Developmental Immunotherapeutics of Allergic Diseases

嗜酸性胃肠道疾病(EGID)是以胃肠道嗜酸性炎症为特征的一系列疾病。在过去的十年中，EGID的发病率急剧增加，尤其是嗜酸性食管炎(EE)。EGID包括嗜酸性胃肠炎(EG)和EE，通常与食物和空气过敏原过敏有关。大多数EGID患者有许多食物过敏，在许多患者中，以氨基酸为基础的元素饮食是一种有效的治疗方法。这表明EGID的发病机制是由于食物过敏原引起的嗜酸性炎症。 目前，我们对EGID的认识和有效治疗的能力存在重大差距。为了解决治疗和发病机制方面的问题，我们最近完成了一项治疗嗜酸性胃肠炎的临床试验。这项研究提出了两个主要问题： 1.抗IgE疗法对嗜酸性胃肠道疾病有临床疗效吗？ 2.EGID的嗜酸性炎症特征是否是IgE依赖的过程？ 对9例EGIDs患者进行了奥马珠单抗的临床试验，其中9例EGIDs患者每2周接受一次奥马珠单抗治疗，疗程为16周，其他治疗保持不变。连续测定血中嗜酸粒细胞绝对计数、组织嗜酸性粒细胞计数、症状评分和游离IgE。在基线和第16周检测变应原皮肤试验、流式细胞仪检测嗜碱性粒细胞活化和FC949；RI。在第16周(34%，p=0.004)和联合第12-16周(42%，p=0.012)时间点，奥马珠单抗与嗜酸性粒细胞绝对计数的减少有关。十二指肠(59%)和胃窦(69%)组织中嗜酸性粒细胞减少，但差异无统计学意义(p=0.074和0.098)。食道嗜酸性粒细胞计数保持不变。嗜碱性粒细胞和树突状细胞Fc-RI表达和游离Ig E均显著降低(p&lt；0.005)。奥马珠单抗将触发一半最大嗜碱性粒细胞激活所需的过敏原浓度增加170倍。变应原皮肤测试风疹和红斑反应分别减少78%和82%。症状评分在研究中期(63%)和研究结束(70%)时间点均降低(P&lt；0.005)。这些结果表明，IgE介导的过程有助于EGIDs嗜酸性炎症的产生，并提示抗IgE治疗可能对这些疾病有效。 奥马珠单抗是一种人源化的抗IgE单抗，被批准用于过敏性哮喘。抗IgE治疗可降低循环中游离IgE的浓度，阻断IgE与Fc和CD23的结合，下调肥大细胞、嗜碱性粒细胞和树突状细胞表面Fc的表达。由于抗-IgE治疗对抗原提呈细胞(APC)的多种作用，推测抗-IgE治疗可能对T细胞具有免疫调节作用。我们假设了两种不同的机制，即抗IgE治疗可以抑制过敏原特异性Th2反应。首先，抗-IgE下调树突状细胞表面的Fc&RI，并阻断CD23介导的过敏原与APC的结合，从而抑制IgE促进APC捕获抗原，进而导致过敏原特异性T细胞活化减少。第二，抗IgE的IgE信号在体内抑制肥大细胞和嗜碱性粒细胞的激活，从而降低IL-4的表达，而IL-4的缺失可能会抑制NAVE T细胞向Th2细胞的分化。为了验证这一假设，我们在上述临床试验中评估了奥马珠单抗对嗜酸性胃肠炎和食物过敏受试者过敏原特异性T细胞反应的抗IgE免疫调节作用。用流式细胞术检测四种变应原特异性T细胞反应(增殖、剂量反应、前体频率和细胞因子表达)。与假设相反，我们发现16周的抗IgE治疗对过敏原特异性增殖、前体频率或细胞因子产生没有影响，并产生了过敏原剂量反应的小幅增加(而不是减少)。总之，我们没有发现证据支持抗IgE治疗对过敏原特异性T细胞有免疫调节或抑制作用的概念。因此，这些数据不支持IgE介导的Ag聚焦在体内增强变应原特异性T细胞反应中的主要作用。

Eosinophilic gastrointestinal diseases (EGIDs) are a spectrum of diseases characterized by eosinophilic inflammation of the gastrointestinal tract. In the past decade, there has been a dramatic increase in the incidence of EGIDs, particularly eosinophilic esophagitis (EE). EGIDs, including eosinophilic gastroenteritis (EG) and EE, are commonly associated with food and aeroallergen hypersensitivity. Most EGID patients have numerous food allergies, and in many patients an amino acid based elemental diet is an effective treatment. This suggests that EGID pathogenesis is due to food allergen driven eosinophilic inflammation. At present, there are major gaps in our understanding of, and ability to effectively treat EGIDs. To address both treatment and pathogenesis questions, we have recently completed a clinical trial of omalizumab (therapeutic monoclonal anti-IgE) for eosinophilic gastroenteritis. This study asks two major questions: 1. Are anti-IgE therapeutics of clinical utility in eosinophilic gastrointestinal diseases? 2. Is the eosinophilic inflammation characteristic of EGIDs an IgE dependent process? A clinical trial of omalizumab was performed in which 9 subjects with EGIDs received omalizumab every 2 weeks for 16 weeks while other therapy was held constant. Blood absolute eosinophil counts, tissue eosinophil counts, symptom scores, and free IgE were serially measured. Allergen skin testing, and flow cytometry for basophil activation and Fc&#949;RI were determined