Serogroup 19 capsule maleability leading to vaccine failure

肺炎链球菌（Streptococcus pneumoniae，简称“肺炎球菌”）是一种重要的人类病原体。一个关键 肺炎球菌适应性和毒力的决定因素是其产生保护性多糖（PS）的能力 胶囊可以采取>100种生物化学上不同的“血清型”的形式。肺炎球菌荚膜PS 偶联疫苗（PCV）诱导保护性抗体，介导调理吞噬杀伤（OPK）， 肺炎球菌，并有效地减少了全球疾病负担所造成的血清型包括 疫苗。尽管取得了这一成功，免疫人群偶尔会经历PCV的突破性感染 血清型，这些“疫苗失败”的原因仍不清楚。疫苗失效调查 主要集中在宿主因素和无效的抗体反应，而微生物方面已经消失， 基本上没有解决。此外，密切相关的血清型19 A和19 F是最常见的血清型 在疫苗失败的情况下，但很少有研究评估其在这一现象中的作用。 认识到胶囊延展性的广度及其对临床结果的影响，我们正在研究 血清型19 A/19 F荚膜变异体、抗荚膜免疫应答逃避之间的潜在联系，以及 疫苗失效初步分析确定了多种候选机制， 在19 A/19 F荚膜聚合酶中，Wzy可以介导相当大的荚膜变异性，同时保留大多数荚膜变异性。 Capsule特色我们还发现了一种通过常规方法血清分型为“19 F”的菌株，但实际上， 产生了一种新的胶囊PS结构，在此称为19 x。因此，19 A/19 F样包膜类型的完全多样性 还没有被定义。因为即使是胶囊结构的微小变化也可以消除交叉保护作用， 免疫力，可能存在一些与19 A/19 F肺炎球菌难以区分的变种， 然而，常规血清分型方法可以通过抗19 A/19 F胶囊抗体逃避OPK。 疫苗接种的个体，并因此刺激归因于这些血清型的疫苗失败。 在这个R21建议中，我们将进行定向诱变以测试Wzy多态性对 19 A/19 F胶囊结构，并测试这些推定的胶囊变化对逃避抗胶囊的影响 体外抗体介导的OPK（目的1）。我们还将从结构/遗传学/抗原学上表征 新型19 x胶囊类型，并对广泛的基因组数据库进行生物信息学分析， 鉴定在免疫群体中发现的其他推定的胶囊变体（目的2）。重要的是，工具和 在这里提出的概念，将推动未来对撞击舱的研究，PS的延展性， 肺炎球菌血清型和其他医学上重要的细菌病原体，采用类似的途径， 聚糖合成。独立于糖生物学进展，19 A/19 F Wzy的分子基础的阐明 酶特异性将立即提高分子分型策略的精确度。

Streptococcus pneumoniae (the “pneumococcus”) is an important human commensal pathogen. A key determinant of pneumococcal fitness and virulence is its ability to produce a protective polysaccharide (PS) capsule which can take the form of >100 biochemically distinct “serotypes”. Pneumococcal capsule PS conjugate vaccines (PCVs) induce protective antibodies that mediate opsonophagocytic killing (OPK) of pneumococci and have effectively reduced the global burden of disease caused by serotypes included in vaccines. Despite this success, immunized people occasionally experience breakthrough infections by PCV serotypes, and the cause for these cases of “vaccine failure” remains unclear. Investigation of vaccine failure has largely focused on host factors and ineffective antibody response, while microbiological aspects have gone largely unaddressed. Furthermore, closely-related serotypes 19A and 19F are the serotypes most commonly implicated in vaccine failure cases, but few studies have evaluated their role in this phenomenon. Appreciating the breadth of capsule malleability and its impact on clinical outcomes, we are examining a potential link between serotype 19A/19F capsule variants, evasion of anti-capsule immune responses, and vaccine failure. Preliminary analyses identified multiple candidate mechanisms through which polymorphisms in the 19A/19F capsule polymerase Wzy can mediate considerable capsule variability while preserving most capsule features. We also found a strain that was serotyped as “19F” by conventional methods, but in fact produces a novel capsule PS structure, herein called 19x. Thus, the full diversity of 19A/19F-like capsule types is yet to be defined. As even small changes in capsule structure can abrogate cross-protective immunity, it is possible that some variants, which are indistinguishable from 19A/19F pneumococci in conventional serotyping methods, can nonetheless evade OPK by anti-19A/19F capsule antibodies in vaccinated individuals and, thus, spur the vaccine failure attributed to these serotypes. In this R21 proposal, we will perform directed mutagenesis to test the impact of Wzy polymorphisms on 19A/19F capsules structure and test the effect of these putative capsule changes on evading anti-capsule antibody-mediated OPK in vitro (Aim 1). We will also structurally/genetically/antigenically characterize the novel 19x capsule type and perform bioinformatics analysis of expansive genomic databases with the goal of identifying other putative capsule variants found among immunized populations (Aim 2). Importantly, tools and concepts developed here will fuel future investigation of the impact capsule PS malleability has in additional pneumococcal serotypes and other medically important bacterial pathogens that employ similar pathways for glycan synthesis. Independent of glycobiological advances, elucidation of the molecular basis of 19A/19F Wzy enzymatic specificity would immediately improve the precision of the molecular typing strategies.