Characterization of the zoonotic potenial of rotaviruses of poultry

轮状病毒是人类和许多动物患胃肠炎的主要原因。两种主要基于人类轮状病毒的疫苗目前正在全球范围内用于预防幼儿严重的轮状病毒疾病。轮状病毒从哺乳动物向人类的传播已被反复描述。相比之下，目前尚不清楚鸟类的轮状病毒是否可以传播给人类，以及这是否会导致混合病毒的产生。这个项目的调查应该会澄清这个问题。作为项目第一阶段的结果，我们可以表明轮状病毒在家禽中广泛分布，并且存在大量不同的类型。首次测定了禽轮状病毒D、F和G组轮状病毒的全基因组序列，表明它们与人类轮状病毒只有较远的亲缘关系。然而，分析也表明，这些病毒可能通过与A组或B组的人轮状病毒重组而产生混合病毒。此外，我们对一只野鸡轮状病毒的基因组分析表明，该病毒含有哺乳动物轮状病毒的基因组片段，表明自然界中哺乳动物和禽类轮状病毒之间存在相互传播。实验室实验表明，人和禽类轮状病毒可以感染这两种宿主的细胞培养物。利用一种新的依赖于辅助病毒的反向遗传学系统，我们最近从鸡和猴轮状病毒中设计出了一种具有复制能力的混合病毒，现在应该对其进行表征。在计划的第二阶段，将继续利用细胞培养的双重感染来进行禽类和哺乳动物混合轮状病毒的特异性工程实验。最近设计的混合病毒将被详细描述。除了在哺乳动物和禽类细胞中复制的能力外，还将评估其与针对其母病毒的抗血清的反应性。这可能会评估目前使用的疫苗对抗这种混合病毒的效率。应用的辅助病毒依赖的反向遗传学系统用于轮状病毒重组体的定向工程的一般用途应该进行测试。这样，到目前为止还没有在细胞培养中复制的抗基因变体可以作为抗原进行繁殖和提供。为了研究轮状病毒基因组的特定变化对宿主谱和复制能力的影响，应继续进行建立非依赖于轮状病毒的反向遗传学系统的实验，其结果将有助于识别轮状病毒的传播途径，记录其变异性，并阐明相关的分子机制。通过这一点，可以估计禽流感轮状病毒向人类传播的风险和开发新的混合病毒的风险，这有助于开发广泛有效的疫苗。

Rotaviruses are a major cause of gastroenteritis in humans and many animal species. Two vaccines, which are mainly based on human rotaviruses, are currently used worldwide for prevention of severe rotavirus disease in young children. Transmission of rotaviruses from mammalian animals to humans has been repeatedly described. In contrast, it is unclear, whether rotaviruses of birds can be transmitted to humans and whether this can result in the creation of mixed viruses. The investigations in this project should clarify this question.As a result of the first phase of the project, we could show that rotaviruses are broadly distributed among poultry and that a high number of different types exist. For the first time, the whole genome sequences of rotaviruses belonging to avian rotavirus groups D, F and G were determined, showing that they are only distantly related to human rotaviruses. However, the analyses also show that these viruses may be able to create mixed viruses through reassortment with human rotaviruses of group A or B. Additionally, our genome analysis of a rotavirus from a pheasant suggests that this virus contains a genome segment from a mammalian rotavirus, indicating a mutual transmission of mammalian and avian rotaviruses in nature. Laboratory experiments showed that human and avian rotaviruses could infect cell cultures of both hosts. Using a novel helpervirus-dependent reverse genetics system, we recently engineered a replication-competent mixed virus from chicken and monkey rotaviruses, which should be characterized now.In the proposed second period of the project, the experiments for the specific engineering of avian/mammalian mixed rotaviruses should be continued using double infections of cell cultures. The recently engineered mixed virus will be characterized in detail. In addition to its ability for replication in mammalian and avian cells, the reactivity with antisera directed against its parent viruses will be assessed. This possibly will allow assessing the efficiency of the currently used vaccines against such mixed viruses. The general use of the applied helpervirus-dependent reverse genetics system for directed engineering of rotavirus reassortants should be tested. By this, antigenetic variants, which do not replicate in cell culture so far, may be propagated and provided as antigens. The experiments to establish a helpervirus-independent reverse genetics system should be continued in order to enable the investigation of the effects of specific changes in the genome of the viruses on their host spectrum and ability of replication.The results will help to identify the transmission pathways of rotaviruses, to record their variability and to elucidate the involved molecular mechanisms. By this, the risk of transmission of avian rotaviruses to humans and of development of novel mixed viruses can be estimated, which can contribute to the development of broadly efficient vaccines.