Glycan Shield and Fusion Activation of a Deltacoronavirus Spike Glycoprotein Fine-Tuned for Enteric Infections

Journal of Virology - Tập 92 Số 4 - 2018
Xiaoli Xiong1, M. Alejandra Tortorici2,3, Joost Snijder1, Craig Yoshioka4, Alexandra C. Walls1, Wentao Li5, Andrew T. McGuire6, F.A. Rey2,3, Berend‐Jan Bosch5, David Veesler1
1Department of Biochemistry, University of Washington, Seattle, Washington, USA.
2CNRS UMR 3569 Virologie, Paris, France
3Institut Pasteur, Unité de Virologie Structurale, Paris, France
4Department of Biomedical Engineering, Oregon Health and Science University, Portland, Oregon, USA
5Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
6Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA

Tóm tắt

ABSTRACT Coronaviruses recently emerged as major human pathogens causing outbreaks of severe acute respiratory syndrome and Middle East respiratory syndrome. They utilize the spike (S) glycoprotein anchored in the viral envelope to mediate host attachment and fusion of the viral and cellular membranes to initiate infection. The S protein is a major determinant of the zoonotic potential of coronaviruses and is also the main target of the host humoral immune response. We report here the 3.5-Å-resolution cryo-electron microscopy structure of the S glycoprotein trimer from the pathogenic porcine deltacoronavirus (PDCoV), which belongs to the recently identified Deltacoronavirus genus. Structural and glycoproteomics data indicate that the glycans of PDCoV S are topologically conserved compared with the human respiratory coronavirus NL63 S, resulting in similar surface areas being shielded from neutralizing antibodies and implying that both viruses are under comparable immune pressure in their respective hosts. The structure further reveals a shortened S 2 ′ activation loop, containing a reduced number of basic amino acids, which participates in rendering the spike largely protease resistant. This property distinguishes PDCoV S from recently characterized betacoronavirus S proteins and suggests that the S protein of enterotropic PDCoV has evolved to tolerate the protease-rich environment of the small intestine and to fine-tune its fusion activation to avoid premature triggering and reduction of infectivity. IMPORTANCE Coronaviruses use transmembrane S glycoprotein trimers to promote host attachment and fusion of the viral and cellular membranes. We determined a near-atomic-resolution cryo-electron microscopy structure of the S ectodomain trimer from the pathogenic PDCoV, which is responsible for diarrhea in piglets and has had devastating consequences for the swine industry worldwide. Structural and glycoproteomics data reveal that PDCoV S is decorated with 78 N-linked glycans obstructing the protein surface to limit accessibility to neutralizing antibodies in a way reminiscent of what has recently been described for a human respiratory coronavirus. PDCoV S is largely protease resistant, which distinguishes it from most other characterized coronavirus S glycoproteins and suggests that enteric coronaviruses have evolved to fine-tune fusion activation in the protease-rich environment of the small intestine of infected hosts.

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Journal of Virology

Tập 92 Số 4

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