Characterisation of B.1.1.7 and Pangolin coronavirus spike provides insights on the evolutionary trajectory of SARS-CoV-2
TL;DR: In this article, the authors examined virus entry by the B.1.7 lineage, commonly referred to as the UK/Kent variant, and found that amino acid deletions within the N-terminal domain (NTD) of spike were important for efficient entry by B. 1.7.
Abstract: The recent emergence of SARS-CoV-2 variants with increased transmission, pathogenesis and immune resistance has jeopardised the global response to the COVID-19 pandemic. Determining the fundamental biology of viral variants and understanding their evolutionary trajectories will guide current mitigation measures, future genetic surveillance and vaccination strategies. Here we examine virus entry by the B.1.1.7 lineage, commonly referred to as the UK/Kent variant. Pseudovirus infection of model cell lines demonstrate that B.1.1.7 entry is enhanced relative to the Wuhan-Hu-1 reference strain, particularly under low expression of receptor ACE2. Moreover, the entry characteristics of B.1.1.7 were distinct from that of its predecessor strain containing the D614G mutation. These data suggest evolutionary tuning of spike protein function. Additionally, we found that amino acid deletions within the N-terminal domain (NTD) of spike were important for efficient entry by B.1.1.7. The NTD is a hotspot of diversity across sarbecoviruses, therefore, we further investigated this region by examining the entry of closely related CoVs. Surprisingly, Pangolin CoV spike entry was 50-100 fold enhanced relative to SARS-CoV-2; suggesting there may be evolutionary pathways by which SARS-CoV-2 may further optimise entry. Swapping the NTD between Pangolin CoV and SARS-CoV-2 demonstrates that changes in this region alone have the capacity to enhance virus entry. Thus, the NTD plays a hitherto unrecognised role in modulating spike activity, warranting further investigation and surveillance of NTD mutations.
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Edward C. Holmes1, Stephen A. Goldstein2, Angela L. Rasmussen3, David Robertson4, Alexander Crits-Christoph5, Joel O. Wertheim6, Simon J. Anthony7, Wendy S. Barclay8, Maciej F. Boni9, Peter C. Doherty10, Jeremy Farrar11, Jemma L. Geoghegan12, Xiaowei Jiang13, Julian L. Leibowitz14, Stuart J. D. Neil15, Tim Skern16, Susan R. Weiss17, Michael Worobey18, Kristian G. Andersen19, Robert F. Garry20, Andrew Rambaut21 •
University of Sydney1, University of Utah2, Vaccine and Infectious Disease Organization3, University of Glasgow4, University of California, Berkeley5, University of California, San Diego6, University of California, Davis7, Imperial College London8, Pennsylvania State University9, University of Melbourne10, Wellcome Trust11, University of Otago12, Xi'an Jiaotong-Liverpool University13, Texas A&M University14, King's College London15, Medical University of Vienna16, University of Pennsylvania17, University of Arizona18, Scripps Research Institute19, Tulane University20, University of Edinburgh21
TL;DR: In this article, a review of the current scientific evidence that may help clarify the origin of SARS-CoV-2 is presented, with a focus on how severe acute respiratory syndrome coronavirus 2 emerged in the human population.
264 citations
TL;DR: In this article , the authors demonstrate substantial evasion of neutralization by Omicron BA.1 and BA.2 variants in vitro using sera from individuals vaccinated with ChAdOx1, BNT162b2 and mRNA-1273.529.
Abstract: Abstract Vaccines based on the spike protein of SARS-CoV-2 are a cornerstone of the public health response to COVID-19. The emergence of hypermutated, increasingly transmissible variants of concern (VOCs) threaten this strategy. Omicron (B.1.1.529), the fifth VOC to be described, harbours multiple amino acid mutations in spike, half of which lie within the receptor-binding domain. Here we demonstrate substantial evasion of neutralization by Omicron BA.1 and BA.2 variants in vitro using sera from individuals vaccinated with ChAdOx1, BNT162b2 and mRNA-1273. These data were mirrored by a substantial reduction in real-world vaccine effectiveness that was partially restored by booster vaccination. The Omicron variants BA.1 and BA.2 did not induce cell syncytia in vitro and favoured a TMPRSS2-independent endosomal entry pathway, these phenotypes mapping to distinct regions of the spike protein. Impaired cell fusion was determined by the receptor-binding domain, while endosomal entry mapped to the S2 domain. Such marked changes in antigenicity and replicative biology may underlie the rapid global spread and altered pathogenicity of the Omicron variant.
