Adjuvant effects elicited by novel oligosaccharide variants of detoxified meningococcal lipopolysaccharides on Neisseria meningitidis recombinant PorA protein: a comparison in mice.

Ojas H Mehta,Gunnstein Norheim,Ian Feavers,Claire Jones,Hannah Chan,Manish Sadarangani,Andrew J Pollard,J Claire Hoe,Jerry C Nagaputra,E Richard Moxon,David J P Ferguson,Jeremy P Derrick,Katherine Makepeace,Muhammad Saleem,Derek W Hood,Christine S Rollier

doi:10.1371/journal.pone.0115713

Abstract

Neisseria meningitidis lipopolysaccharide (LPS) has adjuvant properties that can be exploited to assist vaccine immunogenicity. The modified penta-acylated LPS retains the adjuvant properties of hexa-acylated LPS but has a reduced toxicity profile. In this study we investigated whether two modified glycoform structures (LgtE and IcsB) of detoxified penta-acylated LPS exhibited differential adjuvant properties when formulated as native outer membrane vesicles (nOMVs) as compared to the previously described LgtB variant. Detoxified penta-acylated LPS was obtained by disruption of the lpxL1 gene (LpxL1 LPS), and three different glycoforms were obtained by disruption of the lgtB, lgtE or icsB genes respectively. Mice (mus musculus) were immunized with a recombinant PorA P1.7-2,4 (rPorA) protein co-administered with different nOMVs (containing a different PorA serosubtype P1.7,16), each of which expressed one of the three penta-acylated LPS glycoforms. All nOMVs induced IgG responses against the rPorA, but the nOMVs containing the penta-acylated LgtB-LpxL1 LPS glycoform induced significantly greater bactericidal activity compared to the other nOMVs or when the adjuvant was Alhydrogel. Compared to LgtE or IcsB LPS glycoforms, these data support the use of nOMVs containing detoxified, modified LgtB-LpxL1 LPS as a potential adjuvant for future meningococcal protein vaccines.

Highlights

Neisseria meningitidis is a major cause of meningitis and septicaemia globally
The expected LPS phenotypes of the single and double mutant strains, described in Fig. 2A, were consistently confirmed on five independent occasions by TSDS-PAGE of cell lysates for the single mutants or native outer membrane vesicles (OMVs) (nOMVs) obtained from the double mutants, as shown in Fig. 2B for the strains subsequently used for murine immunization (Fig. 2B)
Production and characterisation of nOMVs nOMVs were extracted from strains H44/76-LgtB-LpxL1, H44/76-LgtE-LpxL1 and H44/76-IcsB-LpxL1 on five occasions, and the resulting nOMVs were characterized by SDS-PAGE, TSDS-PAGE and electron microscopy

Summary

Introduction

Neisseria meningitidis is a major cause of meningitis and septicaemia globally. Efficient polysaccharide-protein glycoconjugate vaccines are available against 4 (A, C, W and Y) of the 5 major disease-causing capsular groups, but not for strains of capsular group B [1]. Lipopolysaccharide (LPS) is a component of the meningococcal outer membrane It is largely responsible for stimulating the destructive inflammatory cascade during invasive disease, and is partially removed from OMV-based vaccines by detergent extraction whereby the relative LPS content is lowered from 20–25% to 5–7% [6], enabling safe administration in humans [7]. Inactivation of lpxL1 allows native OMVs (nOMVs) containing high levels of penta-acylated LPS to be safely administered to humans [7]. This has the additional advantage of retaining low molecular weight antigens such as factor-H binding protein (fHbp), which contribute to enhanced vaccine immunogenicity [7], and would otherwise be removed during detergent-dependent detoxification processes. The adjuvant effect of a modified glycoform of lipopolysaccharide (LPS) (LgtB-LpxL1)

Methods

Results

Conclusion