Exploring the role of staphylococcal superantigens in immune evasion and persistence of Staphylococcus aureus biofilms using humanized mouse models

使用人源化小鼠模型探索葡萄球菌超抗原在金黄色葡萄球菌生物膜免疫逃避和持久性中的作用

• 批准号: 10001860
• 负责人: Govindarajan Rajagopalan
• 金额: $ 25.13万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-05-23 至 2021-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10001860
• 关键词: Acute; Adaptive Immune System; Anti-Bacterial Agents; Antibody Response; Antigen-Presenting Cells; Antigens; Artificial Implants; Binding; Biological; Biological Process; CD4 Positive T Lymphocytes; CD8-Positive T-Lymphocytes; CTLA4 gene; Cancer Model; Catheters; Cells; Chronic; Coupled; Development; Economics; Environment; Exotoxins; Exposure to; Failure; Family; Genus staphylococcus; Growth; HLA-DR3 Antigen; Health; Heart Valves; Helper-Inducer T-Lymphocyte; Histocompatibility Antigens Class II; Human; Immune; Immune Evasion; Immune response; Immune system; Immunoassay; Immunocompetent; Immunology procedure; Immunosuppressive Agents; Impairment; Implant; In Vitro; Infection; Interferon Type II; Interleukin-17; Joint Prosthesis; Kinetics; Knowledge; Lead; Leucocidin; Malignant Neoplasms; Mediating; Microbial Biofilms; Modeling; Molecular; Mus; Myeloid-derived suppressor cells; Natural Immunity; Operative Surgical Procedures; Parasitic infection; Play; Production; Property; Refractory; Regulatory T-Lymphocyte; Reporter; Resistance; Role; SLEB2 gene; Specificity; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus aureus infection; Superantigens; T cell anergy; T-Cell Activation; T-Lymphocyte; Time; Tissues; Toxin; Transgenic Mice; Up-Regulation; Viral; adaptive immune response; adaptive immunity; alpha Toxin; antigen processing; cytokine; exhaustion; humanized mouse; immune activation; implant material; in vivo; inhibiting antibody; innovation; macrophage; monocyte; mouse model; neutrophil; novel; novel therapeutics; prevent; response; therapy resistant; wound

Staphylococcus aureus readily forms biofilms in vivo, whether existing as a colonizer or when causing a spectrum of infections. S. aureus can also easily colonize and tenaciously grow as biofilms on a wide variety implants such as cardiac valves, catheters and prosthetic joints. Staphylococcal biofilms (SB) are refractory to antibacterial therapy, resistant to the host's immune system and hence, persist for long periods of time. Hence, understanding of the mechanisms by which SB evade the host's immune system and persist in vivo is critical. We put forth a novel hypothesis that staphylococcal superantigens (SSAg), a family of potent staphylococcal exotoxins, contributes to the immune evasion and persistence of SB by directly impairing the protective Th1/Th17 adaptive immune responses. SSAg are the most potent activators of the immune system. SSAg bind directly to MHC class II molecules on antigen presenting cells and activate 30-50% of CD4+ and CD8+ T cells irrespective of their antigen specificities. Given the biological properties of SSAg, slow growth of biofilms and the chronicity of SB infections, continued exposure to small amounts of SSAg could potentially cause chronic activation of a wide repertoire of T cells which can lead to their exhaustion, deviation and/or deletion through upregulation of negative costimulatory molecules such as PD-1, LAG-3, TIM-3 and CTLA-4 as shown in other chronic viral, parasitic infections or malignancies. In support of this hypothesis, our recent in vivo studies using wound-associated and catheter-associated biofilm infections have shown that SB do produce SSAgs. However, the kinetics of production of SSAg by SB in vivo and their extent of impact on the adaptive immune system is not fully known. Hence, in Specific Aim 1, we will “Establish the temporal kinetics of production of SSAg by SB in vivo”. Subsequently, in Specific Aim 2, we will “Explore the role of SSAg in immune evasion and persistence of SB in vivo”. These exploratory studies will be conducted using a panel of immunocompetent, immunodeficient and reporter mice transgenically expressing HLA-DR3 using the catheter-associated biofilm infection model. The reasons being, (i) Conventional mice are 1011 times more resistant to SSAg due to poor binding of SSAg to murine compared to human MHC (HLA) class II molecules. Therefore, our humanized mice transgenically expressing HLA-DR3 molecules respond robustly to SSAg. (ii) Catheters are one of the most widely implants and infection of catheters with S. aureus biofilms is very common. Overall, the teleological reasons as to why S. aureus would produce so many different SSAg with similar biological functions have been debated. Given that 80% of staphylococcal infections involve biofilms formation, either on artificial implants or living tissue, and a significant percentage of these isolates produce one or more SSAg, our hypothesis that SSAg may contribute to the growth and survival of staphylococcal biofilms is innovative and the knowledge gained from our study could have a profound impact on treatment/management of SBI and hence, highly significant.