198 citations
Brian J. Willett, Joe Grove, Oscar A. MacLean, Craig Wilkie, Nicola S Logan, Giuditta De Lorenzo, Wilhelm Furnon, Samuel Scott, M. Manali, Agnieszka M. Szemiel, Shirin Ashraf, Elen Vink, William T. Harvey, Chris Davis, Richard J. Orton, Joseph Hughes, P Holland, Vanessa K. A. Silva, David J Pascall, Kathryn Puxty, Ana da Silva Filipe, Gonzalo Yebra, Sharif Shaaban Muhammad Shaaban, Matthew T. G. Holden, Rute Maria Pinto, Rory Gunson, Kate Templeton, Pablo R. Murcia, Arvind H. Patel, John Haughney, David Robertson, Massimo Palmarini, Surajit Ray, E. Thomson
TL;DR: It is shown that immunity from natural infection (without vaccination) is more protective than two doses of vaccine but inferior to three doses, and fundamental changes in the Omicron entry process in vitro, towards TMPRSS2-independent fusion, representing a major shift in the replication properties of SARS-CoV-2.
Abstract: Vaccination-based exposure to spike protein derived from early SARS-CoV-2 sequences is the key public health strategy against COVID-19. Successive waves of SARS-CoV-2 infections have been characterised by the evolution of highly mutated variants that are more transmissible and that partially evade the adaptive immune response. Omicron is the fifth of these Variants of Concern (VOCs) and is characterised by a step change in transmission capability, suggesting significant antigenic and biological change. It is characterised by 45 amino acid substitutions, including 30 changes in the spike protein relative to one of the earliest sequences, Wuhan-Hu-1, of which 15 occur in the receptor-binding domain, an area strongly associated with humoral immune evasion. In this study, we demonstrate both markedly decreased neutralisation in serology assays and real-world vaccine effectiveness in recipients of two doses of vaccine, with efficacy partially recovered by a third mRNA booster dose. We also show that immunity from natural infection (without vaccination) is more protective than two doses of vaccine but inferior to three doses. Finally, we demonstrate fundamental changes in the Omicron entry process in vitro, towards TMPRSS2-independent fusion, representing a major shift in the replication properties of SARS-CoV-2. Overall, these findings underlie rapid global transmission and may alter the clinical severity of disease associated with the Omicron variant.
144 citations
TL;DR: Loading cells with cholesterol from blood serum using the cholesterol transport protein apolipoprotein E (apoE) enhances the entry of pseudotyped SARS-CoV-2 and the infectivity of the virion, and proposes a component of COVID19 severity based on tissue cholesterol level and the sensitivity of ACE2 and furin to cholesterol.
Abstract: Coronavirus disease 2019 (COVID19) is a respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originating in Wuhan China in 2019. The disease is notably severe in elderly and those with underlying chronic conditions. A molecular mechanism that explains why the elderly are vulnerable and why children are resistant is largely unknown. Understanding these differences is critical for safeguarding the vulnerable and guiding effective policy and treatments. Here we show loading cells with cholesterol from blood serum using the cholesterol transport protein apolipoprotein E (apoE) enhances the endocytic entry of pseudotyped SARS-CoV-2. Super resolution imaging of the SARS-CoV-2 entry point with high cholesterol showed almost twice the total number of viral entry points. The cholesterol concomitantly traffics angiotensinogen converting enzyme (ACE2) to the viral entry site where SARS-CoV-2 docks to properly exploit entry into the cell. Cholesterol also increased binding of SARS-CoV-2 receptor binding domains. In mouse lung we found age and high fat diet induced cholesterol loading into lung tissue by up to 40%. Based on these findings, we propose a cholesterol dependent model for COVID19 lethality in elderly and the chronically ill. As cholesterol increases with age and inflammation (e.g. obesity, smoking, and diabetes), the cell surface is coated with viral entry points, optimally assembled viral entry proteins, and optimal furin priming. Importantly our model suggests problems arise when cholesterol levels are high in the tissue, not the blood. In fact, rapidly dropping cholesterol in the blood may indicate severe loading of cholesterol in peripheral tissue and a dangerous situation for escalated SARS-CoV-2 infectivity. Molecules that remove cholesterol from tissue or disrupt ACE2 localization with viral entry points or furin localization for priming in the producer cells, likely reduce the severity of COVID19 in critically ill patients.
