Exploitation of virulent/avirulent strain comparison to detect pathogen & host factors critical to the pathogenesis of bovine mastitis due to S.uberis

奶牛乳房的细菌感染导致一种名为乳房炎的疾病。这种疾病是养殖动物中最常见的传染病；英国每年大约发生100万例病例。乳房炎发生在所有产奶品种中；它是痛苦的，有时会危及生命，并导致牛奶产量的损失或不适合人类食用的牛奶产量。目前只有通过严格注意奶牛的卫生和大规模使用抗生素才能控制这种疾病。尽管采取了这些措施，牛仍然会受到感染。现在，感染不是在牛与牛之间传播，而是仅仅来自环境中的细菌来源(田地、稻草床上用品等)。一种细菌是世界范围内引起这种疾病的常见原因，而且在环境中经常大量存在，这种细菌是uberis链球菌(Strep Uberis)。在这个研究项目中，我们打算确定Uberis链霉菌允许它感染奶牛乳房的部分，并在这样做的过程中确定那些应该用于制造有效疫苗的细菌部分。我们将通过比较这种能够致病(致病)的细菌和其他不能致病(无毒)的细菌来做到这一点。在某些情况下，我们将通过比较每种链霉菌中存在的所有基因，并寻找那些只出现在毒力类型中的基因，来识别毒力和无毒Uberis之间的差异。在其他情况下，我们将识别有毒的uberis表面的蛋白质并释放到它们的周围，看看哪些是从无毒的uberis中缺失的。通过鉴定只由毒力类型产生的蛋白质，我们将能够产生一份可能在导致这种疾病中发挥作用的蛋白质清单。我们确定的每一种蛋白质都是由uberis中的单个基因产生的；因此，我们可以通过使产生特定蛋白质的基因失活并提出问题：缺乏该特定基因/蛋白质的新形式的uberis仍然能够导致疾病吗？要做到这一点，我们必须尝试用这种新型细菌感染奶牛。这是在严格监控的条件下完成的，以确保我们使用尽可能少的动物来获得正确的结果。我们将能够从Uberis链霉菌中识别出一些对疾病至关重要的蛋白质，这些蛋白质将成为预防这种痛苦情况的疫苗的组成部分。我们还打算使用致病和无毒类型的链霉菌来帮助我们识别疾病期间发生的事情，并识别奶牛免疫反应中可以改变以预防疾病的任何部分。感染细菌后，包括人类在内的动物会以化学物质的形式产生信息。这些因素决定了受感染的动物对感染的反应方式，并可能导致与疾病相关的许多特征。在乳房炎的情况下，这些化学信息负责吸引特定类型的白细胞从循环血液进入乳腺，并导致肿胀，导致与疾病相关的疼痛。然而，我们不知道哪些信息控制着响应的哪些部分，因此我们不知道哪些信息有助于控制疾病，哪些信息对疾病本身有贡献。由于我们现在有可能产生无毒的Uberis感染，这不会随后导致疾病，我们可以比较宿主对这种强毒和无毒类型的细菌产生的信息。这些差异将使我们能够确定哪些反应与疾病有关，哪些与疾病无关。这些信息随后可能被用来开发干扰化学信息并降低疾病水平的药物。

Bacterial infection of the udder of dairy cows results in a disease named mastitis. This disease is the most common infectious disease in farmed animals; around one million cases occur each year in the UK. Mastitis occurs in all milk producing species; it is painful, occasionally life threatening and results in the loss of milk production or the production of milk that is unfit for human consumption. The disease is currently controlled only by the rigorous attention to the hygiene of dairy cows and the large scale use of antibiotics. Despite these measures cattle still become infected. Now, rather than the infection spreading from cow to cow, infection comes only from sources of bacteria in the environment (fields, straw bedding etc). One bacterium which is a common cause of this disease world wide and which is often present in high numbers in the environment is Streptococcus uberis (Strep uberis). In this research project we intend to identify parts of the Strep uberis that allows it to infect the cow's udder and in so doing identify those parts of the bacterium that should be used to make effective vaccines. We will do this by comparing versions of this bacterium that are able to cause disease (virulent) with others that cannot (avirulent). We will identify the differences between virulent and avirulent Strep uberis, in some instances, by comparing all the genes present in each and looking for those which occur only in the virulent type. In other instances, we will identify the proteins that virulent Strep uberis have on their surface and release into their surroundings and see which ones are missing from the avirulent Strep uberis. By identifying proteins that are produced only by the virulent type we will be able to produce a list of proteins that may have a part to play in causing this disease. Each protein we identify is produced from a single gene in Strep uberis; therefore we can determine which proteins are essential to cause mastitis by inactivating the gene that produces the particular protein and asking the question: Is the new form of Strep uberis, lacking that particular gene/protein, still able to cause disease? To do this we have to try and infect dairy cattle with the new form of the bacterium. This is done under strictly monitored conditions to ensure that we use the least number of animals possible to obtain the correct results. We will be able to identify a number of proteins from Strep uberis that are essential for disease and these will become components of vaccines to prevent this painful condition. We also intend to use the virulent and avirulent types of Strep uberis to help us identify what happens during disease and to identify any parts of the immune response of the dairy cow that can be altered to prevent disease. After infection with bacteria, animals including humans respond by producing messages in the form of chemicals. These are responsible for the way the infected animal responds to that infection and can result in many features associated with the disease. In the case of mastitis, these chemical messages are responsible such things as attracting specific types of white blood cells from the circulating blood into the mammary gland and for inducing the swelling that leads to pain associated the disease. However, we do not understand which messages control which parts of the response and therefore we do not know which ones are helpful to the control of disease and which contribute to the disease itself. As we now have the possibility of creating infections with avirulent Strep uberis, which do not subsequently result in disease, we can compare the messages produced by the host in response to both virulent and avirulent types of this bacterium. The differences will allow us to identify which responses are associated with disease and which are not. This information could subsequently be used to develop drugs that interfere with the chemical messages and reduce the level of disease.