EB病毒（Epstein-Barr Virus, EBV）是遍佈世界各地的人類疱疹病毒之一員，已證實與多數的腫瘤和淋巴相關疾病的發生關係密切；如同巴氏淋巴瘤（Burkitt’s lymphoma，BL），鼻咽癌（nasopharyngeal carcinoma，NPC），何杰金氏疾病（Hodgkin’s disease），和傳染性單核球增多症（infectious mononucleosis）等，且具有高度潛伏的能力。EB病毒引起的致病機轉包括逃脫免疫系統的偵測及促使細胞處於不死的狀態，而這些現象與病毒產生的蛋白質有高度關聯。以前的研究指出破壞這些病毒的蛋白質會抑制病毒複製及細胞轉型（transformation）的能力，意謂著這些病毒蛋白是具有作為治療目標的發展潛力。潛伏的EB病毒感染以及相關的惡性腫瘤生成都需要EB病毒核抗原1（EBNA1）。有研究指出破壞EBNA1的功能確實能使誘發伯金氏淋巴癌細胞產生凋亡（apoptosis），意謂著EBNA1可能是伯金氏淋巴癌細胞的一個生存因子。所以EBNA1在EB病毒引發的伯金氏淋巴癌的惡化或維持上是絕對重要的樞軸角色。因此，有效抑制EBNA1的功能對EB病毒所形成的惡性腫瘤的治療上將會是相當有用的。而我們使用一個有效DNA vector-based siRNA表現系統和有效率的siRNA篩選策略，找到兩個極為有效的siRNA分子, 能夠有效地執行序列專一性的抑制EBNA1的表現。而在BHK和HEK293細胞中，同步暫時轉染目標基因和siRNA表現的載體，在西方墨點及免疫染色分析結果皆顯示，有效的siRNA可以降低EBNA1生成超過90%。免疫螢光染色配合螢光影像進一步確認有siRNA表現的細胞(表現綠色螢光的細胞)並沒有EBNA1的表現。而利用EBNA1能夠反向活化帶有oriP序列之啟動子的轉錄活性，我們構築了一個含有oriP的冷光報告基因載體。在BHK和HEK293細胞中，我們的確觀察到這個現象。進一步的，當我們將siRNA表現的載體以及報告基因載體共同轉染入穩定表現EBNA1的BHK細胞中，發現最佳的siRNA其抑制效果到達五成左右。而我們也針對EBV-positive B淋巴球的EBNA1，在表現量以及序列上進行分析，提供日後之參考。再者我們已經成功的發展出腺病毒以及反轉錄病毒的載體系統以期達到最好的轉染效率。

　　Epstein-Barr virus (EBV), a world-wide human herpes virus, is highly associated with an increasing number of tumors and lymphoid diseases, such as Burkitt’s lymphoma (BL), nasopharyngeal carcinoma (NPC), Hodgkin’s disease, and infectious mononucleosis, and is able to establish life-long persistent infection. The EBV induced pathogenesis is strongly associated with viral proteins that contribute to cell immortalization and immune evasion. Previous studies have shown that disruptions of these viral proteins result in inhibitions of viral replication or transforming abilities, suggesting that these proteins are potential candidates as therapeutic targets. EBV nuclear antigen 1 (EBNA1) is required for maintenance of latent EBV infection and is essential for EBV-associated malignancies. It has been shown that disruption of EBNA1 causes apoptosis in EBV-positive BL cells, suggesting that EBNA1 serves as a survival factor in these cells. EBNA1 may, therefore, play a pivotal role in the onset, progression or maintenance of BL. Efficient inhibition of EBNA1’s function would likely prove useful in the therapy of EBV associated malignancies. Using an effective DNA vector-based siRNA expression system and efficient active siRNA screening strategy, we have identified two extremely potent siRNA molecules that can effectively trigger sequence-specific inhibition of EBNA1 expression. Transient co-transfection of target and siRNA-expression vectors into BHK and HEK293 cells caused a more than 90% reduction in EBNA1 production in both western blot and immunohistochemistry. It was further confirmed by fluorescent image that EGFP-carry cells as siRNA-expressing cells showed no EBNA1 detected by immunostaining. In addition, EBNA1 can transactivate promoter transcription in an orip-dependent way BHK and HEK293 cells. When we co-transfect siRNA-expressing vectors and reporter plamids into EBNA1 stable line, siA1-3 also inhibits reporter activity about 50%. Furthermore, we have successfully developed two viral vector, adenoviral and retroviral vectors, expect to achieve the best transfection efficiency.

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