Neisseria meningitidis Ig binding protein vaccine

描述（由申请人提供）：脑膜炎奈瑟菌（Nm）是全世界脑膜炎和菌血症的主要病因之一。在发达国家，尽管鼻咽部传播相对常见，但Nm病的发病率相对较低。一些菌株致病而另一些不致病的原因尚不清楚。目前，还没有疫苗可以预防所有Nm菌株引起的疾病，特别是荚膜组b。我们已经发现Orf6的产物是免疫球蛋白（Ig）结合蛋白（Igbp）， Orf6是在原噬菌体DNA中发现的与Nm引起的侵袭性疾病有关的九个基因之一。Orf6与TspB同源，TspB是Ala'Aldeen及其同事早期发现的一种t细胞和b细胞刺激蛋白（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/Orf6（以下简称TspB）仅在Nm细胞表面表达。因此，当细菌在常用的化学培养基或含有动物源补充剂的微生物培养基中培养时，功能活性TspB不表达。后者即使在人血清存在时也能抑制表达。TspB似乎对人类Ig的Fc部分具有特异性，并可能优先识别修饰Fc结构域的聚糖。TspB与小鼠Ig结合，但亲和力较低。然而，小鼠血清不能刺激奈瑟菌中Ig结合活性的表达。人igg与TspB结合导致人补体的激活，但不导致多产的细菌溶解。TspB可能通过破坏人类补体激活机制来阻止细菌溶解。这些发现可能解释了为什么噬菌体与侵袭性脑膜炎球菌分离株有关，为什么Orf6的功能在敲除突变体中不明显，以及为什么TspB刺激T细胞和B细胞。了解TspB的功能使其成为特别有吸引力的候选疫苗，因为阻断该蛋白功能的抗体灭活了可能是人类血液中生存的重要机制，同时高亲和力的抗TspB抗体可能介导补体依赖性细菌溶解。在目的1中，我们提出用Nm菌株来表征TspB的表达，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和子结构域，用于表征TspB的结构和功能，并作为疫苗抗原。在Aim 3中，我们将在小鼠中评估TspB衍生物的免疫原性，并在脑膜炎球菌菌血症的离体人血浆模型中测量抗TspB衍生物抗体在细菌结合、介导血清杀菌活性和保护方面的功能活性。拟议研究的结果将使人们对TspB在侵袭性脑膜炎球菌病中的作用有更深入的了解，并可能产生一种新的候选疫苗，用于预防脑膜炎球菌病，特别是目前还没有广泛保护性疫苗的NmB菌株。

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.