The application of reverse genetics to the study of pathogenicity in avian pneumovirus

禽肺病毒（APV）是一种在禽类，特别是火鸡中引起呼吸道疾病的病毒，给家禽养殖户造成重大损失，也给禽类造成痛苦。这种病毒有8个基因，可以使受感染的细胞产生9种蛋白质，然后以不同的方式对每种蛋白质进行修饰。一些蛋白质能够复制病毒基因组（一种核糖核酸分子，由八个基因组成，在末端和中间有额外的片段）。其他蛋白质与细胞的基因组和膜结合，形成病毒颗粒，然后感染新细胞。这种蛋白质通过直接破坏细胞和禽类免疫系统对细胞的反应来影响由病毒引起的疾病。免疫系统有助于清除病毒感染，但也经常负责疾病的迹象，因为受感染的细胞被破坏。不同的蛋白质在疾病的产生以及作为疫苗使用的弱化病毒产生有效免疫反应中的重要性尚不清楚。这一点很重要，因为疫苗病毒可以再次致病。基因工程使病毒基因组的脱氧核糖核酸（DNA）副本能够被复制到病毒RNA基因组中，并最终成为传染性病毒。通过改变、删除或插入连接在一起组成DNA的核苷酸，可以改变病毒基因组的DNA拷贝。这些修改过的DNA副本可以用来产生病毒，并在细胞培养物和火鸡中研究这些病毒的特性。它提供了一种合理设计疫苗的方法。该项目旨在调查在不同病毒之间观察到的各种变化的重要性，这些变化要么是由于突变，要么是由于火鸡组织中病毒复制和疾病引起的不同细胞类型的蛋白质的不同修饰。还将研究疫苗株变化对保护的重要性，最终目的是确定能够产生能够刺激保护性免疫反应但不能引起疾病的病毒的突变。我们已经知道，删除一个基因会改变病毒对培养细胞的影响，而在相关病毒中，删除一个类似的基因会影响病毒是否在各种动物的鼻子、喉咙或肺部生长得最好。我们将更详细地研究这种未知功能的蛋白质。最终，除了扩大对病毒基因在病毒与宿主相互作用中的功能的了解外，这项研究的信息应该有助于设计更有效的疫苗，使农民（和火鸡！）受益。

Avian pneumovirus (APV) is a virus causing respiratory disease in birds, particularly in turkeys, resulting in significant losses to poultry farmers as well as suffering to the birds. The virus has eight genes that can cause infected cells to produce nine proteins each of which are then modified in various ways. Some of the proteins are able to make copies of the viral genome (a ribonucleic acid [RNA] molecule that comprises the eight genes with extra pieces at the ends and between them). Other proteins combine with the genome and membranes from the cell to form virus particles that may then infect new cells. The proteins affect the disease caused by the virus both by direct damage to cells and by the reaction of the bird's immune system to them. The immune system helps to clear infections by viruses but also is often responsible for signs of disease as the infected cells are destroyed. The importance of different proteins in the production of disease and also in the production of an effective immune response by weakened viruses used as vaccines is not understood. This is important because the vaccine viruses can become disease producing again. Genetic engineering enables deoxyribonucleic acid (DNA) copies of the virus genome to be copied into virus RNA genomes and eventually into infectious virus. It is possible to make changes in the DNA copies of the virus genome by changing, deleting or inserting nucleotides that are linked together to make up the DNA. These modified DNA copies can then be used to generate viruses and the properties of these viruses studied in cell cultures and turkeys. It provides a means of designing vaccines in a rational manner. The project aims to investigate the importance of various changes observed between different viruses either as a result of mutations or of different modifications of the proteins in different cell types on the tissues in the turkeys where the virus replicates and the disease caused. The importance of changes in vaccine strains for protection will also be studied with the ultimate aim of identifying mutations that will allow virus to be produced that can stimulate a protective immune response but is incapable of causing disease. We already know that deletion of one gene alters the effect of the virus on cells in culture, and in a related virus deletion of a similar gene affects whether the virus grows best in the nose and throat or lungs of various animals. We will study this protein, which has no known function, in more detail. Ultimately, as well as expanding knowledge about the functions of the virus genes in the interaction of the virus with its host information from this study should be useful in designing more effective vaccines benefiting farmers (and turkeys!).