FLT3-LIGAND, IMMUNOMODULATION AND THERAPY IN ASTHMA

描述(由申请人提供)：在哮喘患者中，2型T淋巴细胞特征与过敏性呼吸道炎症之间存在直接联系。预防对过敏原的2型反应的一种策略是抑制抗原提呈细胞(APC)向T细胞发送的促过敏信号。肺中最强大的APC是树突状细胞(DC)，最近的研究发现这一群体中存在表型变异，这可以强烈地极化发育中的T细胞。Flt3配体(FL)是树突状细胞的生长因子，可诱导1型T细胞应答。我们最近报道，FL可预防卵蛋白诱导的小鼠过敏性呼吸道炎症，并抑制迟发型过敏反应(LAR)和气道高反应性(AHR)。在这些研究的基础上，我们提出了FL对哮喘宿主具有治疗活性的假设，即FL通过扩增DC1细胞，产生IL-12，并诱导1型T细胞反应，抑制在哮喘中起重要作用的2型T细胞刺激，从而对哮喘宿主具有治疗活性。在特定的目标1中，我们将在过敏性呼吸道炎症的小鼠模型中检测FL逆转LAR、AHR和嗜酸性粒细胞增多的能力，并增强抗原特异性的1型T细胞对激发的过敏原的反应。我们将确定FL治疗活性的剂量反应和作用持续时间。我们还将检查FL对哮喘的临床相关因素的影响，包括致敏但未被过敏原激发的小鼠的基线AHR。此外，我们将通过系统(脾)和区域(纵隔淋巴结和胶原酶消化的肺)ELISPOT分析来检查血清和肺冲洗液中抗过敏原和细胞因子水平的水平和同种类型，以及非抗原和抗原特异性的1型和2型T细胞反应。在曼氏血吸虫致过敏性呼吸道炎症模型中，FL的非特异性治疗作用将被考察。在特定的目标2中，我们将研究FL逆转与慢性哮喘相关的气道重塑的能力。我们将研究FL逆转组织病理变化的能力，包括气管和支气管上皮厚度和亚上皮纤维化，测定促纤维化细胞因子和趋化因子，并检测平滑肌增生。在具体目标3中，我们将研究FL对急、慢性哮喘的治疗作用机制。我们将测定FL对野生型和IL-12基因敲除(KO)小鼠的治疗活性。由于KO小鼠可能具有预先存在的代偿机制，我们还将进行研究，以检验FL在过敏性呼吸道炎症期间给予IL-12中和抗体的动物的治疗活性。

DESCRIPTION (provided by applicant): There is a direct association between type 2 T-lymphocyte profiles and allergic airway inflammation in asthma. One strategy for preventing type 2 responses to an allergen is to suppress the pro-allergic signals that antigen presenting cells (APCs) send to T-cells. The most potent APCs in the lung are dendritic cells (DCs), and recent studies have revealed phenotypic variability in this population, which can strongly polarize the developing T cells. FLT3 Ligand (FL) is a growth factor for DCs, and induces a type 1 T-cell response. We recently reported that FL prevented ovalbumin-induced allergic airway inflammation in mice and suppressed late allergic response (LAR) and airway hyperresponsiveness (AHR). Based on these studies, we developed the hypothesis that FL has therapeutic activity for hosts with asthma by the expansion of DC1 cells, production of IL-12 and induction of a type 1 T cell response that inhibits type 2 T-cell stimulation important in asthma. In Specific Aim 1, we will examine the ability of FL to reverse LAR, AHR, and eosinophilia in a mouse model of allergic airway inflammation and augment an antigen-specific, type 1T cell response to the inciting allergen. We will determine the dose-response for FL therapeutic activity and duration of effect. We will also examine the effect of FL on clinical correlates of asthma including baseline AHR in mice sensitized, but not challenged with the allergen. Further, we will examine the levels and isotype of antibodies to the allergen and cytokine levels in serum and lung washings, in addition to non-antigen and antigen-specific type 1 and 2 T cell responses by Elispot assays both systemically (spleen) and regionally (mediastinal lymph nodes and collagenase digested lungs). Non-specific therapeutic effect of FL will be examined in Schistoma mansoni-induced allergic airway inflammation model. In Specific Aim 2, we will investigate the ability of FL to reverse the airway remodeling associated with chronic asthma. We will study the ability of FL to reverse the histopathologic changes, including tracheal and bronchial epithelial thickness and sub-epithelial fibrosis, measure pro-fibrotic cytokines and chemokines and examine smooth muscle hyperplasia. In Specific Aim 3, we will study the mechanisms of FL therapeutic activity for acute and chronic asthma. We will determine the therapeutic activity of FL in wild type and IL-12( knock-out (KO) mice. As KO mice may have pre-existing compensatory mechanisms, we will also undertake studies examining the therapeutic activity of FL in animals given neutralizing antibodies to IL-12 during allergic airway inflammation.