a neutralizing Fab fragment. Our data show that bile causes two sets of changes. First, bile causes allosteric conformational changes in the epitopes at the top of the P domain that block antibody binding. Second, bile causes the P domain dimer subunits to rotate relative to each other, causing a contraction of the P domain that buries epitopes at the base of the P and shell domains. Taken together, the results show that MNV uses the host's own metabolites to enhance cell receptor binding while simultaneously blocking antibody recognition.
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Abstract
The lumen of the gastrointestinal tract harbors a diverse community of microbes, fungi, archaea, and viruses. In addition to occupying the same enteric niche, recent evidence suggests that microbes and viruses can act synergistically and, in some cases, promote disease. In this review, we focus on the disease-promoting interactions of the gut microbiota and rotavirus, norovirus, poliovirus, reovirus, and astrovirus. Microbes and microbial compounds can directly interact with viruses, promote viral fitness, alter the glycan structure of viral adhesion sites, and influence the immune system, among other mechanisms. These interactions can directly and indirectly affect viral infection. By focusing on microbe–virus interplay, we hope to identify potential strategies for targeting offending microbes and minimizing viral infection.
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