In mice, the OMV vaccine from the mutant elicited higher serum bactericidal antibody responses against a panel of heterologous strains than a control multicomponent recombinant protein vaccine, or a detergent-extracted OMV vaccine that previously had been demonstrated to confer protection against meningococcal disease in humans. Imipramine Hydrochloride Conclusions The data illustrate the potential to develop a broadly immunogenic native OMV vaccine with decreased endotoxin activity that is potentially suitable for testing in humans. Keywords: group B, GNA1870, GNA 1870, factor H-binding protein, recombinant protein, vaccine Introduction No broadly effective vaccine is available against group B strains, which account for half of meningococcal cases in the United States [1, 2], and greater than 80 percent in Europe [3, 4]. group B, GNA1870, GNA 1870, factor H-binding protein, recombinant protein, vaccine Introduction No broadly effective vaccine is available against group B strains, which account for half of meningococcal cases in the United States [1, 2], and greater than 80 percent in Europe [3, 4]. The group B capsule is structurally similar to antigens expressed by neural tissues and, therefore, is a poor immunogen, which also has the potential to elicit autoantibodies. Thus, a polysaccharide-protein conjugate vaccine is unlikely to be feasible for prevention of group B disease [5]. Novel antigens discovered by genome mining are currently under investigation as group B vaccines. One highly promising candidate is factor H-binding protein (fHbp), which was also known as Genome-derived Neisserial Antigen 1870 [6]or LP2086 [7, 8]. FHbp is a surface-exposed lipoprotein present in all strains [6]. This protein can be subclassified into three variants based on sequence similarity and antigenic cross-reactivity. In general, antibodies prepared against fHbp variant 1 (v.1) were bactericidal against strains expressing fHbp Mouse monoclonal to MAPK11 from the v.1 group but not against strains expressing v.2 Imipramine Hydrochloride or v.3 proteins (and vice versa) [6, 9]. Imipramine Hydrochloride The variant 1 antigen is part of a promising investigational meningococcal vaccine consisting of three recombinant proteins, two of which are fusion proteins expressing two antigens each (i.e., a total of five antigens) [10]. In humans, this vaccine elicited serum bactericidal antibody responses against genetically diverse strains [11]. Outer membrane vesicle (OMV) vaccines are safe [12, 13] and efficacious against meningococcal disease [14, 15]. An OMV vaccine was licensed in New Zealand and controlled a long-standing group B epidemic [16-19]. However, serum bactericidal antibodies elicited by OMV Imipramine Hydrochloride vaccines are directed primarily at a major porin protein, PorA [20], which is immunodominant [21], and antigenically variable [22, 23]. OMV vaccines are treated with detergents to extract lipopolysaccharide (LOS) and decrease endotoxin activity. This procedure also removes detergent-soluble antigens such as fHbp or GNA2132, which in mice elicited broadly protective serum antibody responses [6, 24, 25]. To increase protective activity, we previously prepared native OMV vaccines from strains engineered to over-express fHbp v.1 [26, 27]. The sera from immunized mice conferred broader bactericidal activity against genetically diverse strains than sera from control mice immunized with recombinant fHbp v.1, or a native OMV vaccine prepared from the corresponding wildtype strain [26, 27]. The Imipramine Hydrochloride native OMV vaccines were prepared without the use of detergents to avoid extracting fHbp. Thus the endotoxin activity was too high for the vaccine to be administered safely to humans. In the present study, we prepared a native OMV vaccine from a mutant strain engineered to over-express fHbp and in which the LpxL1 gene encoding a late functioning acyl transferase also was inactivated. The deletion resulted in penta- instead of hexa-acylated Lipid A, which in previous studies decreased endotoxin activity while retaining adjuvant activity [28-30]. Our hypothesis was that this OMV vaccine would be less toxic than a native OMV prepared from a wildtype strain while retaining the ability of the mutant OMV to elicit serum anti-fHbp antibodies with broad bactericidal activity. Materials and Methods Meningococcal strains Meningococcal strains used in this study are described in table 1. Strain H44/76 and mutants derived from this strain were used to prepare the OMV vaccines. This strain expresses a fHbp v.1 protein with an amino acid sequence identical to that of strain MC58 [6], which provided the gene to over-express fHbp v.1 (referred to in Table 1 as v. 1.1). The other six strains expressed heterologous PorA proteins to that of the H44/76 vaccine strain and also expressed different subvariants of fHbp v.1 (Table 1). Table 1 strains strains were grown at 37C on GC agar plates in.