IgE is the key mediator of allergic responses.
Omalizumab, an
IgE-specific
monoclonal antibody that depletes
IgE, is effective for treating severe allergic
asthma. The need for frequent administration of the expensive
drug, however, limits its applications. Taking advantage of T cell memory, adoptive T cell
therapy (ACT) targeting
IgE-producing cells has the potential to achieve long-term suppression of
IgE and relief of symptoms for severe allergic diseases. The transmembrane form of
IgE (mIgE), which is present on all
IgE-producing cells, serves as an excellent molecular target for ACT that employs
chimeric antigen receptors (CARs). Here, we designed and tested CARs that use the extracellular domain of high affinity
IgE receptor, FcεRIα, for mIgE recognition. When expressed on Jurkat T cells, FcεRIα-based CARs mediated robust responses in terms of CD69 upregulation to U266 myeloma cells expressing low levels of mIgE. FcεRIα-based CARs specifically recognized cells expressing mIgE, but not cells with secreted
IgE captured through Fcε receptors. CAR+ Jurkat cells did not respond to
LAD2 mast cells with secreted
IgE bound through FcεRI or Ramos cells with secreted
IgE bound through FcεRII. Co-culture of CAR+ Jurkat cells and
LAD2 mast cells with
IgE bound did not trigger
LAD2 cell degranulation. The activity of CAR using wild type FcεRIα for mIgE binding was inhibited by the presence secreted
IgE, which likely blocked CAR-mIgE interaction. The activities of CARs using low affinity mutants of FcεRIα, however, tolerated secreted
IgE at relatively high concentrations. Moreover, primary human CD8+ T cells expressing a low affinity mutant CAR responded to U266 cells with INFγ production and cytotoxicity despite the presence of secreted
IgE. The potency, specificity, and robustness of our CAR design, combined with repaid advances in the safety of ACT, hold promise for novel and highly effective cell-based
therapies against severe allergic diseases.