Comparative investigation of the genealogy of hepatitis B virus

虽然自20世纪80年代以来已经有了有效的乙肝疫苗，但全世界每年有超过80万人死于乙肝病毒(乙肝病毒；家族肝炎病毒科)感染。在过去的十年里，人们描述了几种动物肝炎病毒，其中包括一种能够感染人类肝细胞的蝙蝠乙肝病毒(TMBHBV)，这表明人畜共患HBV的存在，并表明乙肝病毒的宏观进化历史比人们之前认为的要复杂得多。在灵长类动物中，乙肝病毒的增加可能与NTCP受体分子进入肝细胞密切相关。然而，我们的初步数据表明：(I)NtCP的使用超出了灵长类庚型肝炎病毒的范围，(Ii)物种屏障可能涉及Ntcp以外的另一个(共)受体和宿主因素。COMHBV加入了两个PI，这两个PI一直在对来自大量宿主的新型HBV进行协同工作，这些宿主在计算机、进化和体外分析中相结合。COMHBV的中心假设是，乙肝是一种古老的人畜共患病，乙肝病毒祖先感染灵长类干细胞的先决条件是在啮齿动物和蝙蝠等小型哺乳动物中进化出来的。COMHBV将受益于许多领先的发现，包括来自完成的田野调查和对全球数千只动物进行筛查的五种新型庚型核糖核酸病毒。这些主要发现包括来自非洲和拉丁美洲的新的BAT HBV与潜在的人畜共患TMBHBV有遗传关系，以及来自非洲的一种能够与人类NTCP结合的新的啮齿动物乙肝病毒。COMHBV的总体目标是揭开哺乳动物肝病毒的谱系，并调查进入和复制因素在多大程度上影响肝病毒的宿主范围。这些目标将在三个工作包(WP)内实现。在WP1中，我们将确定肝炎病毒基因组的特征，并建立在体外研究新的肝炎病毒所必需的反向遗传学系统。在WP2中，我们将通过将评估适应性进化的计算机方法与评估细胞结合、进入和cccDNA形成和功能的体外方法相结合，来表征与啮齿动物和蝙蝠肝炎病毒进入和复制相关的宿主易感因素。来自WP2的数据将用于WP3，通过在贝叶斯框架中进行进化重建，以及通过在原代细胞和表达基本宿主易感因子的选定哺乳动物细胞系中对潜在的病毒和细胞相关元件进行实验评估，来揭开庚型肝炎病毒的谱系。COMHBV将提供可持续的基础，以确定潜在的NTCP非依赖性进入途径，并重建肝炎病毒谱系。此外，新的啮齿动物乙肝病毒可能为建立一种易处理的小鼠感染模型铺平道路，以确定乙肝病毒发病机制和治疗的关键方面，到目前为止，对其有限的了解阻碍了慢性乙肝的治愈。

Although efficient vaccines against hepatitis B have been available since the 1980s, over 800,000 people die yearly worldwide in consequence of hepatitis B virus (HBV; family Hepadnaviridae) infection. Several animal hepadnaviruses were described over the last decade, including a bat HBV (TMBHBV) capable of infecting human hepatocytes, suggesting zoonotic HBVs exist and indicating that the macro-evolutionary history of HBV is more complex than previously thought. The rise of HBV in primates may be closely linked to usage of the NTCP receptor molecule for hepatocyte entry. However, our preliminary data indicate that (i) NTCP usage expands beyond primate hepadnaviruses and (ii) species barriers may involve another (co-)receptor and host factors besides the NTCP. COMHBV joins two PIs that have been working in synergy on novel HBVs from a plethora of hosts combining in silico, evolutionary and in vitro analyses. COMHBV’s central hypothesis is that hepatitis B is an ancient zoonosis and that the preconditions of HBV ancestors to infect the primate stem lineage evolved in small mammals like rodents and bats. COMHBV will benefit from numerous lead findings, including five novel hepadnaviruses originating from completed fieldwork and screening of thousands of animals globally. Those lead findings include new bat HBVs from Africa and Latin America genetically related to the potentially zoonotic TMBHBV and a new rodent HBV from Africa capable of binding to the human NTCP. The overall goal of COMHBV is to unravel the genealogy of mammalian hepadnaviruses and to investigate to which extent entry and replication factors contribute to the hepadnaviral host range. Those aims will be achieved within three work packages (WP). In WP1, we will characterize hepadnaviral genomes and build the reverse genetics systems necessary to study the new hepadnaviruses in vitro. In WP2, we will characterize host susceptibility factors associated with rodent and bat hepadnaviral entry and replication by combining in silico approaches assessing adaptive evolution with in vitro approaches assessing cell binding, entry and cccDNA formation and function. Data from WP2 will be used in WP3 to unravel the hepadnavirus genealogy by evolutionary reconstructions in a Bayesian framework and by experimental assessments of virus- and cell-related elements underlying the hepadnaviral host range in primary cells and in selected mammalian cell lines expressing essential host susceptibility factors. COMHBV will provide sustainable ground to identify potential NTCP-independent entry pathways and reconstruct the hepadnaviral genealogy. Additionally, the new rodent HBV may pave ways for a tractable murine infection model to determine key aspects of HBV pathogenesis and treatment whose limited understanding prevents cure of chronic hepatitis B so far.