Doctoral candidate University of Delaware University of Delaware College of Arts and Sciences Elkton, Maryland, United States
Background: IgE is the key mediator of allergic immune responses. IgE suppression using omalizumab is highly effective in controlling severe allergic diseases such as severe allergic asthma. The relative short half-life of the antibody-based drug, however, requires frequent administration, leading to high cost and limited applications. Targeting the source of IgE, the IgE-expressing B cells, using adoptive T cell therapy (ACT), represents an attractive alternative approach.
Objective: To redirect T cell specificity to IgE-producing B cells, we designed chimeric antigen receptors (CARs) that recognize the extracellular membrane-proximal domain (EMPD) of membrane IgE (mIgE). mIgE serves as an ideal marker for IgE-expressing B ells since it is expressed exclusively on all IgE-producing B cells at diverse levels. EMPD exists only on mIgE but not on secreted IgE, therefore EMPD-specific CARs cannot be blocked by secreted IgE.
Design/Methods: To generate binders for EMPD, two peptides corresponding to the EMPD region were used to generate four hybridomas that produce EMPD-specific antibodies. Variable regions of four EMPD-specific monoclonal antibodies were cloned from the hybridomas to assemble single chain variable fragments (scFvs) for the construction of second generation CARs containing the 4-1BB costimulatory domain.
Results: EMPD-specific CARs were efficiently expressed on the surface of primary human T cells through lentiviral transduction. One of the CARs, 2E3E10, was shown to mediate potent cytotoxicity and INFγ production in response to U266 cells and Daudi cells expressing mIgE. The responses to U266 cells are especially encouraging since the cells express very low levels of mIgE. Conclusion(s): Our study demonstrates the proof of concept for using T cells expressing EMPD-specific CARs to eliminate IgE-expressing B cells. The rapid advances in the efficacy and safety of ACT should facilitate the development of CAR T cell immunotherapy for severe allergic diseases. Taking advantage of the ability of CAR T cells to persist and continuously eliminate IgE-expressing B cells, the approach may relieve symptoms for an extended period of time with a single treatment.
Authors/Institutions: Brittany L. Fay, Nemours/A.I. duPont Hospital for Children, Wilmington, Delaware, United States; Karen M. Christie, University of Delaware College of Arts and Sciences, Newark, Delaware, United States; Zhengyu Ma, Nemours/A.I. duPont Hospital for Children, Wilmington, Delaware, United States