109 citations
TL;DR: In this paper, the SARS-CoV-2 B.1.7 variant was found to have a higher than typical level of point mutants across its genome, including P681H in the spike S1/S2 cleavage site.
Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the agent behind the current COVID-19 pandemic having emerged in Wuhan China in late 2019 from a yet to be determined animal reservoir. SARS-CoV-2 B.1.1.7, a variant identified in the UK in late 2020, contains a higher than typical level of point mutants across its genome, including P681H in the spike S1/S2 cleavage site. Here, we performed assays using fluorogenic peptides mimicking the S1/S2 sequence from Wuhan-Hu1 and B.1.1.7 and observed no definitive difference in furin cleavage between Wuhan-Hu1 and B.1.1.7 in vitro. We performed functional assays using pseudo-typed particles harboring SARS-CoV-2 spike proteins and observed no significant differences between Wuhan-Hu1, Wuhan-Hu1 P681H or B.1.1.7 spike-carrying pseudo-typed particles in VeroE6 or Vero-TMPRSS2 cells, despite the spikes containing P681H being more efficiently cleaved. Likewise, we or show no differences in cell-cell fusion assays using the spike P681H-expressing cells. Our findings suggest that while the introduction of P681H in the SARS-CoV-2 B.1.1.7 variant may increase spike cleavage by furin-like proteases, this does not significantly impact viral entry or cell-cell spread. We consider that other factors are at play to account for the increased in transmission and disease severity attributed to this variant of concern (VOC).
78 citations
References
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TL;DR: MUSCLE is a new computer program for creating multiple alignments of protein sequences that includes fast distance estimation using kmer counting, progressive alignment using a new profile function the authors call the log-expectation score, and refinement using tree-dependent restricted partitioning.
Abstract: We describe MUSCLE, a new computer program for creating multiple alignments of protein sequences. Elements of the algorithm include fast distance estimation using kmer counting, progressive alignment using a new profile function we call the logexpectation score, and refinement using treedependent restricted partitioning. The speed and accuracy of MUSCLE are compared with T-Coffee, MAFFT and CLUSTALW on four test sets of reference alignments: BAliBASE, SABmark, SMART and a new benchmark, PREFAB. MUSCLE achieves the highest, or joint highest, rank in accuracy on each of these sets. Without refinement, MUSCLE achieves average accuracy statistically indistinguishable from T-Coffee and MAFFT, and is the fastest of the tested methods for large numbers of sequences, aligning 5000 sequences of average length 350 in 7 min on a current desktop computer. The MUSCLE program, source code and PREFAB test data are freely available at http://www.drive5. com/muscle.
37,524 citations
TL;DR: Two unusual extensions are presented: Multiscale, which adds the ability to visualize large‐scale molecular assemblies such as viral coats, and Collaboratory, which allows researchers to share a Chimera session interactively despite being at separate locales.
