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，可引发强效且有效的免疫反应，从而抑制和排斥多种肿瘤及其转移。伴侣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项最近和正在进行的人体临床试验，包括当前用于评估伴侣诱导的人类黑色素瘤和肾癌抑制的三期方案。因此，拟议研究的总体目标是了解伴侣免疫原性的分子机制，以便合理有效地临床使用这些蛋白质。分子伴侣介导的抗肿瘤反应需要抗原呈递细胞 (APC)，其源自：1) 刺激抗原独立的先天免疫反应，包括 APC 成熟、激活和细胞因子分泌，2) 通过引发针对相关抗原的肽特异性免疫反应来激活适应性免疫系统。目前，人们对伴侣引发这些反应的机制知之甚少。拟议研究的目的是确定伴侣引发 APC 免疫反应的机制。我们将通过研究以下内容来做到这一点：1) 伴侣如何访问 APC MHC I 类抗原呈递途径？ 2）分子伴侣如何发挥佐剂作用？ 3) A 类清道夫受体在介导分子伴侣引发的免疫反应中有何贡献？我们最近发现清道夫受体 SR-A 和 SREC-1 作为 gp96 和 CRT 的内吞受体的新作用：A 类清道夫受体 (SR-A) 的表达足以赋予伴侣摄取，而 SR-AV" 巨噬细胞和树突状细胞的此功能受损。此外，SR-A 配体竞争 gp96 相关肽的交叉呈递。研究结果表明，清道夫受体在介导 gp96 和 CRT 刺激的免疫反应中发挥作用，因此，我们建议阐明清道夫受体介导伴侣的免疫作用的机制，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道夫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治疗的基础，这些见解将有利于免疫治疗领域，这些见解将促进这种抗肿瘤治疗的合理开发和应用，以及对伴侣作为免疫分子的理解。

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.