Rossi Raffaella, Konar Monica, Beernink Peter T
Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, UCSF Benioff Children's Hospital Oakland, Oakland, California, USA.
Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, UCSF Benioff Children's Hospital Oakland, Oakland, California, USA
Infect Immun. 2016 May 24;84(6):1735-1742. doi: 10.1128/IAI.01491-15. Print 2016 Jun.
Neisseria meningitidis causes cases of bacterial meningitis and sepsis. Factor H binding protein (FHbp) is a component of two licensed meningococcal serogroup B vaccines. FHbp recruits the complement regulator factor H (FH) to the bacterial surface, which inhibits the complement alternative pathway and promotes immune evasion. Binding of human FH impairs the protective antibody responses to FHbp, and mutation of FHbp to decrease binding of FH can increase the protective responses. In a previous study, we identified two amino acid substitutions in FHbp variant group 2 that increased its thermal stability by 21°C and stabilized epitopes recognized by protective monoclonal antibodies (MAbs). Our hypothesis was that combining substitutions to increase stability and decrease FH binding would increase protective antibody responses in the presence of human FH. In the present study, we generated four new FHbp single mutants that decreased FH binding and retained binding of anti-FHbp MAbs and immunogenicity in wild-type mice. From these mutants, we selected two, K219N and G220S, to combine with the stabilized double-mutant FHbp antigen. The two triple mutants decreased FH binding >200-fold, increased the thermal stability of the N-terminal domain by 21°C, and bound better to an anti-FHbp MAb than the wild-type FHbp. In human-FH-transgenic mice, the FHbp triple mutants elicited 8- to 15-fold-higher protective antibody responses than the wild-type FHbp antigen. Collectively, the data suggest that mutations to eliminate binding of human FH and to promote conformational stability act synergistically to optimize FHbp immunogenicity.
脑膜炎奈瑟菌可引发细菌性脑膜炎和败血症病例。因子H结合蛋白（FHbp）是两种已获许可的B群脑膜炎球菌疫苗的成分。FHbp将补体调节因子H（FH）募集到细菌表面，从而抑制补体替代途径并促进免疫逃逸。人FH的结合会损害对FHbp的保护性抗体反应，而FHbp发生突变以减少与FH的结合则可增强保护性反应。在先前的一项研究中，我们在FHbp变体组2中鉴定出两个氨基酸替换，它们使FHbp的热稳定性提高了21°C，并稳定了保护性单克隆抗体（MAb）识别的表位。我们的假设是，在存在人FH的情况下，将增加稳定性和减少FH结合的替换组合起来会增强保护性抗体反应。在本研究中，我们构建了四个新的FHbp单突变体，它们减少了与FH的结合，并在野生型小鼠中保留了抗FHbp MAb的结合和免疫原性。从这些突变体中，我们选择了两个，即K219N和G220S，与稳定的双突变FHbp抗原组合。这两个三突变体使FH结合减少了200倍以上，使N端结构域的热稳定性提高了21°C，并且与抗FHbp MAb的结合比野生型FHbp更好。在人FH转基因小鼠中，FHbp三突变体引发的保护性抗体反应比野生型FHbp抗原高8至15倍。总体而言，数据表明消除人FH结合并促进构象稳定性的突变具有协同作用，可优化FHbp的免疫原性。
