Conservation and accessibility of an inner core lipopolysaccharide epitopeof Neisseria meningitidis

We investigated the conservation and antibody accessibility of inner core e pitopes of Neisseria meningitidis lipopolysaccharide (LPS) because of their potential as vaccine candidates. An immunoglobulin G3 murine monoclonal an tibody (MAb), designated MAb B5, was obtained by immunizing mice with a gal E mutant of N. meningitidis H44/76 (B.15.P1.7,16 immunotype L3). We have sh own that MAb B5 can bind to the core LPS of wild-type encapsulated MC58 (B. 15.P1.7,16 immunotype L3) organisms in vitro and ex vivo. An inner core str ucture recognized by MAb B5 is conserved and accessible in 26 of 34 (76%) o f group B and 78 of 112 (70%) of groups A, C, W, X, Y, and Z strains. N. me ningitidis strains which possess this epitope are immunotypes in which phos phoethanolamine (PEtn) is linked to the 3-position of the beta-chain heptos e (HepII) of the inner core. In contrast, N. neningitidis strains lacking r eactivity with MAb B5 have an alternative core structure in which PEtn is l inked to an exocyclic position (i.e., position 6 or 7) of HepII (immunotype s L2, L4, and L6) or is absent (immunotype L5). We conclude that MAb B5 def ines one or more of the major inner core glycoforms of N. meningitidis LPS. These findings support the possibility that immunogens capable of elicitin g functional antibodies specific to inner core structures could be the basi s of a vaccine against invasive infections caused by N. meningitidis.