Mechanisms of Chaperone-Mediated Immune Responses

描述（由申请人提供）：钙网蛋白（CRT）和gp96 （GRP94）是内质网衍生的分子伴侣，可引发强效免疫反应，导致多种肿瘤及其转移的抑制和排斥。伴侣蛋白在引发针对小鼠肿瘤的免疫反应方面的功效已经导致了十多个近期和正在进行的人体临床试验，包括目前评估伴侣蛋白诱导的人类黑色素瘤和肾癌抑制的ii期方案。因此，本研究的总体目标是了解伴侣蛋白免疫原性的分子机制，以便合理有效地在临床使用这些蛋白。抗原呈递细胞（APCs）是伴侣介导的抗肿瘤反应所必需的，其来源包括：1)刺激抗原非依赖性先天免疫反应，包括APC的成熟、激活和细胞因子的分泌；2)通过诱导针对相关抗原的肽特异性免疫反应激活适应性免疫系统。目前，伴侣引发这些反应的机制尚不清楚。提出的研究的目的是确定伴侣引起APC免疫反应的机制。我们将通过研究：1)伴侣蛋白如何进入APC MHC 1类抗原呈递途径？2)伴侣蛋白作为佐剂是如何起作用的？3)清道夫受体a类在介导伴侣诱导的免疫应答中的作用是什么？我们最近发现了清扫剂受体SR-A和srec1作为gp96和CRT的内吞受体的新作用：清扫剂受体a类（SR-A）的表达足以赋予伴侣蛋白摄取，而SR-AV的巨噬细胞和树突状细胞在这一功能中受损。此外，SR-A配体竞争gp96相关肽的交叉呈递。基于这些发现，我们假设清道夫受体在介导gp96和CRT刺激的免疫反应中起作用。因此，我们建议阐明清道夫受体介导伴侣免疫作用的机制。我们将使用细胞和分子技术来确定伴侣复合物引发抗原特异性反应的机制，并使用遗传和免疫学技术来评估清除受体对伴侣介导的抗原呈递的贡献。通过阐明目前正在进行临床评估的一种治疗方法的基础，所获得的见解将有益于免疫治疗领域。这些发现将有助于这种抗肿瘤疗法的合理开发和应用，以及对伴侣蛋白作为免疫分子的认识。

DESCRIPTION (provided by applicant): Calreticulin (CRT) and gp96 (GRP94) are endoplasmic reticulum-derived molecular chaperones that elicit potent and effective immune responses that lead to the inhibition and rejection of a variety of tumors and their metastases. The efficacy of chaperones in eliciting immune responses against murine tumors has led to more than a dozen recent and ongoing human clinical trials, including current phase-Ill protocols to evaluate chaperone-induced suppression of human melanoma and renal carcinoma. Therefore, the broad goal of the proposed research is to understand molecular mechanisms of chaperone immunogenicity to enable rational and effective clinical use of these proteins. Antigen-presenting cells (APCs) are required for chaperone-mediated anti-tumor responses, which derive from: 1) stimulation of antigen-independent innate immune responses including APC maturation, activation and cytokine secretion, and 2) activation of the adaptive immune system by eliciting peptide- specific immune responses against associated antigens. At present, the mechanisms by which chaperones elicit these responses are poorly understood. The objective of the proposed studies is to define the mechanisms by which chaperones elicit immune responses from APC. We will do so by investigating: 1) How do chaperones access the APC MHC class-l antigen presentation pathway? 2) How do chaperones function as adjuvants? 3) What is the contribution of Scavenger Receptor Class-A in mediating chaperone-elicited immune responses? We recently identified a novel role for the scavenger receptors SR-A and SREC-1 as endocytic receptors of both gp96 and CRT: expression of Scavenger Receptor Class-A (SR-A) was sufficient to confer chaperone uptake, while SR-AV" macrophages and dendritic cells were impaired in this function. Moreover, SR-A ligands competed for cross-presentation of gp96-associated peptides. On the basis of these findings, we hypothesize that scavenger receptors function in mediating the immune responses stimulated by gp96 and CRT. Thus, we propose to elucidate the mechanisms by which scavenger receptors mediate the immunological effects of chaperones. We will use cellular and molecular techniques to identify the mechanisms by which chaperone complexes elicit antigen-specific responses, and genetic and immunological techniques to evaluate the contribution of scavenger receptors towards chaperone-mediated antigen presentation. Insights obtained will benefit the field of immunotherapy by elucidating the basis of a treatment that is currently undergoing clinical evaluation. These insights will facilitate the rational development and application of this anti-tumor therapy, and the understanding of chaperones as immunological molecules.