Novel vaccine strategies for prevention of N. meningitidis group B disease

描述（由申请人提供）：目前还没有广泛有效的疫苗可用于预防由脑膜炎奈瑟菌B群菌株引起的疾病，而脑膜炎奈瑟菌B群菌株占脑膜炎球菌病病例的50%或更多。由于B族胶囊是一种自身抗原，因此需要替代疫苗策略。我们正在研究因子H结合蛋白（fHbp）的疫苗潜力，这是一种表面暴露的脂蛋白，以前称为GNA1870。血清抗fhbp抗体与细菌结合，激活补体介导的细菌溶解，并抑制人类补体下调蛋白H因子（fH）的结合。在缺乏结合fH的情况下，生物体对补体介导的细菌溶解更敏感。fHbp作为疫苗的一个限制是抗原性变异性（3个组中有一些亚变异体）。变异组1中fHbp诱导的抗fHbp抗体对表达变异2或3蛋白的菌株没有杀菌作用。为了解决这个问题，我们正在构建表达不同变异群表位的重组嵌合fHbp分子。在小鼠中，嵌合fHbp原型疫苗可诱导血清中产生针对表达fHbp变体1、2或3的菌株的杀菌抗体。由于重组fHbp可能不表达所有对激发广泛杀菌活性重要的表位，我们也正在从经过工程改造过表达fHbp的脑膜炎奈索菌菌株中制备天然外膜囊泡（OMV）疫苗。由于洗涤剂处理用于从传统的OMV疫苗中去除内毒素提取fHbp，我们通过灭活脂质a生物合成基因LpxL1来减弱内毒素活性。来自突变体的原生OMV在刺激人pbmc产生促炎细胞因子方面的活性比来自野生型菌株的OMV低1000至10,000倍。在小鼠中，从LpxL1敲除突变体中获得的具有过表达fHbp的天然OMV疫苗比对照重组fHbp或洗涤剂提取的OMV疫苗具有更广泛的杀菌活性。在这项应用中，我们将在这些遗传方法的基础上开发更安全、更广泛有效的疫苗。在Aim 1中，我们将确定两种抗fHbp单抗的表位位置，这两种表位在fHbp变异群中是保守的，并且单抗与第二种抗fHbp单抗协同杀菌活性。在Aim 2中，我们将构建第二代重组嵌合fHbp疫苗，旨在引发比迄今制备的原型嵌合疫苗更广泛的杀菌抗体反应。在Aim 3中，我们将从不同的变异组构建额外的脑膜炎奈索菌突变体，这些突变体具有过表达的fHbp，其中编码不需要抗原的基因被灭活。这些突变体将用于生产高免疫原性和安全的OMV疫苗，这些疫苗将在小鼠和随后的非人幼龄灵长类动物中进行免疫原性评估。拟议的研究将确定这些疫苗方法是否有可能预防所有脑膜炎奈瑟菌病，包括b群。由于其他病原体也结合脑膜炎奈瑟菌以绕过宿主的先天防御，因此所获得的经验教训可能适用于其他疫苗的开发。公共卫生相关性：脑膜炎奈瑟菌是一种侵入血液并引起败血症或脑膜炎的细菌，这可能是致命的或导致脑损伤、截肢或其他并发症。疫苗可用于预防由某些菌株引起的疾病，但没有针对B组菌株的疫苗，B组菌株导致美国一半的病例，欧洲的比例甚至更高。本提案描述了对预防B群脑膜炎球菌病的两种非常有希望的疫苗策略的研究，这可能导致安全且具有广泛保护性的B群疫苗。

DESCRIPTION (provided by applicant): There are no broadly effective vaccines available for prevention of disease caused by group B strains of N. meningitidis, which account for 50% or more of cases of meningococcal disease. Because the group B capsule is an autoantigen, alternative vaccine strategies are needed. We are investigating the vaccine- potential of factor H binding protein (fHbp) a surface-exposed lipoprotein previously called GNA1870. Serum anti-fHbp antibodies bind to the bacteria, activate complement-mediated bacteriolysis, and also inhibit binding of the human complement down-regulatory protein, factor H (fH). In the absence of bound fH, the organism becomes more susceptible to complement-mediated bacteriolysis. One limitation of fHbp as a vaccine is antigenic variability (3 groups with some subvariants within groups). Anti-fHbp antibodies elicited by fHbp in variant group 1 are not bactericidal against strains expressing variant 2 or 3 proteins. To circumvent this problem, we are constructing recombinant chimeric fHbp molecules that express epitopes from different variant groups. In mice, a prototype chimeric fHbp vaccine elicited serum bactericidal antibodies against strains expressing fHbp variant 1, 2 or 3. Because recombinant fHbp may not express all epitopes important for eliciting broad bactericidal activity, we also are preparing native outer membrane vesicle (OMV) vaccines from N. meningitidis strains engineered to over-express fHbp. Since detergent treatments used to remove endotoxin from conventional OMV vaccines extract fHbp, we attenuate endotoxin activity by inactivating a lipid A biosynthesis gene, LpxL1. A native OMV from the mutant was 1000- to 10,000-fold less active in stimulating human PBMCs to produce proinflammatory cytokines than OMV from the wildtype strain. In mice, a native OMV vaccine from an LpxL1 knockout mutant with over-expressed fHbp elicited broader bactericidal activity than control recombinant fHbp or detergent-extracted OMV vaccines. In this application, we will build on these genetic approaches to develop even safer and more broadly effective vaccines. In Aim 1, we will define locations of epitopes of two anti-fHbp mAbs that are of special interest because the epitopes are conserved across fHbp variant groups and the mAbs mediate cooperative bactericidal activity with second anti-fHbp mAbs. In Aim 2, we will construct second-generation recombinant chimeric fHbp vaccines designed to elicit even broader bactericidal antibody responses than the prototype chimeric vaccines prepared to date. In Aim 3, we will construct additional N. meningitidis mutants with over-expressed fHbp from different variant groups, and in which genes encoding unwanted antigens are inactivated. The mutants will be used to produce highly immunogenic and safe OMV vaccines, which will be evaluated for immunogenicity in mice and, subsequently, in nonhuman infant primates. The proposed studies will determine whether these vaccine approaches have the potential to prevent all N. meningitidis disease, including group B. Since other pathogens also bind fH to circumvent innate host defenses, the lessons learned may be applicable to development of other vaccines. PUBLIC HEALTH RELEVANCE: Neisseria meningitidis is a bacterium that invades the bloodstream and causes sepsis or meningitis, which can be fatal or lead to brain damage, amputations or other complications. Vaccines are available for prevention of disease caused by some strains of the bacteria but no vaccine is available against group B strains, which cause half of the cases in the U.S. and an even higher proportion in Europe. This proposal describes studies of two highly promising vaccine strategies for prevention of group B meningococcal disease, which could lead to a safe and broadly protective group B vaccine.