Dataset Information

ImmunoPET imaging of human CD8⁺ T cells with novel ⁶⁸Ga-labeled nanobody companion diagnostic agents.

ABSTRACT:

Background

Although immunotherapy has revolutionized treatment strategies for some types of cancers, most patients failed to respond or obtain long-term benefit. Tumor-infiltrating CD8⁺ T lymphocytes are closely related to the treatment outcome and prognosis of patients. Therefore, noninvasive elucidation of both systemic and tumor-infiltrating CD8⁺ T lymphocytes is of extraordinary significance for patients during cancer immunotherapy. Herein, a panel of ⁶⁸Ga-labeled Nanobodies were designed and investigated to track human CD8⁺ T cells in vivo through immuno-positron emission tomography (immunoPET).

Results

Among the screened Nanobodies, SNA006a showed the highest binding affinity and specificity to both human CD8 protein and CD8⁺ cells in vitro, with the equilibrium dissociation constant (K_D) of 6.4?×?10^-10 M and 4.6?×?10^-10 M, respectively. ⁶⁸Ga-NOTA-SNA006 was obtained with high radiochemical yield and purity, and stayed stable for at least 1 h both in vitro and in vivo. Biodistribution and Micro-PET/CT imaging studies revealed that all tracers specifically concentrated in the CD8⁺ tumors with low accumulation in CD8^- tumors and normal organs except the kidneys, where the tracer was excreted and reabsorbed. Notably, the high uptake of ⁶⁸Ga-NOTA-SNA006a in CD8⁺ tumors was rapid and persistent, which reached 24.41?±?1.00% ID/g at 1.5 h after intravenous injection, resulting in excellent target-to-background ratios (TBRs). More specifically, the tumor-to-muscle, tumor-to-liver, and CD8⁺ to CD8^- tumor was 28.10?±?3.68, 5.26?±?0.86, and 19.58?±?2.70 at 1.5 h, respectively. Furthermore, in the humanized PBMC-NSG and HSC-NPG mouse models, ⁶⁸Ga-NOTA-SNA006a accumulated in both CD8⁺ tumors and specific tissues such as liver, spleen and lung where human CD8 antigen was overexpressed or CD8⁺ T cells located during immunoPET imaging.

Conclusions

⁶⁸Ga-NOTA-SNA006a, a novel Nanobody tracer targeting human CD8 antigen, was developed with high radiochemical purity and high affinity. Compared with other candidates, the long retention time, low background, excellent TBRs of ⁶⁸Ga-NOTA-SNA006a make it precisely track the human CD8⁺ T cells in mice models, showing great potential for immunotherapy monitoring and efficacy evaluation.

SUBMITTER: Zhao H

PROVIDER: S-EPMC7871532 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Publications

ImmunoPET imaging of human CD8<sup>+</sup> T cells with novel <sup>68</sup>Ga-labeled nanobody companion diagnostic agents.

Zhao Haitao H Wang Chao C Yang Yanling Y Sun Yan Y Wei Weijun W Wang Cheng C Wan Liangrong L Zhu Cheng C Li Lianghua L Huang Gang G Liu Jianjun J

Journal of nanobiotechnology 20210209 1

<h4>Background</h4>Although immunotherapy has revolutionized treatment strategies for some types of cancers, most patients failed to respond or obtain long-term benefit. Tumor-infiltrating CD8<sup>+</sup> T lymphocytes are closely related to the treatment outcome and prognosis of patients. Therefore, noninvasive elucidation of both systemic and tumor-infiltrating CD8<sup>+</sup> T lymphocytes is of extraordinary significance for patients during cancer immunotherapy. Herein, a panel of <sup>68</s ...[more]

