Cellular Multispectral Optoacoustic Tomography (MSOT) for therapy monitoring of adoptively transferred T-Lymphocytes

• Applicants: Professor Dr. Reinhard Meier; Professor Dr. Christian Plank
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology ; Medical Physics, Biomedical Technology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 277842002

The adoptive T-cell transfer is a promising approach for the treatment of patients with malignant tumors or infectious diseases. Antigen-specific cytotoxic T lymphocytes (CTLs) have been identified as potent effectors that are responsible for eliminating viruses, such as cytomegalovirus (CMV) or Epstein-Barr virus (EBV), and for mediating tumor regression, e.g., in Hodgkins disease or metastatic melanoma. The advent of new T cell-based therapies requires the quantitative and qualitative assessment of firstly the T-cell migration to the target and secondly their distribution in the organism. The immunological monitoring of patients treated with adoptively transferred T cells can be achieved by flow cytometry with major histocompatibility (MHC)/peptide multimers and by molecular methods in order to detect the T-cell receptors and the introduced marker genes, respectively. These methods can be applied to track T cells in vivo, e.g., in the peripheral blood, the lymph nodes, and the tumor sites. However, these techniques do not allow the direct in vivo tracking of CTLs, but require blood samples or tissue biopsies. The ideal immunomonitoring method for the in vivo determination of both T-cell trafficking and therapeutic effectiveness should be a non-invasive and non-toxic procedure. However, no technology available widely in the clinic provides functional molecular imaging data, crucial for accurate tracking and monitoring of biodistribution. This can be enabled by the use of optical methods with carefully chosen and tailored contrast agents. A recent evolution called multispectral optoacoustic tomography system (MSOT)(shows promising performance in mapping and identifying different photoabsorbers in real time in a living animal, using unmixing technique for spectral identification, enabling molecular and functional imaging while simultaneously gathering anatomical data thanks to the specific absorbance spectra of hemoglobin, oxygenated hemoglobin and fat notably. This led to new insights in the behavior and biodistribution of photoabsorbers such as the FDA approved fluorophore ICG, dPGS based fluorophores or nanoparticles like gold nanostructures. The aim of this project is the evaluation of MSOT as imaging modality for therapy monitoring of cell-based immunotherapy in vivo. Cytotoxic T-lymphocytes will be labeled with fluorophores and gold nanoparticles and visualized in a murine tumor model using MSOT. Furthermore, T-cell specific antibodies will be conjugated to gold nanoparticles, and these will be tested as contrast agent after T-cell transfer in vivo. The survival of the transferred cells and the specific accumulation of these cells in the tumor tissue will be histologically verified, and the influence of the different contrast agents to the function of T-lymphocytes will be analyzed.

• DFG Programme: Research Grants
• Co-Investigators: Dr. Melanie Kimm; Professorin Dr. Kathrin Lang; Professor Dr. Vasilis Ntziachristos