Group A Streptococcal Vaccine Containing Immunogenic Peptides of Streptolysin S

 描述（由申请方提供）：本项目的总体目标是确定A组链球菌溶血素S（SLS）无毒肽的保护性免疫原性，并评估其增强含M和M相关蛋白（Mrp）疫苗有效性的潜力。SLS是GAS的毒力决定因子，以前未被认为是疫苗组分，因为毒素在GAS感染后没有免疫原性。SLS由99%的GAS表达，并且有相当多的证据支持其在GAS感染的发病机制中的突出作用。SLS通过引起软组织损伤、溶解吞噬细胞、介导生物体跨上皮边界的易位、通过RBC溶解促进铁获得、充当上调自身的群体传感器以及通过未翻译的mRNA潜在地充当其他趋化基因的全局调节剂来促成GAS的毒力。活性毒素是一种30个氨基酸的杂环肽，是9个基因Sag操纵子的产物。我们以前已经表明，一个无毒的合成肽复制氨基酸残基10-30的SLS前肽耦合KLH诱发抗体在兔中，完全中和毒素的活性在体外。SLS抗体是非调理的，但当与M蛋白抗血清组合时，SLS抗体显著增强由M抗体介导的GAS的吞噬作用。SLS肽以前没有在动物感染模型中评估保护性免疫原性。我们的假设是，将SLS的免疫原性肽添加到M蛋白和基于Mrp的GAS疫苗中，将通过中和SLS的细胞溶解毒性来增强其总体功效，从而导致细菌毒力降低以及更有效的抗体介导的生物体清除。这项建议的目的是：1）构建含有N-末端M和Mrp肽（具有和不具有SLS肽）的重组多价杂合蛋白，并测定针对两种疫苗蛋白的免疫血清对选定血清型GAS的体外杀菌活性，和2）在GAS小鼠模型中比较含有SLS肽的杂合疫苗蛋白与不含SLS肽的杂合疫苗蛋白的保护性免疫原性感染.在被认为是“通用”GAS疫苗抗原的共有毒力决定簇中，我们假设SLS的免疫原性肽引起中和抗体，通过挫败链球菌发病机制中涉及的一种突出的隐形策略，具有影响整体疫苗效力的最大潜力。

 DESCRIPTION (provided by applicant): The overall goal of goal of this project is to determine the protective immunogenicity of a non-toxic peptide of group A streptococcal streptolysin S (SLS) and to assess its potential to enhance the efficacy of vaccines containing M and M-related proteins (Mrp). SLS is a virulence determinant of GAS that has not previously been considered as a vaccine component because the toxin is not immunogenic following GAS infection. SLS is expressed by 99% of all GAS and there is considerable evidence supporting its prominent role in the pathogenesis of GAS infections. SLS contributes to virulence of GAS by causing soft tissue damage, lysing phagocytes, mediating translocation of the organism across epithelial boundaries, facilitating iron acquisition through lysis of RBCs, acting as a quorum sensor that upregulates itself, and potentially functioning as a global regulator of other virulenc genes via untranslated mRNA. The active toxin is a 30-amino acid heterocyclic peptide that is the product of the nine-gene Sag operon. We have previously shown that a non-toxic synthetic peptide copying amino acid residues 10-30 of the SLS propeptide coupled to KLH evoked antibodies in rabbits that completely neutralized the activity of the toxin in vitro. The SLS antibodies were non-opsonic but when combined with M protein antisera, the SLS antibodies significantly enhanced phagocytosis of GAS that was mediated by M antibodies. SLS peptides have not previously been assessed for protective immunogenicity in animal models of infection. Our hypothesis is that the addition of an immunogenic peptide of SLS to M protein and Mrp-based GAS vaccines will enhance their overall efficacy by neutralizing the cytolytic toxicity of SLS, thus resulting in decreased bacterial virulence coupled with more effective antibody-mediated clearance of the organism. The aims of this proposal are: 1) To construct recombinant multivalent hybrid proteins containing N- terminal M and Mrp peptides with and without SLS peptides and to assay immune sera against both vaccine proteins for in vitro bactericidal activity against selected serotypes of GAS, and 2) To compare the protective immunogenicity of hybrid vaccine proteins containing the SLS peptide to those without the SLS peptide in mouse models of GAS infections. Of the shared virulence determinants that are considered "universal" GAS vaccine antigens, we hypothesize that an immunogenic peptide of SLS that evokes neutralizing antibodies has the greatest potential to impact overall vaccine efficacy by thwarting one of the prominent stealth tactics involved in streptococcal pathogenesis.