Development of improved vaccines effective against emerging strains of the fish pathogen Yersinia ruckeri

尽管在疫苗开发和化学疗法方面取得了进展，但细菌病原体仍然是水产养殖生产的一个重大制约因素，也是野生种群的一个潜在威胁。除了所谓的“新”细菌病原体外，威胁往往来自已建立的病原体的进化，以规避发达的控制策略。这种进化的病原体的一个例子是革兰氏阴性细菌鲁氏耶尔森氏菌，其引起大西洋鲑鱼（萨尔莫salar）和虹鳟鱼（虹鳟鱼）的经济上重要的感染。Y.在英格兰和威尔士，Ruckeri被鉴定为养殖虹鳟鱼肠道红口病（ERM）的病原体已有30多年。这种微生物也会在养殖的大西洋鲑鱼中引起重大的疾病爆发，但人们对Y。在这个物种中的Ruckeri。直到最近，Y。ruckeri对养殖鳟鱼和鲑鱼造成的风险降低，主要是由于广泛使用疫苗接种。然而，越来越多的疫苗在该领域的世界范围内的报告被认为是与新的致病性菌株的Y。ruckeri。传统上，在美国和欧洲虹鳟鱼中的大多数ERM感染是由密切相关的血清型O 1 Y的亚组（生物型）引起的。ruckeri菌株，以所谓的Hagerman菌株为代表。然而，近年来出现了一种新的和独特的血清型O 1生物型，它首先在英国被发现，但现在越来越多地影响整个欧洲和美国的虹鳟鱼生产。从受感染的大西洋鲑鱼中回收的分离株似乎更加多样化，并代表了更广泛的O血清型（O 1、O2和O 5）。初步证据表明，鲑鱼致病性血清型显着降低致病性虹鳟鱼比大西洋鲑鱼。革兰氏阴性菌的外膜（OM）位于病原体和宿主之间的界面，外膜蛋白（OMPs）在宿主-病原体相互作用中起关键作用，如粘附和定殖、营养吸收（特别是铁的获得）、逃避宿主免疫应答和分泌毒力因子。由于这些外膜蛋白中的许多都处于强大的选择压力下（例如来自宿主免疫系统），因此它们可以在单个细菌物种内表现出不同程度的多样性。这种多样性可能赋予菌株不同的毒力属性和宿主向性。此外，许多OMP是表面暴露的和免疫原性的，因此可能用作保护性抗原。尽管Y.尽管Ruckeri是养殖鲑科鱼类的病原体，但其外膜蛋白在不同品系中的多样性及其在疾病过程中的作用知之甚少。此外，关于宿主对Y的免疫反应知之甚少。ruckeri在鲑鱼和鳟鱼或有关细菌的因素负责提供保护免受感染。本项目的目标如下：1.目的：对山东省部分地区人群进行Y. ruckeri在苏格兰鲑鱼，并评估在海水中的生物传播的有效性。2.目的研究耶尔森氏菌主要分离株的OM蛋白质组。Ruckeri从不同生长条件下的鲑鱼和鳟鱼中回收，并通过免疫蛋白质组学鉴定交叉保护性抗原（和潜在的疫苗候选物）。3.比较所选分离物对大西洋鲑鱼和鳟鱼的毒力。4.比较对所选Y.大西洋鲑鱼和鳟鱼中的ruckeri。5.研究不同分离株疫苗的免疫血清型特异性和保护力。大西洋鲑鱼和鳟鱼中的ruckeri。

Despite advances in vaccine development and chemotherapy, bacterial pathogens remain a significant constraint to aquaculture production, as well as a potential threat to wild stocks. In addition to so-called 'new' bacterial pathogens, the threat often comes from established pathogens evolving to circumvent developed control strategies. An example of such an evolving pathogen is the Gram-negative bacterium Yersinia ruckeri which causes economically-important infections of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). Y. ruckeri has been identified as the aetiological agent of enteric redmouth disease (ERM) of farmed rainbow trout in England and Wales for more than thirty years. The organism also causes significant outbreaks of disease in farmed Atlantic salmon but very little is known about the epidemiology of Y. ruckeri in this species. Until recently, Y. ruckeri posed a reduced risk to farmed trout and salmon due largely to the extensive use of vaccination. However, increasing worldwide reports of vaccine breakdown in the field are believed to be associated with the emergence of new pathogenic strains of Y. ruckeri. Traditionally, the majority of ERM infections in rainbow trout in the USA and Europe have been caused by a subgroup (biotype) of closely-related serotype O1 Y. ruckeri strains represented by the so-called Hagerman strain. However, a new and distinct serotype O1 biotype has emerged in recent years that was first identified in the UK but which is now increasingly affecting rainbow trout production across Europe and the USA. Isolates recovered from infected Atlantic salmon appear to be more diverse and represent a wider range of O-serotypes (O1, O2 and O5). Preliminary evidence suggests that salmon-pathogenic serotypes are significantly less pathogenic to rainbow trout than they are to Atlantic salmon. The outer membrane (OM) of Gram-negative bacteria is at the interface between pathogen and host and outer membrane proteins (OMPs) play key roles in host-pathogen interactions such as adherence and colonization, nutrient uptake (specifically iron acquisition), evasion of the host immune response and secretion of virulence factors. Because many of these OMPs are under strong selection pressures (e.g. from the host immune system) they can exhibit varying degrees of diversity within a single bacterial species. This diversity is likely to confer upon strains different virulence attributes and host tropisms. In addition, many OMPs are surface-exposed and immunogenic and are therefore likely to serve as protective antigens. Despite the importance of Y. ruckeri as a pathogen of farmed salmonids, very little is known about the diversity of its OMPs in different strains or their roles in the disease process. Furthermore, very little is known about the host immune response to Y. ruckeri in salmon and trout or about the bacterial factors responsible for providing protection against infection. The aims of this project are as follows: 1. To carry out an epidemiological survey of the prevalence of Y. ruckeri in Scottish salmon and assess the effectiveness of transmission of the organism in seawater. 2. To characterize the OM proteomes of key selected isolates of Y. ruckeri recovered from salmon and trout under different growth conditions and identify cross-protective antigens (and potential vaccine candidates) by immunoproteomics. 3. To compare the virulence of selected isolates for Atlantic salmon and trout. 4. To compare the kinetics of the immune response to selected isolates of Y. ruckeri in Atlantic salmon and trout. 5. To study serotype specificity of immunity and the protection afforded by vaccines prepared from different isolates of Y. ruckeri in Atlantic salmon and trout.