A stabilized glycomimetic conjugate vaccine inducing protective antibodies against Neisseria meningitidis serogroup A

Jacopo Enotarpi,Jeroen D C Codeé,Francesco Berti,Ludovic Auberger,Cristiana Balocchi,Dmitri V Filippov,Hermen S Overkleeft,Daniele Casini,Paolo Costantino,Evita Balducci,Marta Tontini,Filippo Carboni,Gijsbert A Van Der Marel,Cinzia Colombo,Daniela Proietti,Luigi Lay,Roberto Adamo,Daan Van Der Es,Maria Rosaria Romano

doi:10.1038/s41467-020-18279-x

Jacopo Enotarpi, Jeroen D C Codeé + Show 17 more

Open Access

https://doi.org/10.1038/s41467-020-18279-x

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Journal: Nature Communications	Publication Date: Sep 7, 2020
Citations: 21	License type: open-access

Affiliation: University of Milan, Leiden University

Abstract

Neisseria meningitidis serogroup A capsular polysaccharide (MenA CPS) consists of (1 → 6)-2-acetamido-2-deoxy-α-D-mannopyranosyl phosphate repeating units, O-acetylated at position C3 or C4. Glycomimetics appear attractive to overcome the CPS intrinsic lability in physiological media, due to cleavage of the phosphodiester bridge, and to develop a stable vaccine with longer shelf life in liquid formulation. Here, we generate a series of non-acetylated carbaMenA oligomers which are proven more stable than the CPS. An octamer (DP8) inhibits the binding of a MenA specific bactericidal mAb and polyclonal serum to the CPS, and is selected for further in vivo testing. However, its CRM197 conjugate raises murine antibodies towards the non-acetylated CPS backbone, but not the natural acetylated form. Accordingly, random O-acetylation of the DP8 is performed, resulting in a structure (Ac-carbaMenA) showing improved inhibition of anti-MenA CPS antibody binding and, after conjugation to CRM197, eliciting anti-MenA protective murine antibodies, comparably to the vaccine benchmark.

Highlights

Neisseria meningitidis serogroup A capsular polysaccharide (MenA capsular polysaccharides (CPS)) consists of (1 → 6)-2acetamido-2-deoxy-α-D-mannopyranosyl phosphate repeating units, O-acetylated at position C3 or C4
We showed that IgG antibodies could be raised using a protein conjugate of the carbaMenA oligomer with a degree of polymerization of 3 that were capable of recognizing the native MenA CPS33
To overcome the intrinsic lability of the anomeric phosphodiester linkages that connect the repeating units in the natural CPS, we have replaced the ring-oxygen of the constituting N-Acetyl mannosamines for a methylene entity, thereby generating carbaMenA oligomers

Summary

Introduction

Neisseria meningitidis serogroup A capsular polysaccharide (MenA CPS) consists of (1 → 6)-2acetamido-2-deoxy-α-D-mannopyranosyl phosphate repeating units, O-acetylated at position C3 or C4. Glycan-protein antigens enable memory B cell proliferation, ensuring long-lasting protection of the host These features combined with the extensive clinical experience render glycoconjugates amongst the safest and most efficacious vaccines developed so far, and their generation has been one of the greatest success stories in the biomedical sciences[4,8,9]. In which structural changes are implemented to improve specific features of the natural polysaccharide have so far not been incorporated in conjugate vaccines inducing protective immune responses[29]. We showed that IgG antibodies could be raised using a protein conjugate of the carbaMenA oligomer with a degree of polymerization of 3 (i.e., with three repeating units, DP3) that were capable of recognizing the native MenA CPS33. Previous work delivering “natural” synthetic MenA fragments has shown that short oligos (4 repeating units) can be recognized by anti-MenA antibodies but the minimal epitope capable a

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