Evolution and pathogenesis of serotype V group B Streptococcus in humans

项目总结 人类中细菌病原体的出现和进化是一种复杂的相互作用的结果 细菌因素与宿主免疫反应。无乳链球菌(B群链球菌，GBS) 出现在20世纪60年代末和70年代初，是婴儿败血症和脑膜炎的常见原因。 年龄。20年后，GBS也被认为是成人疾病的重要原因。血清交叉- 对GBS壳多糖(CPS)的反应导致识别出10种CPS类型(Ia/Ib，II-IX)。这个 婴儿疾病的流行病学是由CPS Ia和III的GBS毒株定义的，已经进行了许多研究 致力于该年龄段GBS的发病机制和疾病预防。相比之下，成人疾病占主导地位。 由CPS IV和V型菌株引起的，我们对它们的致病机制知之甚少 疾病。结合这样一个事实，在每年发生的约30,000例侵袭性GBS疾病中， 美国三分之二的病例发生在成人中，我们对成人GBS疾病的理解存在着重大的知识差距 机械装置。我们之前进行了一项仅有的检查CPS V GBS的研究，发现 大多数(&gt；85%)是单一序列类型(ST)，ST1，并通过微小的遗传变化而进化 (突变)。在这里，我们扩展了我们之前的分析，包括在开始时分离的CPS V GBS毒株 成人GBS疾病的增加。结合我们之前的分析，我们的数据表明“早期”(1992年前) 与同时代的CPS V GBS相比，CPS V GBS更有可能是ST2，其中 ST1占优势。此外，我们还鉴定了编码一种未被研究的双组分基因的基因。 调控系统(TCS)在ST1群体中高度多态，与CPS中的关键作用一致 V-GBS发病机制。这些数据构成了这一提议的基础，该提议试图检验ST1的假设 由于基因含量的差异，与非ST1菌株相比，GBS改变了宿主与病原体的相互作用 和全球基因监管。体外暴露于人血后的RNA测序和模型 GBS定植与疾病的特异性目标1将决定基因调控差异的贡献 在ST1和非ST1 GBS之间，导致宿主-病原菌相互作用和优势的差异 ST1在当代CPS V GBS中的分布。在特定目标2中，我们检验了已识别的TC的假设 决定了ST1的表型特征和在CPS V GBS中的优势。我们将生成 同基因缺失突变株，并利用RNA测序将转录本与亲本菌株进行比较以确定 塔塔咨询服务的主要监管目标。随后，我们将把基因调控的差异与 利用GBS定植和疾病模型研究宿主-病原体相互作用的差异。完成这些工作 研究将提供有关成人CPS V GBS疾病的关键新信息，并作为 对其他CPS类型的调查。此外，拟议的研究旨在产生关键的初步 深入研究人类中GBS的出现和发病机制所需的数据。

PROJECT SUMMARY Emergence and evolution of bacterial pathogens in humans is the result of a complex interplay between bacterial factors and the host immune response. Streptococcus agalactiae (group B Streptococcus, GBS) emerged in the late 1960s and early 1970s as a frequent cause of sepsis and meningitis in infants <90 days of age. Twenty years later, GBS was also recognized as a significant cause of disease in adults. Serum cross- reactivity to the GBS capsular polysaccharide (CPS) led to the recognition of 10 CPS types (Ia/Ib, II-IX). The epidemiology of infant disease is defined by GBS strains of CPS Ia and III and much research has been devoted GBS pathogenesis and disease prevention in this age group. In contrast, adult disease is dominated by strains of CPS type IV and V of which we understand little of the bacterial mechanisms contributing to disease. Combined with the fact that of the ~30,000 cases of invasive GBS disease that occur annually in the US two-thirds occur in adults, a major knowledge gap exists in our understanding of adult GBS disease mechanisms. We previously performed one of the only studies to examine CPS V GBS and discovered that the majority (>85%) are of a single sequence type (ST), ST1, and evolve by small genetic changes (mutations). Here, we extend our previous analysis to include CPS V GBS strains isolated at the beginning of the rise in adult GBS disease. Combined with our previous analysis, our data indicate that “early” (pre-1992) CPS V GBS disease strains were more likely to be ST2 compared to contemporary CPS V GBS among which ST1 predominates. In addition, we have identified genes encoding an unstudied two-component gene regulatory system (TCS) as highly polymorphic within the ST1 population consistent with a critical role in CPS V GBS pathogenesis. These data form the basis of this proposal which seeks to test the hypothesis that ST1 GBS have altered host-pathogen interaction compared to non-ST1 strains owing to differences in gene content and global gene regulation. Using RNA-sequencing following exposure to human blood ex vivo and models of GBS colonization and disease, Specific Aim 1 will determine the contribution of gene regulatory differences between ST1 and non-ST1 GBS that contribute to differences in host-pathogen interaction and dominance of ST1 among contemporary CPS V GBS. In Specific Aim 2, we test the hypothesis that the identified TCS contributes to ST1 phenotypic characteristics and predominance among CPS V GBS. We will generate isogenic deletion mutants and compare transcriptomes to the parental strains using RNA-sequencing to define the key regulatory targets of the TCS. Subsequently, we will correlate differences in gene regulation to differences in host-pathogen interaction using models of GBS colonization and disease. Completion of these studies will provide critical new information regarding CPS V GBS disease in adults and serve as a model for investigation of other CPS types. Moreover, the proposed studies are designed to generate key preliminary data needed for deeper investigations into GBS emergence and pathogenesis in humans.