key: cord-0762169-c8ugkbp0 authors: Li, Zhiwei; Ma, Zhiqian; Li, Yang; Gao, Sheng; Xiao, Shuqi title: Porcine epidemic diarrhea virus: Molecular mechanisms of attenuation and vaccines date: 2020-10-01 journal: Microb Pathog DOI: 10.1016/j.micpath.2020.104553 sha: 5ccf0a75942b2d92167a612031f28b5cd319e83c doc_id: 762169 cord_uid: c8ugkbp0 Porcine epidemic diarrhea virus (PEDV) causes an emerging and re-emerging coronavirus disease characterized by vomiting, acute diarrhea, dehydration, and up to 100% mortality in neonatal suckling piglets, leading to huge economic losses in the global swine industry. Vaccination remains the most promising and effective way to prevent and control PEDV. However, effective vaccines for PEDV are still under development. Understanding the genomic structure and function of PEDV and the influence of the viral components on innate immunity is essential for developing effective vaccines. In the current review, we systematically describe the recent developments in vaccine against PEDV and the roles of structural proteins, non-structural proteins and accessory proteins of PEDV in affecting viral virulence and regulating innate immunity, which will provide insight into the rational design of effective and safe vaccines for PEDV or other coronaviruses. Since 2010, highly pathogenic variant porcine epidemic diarrhea virus (PEDV) strains 26 have gradually swept the swine industry worldwide and brought substantial economic losses. 27 Such a huge hazard of the virus is inseparable from its strong transmissibility. Generally, the 28 main transmission route of PEDV is fecal-oral, but airborne transmission via the fecal-nasal 29 route may play a significant role in pig-to-pig and farm-to-farm spread [1] . PEDV mainly 30 infects the porcine intestinal epithelial cells. Then, PEDV colonizing the intestines results in 31 atrophy, necrosis, and shedding of intestinal villi, which affected the absorption of nutrients, 32 leading to vomiting, diarrhea, weight loss, anorexia, and depression[2, 3]. When PEDV is 33 excreted into the environment with feces, the contaminated feces may result in a mass 34 epidemic. Obtaining sufficient maternal antibody from the colostrum and milk remains the 35 most promising and effective strategy to protect neonatal suckling piglets against PEDV [4] . 36 Unfortunately, due to the continued mutation of the PEDV genome[5] and the low efficacy 37 to induce mucosal immunity, no effective vaccine has been released yet. Therefore, in-depth 38 research on this disease as well as its pathogens and the rapid development of effective 39 vaccines based on the epidemic strains are urgently needed. Table 1 summarizes the biological roles of PEDV proteins. 58 2.1 Non-structure proteins 59 The Nsp1 protein, a unique structure of alphacoronaviruses and betacoronaviruses, is 60 located at the N-terminus of pp1ab [9] . Nsp1 is considered to be a virulence gene of 61 coronavirus, which widely inhibits host genes' expression to suppress or evade the innate The core neutralization epitope region (COE) of the S1 region has been widely applied to 250 develop PEDV subunit vaccines. Hence, S protein is a major target for the development of risk of reversion to a virulent wild type limits its applicability [149, 150] . The key to 300 developing vaccines is to select low-virulence, high-titer, and highly immunogenic strains. 301 However, the isolation of PEDV strains in vitro is very difficult, especially for the pandemic 302 variable strains, and even if the strains are isolated successfully, they may not necessarily 303 have high titers. As early as 1993, the PEDV tissue-inactivated vaccine could provide piglets 304 with immune protection for up to 6 months [151] . In 1994, the PEDV CV777 strain was 305 attenuated via serial cell culture after 28 passages, providing protection for more than 80% The PEDV S protein is the main target for developing subunit vaccines, which is 354 inseparable from its multiple biological roles. In recent years, the researchers have expressed 355 part of the PEDV S protein including COE and S1 or the full length of the S protein using E. J o u r n a l P r e -p r o o f (2)L. lactis (NZ3900) (3)pNZ8149/NZ3900 (4)pNZ8149-S1/NZ3900 6-8-week-old mice(n=20) Oral No (1)Control (2)NTD 231-501aa (3)NTD 231-501aa/CT mice Oral (1)IgG1, IgG2a and IgG2b in serum (7 w) ↑ (2)SIgA in feces (7 w) ↑ (3)IgA + cells in the LP (7 w) ↑ (2)Neutralizing antibodies titers↑ [206] J o u r n a l P r e -p r o o f (1)Medium control (2)S1-Bac (2)Neutralizing antibodies (0, 14, 28 d) S↑, S1* Pigs： (1)IgG in serum (0, 14, 28 d) ↑ (2)Fecal SIgA (0, 14, 28 d) * (3)Neutralizing antibodies (0, 14, 28 d) S↑, S1* (4)Body weights (7, 21, 35, 49 d) * (5)Stool scores (every day) S↓, S1↑ (6)Fecal viral shedding (every day) S↓, S1↑ [207] E. coli J o u r n a l P r e -p r o o f J o u r n a l P r e -p r o o f An alternative pathway of enteric PEDV dissemination 428 from nasal cavity to intestinal mucosa in swine Full-Length cDNA Clone and Transmission Model for Porcine Epidemic Diarrhea Virus Strain PC22A, mBio Molecular epidemiology of porcine 660 epidemic diarrhea virus in China Identification of two mutation sites in spike and envelope 662 proteins mediating optimal cellular infection of porcine epidemic diarrhea virus from different pathways, 663 Veterinary research Genetic 665 manipulation of porcine epidemic diarrhoea virus recovered from a full-length infectious cDNA clone Genetic characteristics, pathogenicity, 668 and immunogenicity associated with cell adaptation of a virulent genotype 2b porcine epidemic diarrhea virus Identification of two mutation sites in spike and envelope 671 proteins mediating optimal cellular infection of porcine epidemic diarrhea virus from different pathways Porcine epidemic 674 diarrhea virus ORF3 protein causes endoplasmic reticulum stress to facilitate autophagy, Veterinary 675 microbiology Porcine Epidemic Diarrhea Virus (PEDV) ORF3 Enhances Viral Proliferation by Inhibiting Apoptosis of Infected Cells The Accessory Protein ORF3 Contributes to Porcine 679 Epidemic Diarrhea Virus Replication by Direct Binding to the Spike Protein Porcine epidemic diarrhea virus ORF3 gene prolongs 681 facilitates formation of vesicles and promotes the proliferation of attenuated PEDV Porcine Epidemic Diarrhea Virus 684 (PEDV) ORF3 Interactome Reveals Inhibition of Virus Replication by Cellular VPS36 Protein Porcine epidemic diarrhea 687 virus S1 protein is the critical inducer of apoptosis Updated phylogenetic analysis of the spike gene and identification of a novel recombinant porcine 690 epidemic diarrhoea virus strain in Taiwan, Transboundary and emerging diseases Porcine epidemic diarrhea in China Molecular 693 characteristics of the spike gene of porcine epidemic diarrhoea virus strains in Eastern China in 2016 A Single 696 V672F Substitution in the Spike Protein of Field-Isolated PEDV Promotes Cell-Cell Fusion and Replication in 697 VeroE6 Cells Structure 699 of the SARS-CoV-2 spike receptor-binding domain bound to the ACE2 receptor The 3.1-Angstrom Cryo-electron Microscopy Structure of the Porcine 701 Epidemic Diarrhea Virus Spike Protein in the Prefusion Conformation A pan-coronavirus fusion inhibitor targeting the HR1 domain of human coronavirus 704 spike Computational Design of ACE2-Based Peptide Inhibitors of SARS-CoV-2 Structural and Functional Basis of SARS-CoV-2 Entry by Using Human ACE2, Cell Adaptation of SARS-CoV-2 in BALB/c 713 mice for testing vaccine efficacy Porcine aminopeptidase N is a functional receptor for the PEDV coronavirus Metalloprotease ADAM17 717 regulates porcine epidemic diarrhea virus infection by modifying aminopeptidase N Aminopeptidase-N-independent entry of porcine epidemic 719 diarrhea virus into Vero or porcine small intestine epithelial cells Aminopeptidase N is not required for 721 porcine epidemic diarrhea virus cell entry, Virus research Resistance to coronavirus infection in amino peptidase N-deficient pigs The S gene is 726 necessary but not sufficient for the virulence of porcine epidemic diarrhea virus novel variant strain 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in the spike protein of porcine epidemic 750 diarrhea virus The small envelope protein E is not essential for murine coronavirus replication Coronavirus genome structure and replication Porcine epidemic diarrhea 756 virus E protein causes endoplasmic reticulum stress and up-regulates interleukin-8 expression Type III Interferon Restriction by Porcine Epidemic 759 Diarrhea Virus and the Role of Viral Protein nsp1 in IRF1 Signaling Deletion of a 197-amino-acid region in the N-terminal domain of spike protein attenuates 835 porcine epidemic diarrhea virus in piglets The nsp2 replicase proteins of 837 murine hepatitis virus and severe acute respiratory syndrome coronavirus are dispensable for viral replication Murine coronavirus ubiquitin-like domain is important for papain-like protease stability and viral 841 pathogenesis The nsp3 843 macrodomain promotes virulence in mice with coronavirus-induced encephalitis Coronaviruses resistant to a 3C-like protease inhibitor are attenuated for 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