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標題: | 以豬流行性下痢病毒棘突蛋白進行抗原決定位分析、新穎疫苗設計及診斷試劑之開發 Porcine Epidemic Diarrhea Virus Spike-based Epitope Mapping, Novel Vaccine Design, and Diagnostic Tool Development |
作者: | Chia-Yu Chang 張佳瑜 |
指導教授: | 張惠雯 |
共同指導教授: | 蔡沛學 |
關鍵字: | 豬流行性下痢,棘突蛋白,中和抗原決定位,疫苗設計, Porcine epidemic diarrhea,spike protein,epitope mapping,vaccine development, |
出版年 : | 2020 |
學位: | 博士 |
摘要: | 豬流行性下痢(Porcine epidemic diarrhea; PED)是由高度傳染性之豬流行性下痢病毒(Porcine epidemic diarrhea virus, PEDV)所造成的一種豬隻下痢性疾病。受感染仔豬會出現水樣下痢、嘔吐、最後脫水致死。自從2010年以降,高毒力的豬流行性下痢病毒迅速傳播與肆虐於亞洲以及美洲大陸,造成無以計數的哺乳豬隻死亡,因而導致許多國家龐大的經濟損失。台灣無可倖免的在2013年亦受到該波病毒之攻擊,震盪了國內農生經濟體,帶來無法評估之巨大損失。舊有的上市疫苗(CV777-based vaccine)並無法有效的保護新型高毒力病毒感染豬隻,至今市面上仍沒有一支有效的疫苗可以預防該病毒的傳播與疾病爆發,此外,該再興病原之致病機轉以及如何逃脫舊有豬隻免疫力的機制仍不清楚,再加上目前偵測該病毒抗體之血清學檢驗試劑的選擇及敏感度亦是有限,導致免疫後後豬隻體內抗體分析的窒礙難行,無法有效的評估免疫策略的效力,以至於影響疾病的有效控制。在本研究中,首先,我們在豬流行性下痢病毒的棘突蛋白(S)上找到了兩個結構性中和抗原決定位,他們分別坐落於該病毒棘突蛋白的S1A與S1B區段上,其中S1A區段為在過去的研究中不曾發現過之中和抗原決定位,經由比對新型與舊型豬流行性下痢病毒之胺基酸序列後,發現幾個位於此S1A區段突變點可能與病毒的再興及宿主免疫逃脫具有相關性。緊接著進行第二部分是為疫苗之開發研究,四種以棘突蛋白作為骨架之抗原:S-Bac、S1-Bac以及表現棘突蛋白之昆蟲細胞與蠶蛹,分別以不同途徑給予小鼠或豬隻以作為免疫原。實驗證實,使用肌肉注射S-Bac及S1-Bac作為疫苗之策略,能成功地引發全身性免疫反應並且在病毒攻毒試驗中提供良好的保護力,然而和所有開發中的PEDV疫苗一致,都面臨著無法有效地激活黏膜免疫的問題;而直接經口投予表現棘突蛋白之昆蟲細胞與蠶蛹都無法成功地引發免疫反應。因此,在開發腸道病原疫苗與口服疫苗的這條路上,仍有許多未竟之事。為了評估疫苗的效力與族群免疫力,我們也開發了以哺乳動物表現系統為基礎、病毒棘突蛋白作為骨架之酶聯免疫吸附試驗(ELISA),作為評估豬隻血清或母豬乳汁中抗病毒抗體的評估方法。本研究不僅提供了關於新型豬流行性下痢病毒的抗原性之基礎認識,嘗試了不同方式的疫苗開發,更建立了一套血清抗體的檢測試劑套組,提供了未來豬流行性下痢病毒研究的基礎與臨床應用的參考依據。 Porcine epidemic diarrhea (PED), caused by porcine epidemic diarrhea virus (PEDV), is a highly contagious disease characterized by acute watery diarrhea, vomiting, dehydration, and lethal to suckling piglets. After the highly virulent PEDV has emerged and attacked neonatal piglets since 2010 in China and spread to Asia and America since 2013, the uncountable losses of piglets following by uncontrollable outbreaks of the disease had dramatically effected the economy in many countries, including Taiwan. To date, there is no effective vaccine against the new G2b PEDV strain available. The pathogenesis of the new G2b PEDV outbreaks and the mechanisms of how the novel virus escapes from the immunity induced by the CV777 vaccine or the pre-exposed historic PEDV strains are still unknown. Furthermore, limited assays have been developed to accurately evaluate the PEDV-specific antibody titers of pigs leading to the difficulty to determine the strategy and timeline for vaccination in pigs for controlling the PED. In the present study, two conformational neutralizing epitopes of the spike (S) protein were identified in the domain S1A and S1B of G2 PEDV. The novel epitope identified at the domain S1A suggests that the mutations located at this region might be also related to the pathogenesis of immune escape of the new PEDV. Then, four S-based immunogens, including the S-Bac, S1-Bac, S-expressing insect cells, and S-expressing silkworm pupae were constructed, applied as immunogens, and tested in mice and/or pigs. Even though partial success were achieved in S-Bac and S1-Bac vaccination strategy by intramuscular injections, the failure in eliciting the mucosal immunity in the present study is one of the major problems should be solved as all the other PEDV vaccine designs. Oral administration of the S-expressing insect cells and S-expressing silkworm pupae were not able to overcome the immune tolerance and failed to elicit immune response. Finally, two stable and practical serological assays with superior performance have been developed for evaluating the vaccine efficacy or PEDV-specific antibody titers. The study provides not only the fundamental information of PEDV antigenicity, but also the applications of S protein for the developments of PEDV vaccines and serological assays. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/66870 |
DOI: | 10.6342/NTU202000170 |
全文授權: | 有償授權 |
顯示於系所單位: | 獸醫學系 |
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