Neisseria meningitidis is the causative agent of meningococcal meningitis and sepsis and remains a significant public health problem in many countries. Efforts to develop a comprehensive vaccine against serogroup B meningococci have focused on the use of surface-exposed outer membrane proteins. Here we report the use of virus-like particles derived from the core protein of Hepatitis B Virus, HBc, to incorporate antigen domains derived from Factor H binding protein (FHbp) and the adhesin NadA. The extracellular domain of NadA was inserted into the major immunodominant region of HBc, and the C-terminal domain of FHbp at the C-terminus (CFHbp), creating a single polypeptide chain 3.7-fold larger than native HBc. Remarkably, cryoelectron microscopy revealed that the construct formed assemblies that were able to incorporate both antigens with minimal structural changes to native HBc. Electron density was weak for NadA and absent for CFHbp, partly attributable to domain flexibility. Following immunization of mice, three HBc fusions (CFHbp or NadA alone, NadA + CFHbp) were able to induce production of IgG1, IgG2a and IgG2b antibodies reactive against their respective antigens at dilutions in excess of 1:18,000. However, only HBc fusions containing NadA elicited the production of antibodies with serum bactericidal activity. It is hypothesized that this improved immune response is attributable to the adoption of a more native-like folding of crucial conformational epitopes of NadA within the chimeric VLP. This work demonstrates that HBc can incorporate insertions of large antigen domains but that maintenance of their three-dimensional structure is likely to be critical in obtaining a protective response.

脑膜炎奈瑟菌是脑膜炎球菌性脑膜炎和败血症的病因，在许多国家/地区仍然是重要的公共卫生问题。开发针对血清B型脑膜炎球菌的全面疫苗的工作集中在使用表面暴露的外膜蛋白上。在这里，我们报道了使用源自乙型肝炎病毒核心蛋白HBc的病毒样颗粒来整合源自因子H结合蛋白（FHbp）和粘附素NadA的抗原域。将NadA的胞外域插入HBc的主要免疫优势区域，并将FHbp的C末端域插入C端（CFHbp），从而形成一条比天然HBc大3.7倍的多肽链。值得注意的是 冷冻电子显微镜显示，该构建体形成了能够结合两种抗原而对天然HBc的结构变化最小的装配体。NadA的电子密度较弱，而CFHbp则不存在，部分归因于域柔性。免疫小鼠后，三种HBc融合体（仅CFHbp或NadA，NadA + CFHbp）能够以超过1：18,000的稀释度诱导产生针对其各自抗原的IgG1，IgG2a和IgG2b抗体。但是，只有含有NadA的HBc融合蛋白才产生具有血清杀菌活性的抗体。据推测，这种改善的免疫应答归因于嵌合VLP内NadA的关键构象表位的更天然的折叠。