金黄色葡萄球菌容易在体内形成生物膜，无论是作为定植者存在还是当引起细菌感染时， 感染范围。S.金黄色葡萄球菌也可以很容易地定殖和顽强地生长为生物膜上的各种 植入物，如心脏瓣膜、导管和假体关节。葡萄球菌生物膜（SB）是难治性的， 抗细菌治疗，抵抗宿主的免疫系统，因此，持续很长一段时间。因此，我们认为， 了解SB逃避宿主免疫系统并在体内持续存在的机制是至关重要的。 我们提出了一个新的假设，即葡萄球菌超抗原（SSAg），一个强大的葡萄球菌 外毒素通过直接损害保护性Th 1/Th 17细胞， 适应性免疫反应 SSAg是免疫系统最有效的激活剂。SSAg直接与MHC II类分子结合 并激活30-50%的CD 4+和CD 8 + T细胞，而不管它们的抗原 特殊性考虑到SSAg的生物学特性、生物膜的缓慢生长和SB感染的慢性性， 持续暴露于少量SSAg可能会导致广泛的慢性激活， T细胞，其可通过上调负调节因子而导致其耗尽、偏离和/或缺失。 如在其它慢性病毒、寄生虫、真菌和/或真菌中所示，共刺激分子如PD-1、LAG-3、TIM-3和CTLA-4可以是免疫共刺激分子。 感染或恶性肿瘤。为了支持这一假设，我们最近的体内研究使用伤口相关的， 导管相关生物膜感染表明SB确实产生SSAgs。然而， SB在体内产生SSAg及其对适应性免疫系统的影响程度尚不完全清楚。 因此，在具体目标1中，我们将“建立SB体内产生SSAg的时间动力学”。 随后，在具体目标2中，我们将“探索SSAg在免疫逃避和SB持续性中的作用， vivo”。这些探索性研究将使用一组免疫活性、免疫缺陷和 使用导管相关生物膜感染模型转基因表达HLA-DR 3的报告小鼠。的 原因是，（i）由于SSAg与小鼠的结合差，常规小鼠对SSAg的抗性高1011倍。 与人MHC（HLA）II类分子相比，鼠MHC（HLA）II类分子具有更高的活性。因此，我们的人源化小鼠转基因 表达HLA-DR 3分子的人对SSAg有强烈的应答。(ii)导管是最广泛的植入物之一， 以及导管感染S.金黄色葡萄球菌生物膜非常常见。总的来说，S。 金黄色葡萄球菌是否会产生如此多具有相似生物学功能的不同SSAg一直存在争议。鉴于 80%的葡萄球菌感染涉及生物膜的形成，无论是在人工植入物或活组织上， 这些分离株中有很大比例产生一种或多种SSAg，我们假设SSAg可能有助于 葡萄球菌生物膜的生长和存活是创新的，从我们的研究中获得的知识可以 对SBI的治疗/管理具有深远的影响，因此非常重要。