Group A Streptococcal Vaccine Containing Immunogenic Peptides of Streptolysin S

 描述(申请人提供)：本项目的总体目标是确定A组链球菌溶链素S(SLS)的无毒多肽的保护性免疫原性，并评估其增强含有M和M相关蛋白的疫苗效力的潜力。SLS是GAS的毒力决定因素，以前没有被认为是疫苗成分，因为这种毒素在GAS感染后不具有免疫原性。99%的GAS表达SLS，有相当多的证据支持它在GAS感染的发病机制中的重要作用。SLS通过引起软组织损伤、溶解吞噬细胞、调节机体跨上皮边界的移位、通过裂解红细胞促进铁的获取、作为上调自身的群体传感器，以及可能通过未翻译的mRNA作为其他毒力基因的全球调节因子来促进GAS的毒力。活性毒素是一种30个氨基酸的杂环肽，是9个基因的SAG操纵子的产物。我们之前已经证明，一种无毒的合成肽复制氨基酸残基10-30个氨基酸残基的SLS前肽与KLH偶联，在兔体内引起抗体，在体外完全中和毒素的活性。SLS抗体为非调理抗体，但当与M蛋白抗血清联合使用时，可显著增强M抗体介导的GAS吞噬功能。SLS多肽以前没有在动物感染模型中被评估为保护性免疫原性。我们的假设是，将SLS的免疫原肽添加到M蛋白和基于MRP的GAS疫苗中，将通过中和SLS的细胞毒性来增强其整体效力，从而导致细菌毒力的降低和更有效的抗体介导的机体清除。这项建议的目的是：1)构建含有N-末端M和MRP肽的重组多价杂交蛋白，并检测针对这两种疫苗蛋白的免疫血清对选定的GAS血清型的体外杀菌活性；2)在GAS感染小鼠模型中比较含有SLS多肽和不含SLS多肽的杂合疫苗蛋白的保护性免疫原性。在被认为是“通用”GAS疫苗抗原的共同毒力决定因素中，我们假设SLS的一种免疫原肽可以激发中和抗体，通过阻止链球菌致病过程中涉及的一种重要的隐形策略之一，最有可能影响整体疫苗效果。

 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.