title: Meningococcal Factor H Binding Protein Vaccine Antigens with Increased Thermal Stability and Decreased Binding of Human Factor H.
abstract: 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.
authors.affiliation: Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, UCSF Benioff Children's Hospital Oakland, Oakland, California, USA.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Rossi
authors.affiliation: Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, UCSF Benioff Children's Hospital Oakland, Oakland, California, USA.
authors.forename: Monica
authors.initials: M
authors.lastname: Konar
authors.affiliation: Center for Immunobiology and Vaccine Development, Children's Hospital Oakland Research Institute, UCSF Benioff Children's Hospital Oakland, Oakland, California, USA pbeernink@chori.org.
authors.forename: Peter T
authors.identifier: http://orcid.org/0000-0001-5734-083X
authors.initials: PT
authors.lastname: Beernink
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis*; D000911:Antibodies, Monoclonal / Q000096:biosynthesis*; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D003001:Cloning, Molecular; D017242:Complement Factor H / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D057131:Immune Evasion; D000071497:Immunogenicity, Vaccine; D008585:Meningitis, Meningococcal / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D022401:Meningococcal Vaccines / Q000008:administration & dosage / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008958:Models, Molecular; D009154:Mutation; D009345:Neisseria meningitidis / Q000145:classification / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D065288:Serogroup
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D022401:Meningococcal Vaccines; D011994:Recombinant Proteins; C484699:factor H-binding protein, Neisseria meningitidis; D017242:Complement Factor H