Bacterial Surface Structures of Helicobacter Pylori and Campylobacter Jejuni

描述(申请人提供)：细菌组装与其周围环境接触的非凡的表面结构。其中一种结构是被称为脂多糖(LPS)的糖脂，它覆盖在革兰氏阴性细菌的表面。脂蛋白被称为脂类A的脂锚固定在细菌细胞上，脂类A是通过内膜细胞质表面高度保守的途径合成的。紧随其后的是核心低聚糖的添加和分子在内膜上的运输。O抗原多糖连接到周质中的核心类脂A上，完成内毒素的组装。在内毒素向细菌表面运输的过程中，潜伏酶改变了内毒素结构，从而导致了内毒素结构的多样性。在大多数情况下，这些酶的目标是脂类A锚和分子的核心低聚糖域。由于脂类A是脂多糖的生物活性成分，这些修饰可以通过改变哺乳动物天然免疫受体TLR4-MD2对脂多糖的识别，对疾病产生深远的影响。此外，内毒素结构的改变可以直接影响细菌的外膜通透性屏障，以及细菌对宿主抗菌肽的耐药性。这项提案的总体目标是揭示幽门螺杆菌和空肠弯曲菌这两种病原体修改其内毒素结构的分子机制，以及这些修改在毒力中所起的作用。虽然相关，但这些病原体已经进化出独特的修改机制，可能适合它们特定的生态位。本提案的具体目的是：(1)幽门螺杆菌脂多糖修饰机制的表征；(2)空肠弯曲菌中脂类A修饰的表征；(3)幽门螺杆菌和弯曲杆菌脂多糖重塑对宿主先天免疫反应的影响。以下目标的完成将直接有助于我们理解内毒素修饰机制如何影响发病机制。最后，这项工作将带来疫苗开发的新途径，以及产生可用作潜在佐剂和/或内毒素拮抗剂的工程内毒素结构的能力。 公共卫生相关性：革兰氏阴性细菌是许多人类传染病的罪魁祸首。在这些细菌的表面有一种名为脂多糖或脂多糖的分子，它可以激活人类的免疫系统。细菌修改其内毒素结构，直接影响疾病。这项提议将有助于确定与人类疾病相关的细菌如何改变其内毒素结构，可能导致新的治疗方法。

DESCRIPTION (provided by applicant): Bacteria assemble remarkable surface structures that interface with their surrounding environment. One such structure is the glycolipid known as lipopolysaccharide (LPS) that covers the surface of gram-negative bacteria. LPS is anchored to the bacterial cell by its lipid anchor known as lipid A. Lipid A is synthesized via a highly conserved pathway at the cytoplasmic face of the inner membrane. This is followed by addition of the core oligosaccharide and transport of the molecule across the inner membrane. The O-antigen polysaccharide is ligated to the core-lipid A in the periplasm completing LPS assembly. During the trafficking of LPS to the bacterial surface, latent enzymes modify the LPS structure contributing towards the diversity seen in LPS structure. For the most part, these enzymes target the lipid A anchor and the inner core oligosaccharide domains of the molecule. Since the lipid A is the bioactive component of LPS, these modifications can have a profound impact on disease, by altering LPS recognition by the mammalian innate immune receptor TLR4- MD2. Additionally, alteration of the LPS structure can directly impact the outer membrane permeability barrier, and bacterial resistance to host antimicrobial peptides. The overall objective of this proposal is to unravel the molecular mechanisms by which two pathogenic organisms, Helicobacter pylori and Campylobacter jejuni, modify their LPS structure and the role these modifications play in virulence. Although related, these pathogens have evolved unique modification machinery perhaps adapted for their specific ecological niche. The specific aims of the current proposal are: (1) characterization of Helicobacter pylori LPS modification machinery; (2) characterization of lipid A modifications in Campylobacter jejuni; and (3) impact of Helicobacter and Camyplobacter LPS remodeling on the host innate immune response. The completion of the Aims below will directly contribute to our understanding of how LPS modification machinery impacts pathogenesis. Finally, from this work will come new avenues of vaccine development and the ability to generate engineered LPS structures that could serve as potential adjuvants and/or LPS antagonists. PUBLIC HEALTH RELEVANCE: Gram-negative bacteria are responsible for a number of human infectious diseases. On the surface of these bacteria is a molecule called lipopolysaccharide or LPS that activates the human immune system. Bacteria modify their LPS structure which directly impacts disease. This proposal will help determine how bacteria associated with human disease modify their LPS structure possibly leading to novel therapies.