CD8+ T-Cell Density Imaging with 64Cu-Labeled Cys-Diabody Informs Immunotherapy Protocols

Abstract

Noninvasive and quantitative tracking of CD8 T cells by PET has emerged as a potential technique to gauge response to immunotherapy. We apply an anti-CD8 cys-diabody, labeled with Cu, to assess the sensitivity of PET imaging of normal and diseased tissue. Radiolabeling of an anti-CD8 cys-diabody (169cDb) with Cu was developed. The accumulation ofCu-169cDb was evaluated with PET/CT imaging (0, 5, and 24 hours) and biodistribution (24 hours) in wild-type mouse strains ( = 8/group studied with imaging and IHC or flow cytometry) after intravenous administration. Tumor-infiltrating CD8 T cells in tumor-bearing mice treated with CpG and αPD-1 were quantified and mapped ( = 6-8/group studied with imaging and IHC or flow cytometry). We demonstrate the ability of immunoPET to detect small differences in CD8 T-cell distribution between mouse strains and across lymphoid tissues, including the intestinal tract of normal mice. In FVB mice bearing a syngeneic -driven model of mammary adenocarcinoma (NDL),Cu-169cDb PET imaging accurately visualized and quantified changes in tumor-infiltrating CD8 T cells in response to immunotherapy. A reduction in the circulation time of the imaging probe followed the development of treatment-related liver and splenic hypertrophy and provided an indication of off-target effects associated with immunotherapy protocols. Cu-169cDb imaging can spatially map the distribution of CD8 T cells in normal organs and tumors. ImmunoPET imaging of tumor-infiltrating cytotoxic CD8 T cells detected changes in T-cell density resulting from adjuvant and checkpoint immunotherapy protocols in our preclinical evaluation. .

Monitoring CD8a+ T Cell Responses to Radiotherapy and CTLA-4 Blockade Using [64Cu]NOTA-CD8a PET Imaging

“…This is owing to the fact that clinical responses to PD-1/PD-L1 immune checkpoint inhibitors arise most often in patients with high preexisting numbers and/or infiltration of CD8 + cells during therapy [11][12][13][14]. Molecular imaging probes targeting CD8 + have indeed been pursued in preclinical studies primarily utilizing engineered antibody fragments [15][16][17][18] and successfully demonstrated the value of CD8 + PET imaging for evaluation of immunotherapeutic response [16][17][18].…”

Molecular imaging reveals biodistribution of P-cadherin LP-DART bispecific and trafficking of adoptively transferred T cells in mouse xenograft model

“…Additionally, since optical imaging has not yet been adopted as a non-invasive modality in clinic, its application is limited to mechanistic studies in pre-clinical models. It will be interesting to evaluate the trafficking of T cells using newer, potentially translational, PET imaging based immuno-oncology biomarkers like IL-2, Granzyme B and CD8-minibody [30][31][32][33]. In summary, using FMT imaging we have shown the targeting of P-cadherin LP-DART (Pillar 1 and 2) and the trafficking of T cells (Pillar 3) to the tumor microenvironment in pre-clinical models.…”

CAR T cells for brain tumors: Lessons learned and road ahead

“…64 Cu) for visualizing cell‐antigen‐specific targeting with PET. This approach has been most commonly used for cancer cell detection and has been more recently applied to the tracking of endogenous T cells or cells with engineered antigen tags . To reduce signal background and circumvent issues with BBB permeability, these antibodies could be used for ex vivo pre‐labeling of cells to study initial trafficking as long as the antibody stays cell‐associated and radionuclide half‐life is permissible.…”

“…238,239 Recently adopted for PET, 240 we imaged 89 Zr-oxine-labeled CAR T cells in both subcutaneous prostate and intracranial glioma models. 205 more recently applied to the tracking of endogenous T cells 242,243 or cells with engineered antigen tags. 244,245 To reduce signal background and circumvent issues with BBB permeability, these antibodies could be used for ex vivo pre-labeling of cells to study initial trafficking 246 as long as the antibody stays cell-associated and radionuclide half-life is permissible.…”