Engineered ovalbumin-expressing regulatory T cells protect from chicken egg white-induced allergy in vivo

Abstract

Abstract Allergy is a major public health concern, the main treatment for which is symptomatic relief with anti-inflammatory drugs. A key clinical challenge is to induce specific tolerance in order to control allergen-specific memory B and T cells. Our lab recently developed antigen-specific regulatory T cell therapies as a treatment for adverse responses in hemophilia (Kim et al. BLOOD 125: 1107, 2015; Yoon et al. BLOOD 129: 238–245, 2017). In this report, we created a chimeric antigen receptor (CAR) approach in which we engineered the target protein antigen, ovalbumin (OVA), linked with the transmembrane and signal transduction domains, CD28-CD3ζ to directly target B cells to induce tolerance in an allergy model. We named this receptor “BAR” for B-cell Antibody Receptor. Murine Tregs, retrovirally transduced with a BAR containing OVA or control cells, were successfully expanded in vitro and tested in a standard murine OVA-alum allergy model with high titered circulating anti-OVA IgE antibodies. We first confirmed that intravenously injected OVA-BAR Tregs did not directly lead to temperature drops indicative of anaphylaxis. Forty eight hours later, mice were challenged intraperitoneally with 200μg of OVA to induce an anaphylactic reaction, and temperature taken immediately again after challenge for 30 minutes. Our results demonstrated that OVA-BAR Tregs protected mice from hypothermia, whereas the control BARs or PBS-treated mice showed temperature drops indicative of anaphylaxis. These results were repeated and confirmed using human Tregs (CD4+CD25hiCD127low) transduced and expanded and injected into mice. These data provide proof of principle that engineered OVA-BAR Tregs may be useful to treat IgE based allergies.