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

描述（由申请人提供）：肿瘤由除恶性细胞外的多种细胞类型组成，包括基质、脉管系统和浸润性免疫细胞。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性细胞疗法已成为癌症中强大的治疗方法，这就迫切需要能够直接监测肿瘤内的免疫反应。正电子发射断层扫描（PET）提供高灵敏度、非侵入性和定量成像，其可与基于抗体的探针组合以基于细胞表面表型提供体内组织和细胞的分子成像。此外，工程化抗体片段（例如cys-双抗体;单链抗体片段的共价二聚体）已经以最佳动力学产生，使得能够通过免疫PET进行快速体内靶向和清除以用于成像应用。在拟议的工作中，将开发使用识别CD 8（细胞毒性T细胞上的经典细胞表面标志物）的工程抗体片段的免疫PET，以解决直接成像肿瘤中免疫细胞亚群的挑战。具体目标1将集中于成像剂为生物惰性的需要，并将评估体外和体内用抗CD 8 cys-双抗体处理T细胞的生物效应（活化、细胞因子释放）。Specific Aim 2将采用放射性标记的抗CD 8 cys-双抗体，对正常小鼠和经免疫刺激剂（如抗CD 137抗体）处理的荷瘤小鼠的免疫激活进行免疫PET评估。具体目标3将重点关注用逆转免疫抑制（如抗PD-1和抗CTLA-4）并诱导细胞毒性T细胞肿瘤浸润的抗体治疗的荷瘤小鼠中CD 8 +T细胞的免疫PET检测和定量。这些研究将验证CD 8 + T细胞的免疫PET探针在体内研究癌症免疫治疗反应中的作用，提供对活生物体免疫反应的更深入了解，并将为临床前模型和最终人类免疫细胞亚群的成像和定量方法打开大门。

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.