Antibody and fragment-based PET imaging of CTLA-4+ T-cells in humanized mouse models

American Journal of Cancer Research

Peng Huang¹  Christopher D Zahm²  Emily B Ehlerding³  Jonathan W Engle⁴  Dawei Jiang⁵  Carolina A Ferreira⁶  Hye Jin Lee⁷ 

[1] Carbone Cancer Center, University of Wisconsin-Madison, Madison, WI 53705, USA;Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53705, USA;Department of Medical Physics, University of Wisconsin-Madison, Madison, WI 53705, USA;Department of Medicine, University of Wisconsin-Madison, Madison, WI 53705, USA;Department of Radiology, University of Wisconsin-Madison, Madison, WI 53705, USA;Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Laboratory of Evolutionary Theranostics, School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, China;Pharmaceutical Sciences Department, University of Wisconsin-Madison, Madison, WI 53705, USA

关键词: Cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4);    positron emission tomography (PET);    ipilimumab;    humanized mice;    checkpoint immunotherapy;    64Cu;    antibody fragment;   

DOI  :  

学科分类：肿瘤学

来源: e-Century Publishing Corporation

【 摘 要 】

Imaging of immunotherapy targets using positron emission tomography (PET) can allow for noninvasive monitoring of their dynamic expression and may allow for patient stratification in the future. Therefore, two tracers targeting CTLA-4, one a full antibody and the other a F(ab’)2 fragment, were radiolabeled with 64Cu and validated in humanized mouse models. Ipilimumab was digested to develop ipilimumab-F(ab’)2, and both the intact antibody and the fragment were conjugated with NOTA to chelate 64Cu for PET. The tracers were administered to both control NBSGW mice and humanized mice (PBL mice, engrafted with human peripheral blood lymphocytes), and PET was conducted out to 48 h post-injection. PET region-of-interest analysis, ex vivo biodistribution studies, and tissue staining were used to confirm that the tracers specifically accumulated in CTLA-4+ tissues. Following injection of tracers (n = 3-5 per group), specific uptake was noted in the salivary gland tissues of the humanized mice. This uptake, a result of graft-versus-host disease onset, was proven to be due to human T-cells through staining of the tissues for human CD3 and CTLA-4. 64Cu-NOTA-ipilimumab demonstrated the highest absolute uptake in the salivary glands of PBL mice, peaking at 7.00 ± 2.19 %ID/g. In contrast, 64Cu-NOTA-ipilimumab-F(ab’)2 uptake was 2.40 ± 0.86 %ID/g at the same time point. However, the F(ab’)2 agent cleared from circulation more quickly than the intact antibody, providing higher salivary gland-to-blood ratios, which reached 1.78 ± 0.72 at 48 h post-injection, compared to 64Cu-NOTA-ipilimumab at 1.19 ± 0.49. Uptake of the tracers in the salivary glands of control mice, and the nonspecific tracer in the PBL mice, was lower at all time points as well. PET imaging with both 64Cu-NOTA-ipilimumab and 64Cu-NOTA-ipilimumab-F(ab’)2 was able to localize CTLA-4+ tissues. These tracers may thus help elucidate the mechanisms of response to CTLA-4-targeted checkpoint immunotherapy treatments.

【 授权许可】

CC BY-NC