Abstract: The design, implementation, and capabilities of an extensible visualization system, UCSF Chimera, are discussed. Chimera is segmented into a core that provides basic services and visualization, and extensions that provide most higher level functionality. This architecture ensures that the extension mechanism satisfies the demands of outside developers who wish to incorporate new features. Two unusual extensions are presented: Multiscale, which adds the ability to visualize large-scale molecular assemblies such as viral coats, and Collaboratory, which allows researchers to share a Chimera session interactively despite being at separate locales. Other extensions include Multalign Viewer, for showing multiple sequence alignments and associated structures; ViewDock, for screening docked ligand orientations; Movie, for replaying molecular dynamics trajectories; and Volume Viewer, for display and analysis of volumetric data. A discussion of the usage of Chimera in real-world situations is given, along with anticipated future directions. Chimera includes full user documentation, is free to academic and nonprofit users, and is available for Microsoft Windows, Linux, Apple Mac OS X, SGI IRIX, and HP Tru64 Unix from http://www.cgl.ucsf.edu/chimera/.
35,698 citations
TL;DR: It is demonstrated that SARS-CoV-2 uses the SARS -CoV receptor ACE2 for entry and the serine protease TMPRSS2 for S protein priming, and it is shown that the sera from convalescent SARS patients cross-neutralized Sars-2-S-driven entry.
15,362 citations
Bette T. Korber1, Will Fischer1, Sandrasegaram Gnanakaran1, Hyejin Yoon1, James Theiler1, Werner Abfalterer1, Nick Hengartner1, Elena E. Giorgi1, Tanmoy Bhattacharya1, Brian T. Foley1, Kathryn M. Hastie2, Matthew Parker3, David G Partridge, Cariad Evans, Timothy M. Freeman3, Thushan I de Silva3, Adrienne Angyal4, Rebecca Brown4, Laura Carrilero4, Luke R. Green5, Luke R. Green2, Luke R. Green6, Danielle C. Groves6, Katie Johnson6, Alexander J Keeley3, Benjamin B Lindsey4, Paul J. Parsons4, Mohammad Raza, Sarah Rowland-Jones, Nikki Smith, Rachel Tucker, Dennis Wang, Matthew Wyles, Charlene McDanal4, Lautaro G. Perez4, Haili Tang4, Alex Moon-Walker6, Alex Moon-Walker5, Alex Moon-Walker2, Sean P. J. Whelan6, Celia C. LaBranche4, Erica Ollmann Saphire2, David C. Montefiori4 •
TL;DR: A SARS-CoV-2 variant carrying the Spike protein amino acid change D614G has become the most prevalent form in the global pandemic, and it is found that the G614 variant grows to higher titer as pseudotyped virions.
3,302 citations
TL;DR: Key cell entry mechanisms of SARS-CoV-2 that potentially contribute to the immune evasion, cell infectivity, and wide spread of the virus are identified using biochemical and pseudovirus entry assays and the potency and evasiveness are highlighted.
Abstract: A novel severe acute respiratory syndrome (SARS)-like coronavirus (SARS-CoV-2) is causing the global coronavirus disease 2019 (COVID-19) pandemic. Understanding how SARS-CoV-2 enters human cells is a high priority for deciphering its mystery and curbing its spread. A virus surface spike protein mediates SARS-CoV-2 entry into cells. To fulfill its function, SARS-CoV-2 spike binds to its receptor human ACE2 (hACE2) through its receptor-binding domain (RBD) and is proteolytically activated by human proteases. Here we investigated receptor binding and protease activation of SARS-CoV-2 spike using biochemical and pseudovirus entry assays. Our findings have identified key cell entry mechanisms of SARS-CoV-2. First, SARS-CoV-2 RBD has higher hACE2 binding affinity than SARS-CoV RBD, supporting efficient cell entry. Second, paradoxically, the hACE2 binding affinity of the entire SARS-CoV-2 spike is comparable to or lower than that of SARS-CoV spike, suggesting that SARS-CoV-2 RBD, albeit more potent, is less exposed than SARS-CoV RBD. Third, unlike SARS-CoV, cell entry of SARS-CoV-2 is preactivated by proprotein convertase furin, reducing its dependence on target cell proteases for entry. The high hACE2 binding affinity of the RBD, furin preactivation of the spike, and hidden RBD in the spike potentially allow SARS-CoV-2 to maintain efficient cell entry while evading immune surveillance. These features may contribute to the wide spread of the virus. Successful intervention strategies must target both the potency of SARS-CoV-2 and its evasiveness.
2,450 citations