Host dependence of influenza A virus reassortment

当两种甲型流感病毒（IAV）共同感染同一个细胞时， 重组产生多达256种不同的病毒变体。这一进程有可能汇集 病毒基因在不同的宿主物种中进化，这反过来又可以促进人畜共患病的传播。在宿主中 在感染单一病毒群体的情况下，重配可以进一步偶联有益的突变或清除 有害的，从而加速病毒的进化。使用独特的实验系统， 通过对重配的定量分析，我们已经证明了这种遗传交换过程在细胞中是非常有效的。 培养和豚鼠宿主中。事实上，从共同感染的几内亚流出的抗病毒的流行 猪（高达75%）表明重配是自然界中IAV感染的常规特征。IAV以 然而，目前还不清楚我们在几内亚的发现是否 猪也会向这些自然宿主扩散因此，我们建议评估重组的效率， 猪、野鸭、鹌鹑和鸡。雪貂和豚鼠也将作为人类IAV的模型 感染通过比较物种间的结果，我们不仅可以深入了解 重配在自然宿主，但也测试的假设，重配的效率不同， 寄主种类为了研究体内决定IAV重配效率的机制，我们将使用 免疫组织化学法用于追踪接种后一段时间内共感染病毒的传播。我们 假设靶组织内的局灶性扩散有利于重组，从而产生细胞聚集的局部区域 都是以高度的多样性被感染的最后，由于我们在细胞培养中的工作已经揭示了病毒基因组缺乏 一个或多个片段显著增加重配的频率，我们将测试是否流行 病毒基因组的不完整性随宿主物种而异。我们的初步数据强烈表明， 片段的丢失不是在病毒体组装期间，而是在基因组被递送到新的靶细胞之后。的 片段到达复制位点的可能性似乎还取决于来自 靶细胞来源于哪一个。因此，我们认为重配水平可能是宿主依赖性的，部分原因是 不同频率的不完整病毒基因组，并将通过实验来测试这一新概念 在细胞培养和动物模型中。总的来说，提出的研究将深化机制 理解IAV重组，这是小说多样化，进化和出现的关键过程 甲型流感病毒。

When two influenza A viruses (IAVs) co-infect the same cell, exchange of gene segments through reassortment gives rise to up to 256 different viral variants. This process has the potential to bring together viral genes that have evolved in distinct host species, which in turn can facilitate zoonotic transfer. In a host infected with a single virus population, reassortment can furthermore couple beneficial mutations or purge deleterious ones, thereby accelerating viral evolution. Using a unique experimental system that allows direct quantification of reassortment, we have shown that this process of genetic exchange is highly efficient in cell culture and in a guinea pig host. Indeed, the prevalence of reassortant viruses shed from co-infected guinea pigs (up to 75%) suggests that reassortment is a routine feature of IAV infections in nature. IAVs circulate in a wide range of avian and mammalian species, however, and it remains unclear whether our findings in guinea pigs would extend to these natural hosts. We therefore propose to evaluate the efficiency of reassortment in pigs, mallards, quail and chickens. Ferrets and guinea pigs will also be included as models of human IAV infection. By comparing results among species we will not only gain important insight into the incidence of reassortment in natural hosts, but also test the hypothesis that the efficiency of reassortment varies among host species. To investigate the mechanisms determining IAV reassortment efficiency in vivo, we will use immunohistochemistry to track the spread of co-infecting viruses over a time course after inoculation. We hypothesize that reassortment is favored by focal spread within target tissues, creating local areas where cells are infected at high multiplicity. Finally, since our work in cell culture has revealed that viral genomes lacking one or more segments markedly enhance the frequency of reassortment, we will test whether the prevalence of incomplete viral genomes varies with host species. Our preliminary data strongly suggest that missing segments are lost, not during virion assembly, but rather after genomes are delivered to a new target cell. The likelihood of segments reaching the site of replication furthermore appears to depend on the species from which the target cell is derived. Thus, we propose that reassortment levels may be host dependent in part due to differing frequencies of incomplete viral genomes and will test this novel concept through experimentation both in cell culture and in animal models. Overall, the research proposed will deepen mechanistic understanding of IAV reassortment, a critical process in the diversification, evolution and emergence of novel influenza A viruses.