Complement Activation on Neisseria meningitidis

描述（由申请人提供）：血清B组脑膜炎奈瑟菌感染是世界范围内发病率和死亡率的主要原因。补体(C)在对抗neisseries感染中很重要。缺乏维生素C的人易患系列感染。诱导杀菌的抗体（Abs）可以预防侵袭性疾病。我们已经确定了低脂寡糖（LOS）作为C4b的主要靶点，当其他抗包膜抗体被用于调理时。LOS的庚糖2 （Hep2）上的磷酸乙醇胺（PEA）是C4的重要受体（根据我们的数据，C4b通过酰胺键与LOS结合）。在具体的Aim 1中，我们将通过比较仅在Hep2上的PEA位置（3-或6-位置）不同的菌株上的C4b与LOS的结合，研究PEA残基在Hep2 3-和6-位置上接受C4b的相对作用。我们已经确定，Hep1链的取代影响了C4b和LOS之间形成的键（酯或酰胺）的性质。我们将扩展这些发现，并研究Hep2己糖取代（IgtG基因产物）对C4b与LOS结合的影响。在特异性目标2中，我们将研究人类血清中C4亚型在全细菌环境下与LOS结合的能力。在人血清中存在两种具有不同生物活性的C4亚型，称为C4A和C4B。C4B的溶血活性是C4B的3倍，而C4A则通过酰胺键与靶标结合，并更有效地结合补体受体1 （CR1）。在中国仓鼠卵巢（CHO）细胞系中转染了仅含有C4B结合位点的突变CR1分子，研究了血清选择性缺乏C4A和C4B的细菌与CR1结合的能力。最后，在特定的Aim 3中，我们将检查针对一系列细菌抗原的单克隆抗体是否改变了C4b结合的细菌靶标，以努力理解为什么某些抗原靶标（如4类蛋白）尽管被c -固定抗体识别，但不是很好的杀菌靶标。我们还将确定两种将C4b沉积到不同靶标上的单克隆抗体引发c介导的杀伤的相对效率。试图确定候选疫苗引起最有效的杀菌（或抑菌）反应的要求。

DESCRIPTION (provided by applicant): Serogroup B Neisseria meningitidis infections are a major cause of morbidity and mortality worldwide. Complement (C) is important in combating neisserial infections. Individuals with C deficiency are predisposed to neisserial infections. Antibodies (Abs) that induce bactericidal killing protect against invasive disease. We have identified lipooligosaccharide (LOS) as a major C4b target when other than specific anti-capsular Abs are used for opsonization. Phosphoethanolamine (PEA) on heptose 2 (Hep2) of LOS is an important acceptor for C4 (based on our data that C4b binds LOS via amide bonds). In specific Aim 1 we will study the relative roles of PEA residues in the 3- and 6-position of Hep2 in accepting C4b, by comparing C4b binding to LOS on strains that differ only in the location of PEA (either the 3- or 6-position) on Hep2. We have determined that Hep1 chain substitutions influence the nature of the linkage (ester or amide) formed between C4b and LOS. We will extend these findings and study the effect of Hep2 hexose substitutions (the IgtG gene product) on C4b binding to LOS. In Specific Aim 2, we will examine the ability of the isoforms of C4 in human serum to bind to LOS in the context of whole bacteria. Two isoforms of C4 with differing biological activities, called C4A and C4B, exist in human serum. While C4B is ~3 times more hemolytically active, C4A engages its target via exclusively amide linkages and binds complement receptor 1 (CR1) more efficiently. The ability of bacteria opsonized with serum selectively deficient in C4A and C4B to bind to CR1 will be studied in a chinese hamster ovary (CHO) cell line transfected with a mutant CR1 molecule that contains only the C4b binding site. Finally, in specific Aim 3, we will examine whether bacterial targets for C4b binding are altered by mAbs against a repertoire of bacterial antigens, in an effort to understand why certain antigenic targets (such as class 4 protein) are not good bactericidal targets despite being recognized by C-fixing Abs. We will also determine the relative efficiency with which two mAbs that deposit C4b on to different targets elicit C-mediated killing, in an attempt to define the requirements for a vaccine candidate to elicit the most efficient bactericidal (or opsonic) response.