Molecular basis of adaptation of Borna disease virus to a new host species

博尔纳病病毒（BDV）是一种负链RNA病毒，可在家畜中诱导神经系统疾病，可在啮齿动物的大脑中复制。关于病毒适应新动物宿主的关键分子事件知之甚少。我们实验室最近的结果表明，从克隆的cDNA中回收的BDV可以在大鼠脑中有效生长，但令人惊讶的是，在小鼠脑中不能生长。在大鼠中传代一次后，出现了一种很容易在小鼠中生长的病毒变体。该变体与亲本相比共有5个氨基酸变化。这些变化位于聚合酶组分N、P和L。这些观察结果导致了工作假设，即在啮齿动物中，BDV的宿主范围主要由病毒聚合酶的活性谱而不是病毒表面分子决定。在拟议的研究项目中，我们计划使用反向遗传学技术来探索各种BDV聚合酶突变在宿主范围限制中的相对贡献。我们进一步提出了一系列旨在阐明宿主限制的分子基础的实验，这似乎是改变病毒聚合酶活性的直接后果。该项目将提供一种技术，用于产生必要的重组病毒，以阐明博尔纳病小鼠模型系统中病毒发病机制的分子基础。第二，它将产生新的生物学见解的细胞内限制机制，决定宿主范围的嗜神经病毒。

Borna disease virus (BDV), a negative-strand RNA virus that induces neurological disease in farm animals, can be adapted to replicate in the brain of rodents. Little is known about the critical molecular events of virus adaptation to new animal hosts. Recent results from our laboratory showed that BDV recovered from cloned cDNA can efficiently grow in rat brain, but surprisingly not in mouse brain. After a single passage in rats, a virus variant emerged that readily grew in mice. The variant possessed a total of five amino acid changes from the parent. The changes were located in the polymerase components N, P and L. These observations led to the working hypothesis that, in rodents, the host range of BDV is primarily determined by the activity profile of the viral polymerase rather than by viral surface molecules. In the proposed research project we plan to use reverse genetics technology to explore the relative contributions of the various BDV polymerase mutations in host range restriction. We further propose a series of experiments aimed at elucidating the molecular basis of the host restriction that appears to be a direct consequence of altered viral polymerase activity. The project will provide a technology for the generation of recombinant viruses necessary to elucidate the molecular basis of viral pathogenesis in the mouse model system of Borna disease. Second, it will yield new biological insights into an intracellular restriction mechanism that determines the host range of a neurotropic virus.