The Fine Structure of Neisseria meningitidis Lipooligosaccharide from the M986 Strain and Three of Its Variants

Chao-Ming Tsai,Ewa Jankowska-Stephens,Rahman M Mizanur,John F Cipollo

doi:10.1074/jbc.m808209200

Abstract

Neisseria meningitidis is a cause of fatal sepsis and epidemic meningitis. A major virulence factor is cell wall lipooligosaccharide (LOS). The M986 strain has been used extensively in immunological and vaccine research. Yet, the LOS repertoire of this strain is not known. Here we have investigated the LOS structures of M986 and three of its variants OP1, OP2-, and OP2+. This strain and its variants present a series of related LOS families that are increasingly truncated in their listed order. The major structural differences are seen in the lacto-N-neotetraose alpha-chain. The gamma-chain Hep II contains two phosphoethanolamine (PEA) substitutions at C3 and C6/7. These substitutions were seen in all strains except OP2+ where the canonical core Hep II is missing. The PEA disubstitution was present in nearly stoichiometric amounts with only minor amounts of monosubstitution observed, and no glycomers devoid of PEA were seen. This was also the case in LOS with a complete lacto-N-neotetraosyl alpha-chain even though previous reports suggested that the presence of an extended alpha-chain hinders C3 PEA substitution of Hep II. Approximately 50% of gamma-chain GlcNAc was present in its 3-OAc-substituted form. Because Hep II C3 PEA substitution and gamma-chain GlcNAc OAc addition have been reported to negatively interact, the co-existence of these two modifications in these strains is unique. The LOS structures of M986 and three of its variants have been determined, which better defines these strains as tools for immunological and vaccine research.

Highlights

Neisseria meningitidis is a causative agent in fatal sepsis and epidemic meningitis
The ␤-chain extends from the C3 of the core Hep II residue, and in N. meningitidis this extension is limited to addition of Glc␣1,3- [6]
Results show that M986 lipid oligosaccharide (LOS) is unique in terms of its overall structure

Summary

Introduction

Neisseria meningitidis is a causative agent in fatal sepsis and epidemic meningitis. The structure and composition of cell wall lipid oligosaccharide (LOS) can vary markedly from strain to strain as the result of phase variation, which allows immune system avoidance leading to infection. Strains with LOS containing the 3Ј-PEA of Hep II and an ␣-chain LNT or those with the sialo-LNT form tend not to produce antibodies with bactericidal activity. A monoclonal antibody raised to the LOS of a galE, an ␣-chain-deficient strain, has been shown to provide passive protection in mice against a number of N. meningitidis strains [18]. Inoculation of mice with outer membrane vesicles from both encapsulated and non-encapsulated M986 strains has been shown to provide protection against lethal doses of endotoxin and infective doses of live bacteria [19] These strains have been used to investigate immune regulatory properties of N. meningitidis [26, 27] and both LOS and outer membrane vesicles enhance granulocyte recovery in myelosuppressed mice [22]

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Conclusion