An efficient cell free enzyme-based total synthesis of a meningococcal vaccine candidate.

Maria Rosaria Romano,Timm Fiebig,Rita Gerardy-Schahn,Davide Oldrini,Francesco Berti,Barbara Brogioni,Marta Tontini,Paolo Costantino,Roberto Adamo,Laura Santini,Monika Berger

doi:10.1038/npjvaccines.2016.17

Abstract

Invasive meningococcal disease (IMD) is a global health problem and vaccination has proven the most effective way of disease control. Neisseria meningitidis serogroup X (NmX) is an emerging threat in the African sub-Saharan meningitis belt, but no vaccine is available today. Leading vaccines against Nm are glycoconjugates, in which capsular polysaccharides isolated from large-scale pathogen cultures are conjugated to adjuvant proteins. Though safe and efficacious even in infants, high costs and biohazard associated with the production limit abundant application of glycoconjugate vaccines particularly in the most afflicted nations. An existing NmX vaccine candidate (CPSXn-CRM197) produced by established protocols from NmX capsule polysaccharide (CPSX) has been shown to elicit high bactericidal immunoglobulin G titres in mice. Here we describe the scalable in vitro synthesis of CPSXiv from chemically pure precursors by the use of recombinant NmX capsule polymerase. Application of the described coupling chemistry gives CPSXiv-CRM197, which in mouse vaccination experiments behaves identical to the benchmark CPSXn-CRM197. Excluding any biohazards, this novel process represents a paradigm shift in vaccine production and a premise towards vaccine manufacturing in emerging economies.

Highlights

Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis and sepsis worldwide
Because acidic hydrolysis cleaves the phosphodiester bond in Neisseria meningitidis serogroup X (NmX) capsule polysaccharide (CPSX) proximal to the anomeric C-atom (Figure 1b), oligosaccharides obtained from reaction 3 were enzymatically treated to release the phosphate group from the non-reducing end and maximise the concentration of functional primers
CPSX; CPSXn, CPSX obtained from natural source; HPLC-Anion-exchange chromatography (AEC), high-performance liquid chromatography based anion exchange chromatography; p.p.m., parts per million

Summary

Introduction

Neisseria meningitidis (Nm) is a leading cause of bacterial meningitis and sepsis worldwide. The strictly human pathogen causes recurrent devastating epidemics in developing countries, in particular the African sub-Saharan meningitis belt.[1] In Western. Nm infections occur sporadically, but outbreaks have been reported caused by hyper-invasive strains in situations of crowding[2,3] and in communities with increased risk.[4,5] As Nm is the only bacterial pathogen that can spread in epidemic waves, outbreaks present a significant danger for individuals with high susceptibility, that is, small children, adolescents and elderly people.[6]. A chief problem with invasive meningococcal disease (IMD), often characterised by meningitis and sepsis, is rapid progression. Case-fatality rates are high, exceeding 20% even in developed countries.[8]

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Conclusion