TABLE 4.

Serum bactericidal activity induced by fHbp subvariants

Complement source and N. meningitidis strain (fHbp subvariant)Bactericidal titera for anti-fHbp sera against:
Variant 1ChimericVariant 2Variant 3
1.11.41.101.141.551-2,3.x2.162.192.222.253.283.45
Rabbit complement
    MC58 (1.1)[>8,192]>8,1924,096>8,192<16>8,192<1664<161664<64
    M01-0240149 (1.4)512[2,048]1,0241,0241,0242,04864<16<16<16<16<32
    M01-0240185 (1.10)256128[2,048]2,0481,0242,048<16<16<16<16<16<16
    NZ98/254 (1.14)1285122,048[>8,192]256512<1632<16<16<16<16
    M1573 (1.55)<16<16<16<16[<16b]<16<16<16<16<16<16<16
    NL096 (1-2,3.x)<1632<16<16<16[8,192]<16<16<16<16<16<16
    961-5945 (2.16)3212864256<32>8,192[>8,192]>8,1922,0482,0484,096512
    M3153 (2.19)<1632128256<162,0488,192[8,192]2,0481,0241,02464
    C11 (2.22)16<16<16<16<161282562,048[4,096]2562,048<16
    M2552 (2.25)16<16<16<16<321285124,0968,192[512]128<32
    M1239 (3.28)<16<16<16<16<321285121,0242048512[8,192]64
    M01-0240320 (3.45)<32<32<32<32<322,0482,048>8,1921,0244,0964,096[4,096]
Human complement
    MC58 (1.1)[2,048]1,0241616<832<8<8<8<8<8<8
    M01-0240149 (1.4)128[1,024]2561,024<8256<8<8<8<8<8<8
    M01-0240185 (1.10)<8512[1,024]512512512<8<8<8<8<8<8
    NZ98/254 (1.14)6432256[1,024]256128<8<8<8<8<8<8
    M1573 (1.55)<8<8<8<8[<8b]<8<8<8<8<8<8<8
    NL096 (1-2,3.x)<8<8<8<8<8[1,024]<8<8<8<8<8<8
    961-5945 (2.16)<8<8<8<8<832[2,048]51216<8<816
    M3153 (2.19)<8<8<8<8<8256128[512]6412832<8
    C11 (2.22)<8<8<8<8<864128128[512]<8256<8
    M2552 (2.25)<8<8<8<8<8<8128128128[128]<8<8
    M1239 (3.28)<8<8<8<8<8<8<8<8<8<8[512]<8
    M01-0240320 (3.45)<8<8<8<8<8512512512256512256[2,048]
  • a Bactericidal titers are expressed as the reciprocal of the serum dilution of mouse polyclonal antibodies yielding ≥50% bactericidal killing. Antigens were formulated in aluminum hydroxide, and assays were performed with rabbit complement (rSBA) or human complement (hSBA); rSBA titers of ≥128 and hSBA titers of ≥16 (4-fold increase above baseline) are shown in boldface. The values in brackets show the SBA titer obtained for each fHbp subvariant versus the strain expressing the homologous subvariant.

  • b A bactericidal titer of 8,192 was seen for subvariant 1.55 when we used a recombinant MenB strain that was engineered to express the homologous subvariant, demonstrating its immunogenicity. Negative results were obtained for strain M1573, which was highly resistant to killing by all antisera.