Identification and Comparison of Receptor Binding Characteristics of the Spike Protein of Two Porcine Epidemic Diarrhea Virus Strains

Xiaoli Zhong,Feng Deng,Guiqing Peng,Gang Ye,Qianqian Liu,Shaobo Xiao,Muhammad Navid,Zhen Fu,Chunyun Wan,Youwen Li,Qigai He

doi:10.3390/v8030055

Abstract

Porcine epidemic diarrhea virus (PEDV), a member of Alphacoronavirus, has caused huge economic losses for the global pork industry recently. The spike (S) protein mediates PEDV entry into host cells. Herein, we investigated the interactions between the S protein and its receptor porcine aminopeptidase N (pAPN) or co-receptor sugars. The C-terminal domain (CTD) of the S1 domain is bound to pAPN. The prototype strain demonstrated similar receptor-binding activity compared with the variant field isolate. Three loops at the tips of the β-barrel domains did not play crucial roles in the PEDV S-pAPN association, indicating that PEDV conforms to a different receptor recognition model compared with transmissible gastroenteritis virus (TGEV), porcine respiratory CoV (PRCV), and human coronavirus NL63 (HCoV-NL63). The N-terminal domain (NTD) of the PEDV S1 domain could bind sugar, a possible co-receptor for PEDV. The prototype strain exhibited weaker sugar-binding activity compared with the variant field isolate. Strategies targeting the receptor binding domain (RBD) may be helpful for developing vaccines or antiviral drugs for PEDV. Understanding the differences in receptor binding between the prototype and the variant strains may provide insight into PEDV pathogenesis.

Highlights

Coronaviruses are enveloped, single-stranded, positive-sense RNA viruses
The receptor binding domain (RBD) Is Located in the C-Terminal Region of the Porcine epidemic diarrhea virus (PEDV) S1 Domain
The flow cytometry assay results showed that the S19 ́ 638 and S253 ́ 638 fragments revealed the highest binding affinity, the S477 ́629 fragment exhibited moderate porcine aminopeptidase N (pAPN)-binding activity, and the S1 ́434 and S253 ́533 fragments revealed weak binding affinity, whereas the IgG4 Fc protein revealed no binding affinity (Figure 2D). These results suggest that the pAPN-binding domain is located within the C-terminal domain (CTD) of the PEDV S1 domain

Summary

Introduction

Coronaviruses are enveloped, single-stranded, positive-sense RNA viruses. They are globally important infectious agents that are associated with respiratory, digestive, and neurological diseases in humans and animals [1]. The Coronaviridae family consists of four genera known as the α-, β-, γ-, and Deltacoronaviruses [1,2] These viruses use a variety of cellular receptors and co-receptors, including proteins and sugars. Viruses 2016, 8, 55 the Betacoronavirus genus uses angiotensin-converting enzyme 2 (ACE2) as its receptor, and its receptor-binding domain (RBD) is located within CTD of the S1 domain [3]. ACE2 is a receptor for human coronavirus NL63 (HCoV-NL63), in which three discontinuous fragments located within CTD of the S1 domain are responsible for receptor binding [4]. No structural homology has been found between the SARS and HCoV-NL63 RBDs, but they recognize the same receptor (ACE2). Carcinoembryonic antigen cell adhesion molecule (CEACAM) and sugar serve as the receptors for MHV and BCoV, respectively, despite their high sequence homology [6,7]

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Results

Discussion

Conclusion