Purine biosynthesis as a therapeutic target for Helicobacter pylori infection

描述（由申请人提供）幽门螺杆菌是一种革兰氏阴性、微需氧细菌，是最常见的人类细菌病原体之一，慢性感染世界上大约一半人口的胃粘膜。虽然感染可以是无症状的，但H.幽门螺杆菌可引起慢性炎症、十二指肠溃疡和胃溃疡、胃粘膜相关淋巴组织（MALT）淋巴瘤和胃癌。H.幽门螺杆菌被世界卫生组织认为是I类致癌物。 H.幽门螺杆菌感染持续整个生命，除非有机体被根除。抗H.幽门螺杆菌的治疗是可用的，但它们需要在至少7天的过程中与质子泵抑制剂组合的多药方案。除了患者依从性的问题外，对常用抗生素的耐药性正在成为一个重要问题。因此，迫切需要新的抗微生物剂来治疗H。幽门。即便如此，通过抗菌治疗成功根除并不能防止随后的感染。另一种对付H. pylori疫苗 目前的探索/发展研究基金的目标是评估参与嘌呤生物合成的肌苷5 '-单磷酸脱氢酶（IMPDH）作为H.幽门。我们已经认识到可以抑制H的化合物。pylori IMPDH和H. pylori的体外研究。在这里，我们将评估较新的化合物，这些化合物在250 mg/kg剂量下经口给予小鼠时没有显示出毒性，并且我们的同事Lizbeth Hedstrom博士（布兰迪斯大学）已经在隐孢子虫病小鼠模型中进行了测试。我们将测试这些对H的生长抑制。pylori的体外实验和H.幽门感染我们还建立了一个H。pylori菌株，编码IMPDH的基因（guaB）缺失。我们已经表明，这种突变体是营养缺陷型，缺乏IMPDH活性。在这里，我们将测试是否H。pylori guaB突变体在小鼠感染模型中被减弱。随后，它将作为活疫苗进行评估，以提供针对H的保护。幽门感染如果疫苗接种有效，将确定保护机制和保护性抗原。如果guaB突变体未充分减毒，则将检测具有不同营养缺陷型需求的其他嘌呤生物合成突变体。本建议中的实验是确定嘌呤生物合成是否代表H.幽门。

DESCRIPTION (provided by applicant Helicobacter pylori is a Gram-negative, microaerophilic bacterium and one of the most common human bacterial pathogens, chronically infecting the gastric mucosa of approximately half of the world's population. While infection can be asymptomatic, H. pylori can cause chronic inflammation, duodenal and gastric ulcers, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer. As the causative agent of human cancer, H. pylori is considered a class I carcinogen by the WHO. H. pylori infection persists throughout life unless the organism is eradicated. Antimicrobial therapies against H. pylori are available, but they require multidrug regimens in combination with proton-pump inhibitors, over the course of at least 7 days. In addition to problems with patient compliance, resistance to commonly used antibiotics is becoming an important problem. Thus, there is an urgent need for new antimicrobials to treat H. pylori. Even so, successful eradication via antimicrobial therapy does not protect against subsequent infection. Another approach to combat H. pylori is vaccination. The goal of the current Exploratory/Developmental Research Grant is to evaluate the enzyme inosine 5'- monophosphate dehydrogenase (IMPDH), involved in purine biosynthesis, as a viable drug target for H. pylori. We have already recognized compounds that can inhibit H. pylori IMPDH and the growth of H. pylori in vitro. Here we will evaluate newer compounds that display no toxicity at 250 mg/kg when given orally to mice and have been already been tested by our colleague Dr. Lizbeth Hedstrom (Brandeis University) in a mouse model of cryptosporidiosis. We will test these for growth inhibition of H. pylori in vitro and in a mouse model of H. pylori infection. We have also constructed an H. pylori strain with a deletion in the gene (guaB) that encodes IMPDH. We have shown that this mutant is auxotrophic and lacks IMPDH activity. Here, we will test whether the H. pylori ¿guaB mutant is attenuated in a mouse model of infection. Subsequently, it will be evaluated as a live vaccine to provide protection against H. pylori infection. If vaccination is effective, the mechanism of protection and protective antigens will be identified. If the ¿guaB mutant is not sufficiently attenuated other purine biosynthetic mutants with different auxotrophic requirements will be tested. The experiments in this proposal are the appropriate first steps to determine whether purine biosynthesis represents a viable therapeutic target for H. pylori.