Defining the molecular basis of H7 flagellin and as an adhesin and mucosal adjuvant for vaccine development

肠出血性大肠杆菌(EHEC)O157：H7是引起人类严重胃肠道疾病的细菌。细菌释放的毒素会对肾脏和大脑造成危及生命的损害。牛是细菌的主要宿主，人类最初是通过摄入从动物粪便中直接或间接污染的食物或饮料而感染的。预防人类感染EHEC O157的一种方法是阻止或限制这种微生物从牛身上脱落。这可以通过为牛接种疫苗来实现。我们之前的研究已经证明，EHEC O157通常用于细菌运动的鞭状“鞭毛”可以结合到牛的肠道衬里上，以促进定植。如果我们用纯化的鞭毛给牛接种疫苗，肠道中会产生特定的抗体，阻止这种结合并限制细菌的定植。然而，这些抗体的一部分具有负面影响，因为它们与鞭毛的一个区域结合，该区域干扰宿主在感染发生时识别和反应的方式。这项研究主要有两个目的。第一个是定义鞭毛结合所需的鞭毛分子内的特定区域，并将其用于疫苗制备，以研究它如何限制EHEC O157对牛的定植。预计通过仅使用与牛的胃肠道结合所需的鞭毛蛋白区域，或通过改变对刺激哺乳动物炎症反应的区域的识别，我们应该能够生产出含有鞭毛蛋白的有效疫苗，显著减少牛的EHEC O157脱落。研究的第二部分是了解用整个鞭毛蛋白接种牛是如何刺激动物胃肠道表面如此良好的抗体反应的，然后利用这一理解来产生对与鞭毛蛋白相关的其他分子的反应。寻找刺激这种“粘膜”免疫的方法对于许多传染病疫苗的开发是重要的。

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 are bacteria that cause serious gastrointestinal disease in humans. Toxins released by the bacteria cause life-threatening damage to the kidneys and brain. Cattle are the main reservoir host for the bacteria and humans become infected initially by ingesting food or drink that has been contaminated, directly or indirectly, from animal faeces. One way to guard against human infection with EHEC O157 is to block or limit shedding of the organism from cattle. This can be done via vaccination of cattle. Our previous research has demonstrated that the whip-like 'flagella' of EHEC O157 that are usually used for bacterial movement, can bind to the intestinal lining of cattle to promote colonisation. If we vaccinate cattle with purified flagella, specific antibodies are generated in the gut that block this binding and limit bacterial colonisation. However, a subset of these antibodies have a negative impact in that they bind to a region of the flagella that interferes with how the host recognizes and responds to the real infection when it occurs. There are two main aims of the research. The first is to define the specific region within the flagellin molecule required for flagella binding and to use this in a vaccine preparation to study how it limits colonisation of cattle by EHEC O157. It is anticipated that by using only the region of flagellin required for binding in the gastrointestinal tract of cattle or by altering recognition of the region that stimulates inflammatory responses in mammals, we should be able to produce an effective vaccine containing flagellin that significantly reduces EHEC O157 shedding from cattle. The second part of the research is to understand how the vaccination of cattle with whole flagellin stimulates such a good antibody response on the surface of the animals gastrointestinal tract and then exploit this understanding to generate responses to other molecules linked to flagellin. Finding ways to stimulate this 'mucosal' immunity is important for the development of vaccines to many infectious diseases.