Genetic and proteomic analysis of porcine epidemic diarrhea virus and its vaccine development

다국어 초록 (Multilingual Abstract)

Porcine epidemic diarrhea virus (PEDV) was determined as the etiologic agent of porcine epidemic diarrhea (PED). PED is characterized by acute enteritis, watery diarrhea, weight loss, dehydration, and high mortality in neonatal piglets that causes significant economic losses in the swine industry.
The goals of this thesis are to characterize features of virulent PEDVs, particularly virus genetic phylogeny and proteomic analysis, and to develop a novel vaccine against PEDV infection. Genetic analyses of the full-length S gene of 3 Vietnam PEDV isolates (HID9047, HID9048, and HID9049) during 2016-2017 showed that all 3 isolates belong to genogroup 2a with significant variations, share unique genetic features with PEDVs circulated in Vietnam during 2013-2015, and closely relate to the Asian strains. Experiments in animals demonstrated that antisera from guinea pigs immunized with the vaccine strain resulted in higher levels of neutralizing antibody of 5 log2 against the homologous strain, and showed a relatively lower of neutralizing antibody against the field isolates.
The full-length S gene analysis of a Korea PEDV isolate in 2017 (HID9050) revealed that HID9050 belongs to genogroup 1a along with prototype CV777 and Korea isolates prior to 2017. Proteomic analysis of HID9050 and an attenuated PEDV vaccine strain DR13 (avDR13) illustrated that the differences in expression levels of virus proteins were observed in 3 proteins of avDR13 and 44 proteins of HID9050. Notably, 16 expressed proteins were detected only in avDR13, and 10 expressed proteins were found only in HID9050. These results speculate that PEDV infection in cells could be associated with the alteration and rearrangement of protein expression from avDR13 and HID9050, and might contribute to the altered pathogenicity of the virus in pigs.
In order to develop an effective vaccine against PEDV infection, a recombinant adenovirus was employed to express the core neutralizing epitope (COE) of PEDV and the heat-labile enterotoxin B (LTB) of Escherichia coli (rAd-LTB-COE). The rAd-LTB-COE induced good humoral, mucosal immune responses, and cell mediated immune response in mice and piglets. Furthermore, neutralizing antibodies induced by rAd-LTB-COE could inhibit both PEDV genogroups 1 and 2, suggesting a strong candidate for the next generation of PED vaccination strategies.
These findings could contribute to further understanding the pathogenicity of PEDV and suggest a promising vaccine with high efficacy

목차 (Table of Contents)

• Abstract i
• Acknowledgements iv
• Contents v
• List of abbreviations vii
• List of tables xi
• List of figures xii
• Literature review 1
• PEDV classification and organization 1
• Genetic diversity and molecular epidemiology 3
• PEDV infection and pathogenesis 5
• PEDV diagnosis 10
• Disease prevention and control strategies 13
• CHAPTER I 20
• Isolation and characterization of porcine epidemic diarrhea viruses from Vietnam 20
• Abstract 21
• Introduction 22
• Materials and methods 24
• Results 30
• Discussion 41
• CHAPTER II 44
• Differential proteomic analysis of a virulent porcine epidemic diarrhea virus and an attenuated vaccine strain 44
• Abstract 45
• Introduction 46
• Materials and methods 48
• Results 52
• Discussion 65
• CHAPTER III 69
• Recombinant adenovirus carrying a core neutralizing epitope of porcine epidemic diarrhea virus and heat-labile enterotoxin B of Escherichia coli as a mucosal vaccine 69
• Abstract 70
• Introduction 71
• Materials and methods 74
• Results 83
• Discussion 97
• General conclusions 103
• References 106
• Abstract in Korean 137