Pneumococcal capsule and host innate immunity

肺炎球菌荚膜和宿主先天免疫

• 批准号: 8508328
• 负责人: Moon H. Nahm
• 金额: $ 36.63万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2013-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8508328
• 关键词: Acetylation; Antibodies; Antimicrobial Cationic Peptides; Bacterial Infections; Binding; Blood; Clinical; Complement; Development; Disease; Drug resistance; Epidemiologic Studies; Future; Genes; Gram-Positive Bacteria; Health; Human; Human body; Immune; Immunity; In Vitro; Individual; Invaded; Knowledge; Laboratories; Lectin; Life; Mannose Binding Lectin; Mannose-Binding Lectins; Measures; Mediating; Membrane; Methods; Molecular; Muramidase; Mus; Mutation; Nasopharynx; Natural Immunity; Nose; Opsonin; Patients; Peptidoglycan; Phagocytosis; Pneumococcal Infections; Pneumococcal conjugate vaccine; Pneumococcal vaccine; Polysaccharides; Prevalence; Resistance; Role; Sepsis; Serine Protease; Serotyping; Serum; Streptococcus pneumoniae; Structure; Testing; Tissues; Transferase; Vaccine Design; Variant; Work; base; capsule; design; ficolin-beta; improved; in vivo; inhibitor/antagonist; innovation; mannose-binding protein-associated serine proteases; mutant; pathogen; sugar; vaccin protein

DESCRIPTION (provided by applicant): Streptococcus pneumoniae is a Gram-positive bacterium that can express more than 90 different capsule types (serotypes) and is often carried as a commensal in the human nasopharynx (NPX), but can also cause serious diseases by invading deeper tissues. Epidemiologic studies show that the prevalence of carriage and the efficiency of invasion are highly variable (>100-fold) among different pneumococcal serotypes. With the use of pneumococcal conjugate vaccines, the most commonly carried serotypes have changed (called "serotype shift"), with serotype 11A having become one. However, serotype 11A has a very low invasiveness, and the molecular basis for 11A's low invasiveness and high rate of carriage is not known. By inactivating serotype 11A's wcjE and thus causing it to lose an acetyl group from its polysaccharide, we discovered that 11A often becomes 11E during the invasive pneumococcal infection of individual patients. We also found that 11A is more resistant to lysozyme than 11E is and that L-ficolin binds to 11A but not to 11E. L-ficolin is a recently discovered innate opsonin in the blood that resembles mannose binding lectin (MBL) in structure, targets acetyl groups, and initiates the lectin-dependent complement cascade by activating MBL- associated serine protease-2 (MASP-2). Based on these observations, we propose the overarching hypothesis that serotype 11A retains WcjE to resist lysozyme and thus survive in the NPX and that it loses WcjE function to become 11E and thus avoid L-ficolin and survive in the blood. To investigate this hypothesis, we will determine 1) whether L-ficolin is protective against serotype 11A but not against 11E isolates by testing L-ficolin's ability to opsonize serotype 11A but not 11E for phagocytosis, by measuring the serum levels of L-ficolin and MASP-2 in individuals with serotype 11A pneumococcal sepsis, and by testing another common wcjE+ serotype with L-ficolin reactivity for an undiscovered wcjE- subtype without L-ficolin reactivity; 2) whether the WcjE of serotype 11A makes pneumococci resistant to the murami- dase activity of lysozyme by comparing serotypes 11A and 11E isolates for their in vitro resistance to normal and mutant lysozymes and for their nasopharyngeal carriage in mice with or without lysozyme; and 3) whether WcjE enhances lysozyme resistance by helping Adr (attenuator of drug resistance) modify peptidoglycan. Our work is broadly relevant because wcjE is found in many different pneumococcal serotypes and because very little is known about L-ficolin's role in bacterial infections. Our work is also directly relevant to pneumococcal vaccin development because 11A has become one of the most common nasopharyngeal serotypes and because other newly emerging serotypes might be like 11A: they may interact with innate opsonins and thus be less of a health threat even if they become more common. Our work would also expand the concept of "serotype" to include serotype specific interactions with innate opsonins, as well as antibodies, and this new concept may bring further innovations in vaccine designs against many pathogens.

描述（由申请人提供）：肺炎链球菌是一种革兰氏阳性细菌，可表达90多种不同的胶囊型（血清型），通常作为共生体携带在人鼻咽部（NPX）中，但也可通过侵入深层组织引起严重疾病。流行病学研究表明，在不同的肺炎球菌血清型中，携带率和入侵效率差异很大（约100倍）。随着肺炎球菌结合疫苗的使用，最常携带的血清型发生了变化（称为“血清型转移”），血清型11A已成为其中之一。然而，11A血清型具有非常低的侵袭性，11A低侵袭性和高携带率的分子基础尚不清楚。通过灭活11A血清型的wcjE，从而使其多糖失去一个乙酰基，我们发现在个体患者的侵袭性肺炎球菌感染过程中，11A经常变成11E。我们还发现11A对溶菌酶的抗性比11E强，并且L-ficolin与11A结合而不与11E结合。L-ficolin是最近在血液中发现的一种天然调理素，其结构类似于甘露糖结合凝集素（MBL），靶向乙酰基，并通过激活MBL相关丝氨酸蛋白酶-2 （MASP-2）启动凝集素依赖性补体级联。基于这些观察结果，我们提出了一个总体假设，即11A血清型保留WcjE以抵抗溶菌酶，从而在NPX中存活，而11A血清型失去WcjE功能成为11E，从而避免L-ficolin并在血液中存活。为了研究这一假设，我们将确定1)L-ficolin是否对11A血清型具有保护作用，而对11E血清型没有保护作用，通过检测L-ficolin对11A血清型而不是11E血清型的吞噬能力，通过检测11A血清型肺炎球菌脓毒症患者血清中L-ficolin和MASP-2的水平，通过检测另一种常见的wcjE+血清型和L-ficolin反应性来检测一种未发现的wcjE-亚型没有L-ficolin反应性；2)通过比较11A和11E两种血清型对正常溶菌酶和突变溶菌酶的体外耐药性以及有无溶菌酶小鼠的鼻咽携带情况，判断11A血清型WcjE是否使肺炎球菌对溶菌酶村上酶活性产生耐药性；3) WcjE是否通过帮助Adr（耐药衰减剂）修饰肽聚糖而增强溶菌酶耐药性。我们的工作具有广泛的相关性，因为wcjE存在于许多不同的肺炎球菌血清型中，而且我们对L-ficolin在细菌感染中的作用知之甚少。我们的工作也与肺炎球菌疫苗的开发直接相关，因为11A已经成为最常见的鼻咽血清型之一，因为其他新出现的血清型可能像11A一样：它们可能与先天调理素相互作用，因此即使它们变得更常见，对健康的威胁也较小。我们的工作还将扩展“血清型”的概念，包括与先天调理素以及抗体的血清型特异性相互作用，这一新概念可能会为针对许多病原体的疫苗设计带来进一步的创新。

项目成果

Commercially available complement component-depleted sera are unexpectedly codepleted of ficolin-2.

市售的补体成分耗尽血清意外地同时去除了 ficolin-2。

• DOI: 10.1128/cvi.00370-14
• 发表时间: 2014
• 期刊: Clinical and vaccine immunology : CVI
• 作者: Brady,AllisonM;Geno,KAaron;Dalecki,AlexG;Cheng,Xiaogang;Nahm,MoonH
• 通讯作者: Nahm,MoonH