Table 3

Summary of fHbp ID 22 mutantsa

ResiduePosition(s)bMutant(s)Hydrogen bondcSalt bridgecEffect on fH bindingdEffect on MAb JAR 4 bindingeEffect on immunogenicityf
Q38A+NoneNDND
Q126A+NoneNDND
D201A+NoneNDND
E202ANoneNDND
A235GNoneNDND
R80A+ImpairedImpairedImpaired
JAR 4
D211A++ImpairedNoneNone
E218A++ImpairedNoneNone
T, H220, 222A, A+ImpairedNoneNone
G236IImpairedImpairedImpaired
E248ANonePartialImpaired
  • a ID 22 is in variant group 2.

  • b Refers to amino acid position using fHbp ID 1 as a reference. Position 1 is the lipidated cysteine at the N terminus of the mature protein.

  • c A plus sign refers to a prediction that the residue is involved in the formation of either a hydrogen bond or a salt bridge in at least one model.

  • d None, >50% binding of fH compared with binding of fH by wild-type fHbp. Impaired, <95% fH binding compared with binding of fH by wild-type fHbp (Fig. 6). Q126A, D201A, and E202A showed a slight increase in fH binding (data not shown).

  • e ND, not done; none, no significant effect on MAb JAR 4 binding compared to binding to the corresponding wild-type fHbp (Fig. 7); impaired, >95% decrease in JAR 4 binding; partial, >50% decrease. There was no effect of the amino acid substitutions on binding of the other 5 MAbs tested (Fig. 7).

  • f Immunogenicity was tested in wild-type mice whose serum mouse fH did not bind to any of the vaccines. Impaired, reciprocal GMT significantly lower than elicited by control fHbp ID 22 wild-type vaccine (P ≤ 0.055, two-tailed; see Fig. 8 and text); none, reciprocal GMT was not significantly different than that of the control wild-type fHbp vaccine (P > 0.10, two-tailed).