Applying recombinant technologies to define the secretome of M.a. paratuberculosis for the discovery of potential immunogens and diagnostic reagents

约翰氏病（JD）是一种无法治愈的慢性消耗性疾病，影响反刍动物，如牛、山羊、绵羊、麋鹿和鹿。动物通过食用食物、水或牛奶中的活禽分枝杆菌亚种副结核（MAP）细菌而受到感染。JD影响加拿大所有地区的奶牛群，高达40%的奶牛群报告有受感染的动物。受感染动物的畜群因产奶量、生育力下降和对病畜的扑杀增加而遭受非常重大的经济损失。人们还担心MAP与某些人类克罗恩病病例之间可能存在关联。这些担忧将持续下去，直到有确凿的证据证明这种联系，但如果这种联系建立起来，对养牛业将是毁灭性的。目前没有保护动物免受感染的疫苗，也没有预防或减少MAP在粪便和牛奶中传播的治疗方法。然而，JD可以通过阻止MAP在奶牛之间的传播来控制，这一目标可以通过在感染动物开始脱落细菌之前识别和去除它们来实现。然而，目前的诊断测试缺乏灵敏度和特异性来检测早期（或亚临床）疾病的动物。为了开发这种测试，需要进行研究工作，以我们对MAP细菌的生物学和遗传学的理解为基础，并发现可用于设计MAP特异性诊断分析和可能的疫苗的MAP成分。迄今为止，只有少数MAP蛋白被鉴定和完全表征。我们的研究目的是利用现有的重组技术来表征MAP分泌的蛋白质。分泌的蛋白质首先与宿主接触，决定感染的进程，并含有被宿主免疫系统识别的抗原，诱导抗体和细胞介导的反应。表征分泌蛋白也有实际应用在发现新的试剂分析宿主免疫反应，感染的诊断和区分接种和感染的宿主。

Johne's disease (JD) is an incurable chronic and wasting disease affecting ruminant animals such as cows, goats, sheep elk and deer. Animals become infected by eating live Mycobacterium avium subspecies paratuberculosis (or MAP) bacteria in food, water or milk. JD affects herds in all regions of Canada with up to 40% of dairy herds reporting an infected animal. Herds with infected animals suffer very significant economic looses from decrease in milk production, fertility and increased culling of sick animals. There is also concern regarding the possible association between MAP and some cases of Crohn's disease in humans. These concerns will continue until there is definitive proof against such a link but it would be devastating to the cattle industry if such link were established. Currently there are no vaccines that protect animals against infection and no treatments that prevent or reduce MAP shedding in feces and milk. However, JD can be controlled by stopping the cow-to-cow spread of MAP and this goal can achieved by identifying and removing infected animals before they start shedding the bacterium. However, the current diagnostic tests lack the sensitivity and specificity to detect animals with early stage (or subclinical) disease. To develop such tests, research effort is needed to build on our understanding of the biology and genetics of MAP bacteria and to discover MAP components that can be used to design MAP-specific diagnostic assays and possibly vaccines. To date only a few MAP proteins have been identified and fully characterized. The purpose of our study is to use current recombinant technologies to characterize the proteins secreted by MAP. Secreted proteins make first contact with the host, determine the course of infection and contain the antigens recognized by the host immune system to induce antibody and cell mediated responses. Characterizing secreted proteins also has practical application in the discovery of novel reagents for profiling host immune responses, diagnosis of infection, and differentiation between vaccinated and infected hosts.