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，影响奶牛、山羊、绵羊、麋鹿和鹿等反刍动物。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(或MAP)细菌而感染。JD影响加拿大所有地区的牛群，高达40%的奶牛群报告有受感染的动物。有受感染动物的牛群因产奶量减少、生育力下降和对患病动物的扑杀增加而遭受非常重大的经济损失。也有人担心MAP与人类克隆氏病的一些病例之间可能存在关联。这些担忧将持续下去，直到有确凿证据反对这种联系为止，但如果建立这种联系，将对养牛业造成毁灭性的打击。目前还没有保护动物免受感染的疫苗，也没有预防或减少MAP在粪便和牛奶中脱落的治疗方法。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受感染的动物开始脱落细菌之前识别和清除它们来实现。然而，目前的诊断试验缺乏检测早期(或亚临床)疾病动物的敏感性和特异性。为了开发这种测试，需要进行研究工作，以加深我们对MAP细菌的生物学和遗传学的理解，并发现可用于设计MAP特异性诊断分析和可能的疫苗的MAP组件。到目前为止，只有几个MAP蛋白被鉴定和充分鉴定。本研究的目的是利用现有的重组技术对MAP分泌的蛋白质进行鉴定。分泌的蛋白质与宿主第一次接触，决定感染的过程，并含有宿主免疫系统识别的抗原，以诱导抗体和细胞介导的反应。对分泌蛋白进行表征还可用于发现新的试剂，用于分析宿主免疫反应、诊断感染以及区分疫苗接种和感染宿主。

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.