Evaluation of novel Streptococcus pyogenes vaccine candidates incorporating multiple conserved sequences from the C-repeat region of the M-protein

Abstract

A major challenge for Streptococcus pyogenes vaccine development is the identification of epitopes that confer protection from infection by multiple S. pyogenes M-types. Here we have identified and characterised the distribution of common variant sequences from individual repeat units of the C-repeat region (CRR) of M-proteins representing 77 different M-types. Three polyvalent fusion vaccine candidates (SV1, SV2 and SV3) incorporating the most common variants were subsequently expressed and purified, and demonstrated to be alpha-helical by Circular Dichroism (CD), a secondary conformational characteristic of the CRR in the M-protein. Antibodies raised against each of these constructs recognise M-proteins that vary in their CRR, and bind to the surface of multiple S. pyogenes isolates. Antibodies raised against SV1, containing five variant sequences, also kill heterologous S. pyogenes isolates in in vitro bactericidal assays. Further structural characterisation of this construct demonstrated the conformation of SV1 was stable at different pHs, and thermal unfolding of SV1 is a reversible process. Our findings demonstrate that linkage of multiple variant sequences into a single recombinant construct overcomes the need to embed the variant sequences in foreign helix promoting flanking sequences for conformational stability, and demonstrates the viability of the polyvalent candidates as global S. pyogenes vaccine candidates.

Disease Manifestations and Pathogenic Mechanisms of Group A Streptococcus

“…Protection has been observed following heterologous expression of the C-repeat region by vaccinia virus (547) and Lactococcus lactis (548). Conformationally restricted C-repeat-region peptides (J8 and J14 and derivatives thereof and StreptInCor, a 55-mer peptide containing Band T-cell epitopes from the conserved region of the M5 protein) have been extensively studied and were observed to induce bactericidal and/or protective antibodies in animal-based trials (549)(550)(551)(552)(553)(554)(555)(556)(557)(558)(559)(560).…”

Staphylococcal and Streptococcal Superantigen Exotoxins

“…However, major studies to vaccinate against group A streptococci, like for S. aureus, are directed against surface antigens, particularly M protein (322)(323)(324) and C5a peptidase (325). These studies are also in their infancy.…”

An efficient, chemically-defined semisynthetic lipid-adjuvanted nanoparticulate vaccine development system

“…Slides were prepared as described. 20 A colony of each GAS strain was grown overnight at 37 °C (without shaking) in Todd Hewitt broth (5 mL) supplemented with 1 % yeast extract (THBY) and 28 µm E-64 (to inhibit M protein proteolysis by SpeB). …”