Giuntini Serena, Pajon Rolando, Ram Sanjay, Granoff Dan M
Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, Oakland, California, USA.
Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Infect Immun. 2015 Apr;83(4):1536-45. doi: 10.1128/IAI.02984-14. Epub 2015 Feb 2.
Among 25 serogroup B Neisseria meningitidis clinical isolates, we identified four (16%) with high factor H binding protein (FHbp) expression that were resistant to complement-mediated bactericidal activity of sera from mice immunized with recombinant FHbp vaccines. Two of the four isolates had evidence of human FH-dependent complement downregulation independent of FHbp. Since alternative complement pathway recruitment is critical for anti-FHbp bactericidal activity, we hypothesized that in these two isolates binding of FH to ligands other than FHbp contributes to anti-FHbp bactericidal resistance. Knocking out NspA, a known meningococcal FH ligand, converted both resistant isolates to anti-FHbp susceptible isolates. The addition of a nonbactericidal anti-NspA monoclonal antibody to the bactericidal reaction also increased anti-FHbp bactericidal activity. To identify a role for FH ligands other than NspA or FHbp in resistance, we created double NspA/FHbp knockout mutants. Mutants from both resistant isolates bound 10-fold more recombinant human FH domains 6 and 7 fused to Fc than double knockout mutants prepared from two sensitive meningococcal isolates. In light of recent studies showing functional FH-PorB2 interactions, we hypothesized that PorB3 from the resistant isolates recruited FH. Allelic exchange of porB3 from a resistant isolate to a sensitive isolate increased resistance of the sensitive isolate to anti-FHbp bactericidal activity (and vice versa). Thus, some PorB3 variants functionally bind human FH, which in the presence of NspA enhances anti-FHbp resistance. Combining anti-NspA antibodies with anti-FHbp antibodies can overcome resistance. Meningococcal vaccines that target both NspA and FHbp are likely to confer greater protection than either antigen alone.
在25株B群脑膜炎奈瑟菌临床分离株中，我们鉴定出4株（16%）具有高因子H结合蛋白（FHbp）表达，它们对用重组FHbp疫苗免疫的小鼠血清的补体介导杀菌活性具有抗性。这4株分离株中有2株有证据表明存在不依赖于FHbp的人FH依赖性补体下调。由于替代补体途径的募集对于抗FHbp杀菌活性至关重要，我们推测在这2株分离株中，FH与FHbp以外的配体结合有助于抗FHbp杀菌抗性。敲除已知的脑膜炎球菌FH配体NspA，可使这2株抗性分离株转变为对FHbp敏感的分离株。在杀菌反应中添加非杀菌性抗NspA单克隆抗体也可增加抗FHbp杀菌活性。为了确定除NspA或FHbp以外的FH配体在抗性中的作用，我们构建了双NspA/FHbp敲除突变体。与从2株敏感脑膜炎球菌分离株制备的双敲除突变体相比，来自这2株抗性分离株的突变体结合与Fc融合的重组人FH结构域6和7的量多10倍。鉴于最近的研究表明FH与PorB2存在功能性相互作用，我们推测来自抗性分离株的PorB3募集了FH。将抗性分离株的porB3等位基因交换到敏感分离株可增加敏感分离株对抗FHbp杀菌活性的抗性（反之亦然）。因此，一些PorB3变体可功能性结合人FH，在存在NspA的情况下可增强抗FHbp抗性。将抗NspA抗体与抗FHbp抗体联合使用可克服抗性。同时靶向NspA和FHbp的脑膜炎球菌疫苗可能比单独使用任何一种抗原提供更大的保护。
