Regulation of the life cycle of HDV by the drug resistance mutations of HBV

摘要 丁型肝炎病毒(HDV)是一种天然的乙肝病毒亚病毒病原体，它利用HBV膜 蛋白质(即表面抗原、乙肝表面抗原)形成病毒粒子，通过乙肝病毒受体感染肝细胞。满分257分 全球约有2000万人慢性感染HDV。 HDV仍然是一种重要的人类病原体。HDV感染会导致额外的肝脏病变，并可以 加速肝脏疾病，可导致更迅速和更频繁的肝硬变，并可增加肝细胞癌的风险 癌症(HCC)。抗乙肝药物不能阻断HDV感染。临床上尚无直接针对HDV的药物。 HDV感染的机制还远未完全清楚，这影响了治疗方案的选择。HDV-乙肝病毒 相互作用是复杂的，也没有得到充分的研究。丁型肝炎病毒耐药突变株对其生活史的调控 对乙肝病毒的研究也仍然不足。因此，这项提案将研究耐药突变是如何在 在FDA批准的抗乙肝药物拉米夫定、阿德福韦、 替比夫定、恩替卡韦或替诺福韦可以影响HDV感染。在公开场合发生的主要突变 乙型肝炎病毒聚合酶的读框(ORF)可导致相应的耐药突变(DRM) 重叠的HBs Ag开放阅读框架。在主要抗原环--胞浆大环(LCL)中发现DRMS (MAL)，HDV结合位点(HDV-BS)，以及第二、第三和第四跨膜结构域(TMDS II-IV) 乙肝表面抗原。MAL对乙肝病毒和丁型肝炎病毒的传染性起关键作用，是乙肝病毒抗原性的主要调节因子。 HDV病毒粒子(即抗HBs Ag抗体对病毒粒子的识别)。HDV-BS介导的乙肝表面抗原相互作用 在HDV组装过程中与大的Delta抗原结合。因此，DRM有望调节 HDV的组装和感染性，并可能影响HDV与宿主的相互作用。我们之前的工作表明 病毒粒子的传染性、病毒传播和双重感染(I)可以决定最初的HDV感染是否会 被清除，否则将成为持续性(即慢性)感染，以及(Ii)也可能对维持 丁型肝炎病毒感染的慢性状态。我们还发现，调节乙肝病毒表面抗原组装的氨基酸 HDV病毒粒子也会影响它们的传染性。此外，HDV组装的效率可以大大提高 影响HDV传播和超级感染。目前对DRM如何调节 HDV的组装性和感染性以及抗-HBs抗体对HDV的识别作用非常有限。因此， 目标1将详细分析携带HBs Ag的DRM如何调节HDV的组装，并影响HDV 抗HBIg抗体对HDV病毒粒子的识别作用此外， 目的2研究DRM对HDV病毒粒子感染性的影响。总体而言，这项提议将在很大程度上 加深对乙肝病毒耐药突变株影响乙肝病毒感染机制的认识。 HDV相互作用，并调节HDV病毒粒子的组装、感染性和抗原性，这有望 影响HDV感染的转归和致病程度。

Abstract Hepatitis delta virus (HDV) is a natural sub-viral agent of hepatitis B virus (HBV), which uses HBV envelope proteins (i.e., surface antigen, HBsAg) to form the virions and infect hepatocytes via HBV receptor. Out of 257 million people chronically infected with HBV worldwide about 20 million are also chronically infected with HDV. HDV remains a significant human pathogen. HDV infection causes additional liver pathogenesis, and can accelerate liver disease, can cause more rapid and frequent cirrhosis, and can elevate risk of hepatocellular carcinoma (HCC). Anti-HBV drugs do not block HDV infection. No drugs directly targeting HDV exist in clinic. Mechanism of HDV infection is far from being fully understood, which affects the treatment options. HDV-HBV interactions are complex and under-studied. The regulation of HDV life cycle by the drug-resistant mutants of HBV remains under-studied as well. Therefore, this proposal will examine how the drug resistance mutations in HBV genome selected during the treatment with FDA-approved anti-HBV drugs, lamivudine, adefovir, telbivudine, entecavir or tenofovir, can influence HDV infection. The primary mutations that occur in the open reading frame (ORF) of HBV polymerase can lead to the corresponding drug resistance mutations (DRMs) in the overlapping ORF for HBsAg. DRMs were found in the large cytosolic loop (LCL), major antigenic loop (MAL), HDV-binding site (HDV-BS), and second, third and fourth transmembrane domains (TMDs II-IV) of HBsAg. MAL is critical for infectivity of HBV and HDV, and it is a major regulator of the antigenicity of HBV and HDV virions (i.e., recognition of the virions by anti-HBsAg antibodies). HDV-BS mediates HBsAg interactions with the large delta antigen during HDV assembly. Thus, DRMs are expected to regulate the mechanisms of the HDV assembly and infectivity, and could affect HDV-host interactions. Our previous work suggested that the infectivity of the virions, virus spread and super-infection (i) could determine if initial HDV infection will be cleared or it will become persistent (i.e., chronic) infection, and (ii) also could be critical for the maintenance of the chronic state of HDV infection. We also found that amino acids of HBsAg that regulate the assembly of HDV virions can influence their infectivity as well. Furthermore, the efficiency of HDV assembly can greatly affect HDV spread and super-infection. Current understanding of the mechanisms how DRMs regulate the assembly and infectivity of HDV, and recognition of HDV by anti-HBsAg antibodies is very limited. Therefore, Aim 1 will analyze in detail how HBsAg bearing DRMs can regulate the assembly of HDV and affect the recognition of HDV virions by anti-HBsAg antibodies of the hepatitis B immune globulin (HBIg). Furthermore, Aim 2 will examine the effects of DRMs on the infectivity of HDV virions. Overall, the proposal will considerably advance our understanding of the mechanisms of how the drug-resistant mutants of HBV influence the HBV- HDV interactions, and regulate the assembly, infectivity and antigenicity of HDV virions, which is expected to influence the outcomes of HDV infection and the extent of HDV pathogenesis.