The role of wcjE disruption in pneumococcal serotype 11A humoral escape

描述（由申请人提供）：肺炎链球菌（肺炎球菌）作为人类病原体的成功在很大程度上是由于它能够利用多糖（PS）胶囊来避免宿主免疫。最近对肺炎球菌11E血清型的发现和鉴定强烈表明，荚膜合成基因wcjE8的失活在逃避宿主对密切相关的11A血清型的体液免疫应答中起重要作用，该基因编码一种推定的o -乙酰转移酶。由于许多流行病学上流行的血清型也含有该基因，因此，识别wcje介导的变量o -乙酰化对11A和11E血清型血清学特性的影响，将有助于了解肺炎球菌的病理学，确定新出现的肺炎球菌血清型的趋势，以及设计有效的基于ps的疫苗。以前血清型为11A， 11E的真正流行病学性质尚不清楚。最初血清型为11A的临床分离株将使用血清特异性单克隆抗体重新修饰以表达11E胶囊。为了了解这些血清型的血清学灵活性，将进一步研究导致11A和11E之间血清转换的遗传特性。此外，wcjE灭活在避免人类体液反应中的作用将通过体外opsonophagocytosis杀死实验（OPKA）来评估，该实验使用接种了包含11A PS的23价多糖疫苗的人血清进行。将比较表达11A和11E胶囊的菌株的独立和竞争OPKA存活，并确定纯化的11A和11E PS抑制功能抗体的能力。最后，将在小鼠感染模型中验证血清型11A通过wcjE-失活来逃避11A特异性体液反应的能力及其对病理的影响。将比较11A和11E菌株在初始条件下、被动11A特异性免疫以及对11A和11E PS的预免疫的存活情况。这些试验也将为使用11E作为两种血清型的潜在疫苗提供初步信息。

DESCRIPTION (provided by applicant): The success of Streptococcus pneumonia (pneumococcal) as a human pathogen is largely due to its capability to employ a polysaccharide (PS) capsule to avoid host immunity. Recent discovery and characterization of the pneumococcal serotype 11E strongly suggested that inactivation of the capsule synthesis gene wcjE8 which encodes a putative O-acetyltransferase, plays an important role in escaping a host humoral immune response to the closely related serotype 11A. Since many epidemiologically prevalent serotypes also contain the gene, discerning the effects of WcjE-mediated variable O-acetylating on the serological properties of serotypes 11A and 11E will aid in understanding pneumococcal pathology, in determining trends of emerging pneumococcal serotypes and in designing effective PS-based vaccines. Previously serotype as 11A, the true epidemiological nature of 11E is unclear. Clinical isolates originally serotype as 11A will be readdressed for the expression of 11E capsule using serospecific monoclonal antibodies. To understand the serological flexibility of these serotypes, the genetic properties that lead to seroswitching between 11A and 11E will be further studied. Additionally, the role wcjE inactivation plays in avoiding a human humoral response will be evaluated using an in vitro opsonophagocytosis killing assay (OPKA) with sera from humans vaccinated with the 23- valent polysaccharide vaccine, which includes 11A PS. Independent and competitive OPKA survival of strains expressing 11A and 11E capsule will be compared, and the capacity of purified 11A and 11E PS to inhibit functional antibodies will be determined. Finally, the capacity of serotype 11A to escape an 11A-specific humoral response through wcjE- inactivation in vivo and the effects on pathology will be verified in a murine infection model. The survival of 11A and 11E strains will be compared under naove conditions, with passive 11A-specific immunization, and with preimmunization against 11A and 11E PS. These assays will also provide preliminary information on the use of 11E as a potential vaccine against both serotypes. PUBLIC HEALTH RELEVANCE: Understanding how Streptococcus pneumonia serotypes escape an immune response is important for the design of interventional and preventative strategies against this significant human pathogen. This proposed research will study the effects of O-acetylating modification of S. pneumonia capsule on antibody-dependent clearance of the bacteria, in relation to the prevalent serotype 11A and the closely related serotype 11E.