IDENTIFICATION OF COMPLEMENT RESISTANCE DETERMINANTS IN ESCHERICHIA COLI

大肠杆菌中补体抗性决定因素的鉴定

• 批准号: 3768848
• 负责人: T A RUSSO
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3768848
• 关键词: Escherichia coli; Escherichia coli infections; bacterial capsules; bacterial genetics; bactericidal immunity; complement inhibitors; complement pathway; laboratory mouse; nucleic acid sequence; transposon /insertion element; virulence

Complement resistance is an important virulence determinant in the pathogenesis of bacterial gram-negative infections. A more complete understanding of complement resistance determinants may lead to novel therapies in the treatment of disease caused by these organisms. We have used transposon mutagenesis (TnphoA) to randomly mutate a clinical blood isolate of Escherichia coli (CP9, 04/K54/H5) that we are using as a model pathogen for extra-intestinal disease. This strain possesses a group 2 capsule and is highly serum resistant, as is characteristic of clinical isolates. Isogenic mutants have been identified that have an increased sensitivity to serum. Some of these mutants have been identified as being capsule-minus. We have defined at least 3 physical loci that are involved in capsule production in our strain and they are linked. DNA sequence analysis has demonstrated that we have disrupted at least 5 separate genes and that one has homology with capsular transport genes of Escherichia coli serotype K1, Haemophilus influenza and Neisseria meningitidis. In vitro biologic studies have established that the K54 capsule protects against complement killing that is mediated via the alternative complement pathway. C3 binding is equal in capsule-positive and capsule- minus strains suggesting the mechanism of complement resistance conferred by the K54 capsule is different than that of the K1 capsule. Additional in vitro studies have demonstrated that the K54 capsule protects against killing by neutrophils. Three different animal models were used to test whether the K54 capsule conferred protection in vivo as well. In summary, these studies demonstrated that the possession of the K54 capsule resulted in a significant decrease of the LD50 in a mouse model of systemic infection, significantly decreased intra-vascular clearance and protected against killing in a local infection model. These studies also demonstrated that the K54 capsular polysaccharide may be one of the bacterial antigens responsible for inciting the cascade of events that leads to septic shock. They also demonstrated that other bacterial factors are induced in vivo that enhance survival and are important in the pathogenic process.

补体抗性是决定病毒毒力的一个重要因素。 细菌革兰氏阴性菌感染的发病机制。一个更完整的 对补体抵抗决定因素的了解可能会导致新的 治疗由这些微生物引起的疾病的疗法。我们有 利用转座子突变(TnPhoA)随机突变临床血液 我们用来作为模型的大肠杆菌(CP9，04/K54/H5)的分离 肠外疾病的病原体。该菌株具有第2群 胶囊，具有很高的血清抵抗力，这是临床的特点 分离株。已发现的同基因突变体具有更高的 对血清敏感。这些突变体中的一些已被鉴定为 是没有胶囊的。我们已经定义了至少3个物理位置 在我们的菌株中参与胶囊生产，它们是联系在一起的。脱氧核糖核酸 序列分析表明，我们已经干扰了至少5个 分离的基因，并且与囊膜运输基因有同源性 K1型大肠埃希菌、流感嗜血杆菌和奈瑟氏菌 脑膜炎。 体外生物学研究已证实K54胶囊具有保护作用 通过另一种选择来对抗补体杀死 补体途径。C3结合在包膜阳性和包膜阳性中是相同的 补体耐药机制的负性菌株 K54胶囊与K1胶囊赋予的不同。 更多的体外研究表明，K54胶囊 防止中性粒细胞致死。三种不同的动物模型 用来测试K54胶囊在体内是否具有保护作用 也是。总而言之，这些研究表明，拥有 K54胶囊能显著降低小鼠的半数致死量 全身性感染模型，血管内显著减少 在本地感染模型中清除并保护免受杀戮。 这些研究还表明，K54囊膜多糖可能 是一种细菌抗原，可引发一系列 导致感染性休克的事件。他们还证明了另一个 细菌因子是在体内诱导的，可以提高存活率，并 在致病过程中很重要。