細胞常藉由調控程式化凋亡來清除被病毒感染之宿主細胞。神經壞死病毒感染宿主細胞時，已知可引起細胞凋亡，但病毒如何促進或抑制宿主凋亡之機制尚不清楚。利用西方轉印免疫實驗中，首次發現在病毒感染後24 小時，B2 蛋白質(8.3 KD)開始持續表現。為探討此神經壞死病毒B2 蛋白所扮演之功能，我們從病毒次基因體RNA3 中，選殖出此非結構性蛋白基因B2。B2基因全長含有228 個核苷酸，可轉譯出75 個胺基酸。若將B2基因接到黃色螢光基因(EYFP)後面形成融合基因，並轉染至細胞內，表現B2 蛋白會進入粒線體內。如果將B2基因短暫的表現於石斑魚肝臟細胞株(GL-av)內，可誘發細胞凋亡。同時，當我們短暫表現B2 基因與抗斑馬魚凋亡基因Bcl-xL 及Mcl-1a 時，則可減緩B2所誘發之細胞凋亡現象。此外，當利用基因knockdownz 方式之小片段干擾性RNA(siRNA)可有效阻斷B2 蛋白之表現，則可減少細胞凋亡及減緩病毒複製。由本論文之研究，證實B2 蛋白是屬早期表現之粒線體蛋白。其功能則與誘發宿主細胞凋亡及病毒複製與蛋白表現有密切相關。希望此研究之發現，能對防治或預防神經壞死病毒所誘發之疾病有所助益。

　　Apoptosis is a genetically-controlled preprogrammed event which eliminates cells during viral infection with host cells. Recently,betanodavirus-induced host cell death through apoptosis have been reported, but virus how to involved in regulate the host cell death is still a few understood. We found that B2 protein was expression occurred at 24 h post-infection (p.i.). So, we interest to know its function, then B2 gene be cloned and characterized was done. The betanodavirus TN1 strain B2 cDNA is 228 nucleotides long, encoding a polypeptide of 75 amino acids that protein size about 8.3 kDa in grouper liver (GL-av) cells. EYFP as a reporter gene was used for tracing B2 protein that also found localized in mitochondria in GL-av cell after 24 h p.i. When overexpression of B2 gene that significantly induces GL-av apoptotic cell death, but also prevents cell death by extra expression of Bcl-2 member Bcl-XL and Mcl-1a, which were cloned from zebrafish. Moreover, siRNA approaches are used for knockdowned B2 expression in transient and stable expression cell line in GL-av cell, which can enhances the cell viability up to 30% at 24 h p.i. and reduces the lose of mitochondria membrane potential during NNV infection up to 20% from 24 h to 72 h p.i., respectively. Taken results suggest that B2 is an early expression gene which may play an important role on either induces the host post-apoptotic necrosis or may regulate the viral replication. This finding may thus provide an important insight into the control or prevention of nodavirus-induced diseases.

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