Protection against Group A Streptococcus by Immunization with J8–Diphtheria Toxoid: Contribution of J8‐ and Diphtheria Toxoid–Specific Antibodies to Protection

Abstract

A conformationally constrained, minimally conserved peptide from the M protein of group A streptococcus (GAS) has been defined. It consists of 12 amino acids from the C-repeat region within a non-M protein helix-forming sequence and is referred to as "J8." Here, we investigate the immunogenicity of a J8-diphtheria toxoid (DT) conjugate adjuvanted with the human-compatible adjuvants, SBAS2 and alum, and demonstrate that it is capable of inducing opsonic antibodies and can protect outbred mice from virulent challenge. In a range of experiments, protection correlated with the titer of J8-specific antibodies and not with the induction of J8-specific T cells. However, DT-specific antibodies (as well as J8-specific antibodies) were shown to stain the surface of fixed GAS and to be capable of opsonizing live organisms. DT may be an ideal carrier protein for J8 and other GAS peptides for GAS vaccines.

JJo, a Recombinant Dimer of Conformationally Restricted Peptide Elicits Protective Response against Group A Streptococcus (GAS) Isolates from a GAS-Endemic Region

“…To assess whether the recombinant vaccine candidate JJo could stimulate an antibody response against the parent peptide (J14) in mice of different genetic backgrounds, we determined the immunogenicity of purified JJo in Balb/c, C3HeJ and B10BR mice following methods previously described [8]. In addition, antibodies were also raised in Quackenbush mice to assess functionality in an out bred strain.…”

“…A full tail bleed (~200 μl) was taken 7 days after the final boost on day 42. The antibody responses in individual mice of the same genetic background were quantified by ELISA as described earlier [8]. Whole cell ELISAs were also carried out with sera from Balb/c and C3HeJ immunised mice [15].…”

“…Slides were visualized at 520 nm under a confocal microscope (LSM-510 meta, Zeiss). The cell suspensions prepared for immunofluorescence were also processed in parallel for flow cytometric analysis as described earlier [8] with slight modifications. Cells were blocked with 3% bovine serum albumin (BSA) and human IgG prior to incubation with pooled anti-JJo or sham control serum (1:50 dilution).…”

“…When conjugated to diphtheria toxoid, J14 elicits an immune response that reacts against multiple M types [8]. However, to date the efficacy of J14 has largely been shown against commonly circulating strains in developed countries [9].…”

Host–pathogen interactions in Streptococcus pyogenes infections, with special reference to puerperal fever and a comment on vaccine development

“…However, work is in progress to develop a multivalent vaccine based on a combination of many different HVRs, which may not elicit unwanted cross-reactivities [33]. Possibly, a vaccine could also be based on the conserved parts of M protein [34,35] although antibodies directed against this part might be expected to have poor activity because they do not block the antiphagocytic function of the HVR. Another interesting vaccine candidate expressed by all strains of S. pyogenes is ScpA, a surface localized C5a-peptidase that shows a high degree of conservation between strains [36].…”