A panel of 6 murine monoclonal antibodies (MAbs) recognizing inner core lipopolysaccharide (LPS) epitopes of was prepared and characterized in order to determine the diversity of inner core LPS glycoforms among disease and carrier isolates. with L3B5, cell surface binding of L2-16 or LPT 3-1 did not correlate with functional activity as determined by bactericidal or infant rat passive protection assays against wild-type strains. These findings are provocative with respect to the requirements for protective activity of antibodies and the development of inner core LPS vaccines against invasive meningococcal disease. Invasive meningococcal disease remains a major cause of meningitis and septicemia in children under 2 years of age. Effective polysaccharide-based conjugate vaccines are available for all the major serogroups except for serogroup B, which remains the most common cause of meningococcal meningitis and septicemia in the developed world (36). There is an urgent requirement for Fosaprepitant dimeglumine a serogroup B vaccine. Fosaprepitant dimeglumine The capsular polysaccharide of group B (NmB) is -2,8-linked polysialic acid, which is also expressed on human neuronal cell adhesion and other surface-expressed molecules, and therefore poses potential problems of autoimmunity as a vaccine candidate (6). Alternative approaches include outer membrane vesicles (7, 28), a variety of outer membrane proteins identified through exploitation of whole genome sequences (26, 31, 41), signature-tagged mutagenesis (40), and an approach based on the induction of cross-reactive antigens of (29). We have taken an approach that involves the use of inner core lipopolysaccharide (LPS) epitopes of as vaccine candidates (32, 33, 34, 35). The LPS structure of comprises a lipid A backbone attached to a core oligosaccharide unit with an inner core di-heptose-(13); (9); (39); and (21, 22); (14); and (2). A characteristic of meningococcal LPS is reversible, high-frequency phase variation of outer core oligosaccharide structures mediated by mutation in homopolymeric DNA tracts present in LPS biosynthetic genes (16). These homopolymeric tracts are absent in inner core LPS biosynthetic genes such as LPS has provided us with the genetic tools to construct genetically defined mutants, including those expressing truncated LPS glycoforms. These have been used to produce and characterize antibodies to defined inner core LPS structures. The absence of galactose residues in the conserved inner core structure of meningococcal LPS has led to the utilization of mutants defective in the enzyme UDP glucose-4-epimerase (GalE) in the construction of truncated LPS structures. This enzyme is essential for to synthesize UDP-Gal Fosaprepitant dimeglumine for incorporation of galactose into its LPS and is encoded by the gene (15). Mutation of this gene results in truncation of the oligosaccharide chain at the glucose residue attached to HepI. Previously we have described an inner core LPS epitope defined by a MAb, L3B5, that is conserved in 76% of NmB strains (70% of all major serogroups) and is accessible in fully encapsulated (33). This epitope is accessible in grown in vivo, and the MAb has functional activity in vitro (bactericidal, opsonic) and in vivo against wild-type NmB strains (32, 34, 35). L3B5 recognizes an inner core LPS epitope in immunotype L3 that has an absolute IL13BP requirement for PEtn at position 3 of HepII (33) (Fig. ?(Fig.1c).1c). In previous studies of L3B5 reactivity, it was clear that two genes, and codes for an LPS PEtn transferase that adds PEtn to position 3 of HepII and competes with is switched on or off depends on the number of cytidines in the homopolymeric tract that affects whether the gene is in or out of frame and therefore affects the nature and functionality of the translated product. One mechanism Fosaprepitant dimeglumine resulting in strains that do not react with L3B5 is when the gene has a number of cytidines permissive for transcription of LPS structures of the immunotypes. (b to h) Three-dimensional space-filling molecular models of the.