化脓性链球菌(A组链球菌;StrepA)covR/S调节系统内的突变与几种毒力因子上调导致的高毒力表型有关,包括成孔毒素,链球菌溶血素O(SLO)。在这项研究中,我们利用了一系列的covR/S突变体,包括M1T1克隆菌株(5448和通过小鼠传代产生的称为5448AP的covS突变体),探讨SLO在covR/S突变型StrepA病发病机制中的作用。5448AP中slo的上调导致SLO介导的溶血增加,与StrepA共培养后树突状细胞(DC)活力降低,并增加DC产生的肿瘤坏死因子(TNF)和单核细胞趋化蛋白1(MCP-1)。等基因5448slo缺失突变体的小鼠传代导致在5448Δslo背景中恢复了几个covR/S突变体。传代还在非covR/S基因中引入了突变,但这些被认为对毒力没有影响。尽管slo缺陷突变体表现出特征性的covR/S控制的毒力因子上调,这些突变体导致DC活力增加,同时感染的DC产生的炎性细胞因子减少.在体内,slo表达与感染后3天感染小鼠皮肤DC数量减少和显著菌血症相关,感染部位有严重的病理。相反,感染菌株(covR/S突变体或野生型)中不存在slo导致在脓皮病小鼠模型中检测到皮肤中的DC并减弱毒力。足够和缺陷的covR/S突变体对由保守的M蛋白肽和来自CXC趋化因子蛋白酶SpyCEP的肽组成的组合疫苗介导的免疫清除敏感。重要性化脓性链球菌是造成大量侵袭性和非侵袭性感染的原因,这些感染在全球范围内导致显著的发病率和死亡率。在covR/S系统中具有突变的StrepA分离株显示出更大的导致严重侵袭性疾病的倾向。每年造成超过163,000人死亡。这是由于毒力因子的上调,包括成孔毒素链球菌溶血素O.利用covR/S和slo敲除突变体,我们研究了SLO在毒力中的作用。我们发现SLO改变了与宿主细胞群的相互作用,并增加了在宿主无菌位点的StrepA活力,比如血,并且它的缺失导致毒力大大降低。这项工作强调了SLO在StrepA毒力中的重要性,同时强调了StrepA发病机理的复杂性。这种对宿主-病原体相互作用的改进的了解将使人们能够更好地了解宿主免疫逃避机制并为链球菌疫苗开发计划提供信息。
Mutation within the Streptococcus pyogenes (Streptococcus group A; Strep A) covR/S regulatory system has been associated with a hypervirulent phenotype resulting from the upregulation of several virulence factors, including the pore-forming toxin, streptolysin O (
SLO). In this study, we utilized a range of covR/S mutants, including M1T1 clonal strains (5448 and a covS mutant generated through mouse passage designated 5448AP), to investigate the contribution of
SLO to the pathogenesis of covR/S mutant Strep A disease. Up-regulation of
slo in 5448AP resulted in increased
SLO-mediated hemolysis, decreased dendritic cell (DC) viability post coculture with Strep A, and increased production of tumor necrosis factor (TNF) and monocyte chemoattractant protein 1 (MCP-1) by DCs. Mouse passage of an isogenic 5448
slo-deletion mutant resulted in recovery of several covR/S mutants within the 5448Δslo background. Passage also introduced mutations in non-covR/S genes, but these were considered to have no impact on virulence. Although slo-deficient mutants exhibited the characteristic covR/S-controlled virulence factor upregulation, these mutants caused increased DC viability with reduced inflammatory cytokine production by infected DCs. In vivo, slo expression correlated with decreased DC numbers in infected murine skin and significant bacteremia by 3 days postinfection, with severe pathology at the infection site. Conversely, the absence of slo in the infecting strain (covR/S mutant or wild-type) resulted in detection of DCs in the skin and attenuated virulence in a murine model of pyoderma. slo-sufficient and -deficient covR/S mutants were susceptible to immune clearance mediated by a combination vaccine consisting of a conserved M protein peptide and a peptide from the CXC chemokine protease SpyCEP. IMPORTANCE Streptococcus pyogenes is responsible for significant numbers of invasive and noninvasive infections which cause significant morbidity and mortality globally. Strep A isolates with mutations in the covR/S system display greater propensity to cause severe invasive diseases, which are responsible for more than 163,000 deaths each year. This is due to the upregulation of virulence factors, including the pore-forming toxin streptolysin O. Utilizing covR/S and
slo-knockout mutants, we investigated the role of
SLO in virulence. We found that SLO alters interactions with host cell populations and increases Strep A viability at sterile sites of the host, such as the blood, and that its absence results in significantly less virulence. This work underscores the importance of SLO in Strep A virulence while highlighting the complex nature of Strep A pathogenesis. This improved insight into host-pathogen interactions will enable a better understanding of host immune evasion mechanisms and inform streptococcal vaccine development programs.