Mechanisms of Chaperone-Mediated Immune Responses

描述（由申请方提供）：钙网蛋白（CRT）和gp 96（GRP 94）是内质网衍生的分子伴侣，可引发强效和有效的免疫应答，从而抑制和排斥多种肿瘤及其转移。分子伴侣在引发针对鼠肿瘤的免疫应答中的功效已经导致了十几项最近和正在进行的人类临床试验，包括目前的III期方案，以评估分子伴侣诱导的对人类黑色素瘤和肾癌的抑制。因此，拟议研究的广泛目标是了解分子伴侣免疫原性的分子机制，以使这些蛋白质的合理和有效的临床使用。抗原呈递细胞（APC）是分子伴侣介导的抗肿瘤应答所需的，其来源于：1）刺激抗原非依赖性先天免疫应答，包括APC成熟、活化和细胞因子分泌，和2）通过引发针对相关抗原的肽特异性免疫应答来活化适应性免疫系统。目前，分子伴侣引起这些反应的机制知之甚少。所提出的研究的目的是确定分子伴侣引起APC免疫应答的机制。我们将通过研究：1）分子伴侣如何进入APC MHC I类抗原呈递途径？2)分子伴侣是如何作为佐剂发挥作用的？3)A类清道夫受体在介导伴侣诱导的免疫应答中的作用是什么？我们最近发现了清道夫受体SR-A和SREC-1作为gp 96和CRT的内吞受体的新作用：清道夫受体A类（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在此功能中受损。此外，SR-A配体竞争gp 96相关肽的交叉呈递。基于这些发现，我们推测清道夫受体在介导gp 96和CRT刺激的免疫应答中起作用。因此，我们建议阐明清道夫受体介导的伴侣蛋白的免疫学效应的机制。我们将使用细胞和分子技术来确定伴侣复合物引起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。所获得的见解将通过阐明目前正在进行临床评估的治疗的基础而使免疫治疗领域受益。这些认识将有助于这种抗肿瘤治疗的合理开发和应用，以及对分子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.