The Adhesin Complex Protein (ACP) of Neisseria meningitidis: vaccine potential and biological properties

脑膜炎奈瑟菌在世界范围内引起脑膜炎和败血症。最重要的致病原因是A、B、C、W135和Y群的脑膜炎双球菌。幸运的是，现在有了针对A、C、W135和Y群的疫苗，这些疫苗的基础是将糖衣从这些生物中分离出来，并将它们与白喉或破伤风等常见疫苗联系起来形成结合物。这些疫苗在那些引进它们的国家几乎消除了疾病，例如在英国和美国，C组疾病的减少了95%。通过疫苗在人体内诱导抗体杀死生物体的能力来提供保护。然而，这种糖衣结合策略对B型脑膜炎球菌(MenB)不起作用，因为B糖衣不能产生能杀死有机体的抗体，而且它与人类蛋白质有相似之处，所以任何使用MenB糖衣生产的疫苗都将是有问题的。还有其他选择吗？多年来，奈瑟氏菌的研究界一直在探测MenB糖衣下的膜，试图识别那些可以诱导抗体杀死MenB细菌的结构或蛋白质。已经使用了几种技术，例如分析有机体的遗传构成(“反向疫苗学方法”)、分析细胞膜的结构(“蛋白质组学”、“结构疫苗学”方法)以及人类对有机体感染或定居的反应(“免疫蛋白质组学”方法)。反向疫苗学方法现在已经开发出第一代已定义的MenB疫苗，称为Bexsero/4CMenB(最近得到了欧洲药品管理局的肯定意见)。这种疫苗含有3种蛋白质，与新西兰一种用于控制疾病的疫苗的膜混合，是寻找针对MenB的通用疫苗的重要一步。但即使这样也不是没有问题：重要的是，据预测，Bexsero只能保护种群中73%的MenB微生物。那么剩下的27%呢？因此，迫切需要确定生物体的其他成分，以提供更广泛的保护，以抵御大量的MenB菌株。我们提出的研究是基于我们对可能造成差异的成分的识别。利用蛋白质组学的方法，我们在MenB膜上鉴定出一种叫做粘附素复合蛋白(ACP)的蛋白质。我们证明ACP能够在动物体内诱导抗体，从而杀死脑膜炎双球菌。重要的是，脑膜炎双球菌在200种不同的菌株中只产生3种不同的ACP蛋白(不同于Bexsero中的蛋白质，后者更具变异性)，而针对一种ACP蛋白的抗体可以杀死拥有其他类型ACP的细菌。这是交叉保护的证据。我们还表明，ACP对于生物体附着在人类细胞上很重要。我们的研究计划是通过收集关于ACP蛋白特性的进一步信息来研究ACP用于MenB疫苗纳入的可能性。我们有一个由两部分组成的计划：在第一部分(疫苗潜力)中，我们将检查在大量的MenB菌株(~600株)中是否存在超过3种类型的ACP蛋白，看看这些菌株是否产生这种蛋白，并推断ACP的结构。我们还将准备新的基于ACP的疫苗在实验室动物身上进行测试，看看我们是否可以杀死更多不同的MenB菌株。在第二部分(生物学作用)中，我们将推导ACP如何使MenB黏附到人类细胞上并识别相关的人类分子，研究ACP是否与其他MenB蛋白一起工作以实现黏附，以及ACP黏附会触发人类细胞的哪些反应。总而言之，我们的提议是令人兴奋的、雄心勃勃的、及时的和创新的；我们的研究将建立在我们已经收集的有希望的结果的基础上，并提供确凿的证据，证明ACP应该被包括在新的MenB疫苗中。

Neisseria meningitidis (Men) causes meningitis and septicaemia worldwide. The most important causes of disease are meningococci of groups A, B, C, W135 and Y. Fortunately, vaccines are now available for protection against A, C, W135 and Y and these are based on separating the sugar coat from these organisms and linking them to a common vaccine such as diphtheria or tetanus to form a conjugate. These vaccines have virtually eliminated disease in those countries that have introduced them, e.g. in the UK and US the reduction in group C disease has been >95%. Protection is provided by the ability of the vaccines to induce antibodies in humans that can kill the organisms. However, this sugar coat-conjugate strategy will not work for B meningococci (MenB), because the B sugar coat is poor at generating antibodies that can kill the organism and moreover it shares similarities with human proteins, so any vaccine produced using the MenB sugar coat would be problematical. What are the alternatives? For many years, the Neisseria research community has probed the membrane underneath the MenB sugar coat to try and identify those structures or proteins that can induce antibodies capable of killing MenB bacteria. Several techniques have been used, e.g. analyzing the genetic make-up of the organism (the 'reverse vaccinology approach'), analyzing the structure of the membrane (the 'proteomic', 'structural vaccinology' approach) and the human response to infection or colonization by the organism (the 'immuno-proteomic' approach). The reverse vaccinology method has now developed the first generation of defined MenB vaccines, called Bexsero/4CMenB (recently received positive opinion from the European Medicines Agency). This vaccine contains 3 proteins mixed with the membrane from a vaccine used to control disease in New Zealand and is a major step in finding a universal vaccine for MenB. But even this is not without problems: importantly, it is predicted that Bexsero will only protect against 73% of the MenB organisms present in the population. So what about the remaining 27%? Thus, there is a pressing need to identify other components of the organism that can provide broader protection against a larger number of MenB strains. Our proposed research is based on our identification of a component that may make up the difference. Using the 'proteomic' approach we identified a protein in the MenB membrane called the Adhesin Complex Protein (ACP). We show that ACP is able to induce antibodies in animals that can kill meningococci. Importantly, meningococci produce only 3 different ACP proteins in a collection of 200 different strains (unlike the proteins in Bexsero which are more variable) and antibodies to one ACP protein can kill bacteria that possess other types of ACP. This is proof of cross-protection. We also show that ACP is important for the organism to stick to human cells. Our research plans are to investigate the potential of ACP for MenB vaccine inclusion by gathering further information on the properties of this protein. We have a two-part plan to do this:In Part 1 ('the vaccine potential'), we will examine whether there are more than 3 types of ACP proteins in a larger number of MenB strains (~600), look to see if these strains produce the protein and also deduce the structure of ACP. We will also prepare new ACP-based vaccines for testing in laboratory animals to see if we can kill a larger variety of different MenB strains.In Part 2 ('the biological role'), we will deduce how ACP allows MenB to stick to human cells and identify the human molecules involved, examine whether ACP works with other MenB proteins to enable sticking and what responses by human cells are triggered by ACP sticking.In summary, our proposal is exciting, ambitious, timely and innovative; our research will build on the promising results we have already collected and provide conclusive proof that ACP should be included in new MenB vaccines.