Host factors in determining resistance to cryptosporidiosis in cattle

隐孢子虫寄生虫是英国和全球幼牛肠道疾病的最重要原因，也是人类婴儿腹泻的主要原因之一[1]。新生小牛非常容易感染隐孢子虫病，由于严重腹泻和脱水导致显著发病率，并且有越来越多的死亡报告。隐孢子虫病是控制的一个挑战，因为受感染的动物将数十亿个具有感染性、长寿的卵囊排入环境中，这些是其他动物和人类的感染源。这种疾病已经成为一个日益严重的问题，在牛乳单位，畜牧业领导人非常关注缺乏安全有效的治疗方法或疫苗，以帮助预防和控制隐孢子虫病，并给予他们强烈支持这一建议。我们对决定疾病结果的宿主-病原体相互作用的理解是有限的。新生小牛非常容易受到感染，并经常表现出临床疾病，而年龄较大的小牛更具抵抗力。参与决定这种年龄相关易感性的因素尚不清楚，该项目旨在通过在体内应用新颖和创新的方法，离体和体外技术，以详细检查宿主寄生虫在小牛急性感染和恢复期间的相互作用。缺乏简单的研究系统，无法详细分析宿主与寄生虫的相互作用。啮齿动物模型是公认的临床疾病的比较差的隐孢子虫病，特别是在体外培养隐孢子虫寄生虫的能力是非常有限的。该项目旨在通过利用体内和体外牛系统的组合来评估先天性和适应性细胞免疫反应并检查隐孢子虫与肠道上皮细胞的相互作用来解决这些能力差距。此外，创新的3D牛肠道类器官体外培养系统将被应用于详细分析牛肠道上皮中的宿主寄生虫相互作用。来自实验研究的数据将通过与从研究农场自然感染的小牛中获得的类似数据进行比较来验证。该项目将对牛如何抵抗隐孢子虫寄生虫感染进行迄今为止最全面的探索。对所涉及的宿主反应的详细描述将提供一个重要的知识平台，使疫苗的开发能够帮助疾病预防，并确定相关的生物标志物，使选择性育种方案能够提高复原力。此外，新的体外牛系统的开发将彻底改变我们研究隐孢子虫宿主-病原体相互作用的能力，从而最大限度地减少使用动物模型的需要。该项目的成果将对动物健康行业，畜牧业生产者，环境和公共卫生工作者以及学术研究人员产生兴趣。制定有效的控制战略将对动物生产的可持续效率产生重大影响，保障粮食安全，改善动物健康和福利，减少废物和环境污染，并改善公众和环境健康。[1]Streipen B（2013）Nature 503：189

Cryptosporidium parasites are the most important cause of enteric disease in young cattle in UK and worldwide and are also one of the leading causes of infant diarrhoea in humans [1]. Neonatal calves are very vulnerable to cryptosporidiosis resulting in significant morbidity due to severe diarrhoea and dehydration and there are increasing reports of mortality. Cryptosporidiosis is a challenge to control as infected animals shed billions of infective, long lived oocysts into the environment and these are a source of infection for other animals as well as people. The disease has emerged as an increasing problem in beef suckler units, and livestock industry leaders are very concerned about the lack of safe and effective treatments or vaccines available to help prevent and control cryptosporidiosis and have given their strong support for this proposal. Our understanding of the host-pathogen interactions that determine disease outcome is limited. Neonatal calves are very vulnerable to infection and often exhibit clinical disease, whereas older calves are more resistant. The factors involved in determining this age-related susceptibility are unclear and this project aims to address the host factors involved in resistance to cryptosporidiosis by applying novel and innovative in vivo, ex vivo and in vitro technologies to examine in detail the host parasite interaction during acute infection and recovery in calves.One of the constraints for improving our understanding of the factors that determine disease resistance has been the lack of simple research systems that permit the detailed analysis of host parasite interactions. The rodent model is an acknowledged poor comparator for clinical disease in cryptosporidiosis in particular, and the capability for culturing Cryptosporidium parasites in vitro is very limited. This project aims to tackle these gaps in capability by utilising a combination of in vivo and in vitro bovine systems to assess innate and adaptive cellular immune responses and examine the interaction of Cryptosporidium with gut epithelial cells. In addition, innovative 3D bovine gut organoid in vitro culture systems will be applied to enable a detailed analysis of host parasite interactions in the bovine gut epithelium. Data derived from the experimental studies will be validated by comparison to similar data obtained from naturally infected calves on a study farm.This project will provide the fullest exploration yet of how cattle resist infection with Cryptosporidium parasites. A detailed account of the host responses involved will provide an important knowledge platform that will enable the development of vaccines to aid disease prevention and the identification of relevant biomarkers that will enable selective breeding programmes to improve resilience. In addition, the development of novel in vitro bovine systems would revolutionise our capability to study host-pathogen interactions with Cryptosporidium minimising the need for use of animal models.Outputs from the project will be of interest to the animal health industry, livestock producers, environmental and public health workers and to academic researchers. The development of effective control strategies will have a significant impact on the sustainable efficiency of animal production, safeguard food security, improve animal health and welfare, reduce waste and environmental contamination and improve public and environmental health. [1] Streipen B (2013) Nature 503:189