An engineered meningococcal OMV vaccine for Africa against all capsular groups

描述（由申请人提供）：脑膜炎奈瑟菌在撒哈拉以南非洲引起爆发性流行病。大多数是由荚膜A群菌株引起的。然而，W-135群和X群毒株也在该地区引起流行，一旦采用A群多糖-蛋白结合疫苗进行大规模免疫，这些毒株可能会出现。我们的目标是为非洲开发一种针对所有荚膜群菌株的脑膜炎球菌疫苗。我们的方法将是使用新的蛋白质抗原确定的“组B疫苗”，这也引发了保护性抗体，对菌株与其他胶囊。这些“非常规”抗原将被呈递在具有有效天然佐剂的简单外膜囊泡（OMV）中。我们的研究将建立在清洁剂提取的OMV疫苗的经验基础上，这些疫苗已被证明对人类安全有效。它们的主要局限性是它们引发主要针对PorA的血清杀菌抗体，PorA是抗原可变的。为了延长对具有异源PorA的菌株的保护，我们制备了B组菌株的突变体，其被工程化以过表达H因子结合蛋白（fHbp），这是两种有前途的B组重组蛋白疫苗中的新抗原。通过在LPS生物合成中引入额外的突变，我们减弱了内毒素活性。在小鼠中，由突变体制备的未经去污剂处理的OMV疫苗引发了针对遗传多样性的B组菌株以及来自非洲的流行性A组、W-135和X菌株的血清杀菌抗体应答。我们的假设是，从非洲突变株制备的天然OMV疫苗将引发针对PorA、fHbp和非洲菌株表达的其他抗原的更广泛的杀菌抗体。此外，LPS突变将消除对OMV的去污剂提取的需要，去污剂提取用于减少常规OMV疫苗中的LPS，而且还提取期望的抗原如fHbp。在目标1中，我们将调查200个脑膜炎球菌分离株的遗传谱系和编码fHbp，PorA和其他疫苗抗原的基因的序列多样性，这些分离株来自非洲的地理上不同的菌株。在目标2中，我们将通过定量捕获ELISA测量抗原表达，并通过流式细胞术测量活细菌上的抗原表面可及性。在目标3中，我们将创建最近非洲流行菌株的突变体，其将被工程化以表达一种以上的PorA分子，过表达fHbp，并具有减毒的内毒素。还将选择天然高表达粘附素/侵袭素NadA的疫苗株。我们将从突变体制备天然OMV疫苗，并通过测量与疫苗一起体外孵育的人PBMC的炎性细胞因子应答来评估OMV毒性。我们将对小鼠和幼年灵长类动物进行免疫，并测量针对非洲菌株的血清杀菌抗体反应。这些结果将提供OMV疫苗可能在人类中耐受良好并引起广泛保护性免疫的原则证据。这些发现将支持在人类中测试OMV疫苗的应用，以控制撒哈拉以南地区由所有荚膜群菌株引起的脑膜炎球菌流行病。 公共卫生相关性：脑膜炎球菌在撒哈拉以南非洲引起脑膜炎的爆发性流行，在几个月内可能涉及10万多例病例。大多数流行病是由被包囊的A群菌株引起的，但来自其他荚膜群的菌株也开始在该地区引起流行病。目前正在为非洲开发一种针对A组疾病的多糖结合疫苗，但人们严重关切的是，一旦采用A组结合疫苗进行大规模免疫接种，可能会出现带有其他胶囊的菌株并引起流行病。我们建议开发一种外膜囊泡疫苗突变脑膜炎球菌菌株，工程过表达的有前途的蛋白质疫苗抗原，作为一种通用的脑膜炎球菌疫苗，非洲对疾病引起的菌株从所有的荚膜组。

DESCRIPTION (provided by applicant): Neisseria meningitidis causes explosive epidemics in sub-Saharan Africa. Most are caused by capsular group A strains. However, group W-135 and X strains also cause epidemics in this region, and these strains may emerge once mass immunization with a group A polysaccharide-protein conjugate vaccine is introduced. Our goal is to develop a meningococcal vaccine for Africa that targets strains from all capsular groups. Our approach will be to use novel protein antigens identified for "group B vaccines", which also elicit protective antibodies against strains with other capsules. These "unconventional" antigens will be presented in simple outer membrane vesicles (OMV) that have potent natural adjuvants. Our studies will build on previous experience with detergent-extracted OMV vaccines, which are proven to be safe and effective in humans. Their major limitation is that they elicit serum bactericidal antibodies primarily directed at PorA, which is antigenically variable. To extend protection to strains with heterologous PorA, we prepared mutants of group B strains that were engineered to over-express factor H binding protein (fHbp), which is a novel antigen in two promising group B recombinant protein vaccines. By introducing an additional mutation in LPS biosynthesis, we attenuated endotoxin activity. In mice, non-detergent-treated OMV vaccines prepared from the mutants elicited serum bactericidal antibody responses against genetically diverse group B strains, as well as epidemic group A, W-135 and X strains from Africa. Our hypothesis is that a native OMV vaccine prepared from mutant strains from Africa will elicit even broader bactericidal antibodies directed at PorA, fHbp and other antigens expressed by strains from Africa. Further, the LPS mutation will eliminate the need for detergent extraction of the OMV, which is used to decrease LPS in conventional OMV vaccines, but also extracts desirable antigens such as fHbp. In Aim 1, we will investigate genetic lineages and sequence diversity of genes encoding fHbp, PorA and other vaccine antigens among 200 meningococcal isolates from a geographically diverse collection of strains from Africa. In Aim 2, we will measure antigen expression by a quantitative capture ELISA, and antigen surface-accessibility on live bacteria by flow cytometry. In Aim 3, we will create mutants of recent African epidemic strains, which will be engineered to express more than one PorA molecule, over-express fHbp, and have attenuated endotoxin. The vaccine strains also will be selected for naturally high expression of an adhesin/invasin, NadA. We will prepare native OMV vaccines from the mutants, and assess OMV toxicity by measuring inflammatory cytokine responses of human PBMCs incubated in vitro with the vaccine. We will immunize mice and infant primates and measure serum bactericidal antibody responses against strains from Africa. The results will provide proof of principle that the OMV vaccine is likely to be well-tolerated in humans and elicit broad protective immunity. These findings would support an application to test the OMV vaccine in humans for control of meningococcal epidemics in sub-Sahara caused by strains from all capsular groups. PUBLIC HEALTH RELEVANCE: Meningococci cause explosive epidemics of meningitis in sub-Sahara Africa that can involve more than 100,000 cases in a few months. Most epidemics have been caused by encapsulated group A strains but strains from other capsular groups also have begun to cause epidemics in the region. A polysaccharide conjugate vaccine against group A disease is being developed for Africa but there is grave concern that strains with other capsules may emerge and cause epidemics once mass immunization with the group A conjugate vaccine is introduced. We propose to develop an outer membrane vesicle vaccine from mutant meningococcal strains, engineered for over-expression of promising protein vaccine antigens, as a universal meningococcal vaccine for Africa against disease caused by strains from all capsular groups.