Neisseria meningitidis Ig binding protein vaccine

描述（由申请方提供）：脑膜炎奈瑟菌（Nm）是全球脑膜炎和菌血症的主要原因之一。在发达国家，尽管鼻咽携带相对常见，但Nm疾病的发病率相对罕见。一些菌株致病而另一些菌株不致病的原因尚不清楚。目前，没有疫苗可以预防由所有Nm菌株引起的疾病，特别是荚膜组B。我们已经发现，在原噬菌体DNA中发现的与Nm引起的侵袭性疾病相关的九个基因之一Orf 6的产物是免疫球蛋白（IG）结合蛋白（Igbp）。Orf 6与TspB同源，TspB是一种T细胞和B细胞刺激蛋白，由Ala'Alfonge及其同事早期鉴定（1-4）。重要的是，我们还发现，当细菌在人血清存在下培养时，TspB/Orf 6（下文中TspB）仅在Nm细胞的表面上表达。因此，当细菌在含有来源于动物源的补充物的常用化学成分确定的培养基或微生物培养基中培养时，功能活性TspB不表达。后者抑制表达，甚至当人血清存在时。TspB似乎对人IG的Fc部分具有特异性，并且可以优先识别修饰Fc结构域的聚糖。TspB与小鼠IG结合，但亲和力较低。然而，小鼠血清不刺激奈瑟氏菌中IG结合活性的表达。TspB与人IG的结合导致人补体的活化，但不导致有效的溶菌作用。TspB可能通过颠覆人补体激活机制来防止细菌溶解。这些发现提供了可能的解释，为什么原噬菌体与侵袭性脑膜炎球菌分离株相关，为什么Orf 6的功能在敲除突变体中不明显，以及为什么Tsp B刺激T和B细胞。了解TspB的功能使其成为特别有吸引力的疫苗候选物，因为阻断蛋白质功能的抗体可能是在人血液中存活的重要机制，而同时高亲和力抗TspB抗体可能介导补体依赖性溶菌作用。在目的1中，我们提出表征Nm菌株的TspB表达，并鉴定人血清中刺激表面表达的分子。在目标2中，我们将生产重组TspB和亚结构域，用于表征TspB的结构和功能，并作为疫苗抗原。在目的3中，我们将评估TspB衍生物在小鼠中的免疫原性，并测量抗TspB衍生物抗体在脑膜炎球菌菌血症的离体人血浆模型中关于细菌结合、介导血清杀菌活性和保护的功能活性。拟议研究的结果将使人们更好地了解TspB在侵袭性脑膜炎球菌病中的作用，并可能成为预防脑膜炎球菌病的新疫苗候选者，特别是对于没有广泛保护性疫苗的NmB菌株。 公共卫生相关性：拟议的项目将是表征一种与侵袭性脑膜炎球菌病有关的基因的表达，并确定该基因编码的蛋白质是否可用作疫苗，提供广泛的保护，防止脑膜炎奈瑟氏菌引起的疾病。

DESCRIPTION (provided by applicant): Neisseria meningitidis (Nm) is one of the major causes of meningitis and bacteremia world-wide. The incidence of Nm disease is relatively rare in developed countries despite relatively common nasal pharyngeal carriage. The reasons why some strains cause disease but others do not are unknown. Currently, there is no vaccine that can prevent disease caused by all Nm strains, particularly capsular group B. We have discovered that the product of Orf6, one of nine genes found in prophage DNA that has been linked to invasive disease caused by Nm is an immunoglobulin (Ig) binding protein (Igbp). Orf6 is homologous to TspB, a T-cell and B-cell stimulating protein identified earlier by Ala'Aldeen and coworkers (1-4). Importantly, we also found that, TspB/Orf6 (hereafter TspB) is only expressed on the surface of Nm cells when the bacteria are cultured in the presence of human serum. Thus, functionally active TspB is not expressed when bacteria are cultured in commonly used chemically defined media or microbiological media that contains supplements derived from animal sources. The latter suppresses expression even when human serum is present. TspB appears to be specific for the Fc portion of human Ig and may preferentially recognize glycans modifying the Fc domain. TspB binds to mouse Ig but with lower affinity. However, mouse serum does not stimulate expression of Ig binding activity in Neisseria. Human Ig binding by TspB results in activation of human complement but does not lead to productive bacteriolysis. TspB may function by subverting the mechanism of human complement activation to prevent bacteriolysis. These discoveries provide possible explanations for why the prophage is associated with invasive meningococcal isolates, why a function for Orf6 was not apparent in knock out mutants, and why TspB stimulates T and B cells. Knowing the function of TspB makes it a particularly attractive vaccine candidate since antibodies that block the function of the protein inactivate what may be an important mechanism for survival in human blood while at the same time high affinity anti-TspB antibodies may mediate complement dependent bacteriolysis. In Aim 1 we propose to characterize the expression of TspB by Nm strains and identifying molecules in human serum that stimulate surface expression. In Aim 2 we will produce recombinant TspB and subdomains for use in characterizing the structure and function of TspB and as vaccine antigens. In Aim 3 we will evaluate the immunogenicity of TspB derivatives in mice and measure the functional activity of anti-TspB derivative antibodies with respect to bacterial binding, mediating serum bactericidal activity and protection in an ex vivo human plasma model of meningococcal bacteremia. The results of the proposed studies will lead to a greater understanding of the role of TspB in invasive meningococcal disease and possibly a new vaccine candidate for preventing meningococcal disease, particularly by NmB strains for which there is no broadly protective vaccine. PUBLIC HEALTH RELEVANCE: The proposed project will be to characterize expression of a gene that has been linked to invasive meningococcal disease and to determine whether the protein encoded by the gene is useful as a vaccine to provide broad protection against disease caused by Neisseria meningitidis bacteria.