Monitoring immune cells-mediated cytolysis through impedance technology allows kinetic analysis of reagent efficacy
Leyna Zhao, Fabio Cerignoli, Biao Xi, Garret Guenther, Lincoln Muir, Brandon Lamarche, Yama Abassi ACEA Biosciences Inc, San Diego, CA
In vitro characterization of immunotherapy reagents efficacy and combination synergies is necessary before moving to expensive animal models and clinical studies. However, current standard assays like Chromium-51 release, ATP-based luminescence cell monitoring or flow cytometry are difficult to implement in a high throughput environment and are based on end point methodologies that are unable to capture the full dynamic of the immune response. Here we validate an impedance-based platform for monitoring cytotoxic activity of immune cells in the context of cancer immunotherapy assays. The technology detects cell death and proliferation of adherent cells by measuring changes in conductance of microelectrodes embedded in 96 and 384-wells cell culture plates, without the use of labeling or cell modification. We present a large set of validation including CD19 Car T models, EpCAM/CD3 BiTE antibodies and checkpoint combination therapies with anti PD-1/PD-L1 and CTLA-4 antibodies. Data comparison with Annexin V staining/Flow Cytometry shows perfect correlation between the drop in impedance signal and % of apoptotic cells. Long time monitoring (> 7 days) in combination with low effector:target ratios reveal the occurrence of resistance mechanisms in target cells and exhaustion in effector cells. Such dynamic response has been observed in animal models and patient clinical trials, but it is difficult to monitor in short time assays. Overall, our results demonstrate the value of such label-free approach in measuring the cytotoxic response across the temporal scale, an aspect that is otherwise very difficult to assess with more canonical end point assays but that is highly relevant when testing combinations. Thanks to the availability of 384-wells format and minimal sample handling, the technology is also ideally suited for applications in large reagent validation screening or therapeutic protocol validation directly on patient samples.
Credits: None available.
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