Abstract 1612: Production of CD3+ cells using ferrofluids for cell isolation, activation, expansion and subsequent transfection for adoptive cell therapy
Authors: Ritter Dustin W. , Khristov Todor R. , Liberti Paul A. 
Published: July 2017

Abstract
The purpose of the study is to demonstrate whether magnetic nanoparticles functionalized with monoclonal antibodies in conjunction with solution-phase monoclonal antibodies can be used to activate T cells for expansion in vitro. The activation, expansion and transfection/transduction of immune cells—particularly T cells—has become an area of significant interest based on encouraging data generated from employing such genetically modified cells for cancer immunotherapies. The promise of soon being able to cure various types of cancers has resulted from years of methodical experimentation in the fields of oncology, immunology, and genetics, as well as the development of a vast array of enabling technological advances. BioMagnetic Solutions has developed colloidal magnetic nanoparticles—referred to as ferrofluids—which can be used to isolate a cell population through an immunomagnetic separation. These ferrofluids comprise a crystalline core of magnetite (ca. 100 nm in diameter) coated with multilayers of clinical-grade human serum albumin and further functionalized with a clinical-grade rat anti-mouse IgG1 monoclonal antibody. These “common-capture ferrofluids” (ca. 130 nm in diameter) are capable of binding cells which have been labeled with a monoclonal mouse IgG1 antibody; for example, CD3+ cells can be readily isolated from a complex cell mixture by labeling with a monoclonal mouse anti-human CD3 antibody, adding common-capture ferrofluid, and subjecting the sample to a magnetic field gradient. This technology can therefore be employed at the clinical scale to isolate T cells from an apheresis product. In this study, we investigated whether T cells isolated using common-capture ferrofluids could subsequently be activated and induced to expand in vitro. Based on preliminary experiments showing that T cell-bound common-capture ferrofluid has excess antibody-binding capacity, we designed experiments to test the hypothesis that solution-phase CD28 could be added to isolated T cells, which would bind to both CD28 determinants on the cell surface as well as to the cell-bound common-capture ferrofluid. Activation was quantified by measuring CD25 expression after four days in culture and expansion was monitored over 15 days. Following an immunomagnetic separation of CD3+ cells, magnetically isolated cells were re-suspended in expansion medium (STEMCELL) supplemented with 100 IU/mL IL-2 (Gibco) to a total concentration of 106 cells/mL and incubated at 37 °C. The following day, 0.5 µg/mL mouse anti-human CD28 monoclonal antibody (Mabtech) was added, and thereafter, cells were periodically agitated and diluted to 106 cells/mL with expansion media. After four days in culture, 88.4% of cells expressed CD25, while a 311-fold expansion was observed after 15 days. In summary, we have demonstrated that common-capture ferrofluids can be used to activate T cells for expansion in vitro.
Citation Format: Dustin W. Ritter, Todor R. Khristov, Paul A. Liberti. Production of CD3+ cells using ferrofluids for cell isolation, activation, expansion and subsequent transfection for adoptive cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1612. doi:10.1158/1538-7445.AM2017-1612