PMID: 33563286

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Project description:BackgroundCD70-CD27 is a costimulatory ligand-receptor pair in the tumor necrosis factor receptor family. With only limited expression in normal tissues, CD70 is constitutively expressed in a variety of solid tumors and hematologic malignancies, facilitating immunosuppression through CD27 signaling in the tumor microenvironment by enhanced survival of regulatory T cells, induction of T cell apoptosis, and T cell exhaustion. Consequently, CD70 is an increasingly recognized target for developing antibody-based therapies, but its expression patterns vary among different tumor types in spatial distribution, magnitude of expression and percentage of positive cells. In that regard, individual confirmation of CD70 expression at screening and during treatment could enhance the successful implementation of anti-CD70 therapies. Here, we developed a gallium-68 (68Ga) radiolabeled single-domain antibody-fragment targeting CD70 for in vivo positron emission tomography (PET) imaging.ResultsAn anti-CD70 VHH construct containing a C-direct-tag with a free thiol was developed to enable site-specific conjugation to a NOTA bifunctional chelator for 68Ga radiolabeling. [68Ga]Ga-NOTA-anti-CD70 VHH was obtained in good radiochemical yield of 30.4 ± 1.7% and high radiochemical purity (> 94%). The radiolabeled VHH showed excellent in vitro and in vivo stability. Specific binding of [68Ga]Ga-NOTA-anti-CD70 VHH was observed on CD70high 786-O cells, showing significantly higher cell-associated activity when compared to the blocking condition (p < 0.0001) and CD70low NCl-H1975 cells (p < 0.0001). PET imaging showed specific radiotracer accumulation in CD70 expressing human tumor xenografts, which was efficiently blocked by prior injection of unlabeled anti-CD70 VHH (p = 0.0029). In addition, radiotracer uptake in CD70high tumors was significantly higher when compared with CD70low tumors (p < 0.0001). The distribution of the radioactivity in the tumors using autoradiography was spatially matched with immunohistochemistry analysis of CD70 expression.Conclusion[68Ga]Ga-NOTA-anti-CD70 VHH showed excellent in vivo targeting of CD70 in human cancer xenografts. PET imaging using this radioimmunoconjugate holds promise as a non-invasive method to identify and longitudinally follow-up patients who will benefit most from anti-CD70 therapies.

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Project description:IntroductionThe yield per elution of a 68Ge/68Ga generator decreases during its lifespan. This affects the number of patients injected per elution or the injected dose per patient, thereby negatively affecting the cost of examinations and the quality of PET images due to increased image noise. We aimed to investigate whether AI-based PET denoising can offset this decrease in image quality parameters.MethodsAll patients addressed to our PET unit for a 68Ga-DOTATOC PET/CT from April 2020 to February 2021 were enrolled. Forty-four patients underwent their PET scans according to Protocol_FixedDose (150 MBq) and 32 according to Protocol_WeightDose (1.5 MBq/kg). Protocol_WeightDose examinations were processed using the Subtle PET software (Protocol_WeightDoseAI). Liver and vascular SUV mean were recorded as well as SUVmax, SUVmean and metabolic tumour volume (MTV) of the most intense tumoural lesion and its background SUVmean. Liver and vascular coefficients of variation (CV), tumour-to-background and tumour-to-liver ratios were calculated.ResultsThe mean injected dose of 2.1 (0.4) MBq/kg per patient was significantly higher in the Protocol_FixedDose group as compared to 1.5 (0.1) MBq/kg for the Protocol_WeightDose group. Protocol_WeightDose led to noisier images than Protocol_FixedDose with higher CVs for liver (15.57% ± 4.32 vs. 13.04% ± 3.51, p = 0.018) and blood-pool (28.67% ± 8.65 vs. 22.25% ± 10.37, p = 0.0003). Protocol_WeightDoseAI led to less noisy images than Protocol_WeightDose with lower liver CVs (11.42% ± 3.05 vs. 15.57% ± 4.32, p < 0.0001) and vascular CVs (16.62% ± 6.40 vs. 28.67% ± 8.65, p < 0.0001). Tumour-to-background and tumour-to-liver ratios were lower for protocol_WeightDoseAI: 6.78 ± 3.49 vs. 7.57 ± 4.73 (p = 0.01) and 5.96 ± 5.43 vs. 6.77 ± 6.19 (p < 0.0001), respectively. MTVs were higher after denoising whereas tumour SUVmax were lower: the mean% differences in MTV and SUVmax were + 11.14% (95% CI = 4.84-17.43) and -3.92% (95% CI = -6.25 to -1.59).ConclusionThe degradation of PET image quality due to a reduction in injected dose at the end of the 68Ge/68Ga generator lifespan can be effectively counterbalanced by using AI-based PET denoising.

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Dataset Information

ImmunoPET imaging of human CD8⁺ T cells with novel ⁶⁸Ga-labeled nanobody companion diagnostic agents.

Background

Results

Conclusions

Publications

ImmunoPET imaging of human CD8<sup>+</sup> T cells with novel <sup>68</sup>Ga-labeled nanobody companion diagnostic agents.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Dataset Information

ImmunoPET imaging of human CD8+ T cells with novel 68Ga-labeled nanobody companion diagnostic agents.

Background

Results

Conclusions

Publications

ImmunoPET imaging of human CD8<sup>+</sup> T cells with novel <sup>68</sup>Ga-labeled nanobody companion diagnostic agents.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

ImmunoPET imaging of human CD8⁺ T cells with novel ⁶⁸Ga-labeled nanobody companion diagnostic agents.