Molecular Genetics Unit, Novartis Vaccines, Via Fiorentina, 1, 53100 Siena, Italy.
Infect Immun. 2011 Feb;79(2):970-81. doi: 10.1128/IAI.00891-10. Epub 2010 Dec 13.
Neisseria meningitidis is a commensal of the human nasopharynx but is also a major cause of septicemia and meningitis. The meningococcal factor H binding protein (fHbp) binds human factor H (fH), enabling downregulation of complement activation on the bacterial surface. fHbp is a component of two serogroup B meningococcal vaccines currently in clinical development. Here we characterize 12 fHbp subvariants for their level of surface exposure and ability to bind fH, to mediate serum resistance, and to induce bactericidal antibodies. Flow cytometry and Western analysis revealed that all strains examined expressed fHbp on their surface to different extents and bound fH in an fHbp-dependent manner. However, differences in fH binding did not always correlate with the level of fHbp expression, indicating that this is not the only factor affecting the amount of fH bound. To overcome the issue of strain variability in fHbp expression, the MC58ΔfHbp strain was genetically engineered to express different subvariants from a constitutive heterologous promoter. These recombinant strains were characterized for fH binding, and the data confirmed that each subvariant binds different levels of fH. Surface plasmon resonance revealed differences in the stability of the fHbp-fH complexes that ranged over 2 orders of magnitude, indicating that differences in residues between and within variant groups can influence fH binding. Interestingly, the level of survival in human sera of recombinant MC58 strains expressing diverse subvariants did not correlate with the level of fH binding, suggesting that the interaction of fHbp with fH is not the only function of fHbp that influences serum resistance. Furthermore, cross-reactive bactericidal activity was seen within each variant group, although the degree of activity varied, suggesting that amino acid differences within each variant group influence the bactericidal antibody response.
脑膜炎奈瑟菌是人类鼻咽部的共生菌，但也是败血症和脑膜炎的主要原因。脑膜炎奈瑟菌因子 H 结合蛋白（fHbp）与人因子 H（fH）结合，使细菌表面补体激活下调。fHbp 是两种目前正在临床开发的 B 群脑膜炎球菌疫苗的成分。在这里，我们对 12 种 fHbp 亚变体进行了特征分析，以确定其表面暴露水平、与 fH 结合的能力、介导血清抗性的能力以及诱导杀菌抗体的能力。流式细胞术和 Western 分析表明，所有检测的菌株在表面不同程度地表达 fHbp，并以 fHbp 依赖的方式结合 fH。然而，fH 结合的差异并不总是与 fHbp 表达水平相关，表明这不是影响结合 fH 数量的唯一因素。为了克服 fHbp 表达的菌株变异性问题，使用遗传工程将 MC58ΔfHbp 菌株构建为从组成型异源启动子表达不同亚变体。这些重组菌株的 fH 结合特性得到了表征，数据证实了每个亚变体都结合不同水平的 fH。表面等离子体共振揭示了 fHbp-fH 复合物的稳定性存在差异，差异范围超过 2 个数量级，表明变体组内和组间残基的差异会影响 fH 结合。有趣的是，表达不同亚变体的重组 MC58 菌株在人血清中的存活率与 fH 结合水平不相关，这表明 fHbp 与 fH 的相互作用不是影响血清抗性的 fHbp 唯一功能。此外，在每个变体组内都观察到交叉反应性杀菌活性，尽管活性程度不同，这表明每个变体组内的氨基酸差异会影响杀菌抗体反应。
