By adsorption, we found that nearly all of the SBA against this strain was directed at fHbp. 88 to >95 percent of the SBA was directed against fHbp. Four subjects developed 4-collapse raises in SBA titer against a test strain having a heterologous fHbp variant 2 antigen and a homologous NHba amino acid sequence that matched the vaccine antigen (GMT <1:4 baseline, to 1 1:45). SBA was directed primarily against NHba in one subject, against fHbp in a second, while depletion of either anti-NHba or anti-fHbp antibody eliminated the majority of SBA in sera from two subjects. In all four subjects, depletion of both anti-fHbp and anti-NHba antibodies eliminated more SBA than depletion of either antibody separately. Combining a mouse non-bactericidal anti-fHbp variant 1 antiserum having a mouse anti-NHba antiserum also augmented the anti-NHba SBA titer against this test strain. For meningococcal vaccines that target relatively sparsely-exposed antigens such fHbp or NHba, non-bactericidal antibodies against individual antigens can cooperate and elicit SBA. Keywords:Neisseria meningitidis, vaccine, fHbp, NHba, GNA NBD-556 2132, match == I. Intro == Meningococcal vaccines for the prevention of disease caused by group B strains ofNeisseria meningitidisare currently in clinical tests. One of the vaccines consists of recombinant element H binding proteins (fHbp) from two antigenic variants [1]. NBD-556 Another consists of an outer membrane vesicle vaccine (OMV) [2] combined with three recombinant proteins: NadA, and two fusion NBD-556 proteins, fHbp in the variant 1 (v.1) group fused with GNA2091 (GNA2091-fHbp), and Neisserial heparin binding antigen (NHba) [3] fused with GNA1030 (NHba-GNA1030) [4]. NHba was previously referred to as GNA2132 [5,6]. In mice immunized with the three recombinant proteins, the principal antigenic focuses on of serum bactericidal antibody (SBA) were fHbp, NHba, and NadA [4]. The combination of the three proteins also elicited higher SBA titers than any of the individual proteins only [4]. In humans a vaccine with the three recombinant proteins (no OMV) also elicited SBA reactions [7] but the contributions of the antibodies elicited by the individual antigens toward the observed SBA were unclear. Investigating the functional contributions of Ptgs1 individual antibody populations in a mixture of serum antibodies can be difficult because of the potential positive or bad relationships of antibodies binding to multiple antigenic focuses on within the bacterial surface [810]. The purpose of the present study was to determine the part of antibodies to two of the antigens, fHbp and NHba, in eliciting serum bactericidal activity in immunized humans. Genes encoding these two antigens are present in nearly all disease-causing meningococcal isolates [1,1114]. == 2. Materials and Methods == == 2.1. Human being serum samples NBD-556 == Stored serum samples were available from six adults immunized intramuscularly with an investigational meningococcal vaccine that contained recombinant GNA2091-fHbp, NHba-GNA1030, and NadA [4]. The samples were selected from 36 sera previously investigated from adult NBD-556 participants of phase I studies primarily designed to evaluate vaccine security and tolerability [7]. The participants were given 3 doses of the vaccine spaced one month apart. Each dose contained 50 g of each of the three proteins adsorbed with aluminium hydroxide. Blood samples were obtained immediately prior to the 1st immunization and one month after the third immunization. All subjects provided informed written consent. For the present study, we selected serum samples based on availability of sufficient quantities for the adsorption studies described below. Use of the serum samples for this study was authorized by the institutional review table of Childrens Hospital & Research Center, Oakland. == 2.2. Mouse serum samples == Stored sera were available from earlier experiments in female CD-1 mice (Charles River) immunized having a recombinant NHba vaccine (gene from NZ98/254) [6], or perhaps a fHbp ID 1 vaccine. The amino acid sequences of the respective vaccine antigens matched those of the.