Mechanisms of Chaperone-Mediated Immune Responses

说明(申请人提供)：钙网状蛋白(CRT)和gp96(GRP94)是内质网衍生的分子伴侣蛋白，可诱导强大而有效的免疫反应，从而抑制和排斥各种肿瘤及其转移。伴侣在诱导抗小鼠肿瘤免疫反应方面的有效性已导致最近和正在进行的十几项人类临床试验，包括目前评估伴侣诱导的抑制人类黑色素瘤和肾癌的Ill期方案。因此，这项研究的主要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上使用这些蛋白。抗原提呈细胞(APC)是伴侣蛋白介导的抗肿瘤反应所必需的，其来源包括：1)刺激抗原非依赖性的先天免疫反应，包括APC的成熟、激活和细胞因子的分泌；2)通过激发针对相关抗原的多肽特异性免疫反应来激活适应性免疫系统。目前，人们对伴侣引起这些反应的机制知之甚少。本研究的目的是明确伴侣蛋白诱导APC免疫反应的机制。我们将通过研究：1)伴侣如何进入APC MHC类-L抗原提呈途径？2)伴侣如何作为佐剂发挥作用？3)清道夫A类受体在介导伴侣诱导的免疫反应中有何贡献？我们最近发现了清道夫受体SR-A和SREC-1作为gp96和CRT的内源性受体的一个新的作用：清道夫受体A类(SR-A)的表达足以提供伴侣的摄取，而SR-AV的巨噬细胞和树突状细胞在这一功能中受到损害。此外，SR-A配体竞争gp96相关多肽的交叉呈递。在这些发现的基础上，我们假设清道夫受体在介导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蛋白免疫效应的机制。我们将使用细胞和分子技术来确定伴侣蛋白复合体诱导抗原特异性反应的机制，并使用遗传学和免疫学技术来评估清道夫受体在伴侣蛋白介导的抗原提呈中的作用。通过阐明目前正在进行临床评估的治疗方法的基础，所获得的见解将有益于免疫治疗领域。这些认识将有助于合理开发和应用这种抗肿瘤治疗方法，并有助于理解伴侣作为免疫分子的作用。

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.