Development of in vitro assays to determine vaccine efficacy in fish

在过去的20年里，英国的养鱼业大幅增长。苏格兰目前生产超过13万吨大西洋三文鱼，是全球第三大养殖三文鱼生产国。英国每年还生产约1.6万吨彩虹鲑鱼。在过去的十年里，消费者对养殖鱼的消费量增加了两倍，现在英国每天吃100万份三文鱼粉。在影响该行业可持续性的各种因素中，鱼类健康是一些特别令人关注的疾病问题的关键。因此，为了获得可持续的水产养殖业，健康管理是必要的，这种管理的核心是开发新的疫苗，在它们可以上市之前需要进行彻底的测试。这涉及到大量的鱼暴露在病原体中，死亡率被用作测试疫苗效力的终点。开发一种方法，使研究人员能够更人性化地确定疫苗效力，将显著减少鱼类在这些试验中的痛苦。疫苗接种的保护依赖于特定抗体的产生和T细胞的激活，这些T细胞介导特定的细胞介导的反应，能够杀死受感染的宿主细胞并激活非特异性防御。对这些细胞反应的研究是减少疫苗试验期间鱼类痛苦的关键。一些T细胞(T辅助细胞)释放被称为细胞因子的介质，启动和调节宿主的反应。根据释放的细胞因子的不同，可以产生不同的反应。免疫后对这些分子的测量可以与免疫所提供的保护相关联，免疫是一种在哺乳动物中得到相当成功的公认的方法。在这项研究中，我们将确定针对两种细菌病原体(ruckeri耶尔森菌或沙门氏气单胞菌)之一的疫苗接种并暴露于同源或异源病原体后，鲑鱼体内产生两种细胞因子(IL-17和IL-22)的细胞数量。选择IL-17和IL-22是因为它们与T辅助细胞亚群相关，这些T辅助细胞亚群负责保护哺乳动物免受这些类型的病原体的侵袭。它们的生产将被评估为体外保护相关性，结果将更普遍地作为鱼类的原则证明，以期开发一种方法，在不需要致命挑战实验的情况下进行大量疫苗优化。通过这种方式，这项工作将有助于在未来的疫苗开发研究中减少鱼类的痛苦。

Fish farming in the UK has increased dramatically over the last two decades. Scotland currently produces over 130,000 tonnes of Atlantic salmon and is the third largest producer of farmed salmon globally. Around 16,000 tonnes of rainbow trout are also produced in the UK annually. Consumer consumption of farmed fish has trebled in the last ten years, with 1 million salmon meals now eaten each day in the UK. Of various factors that impact on the sustainability of the industry, fish health is key with a number of disease issues of particular concern. To obtain a sustainable aquaculture industry health management is thus necessary and at the heart of this management is the development of new vaccines, which require thorough testing before they can be marketed. This involves large numbers of fish exposed to disease agents, where mortality is used as the end point to test vaccine efficacy. The development of a method that would allow researchers to establish vaccine efficacy more humanely, would significantly reduce the suffering of fish in these trials. Protection by vaccination relies on the production of specific antibodies and the activation of T cells that mediate specific cell-mediated responses, capable of killing infected host cells and activating non-specific defences. The study of these cellular responses is key to reducing the suffering of fish during vaccine trials. Some T cells (T-helper cells) release mediators called cytokines that initiate and regulate the host responses. Different responses can be generated dependent upon the cytokines released. The measurement of these molecules after vaccination can be correlated with the protection conferred by immunisation, a well established method used with reasonable success in mammals.In this study we will determine the numbers of cells producing two cytokines (IL-17 and IL-22) in trout, following vaccination against one of two bacterial pathogens (Yersinia ruckeri or Aeromonas salmonicida) and exposure to the homologous or heterologous pathogen. IL-17 and IL-22 were chosen as they are associated with T-helper cell subpopulations responsible for protection against these types of pathogens in mammals. Their production will be assessed as an in vitro correlate of protection, and the results will serve more generally as a proof of principle for fish, with a view to develop a means to undertake a great deal of vaccine optimisation without the need for lethal challenge experiments. In this way this work will help to reduce fish suffering in future vaccine development studies.