Type III Secretion Systems as Vaccine Targets

描述（由申请人提供）：没有比接种疫苗更广泛有效的疾病预防方法。不幸的是，目前几乎没有针对细菌病原体的明确定义的疫苗。确定可成为有效疫苗靶点的细菌表面成分显然是公共卫生的优先事项。一个这样的靶标是III型分泌系统（T3 SS），其被许多革兰氏阴性病原体用于将毒力蛋白递送至真核细胞以改变其正常功能。T3 SS是表面暴露的超分子机器，由两个主要结构特征组成：a）跨越细菌内膜和细菌外膜的复杂基体;和B）表面暴露的针，由单个蛋白质的多个拷贝组成，并用尖端复合物加帽，所述尖端复合物是感测宿主细胞接触以促进细菌蛋白质有效插入宿主细胞膜所需的。对于福氏志贺菌，病原体细菌性痢疾，针单体是MxiH，尖端复合物由侵袭质粒抗原iPad组成。这两种蛋白质都是志贺氏菌毒力所必需的，并锚定在病原体的表面，在那里它们暴露于细胞外环境。我们假设这两种蛋白质代表了疫苗接种的有吸引力的靶点。识别外部T3 SS组分的一类新疫苗预计将提供针对广泛的革兰氏阴性病原体的保护。为了验证这一假设，拟议研究的具体目的是：1）评估MxiH和/或iPad特异性抗体对志贺氏菌毒力相关功能的影响; 2）直接评估MxiH和iPad作为预防志贺氏菌感染的疫苗的有效性。拟议的研究符合R21资助机制，该机制针对潜在的高风险试点项目，其成功将对公共卫生产生重大影响和生物防御相关性。组建的调查小组拥有完成拟议研究的专业知识，并将其扩展为具有实际公共卫生影响和生物防御应用的更大和高度重要的研究计划。敷设总结：我们建议针对构成III型分泌系统暴露部分的蛋白质来测试预防细菌性痢疾的新疫苗。如果成功的话，一种新的疫苗将可以预防许多重要的细菌病原体的感染。

DESCRIPTION (provided by applicant): There is no disease prevention approach more broadly powerful than vaccination. Unfortunately, few well-defined vaccines against bacterial pathogens are available today. Identification of bacterial surface components that would make effective vaccine targets is clearly a public health priority. One such target is the type III secretion system (T3SS) used by many Gram-negative pathogens to deliver virulence proteins to eukaryotic cells for altering their normal functions. T3SSs are surface exposed supramolecular machines composed of two main structural features: a) a complex basal body that spans the inner and outer bacterial membranes; and b) a surface exposed needle composed of multiple copies of a single protein and capped with a tip complex that is needed to sense host cell contact to facilitate efficient insertion of bacterial proteins into the host cell membrane. For Shigella flexneri, the causative agent bacillary dysentery, the needle monomer is MxiH and the tip complex is composed of the invasion plasmid antigen IpaD. Both of these proteins are essential for Shigella virulence and are anchored on the pathogen's surface where they are exposed to the extracellular milieu. We hypothesize that these two proteins represent attractive targets for vaccination. A new class of vaccines that recognize external T3SS components would be expected to provide protection against a broad range of Gram-negative pathogens. To test this hypothesis, the specific aims of the proposed research are to: 1) assess the effects that MxiH- and/or IpaD-specific antibodies have on Shigella virulence-related functions; and 2) directly assess the effectiveness of MxiH and IpaD as vaccines that protect against Shigella infection. The proposed research is in line with the R21 funding mechanism which targets potentially high risk pilot projects whose success would have significant high public health impact and biodefense relevance. The assembled investigative team has the expertise to complete the study as proposed and extend it into a larger and highly significant research program with practical public health implications and biodefense applications. Lay summary: We propose to target the proteins that make up the exposed portions of the type III secretion system to test a new vaccine for the prevention of bacterial dysentery. If successful, a new class of vaccines will be within reach for prevention of infection by many important bacterial pathogens.