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Review
. 2023 Mar 28;8(1):48.
doi: 10.1038/s41541-023-00639-5.

Progress towards a glycoconjugate vaccine against Group A Streptococcus

Keira Burns  1   2 , Helge C Dorfmueller  3 , Brendan W Wren  2 , Fatme Mawas  1 , Helen A Shaw  4
Affiliations
Review

Progress towards a glycoconjugate vaccine against Group A Streptococcus

Keira Burns et al. NPJ Vaccines. .

Abstract

The Group A Carbohydrate (GAC) is a defining feature of Group A Streptococcus (Strep A) or Streptococcus pyogenes. It is a conserved and simple polysaccharide, comprising a rhamnose backbone and GlcNAc side chains, further decorated with glycerol phosphate on approximately 40% GlcNAc residues. Its conservation, surface exposure and antigenicity have made it an interesting focus on Strep A vaccine design. Glycoconjugates containing this conserved carbohydrate should be a key approach towards the successful mission to build a universal Strep A vaccine candidate. In this review, a brief introduction to GAC, the main carbohydrate component of Strep A bacteria, and a variety of published carrier proteins and conjugation technologies are discussed. Components and technologies should be chosen carefully for building affordable Strep A vaccine candidates, particularly for low- and middle-income countries (LMICs). Towards this, novel technologies are discussed, such as the prospective use of bioconjugation with PglB for rhamnose polymer conjugation and generalised modules for membrane antigens (GMMA), particularly as low-cost solutions to vaccine production. Rational design of "double-hit" conjugates encompassing species specific glycan and protein components would be beneficial and production of a conserved vaccine to target Strep A colonisation without invoking an autoimmune response would be ideal.

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Conflict of interest statement

H.C.D. holds a patent on the rhamnose polysaccharide platform technology (WO2020249737A1). B.W.W. holds a patent for an E. coli bioconjugation strain (US20150344928A1).

Figures

Fig. 1
Fig. 1. Structures of the GAC trisaccharide repeating unit.
GAC is composed of a polyrhamnose backbone and GlcNAc side chains, decorated with glycerol phosphate. The wildtype repeating unit is [3)α-l-Rhap(1→ 2)[β-d-GlcpNAc(1 → 3)]α-l-Rhap] for 70% of the repeating units (i), and 30% modified on GlcNAc side chains with glycerol phosphate (ii) [3)-α-l-Rhap-(1 → 2)[β-d-GlcpNAc6P(S)Gro-(1 → 3)]-α-l-Rhap-(1 → 3)]. ΔgacI mutants and certain GAS strains passaged in mice have the repeating structure [3)-α-L-Rhap-(1 → 2)α-L-Rhap-(1 → 3)-α] deficient in GlcNAc sidechains (iii).
Fig. 2
Fig. 2. Simplified schematic representation of chemical conjugation.
Polysaccharide (PS) extracted from the native organism, e.g., GAC from Strep A cells (a), and recombinant protein carriers expressed and purified from E. coli cells (b). Extracted PS and recombinant protein carriers containing compatible reactive groups are conjugated together using a compatible cross-linking chemical reagent (c) yielding heterogenous glycoconjugate vaccine candidates depending on the selected approach (d). Schematic shows different approaches yielding different glycoconjugate species, with reducing end chemistries leading to terminal single ended glycoconjugate products (sun-like structures), and random activation chemistries yielding cross-linked mesh-like structures of higher molecular weights with several attached protein - polysaccharide molecules.
Fig. 3
Fig. 3. Glycoconjugate production using C. jejuni PglB bioconjugation inside E. coli host cells.
a Plasmids containing genes encoding polysaccharide (PS) biosynthesis (green), the protein acceptor (blue) containing a glycotag (yellow star), and the oligosaccharyltransferase (OST) PglB (red) are co-transformed into E. coli host cells. b Bioconjugates are produced as follows; (1) The PS biosynthesis locus is expressed and built onto undecaprenol-pyrophosphate (Und-PP) lipid linkers within the inner membrane. (2) The PS is flipped from the cytoplasm to the periplasm by a specific flippase enzyme. (3) Synthesised carrier proteins are exported to the periplasm through the Sec secretion system. (4) In the periplasm both the PS, and the carrier protein containing a specific glycotag can be recognised by the PglB OST enzyme. PglB transfers the PS from Und-PP onto the asparagine residue within the glycotag D/E-X-N-X-S/T motif on the fully folded carrier protein, resulting in protein glycosylation. (5) An inexhaustible supply of glycoproteins can be subsequently purified from E. coli cells.
Fig. 4
Fig. 4. The gac operon in Strep A produces GAC containing a polyrhamnose backbone decorated with alternate GlcNAc side chains.
a Schematic representation of the gac operon (gacA-L) in Strep A. Horizontal arrows represent each gene designation with colour denoting predicted gene function. Green, polyrhamnose biosynthesis; blue, GlcNAc biosynthesis. b Schematic diagram of GAC biosynthesis. GAC biosynthesis is initiated on lipid linked GlcNAc attached to the inner leaflet of the periplasmic membrane for polyrhamnose synthesis catalysed by rhamnosyltransferase enzymes (GacBCFG). After polymerisation, the polyrhamnose backbone is flipped to the outer leaflet by an ABC transporter (GacDE complex) before GlcNAc (GacL) and glycerol phosphates (GacH) are transferred to the polyrhamnose backbone as a sidechain modification. A LytR-CpsS-Psr (LCP) phosphotransferase protein is hypothesised to attach GAC to peptidoglycan via a phophodiester bond.
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References

    1. Bonanni P. Demographic impact of vaccination. Vaccine. 1999;17:120–125. doi: 10.1016/S0264-410X(99)00306-0. - DOI - PubMed
    1. Vekemans J, et al. The path to Group A Streptococcus vaccines: WHO research and development technology roadmap and preferred product characteristics. Clin. Infect. Dis. 2019;16:877–883. doi: 10.1093/cid/ciy1143. - DOI - PMC - PubMed
    1. Fay K, et al. Patterns of antibiotic nonsusceptibility among invasive group A Streptococcus Infections—United States, 2006–2017. Clin. Infect. Dis. 2021;73:1957–1964. doi: 10.1093/cid/ciab575. - DOI - PubMed
    1. WHO. The Current Evidence for the Burden of Group A Streptococcal Diseases. https://apps.who.int/iris/handle/10665/69063 (2005).
    1. Watkins DA, et al. Global, regional, and national burden of rheumatic heart disease 1990–2015. N. Engl. J. Med. 2017;377:713–722. doi: 10.1056/NEJMoa1603693. - DOI - PubMed