Mechanisms of enhanced food allergy by S. aureus skin colonization in Atopic Dermatitis

摘要 AD患者的皮肤通常由产生超抗原(SAG)的金黄色葡萄球菌菌株定植，主要是 葡萄球菌肠毒素B(SEB)。金黄色葡萄球菌皮肤定植与 AD中的食物过敏。这种关联的机制尚不清楚。我们已经观察到 皮下应用卵清蛋白(OVA)和产生SAG的金黄色葡萄球菌，或OVA和SEB，导致 与EC单独应用OVA相比，选择性地夸大OVA口服激发的过敏反应。 此外，在小鼠被动口服BSA-TNP时，会导致夸大的全身过敏反应。 用IgE抗TNP致敏，表明食物过敏反应的增强是非抗原特异性的和 由IgE抗体水平或亲和力差异以外的因素决定。我们建议仔细分析一下 SEB增强IgE介导的口腔过敏反应。 初步数据显示，OVA+SEB增加了小鼠EC对口服过敏反应的敏感性 与血清IL-4水平升高有关，依赖于肠上皮细胞IL-4和IL-4R的表达 细胞(IECs)，并伴有肠通透性(IP)增加。增强的敏感性被以下因素抑制 Divertin，一种小分子，通过旁细胞途径抑制肠道对抗原的吸收 阻断肌球蛋白轻链激酶(MLCK)募集到连接周围的放线肌球蛋白环，在那里它 破坏上皮性紧密连接。这表明MLCK在食物过敏中起着关键作用。此外，数据显示， EC应用SEB会导致大量嗜碱性粒细胞涌入皮肤引流淋巴结(DLN)，这是 依赖于CD40来源的角质形成细胞(KC)来源的IL-33和T细胞。招募的嗜碱性粒细胞增强了这种能力 皮肤DLN中的树突状细胞(DC)驱动Th2极化。IL-4对体外培养树突状细胞的保护作用 提升了他们驱动Th2极化的能力。 我们建议检验这一假设，即定植于AD皮肤的金黄色葡萄球菌SEB与KCs上的CD40结合 并触发caspase 8介导的生物活性IL-33的切割和释放，从而诱导T细胞释放IL-3 导致嗜碱性粒细胞在DLN中的招募。嗜碱性粒细胞来源的IL-4促进Th2极化能力 捕获了皮肤中遇到的抗原的DC。这些事件促使Th2的系统性水平上升。 衍生的IL-4。IECS中IL-4信号的增加与MCs释放的介质协同促进MLCK 通过引起紧密连接蛋白的重新分布来依赖屏障损失。由此产生的抗原增加 吸收触发MC激活的正向放大周期，从而夸大对以下食物的过敏反应 病人已经被致敏了。 提出的研究将确定金黄色葡萄球菌皮肤定植加重食物的机制。 并将揭示MLCK在这种疾病中的核心作用。它们可能会导致食物过敏的新疗法 这将针对金黄色葡萄球菌的皮肤定植，皮肤中的CD40，IL-33和MLCK。

Abstract The skin of AD patients is often colonized by S. aureus strains that produce superantigens (SAg), primarily staphylococcal enterotoxin B (SEB). There is a positive association between S. aureus skin colonization and food allergy in AD. The mechanism of this association is unknown. We have made the observation that epicutaneous (EC) application of ovalbumin (OVA) and SAg producer S. aureus, or OVA and SEB, results in the selective exaggeration of anaphylaxis to oral challenge with OVA compared to EC application of OVA alone. Moreover, it results in exaggerated systemic anaphylaxis to oral challenge with BSA-TNP in mice passively sensitized with IgE anti-TNP, indicating that the enhancement of food anaphylaxis was non-antigen-specific and determined by factors beyond differences in IgE Ab levels or affinity. We propose to dissect the mechanisms of SEB enhancement of IgE mediated oral anaphylaxis. Preliminary data show that enhanced susceptibility to oral anaphylaxis in mice EC exposed to OVA+SEB is associated with elevated levels of serum IL-4, dependent on IL-4 and IL-4R expression by intestinal epithelial cells (IECs),and accompanied by increased intestinal permeability (IP). Enhanced susceptibility is inhibited by Divertin, a small molecule that suppresses intestinal absorption of antigen via the paracellular pathway by blocking the recruitment of myosin light chain kinase (MLCK) to the peri-junctional actinomyosin ring, where it disrupts epithelial tight junctions. This suggests a critical role for MLCK in food allergy. In addition, the data show that EC application of SEB causes a massive influx of basophils in skin-draining lymph nodes (dLNs) that was dependent on CD40 keratinocyte (KC)-derived IL-33, and T cells. The recruited basophils enhanced the ability of dendritic cells (DCs) from skin dLNs to drive Th2 polarization. Pretreatment of DCs in vitro with IL-4 also promoted their capacity to drive Th2 polarization. We propose to test the hypothesis that SEB from S. aureus that colonizes AD skin binds to CD40 on KCs and triggers caspase 8 mediated cleavage and release of bioactive IL-33 which induces IL-3 release by T cells leading to recruitment of basophils in dLNs. There, basophil-derived IL-4 promotes the Th2 polarizing ability of DCs that have captured antigen encountered in the skin. These events drive a rise in systemic levels of Th2 derived IL-4. Increased IL-4 signaling in IECs synergizes with mediators released by MCs to promote MLCK dependent barrier loss by causing redistribution of tight junction proteins. The resulting increased antigen absorption triggers a forward amplification cycle of MC activation that exaggerates allergy to foods against which the patient has been sensitized. The studies proposed will define the mechanisms by which S. aureus skin colonization aggravates food allergy and will uncover a central role of MLCK in this disease. They may lead to novel therapies for food allergy that would target S. aureus skin colonization, CD40 in skin, IL-33 and MLCK.