Non-invasive in vivo imaging of the mode and sites of action of tumor associated antigen-specific T cells (SFB 685 – Project B6)
We develop T cell labeling protocols that allow monitoring T cell homing patterns non-invasively in vivo by combined positron emission tomography (PET) and computed tomography (CT) or optical imaging (OI). PET/CT and OI unraveled unexpected homing patterns of tumor associated antigen (TAA) specific T cells, depending on the mode of T cell administration, which subsequently determines the treatment efficiency of solid tumors. As a next step, we will elucidate the homing kinetics and mode and sites of action of therapeutic TAA T cells in T cell based immunotherapy of cancer.
Analysis of the impact of reactive oxygen species and NF-kB signaling during hapten-induced acute and chronic skin inflammation (CRC156 – Project C3)
The crosstalk of ROS and NF-κB signaling in inflammatory immune responses of the skin is still poorly understood. Thus, we aim to analyze how the temporal dynamics of ROS-induction translate into the activation of the canonical (p50) and non-canonical (p52) NF-κB signaling pathway. We will measure ROS generation and NF-κB activation non-invasively in vivo in mice with hapten-induced acute and chronic contact hypersensitivity reaction. Subsequently, we will focus on identifying the important ROS components, the cellular sources of ROS, differently regulated ROS target genes and will analyse the impact of ROS-induced NF-κB activation on leukocyte homing. Based on our preliminary data we postulate that ROS-induced NF-κB regulation is crucial for either termination or chronification of T cell driven inflammatory skin diseases, also in patients.
Amplifying CD4+ T cell driven tumor antigen (TA) specific anti-tumoral therapy with immune-checkpoint blocking antibodies for efficient treatment of mice with progressed pancreatic cancer
TA-specific IFN-y secreting CD4+ T cells (Th1) mediate strong anti-tumoral effects in mice and humans and can induce senescence in cancer cells in a TNF and IFN-y dependent manner (Braumüller et al. Nature 2013). Immune and tumor cells express inhibitory immune checkpoint (ICP) ligands (e.g. programmed death ligand 1 (PD-L1) and lymphocyte activation gene 3 (LAG-3)) that paralyze tumor infiltrating T cells. ICP-blockade by specific antibodies such as PD-L1 and LAG-3 can restore T cell functions. We establish a novel highly efficient TA-Th1 cell and checkpoint inhibitor-based combined immunotherapy (CIT) in RIP1-Tag2 mice with advanced endogenous pancreatic insular cell carcinomas where ICP-blockade alone is not sufficient.
Therapy response monitoring of a checkpoint inhibitor-based immunotherapy in mice with progressed pancreatic cancer with 18F-FDG-PET/MRI
Both malignant cells as well as immune cells express inhibitory receptor-ligand pairs inhibiting anti-tumoral T cells functions. Blockade of these inhibitory receptor-ligands such as lymphocyte activation gene 3 (LAG-3) and programmed death ligand 1 (PD-L1) with specific antibodies is applicable to restore T cell functions. We monitor tumor progression by 7 T MRI and glucose metabolism as an indicator of T cell activation in the spleen and lymph nodes in RIP1-Tag2 mice with advanced endogenous pancreatic insular cell carcinomas with 18F-FDG-PET/MRI. 18F-FDG-PET/MRI enables us to monitor enhanced T cell activity in the spleen of PD-L1 and LAG-3 treated RIP1-Tag2 mice. Thus, 18F-FDG PET imaging of T cell activation might enable us to distinguish checkpoint inhibitor therapy responders from non-responders in the clinical setting.
Administration route-specific homing of TH1 cells modulates the host immune system, tumor microenvironment, and antitumoral efficiency during immunotherapy in pancreatic cancer
Cancer treatment with adoptively transferred tumor-associated-antigen-specific CD4+-T helper cells is a promising immunotherapeutic approach. We found that the administration route of therapeutic TH1 cells is an important issue affecting the efficiency of the immunotherapy. I.v. transferred tumor-antigen specific TH1 cells were more efficient in inducing tumor senescence than i.p. transferred TH1 cells despite fundamentally different migration patterns and no initial homing to the tumor side. Both administration routes modulated the host immune system systemically and the tumor microenvironment. Thus, especially for the clinical application of cellular immunotherapies, administration route-specific effects must be considered to achieve the greatest therapeutic efficiency.
Positron Emission Tomography (PET)-based cell tracking with a Cre-switchable sr39tk PET reporter mouse line
Tracking single cells or cell populations in vivo under healthy or diseased conditions is a central approach in biomedical research. Stable integration of reporter transgenes into the target genome is a powerful strategy to label cells, especially for longitudinal imaging studies. In this context, site-specific recombinases (e.g., Cre or ligand-inducible CreERT2) are key tools to induce reporter gene expression in a given cell type and also in a time-dependent manner. However, this approach has not yet been realized for reporter genes detectable through PET. Such a reporter gene is sr39tk, an engineered thymidine kinase from Herpes simplex virus that is used with PET tracers like [18F]FHBG. Our cooperation partners (Institute of Biochemistry – Prof. Robert Feil & Dr. Martin Thunemann) generated and characterized a transgenic mouse line that allows flexible labeling of different cell types for PET-based cell tracking by activating sr39tk expression in a Cre-dependent manner.
Analysis of the role of Cathepsin B: An important player during the effector phase of acute cutaneous delayed-type hypersensitivity reactions
Cysteine-type cathepsins such as cathepsin B are involved in various steps of inflammatory processes. We uncover the role of cysteine-type cathepsins in the effector phase of cutaneous delayed-type hypersensitivity reactions (DTHR) and its implication for therapeutic cathepsin B specific inhibition by in vivo optical imaging and the activity of cathepsin B ex vivo by active site labeling. We will quantify the cathepsin B expressing leucocytes in the inflamed tissue and draining lymph nodes and will topically apply the specific cathepsin B inhibitor CA-074 and the selective p38 MAPK inhibitor LN950. As cathepsin B might be actively involved during DTHR, cathepsin B inhibitors might effectively limiting DTHR such as contact dermatitis or psoriasis.
Non-invasive in vivo monitoring of hypoxia in inflammation using small animal Positron Emission Tomography
Hypoxia and the expression of hypoxia-inducible factore-1α (HIF-1α) are essential for the development of autoimmune diseases such as rheumatoid arthritis (RA). Hypoxia is frequently associated with the expression of reactive oxygen species (ROS). The aim of this study is to demonstrate the feasibility of measuring hypoxia non-invasively in vivo in arthritic ankles with positron emission tomography (PET)/magnetic resonance imaging (MRI) using the hypoxia tracers [18F]fluoromisonidazole (FMISO) and [18F]fluoroazomycinarabinosid (FAZA). Additionally, we will focus on differences in the temporal dynamics of hypoxia and ROS stress using L-012, which is a ROS-sensitive chemiluminescence optical imaging (OI) probe.
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