D型肝炎病毒增進B型肝炎病毒之產量

Abstract

B型肝炎病毒為一種含有核衣殼的小型DNA病毒，帶有3.2-kb的病毒基因體，且外圍被外套所包覆。B型肝炎病毒已在世界各地感染約20億人，其中有3億5千萬人屬於慢性感染。慢性B型肝炎病毒感染會引發嚴重的肝臟疾病，如肝硬化與肝癌。而D型肝炎病毒為B型肝炎病毒之衛星病毒，需要B型肝炎表面抗原才能組裝成D型肝炎病毒顆粒以進行感染。D型肝炎病毒感染約1千5百萬人。如果慢性B型肝炎病毒感染的患者同時感染D型肝炎病毒，會大大提高嚴重併發症之風險，並引發更快速的癌症發展。最近，有研究指出sodium taurocholate cotransporting polypeptide (NTCP)為B型與D型肝炎病毒之受體。在本研究中，表現人類NTCP以建立肝臟細胞專一性的體外B型肝炎病毒感染系統，並以體外方式製備B型與D型肝炎病毒顆粒。B型肝炎病毒顆粒可藉由HepG2.2.15細胞株穩定且持續生產。而利用猿猴病毒40早期啟動子調控表現雙套D型肝炎病毒cDNA的pSVD2質體轉染HepG2.2.15細胞株之系統則可以得到D型肝炎病毒顆粒。本研究同時發現D型肝炎病毒存在時會提高HepG2.2.15細胞株系統中B型肝炎病毒顆粒的生產量。此外，當HepG2細胞株轉染表現肝臟細胞專一性外源人類NTCP蛋白質時，可被B型肝炎病毒感染。本研究所建立之肝臟細胞專一性體外B型肝炎病毒感染系統或許可提供一簡便的平台以研究病毒感染、病毒間交互作用、致病機轉以及藥物評估。

Hepatitis B virus (HBV) is a small DNA virus consisting of a nucleocapsid, with a 3.2-kb viral genome, surrounded by an envelope. HBV has infected 2 billion people worldwide, of which 350 million are chronically infected. Chronic HBV infection contributes to severe liver diseases, including cirrhosis and hepatocellular carcinoma. Hepatitis delta virus (HDV) is a satellite virus of HBV as it is coated with the hepatitis B surface antigen (HBsAg) important for the virus infection. HDV has infected 15 million people. Super-infection of chronic HBV patients with HDV highly increases the risk of severe symptoms and accelerates cancer progression. Recently, studies identified sodium taurocholate cotransporting polypeptide (NTCP) as a host receptor for HBV and HDV entry. In this study, a liver-specific human NTCP-expressing in vitro system for HBV infection was established. HBV and HDV infectious particles were prepared in vitro. HBV particles can be stably and continuously produced in HepG2.2.15 cells. While HDV particles were produced by transfecting HepG2.2.15 cells with pSVD2 that contains a dimeric HDV cDNA under the control of the simian virus 40 early promoter. In addition, this study revealed that the presence of HDV increased the level of HBV particles produced by HepG2.2.15 cells. Furthermore, liver-specific expression of exogenous human NTCP conferred the susceptibility in HepG2 cells for HBV infection. The system would provide a convenient platform to study viral infection, virus-virus interaction, pathogenesis, and drug evaluation.