(PQC4) Imaging CD8 T Cells In Tumor Immunotherapy By Immunopet

描述(申请人提供)：除恶性细胞外，肿瘤还包括各种类型的细胞，包括间质、血管和浸润性免疫细胞。了解这些其他细胞成分的身份、数量和状态，对于了解肿瘤的生物学及其对治疗的反应显然很重要，如NCI挑衅性问题C4所述。最近，免疫调节疗法和过继细胞疗法已被确定为癌症的有效治疗方法，这提高了能够直接监测肿瘤内免疫反应的迫切需求。正电子发射断层成像(PET)提供了高灵敏度、非侵入性和定量的成像，它可以与基于抗体的探针相结合，根据细胞表面的表型提供体内组织和细胞的分子成像。此外，工程抗体片段(如环二亚基；单链抗体片段的共价二聚体)的产生具有最佳的动力学，使免疫PET能够快速体内靶向和清除成像应用。在这项拟议的工作中，将开发使用识别CD8的工程抗体片段的免疫PET，CD8是细胞毒性T细胞上的经典细胞表面标记，以解决直接成像肿瘤免疫细胞亚群的挑战。具体目标1将侧重于显像剂生物惰性的需要，并将在体外和体内评估用抗CD8胞质抗体处理T细胞的生物学效应(激活、细胞因子释放)。特殊目的2将使用放射性标记的抗CD8细胞抗体用于免疫PET评估正常小鼠和用抗CD137抗体等免疫刺激剂治疗的荷瘤小鼠的免疫活性。具体目标3将侧重于免疫PET检测和定量检测用抗体(如抗PD-1和抗CTLA-4)逆转免疫抑制(如抗PD-1和抗CTLA-4)并通过细胞毒性T细胞诱导肿瘤浸润的荷瘤小鼠中CD8+T细胞的数量。这些研究将验证CD8+T细胞的免疫PET探针在研究体内对癌症免疫治疗的反应方面的作用，提供对生物体内免疫反应的更深入了解，并将为临床前模型以及最终人类的免疫细胞亚群成像和定量的广泛方法打开大门。

DESCRIPTION (provided by applicant): Tumors are comprised of a variety of cell types in addition to the malignant cells, including stroma, vasculature, and infiltrating immune cells. An understanding of the identities, numbers, and states of these other cellular components is clearly important to understanding the biology of tumors, and their responses to therapy, as outlined in the NCI Provocative Question C4. Recently, immune-modulatory therapies and adoptive cell therapies have become established as powerful therapeutic approaches in cancer, raising a critical need to be able to monitor immune responses directly within tumors. Positron emission tomography (PET) provides highly sensitive, non-invasive and quantitative imaging, which can be combined with antibody-based probes to provide molecular imaging of tissues and cells in vivo based on cell surface phenotype. Furthermore, engineered antibody fragments (such as cys-diabodies; covalent dimers of single-chain antibody fragments) have been generated with optimal kinetics enabling rapid in vivo targeting and clearance for imaging applications by immunoPET. In the proposed work, immunoPET using engineered antibody fragments that recognize CD8, a classic cell surface marker on cytotoxic T cells, will be developed to address the challenge of direct imaging of immune cell subsets in tumors. Specific Aim 1 will focus on the need for imaging agents to be biologically inert, and will assess biological effects (activation, cytokine release) of treating T cells with anti- CD8 cys-diabodies,in vitro and in vivo. Specific Aim 2 will employ radiolabeled anti-CD8 cys-diabodies for immunoPET assessment of immune activation in normal mice and tumor-bearing mice treated with immune stimulants such as anti-CD137 antibodies. Specific Aim 3 will focus on immunoPET detection and quantification of CD8+T cells in tumor-bearing mice treated with antibodies that reverse immunosuppression (such as anti-PD-1 and anti-CTLA-4) and induce tumor infiltration by cytotoxic T cells. These studies will validate the role of immunoPET probes for CD8+ T cells to study responses to cancer immunotherapy in vivo, provide a deeper understanding of immune responses in living organisms, and will open the door to broad methods for imaging and quantitating immune cell subsets in preclinical models and eventually humans.