at baseline and at week 16. Omalizumab was associated with a decrease in absolute eosinophil counts at both the 16 week (34%, p=0.004) and combined weeks 12-16 (42%, p=0.012) time points. Tissue eosinophils decreased in the duodenum (59%) and gastric antrum (69%), but did not reach statistical significance (p=0.074 and 0.098, respectively). Esophageal eosinophil counts remained unchanged. Basophil and dendritic cell Fc&#949;RI expression, and free IgE were all significantly decreased (p<0.005). Omalizumab increased the concentration of allergen required to trigger half-maximal basophil activation by 170-fold. Allergen skin test wheal and erythema responses decreased by 78% and 82%, respectively. Symptom scores were decreased at both the midstudy (63%) and end of study (70%) time points (p<0.005 for both). These results demonstrate that IgE-mediated processes contribute to the generation of eosinophilic inflammation in EGIDs, and suggest that anti-IgE therapy may be effective in these disorders. Omalizumab is a humanized anti-IgE monoclonal antibody approved for use in allergic asthma. Anti-IgE therapy reduces the concentration of circulating free IgE, blocks IgE binding to both Fc&#949;RI and CD23, and down regulates surface Fc&#949;RI on mast cells, basophils and dendritic cells. Because of the multiple actions of anti-IgE therapy that affect antigen presenting cells (APCs), it has been postulated that anti-IgE therapy may have immunomodulatory activity on T cells. We hypothesized two distinct mechanisms whereby anti-IgE therapy could inhibit allergen specific Th2 responses. First, anti-IgE down regulates Fc&#949;RI on dendritic cells and blocks CD23 mediated allergen binding to APCs, thereby inhibiting IgE facilitated Ag capture by APCs, which in turn could result in decreased allergen specific T cell activation. Second, IgE signaling of anti-IgE inhibits mast cell and basophil activation in vivo, which may decrease IL-4 expression, the lack of which could inhibit nave T cell differentiation into Th2 cells. To test this hypothesis, we assessed anti-IgE immunomodulation of allergen specific T cell responses during the above clinical trial of omalizumab in subjects with eosinophilic gastroenteritis and food allergy. Four allergen specific T cell responses (proliferation, dose response, precursor frequency, and cytokine expression) were measured using flow cytometry. In contradistinction to the hypothesis, we found that 16 weeks of anti-IgE therapy had no effect on allergen specific proliferation, precursor frequencies, or cytokine production, and yielded a small augmentation (not reduction) of the allergen dose response. In sum, we found no evidence to support the concept that anti-IgE therapy has an immunomodulatory or inhibitory effect on allergen specific T cells. As such, these data do not support a major role for IgE mediated Ag focusing in augmenting allergen specific T cell responses in vivo.