Retroviral transfer for a chimeric antigen receptor to generate regulatory T-like cells for the suppression of undesired immune responses.

Adoptive transfer of antigen specific regulatory T (Treg) cells was shown to be beneficial for the suppression of autoimmunity and Graft versus Host Disease (GvHD). To create a cellular regimen for the targeted suppression of unwanted immune responses, we engineered mouse MHC-class II specific Treg-like cells. The restricted expression of MHCII to professional antigen presenting cells and presence at high levels at all inflammatory sites, allow the employment of MHCII specific Treg-like cells for suppression in various inflammatory settings. A mouse MHCII-specific Chimeric Antigen Receptor (CAR) was used to redirect the specificity of T cells via retroviral transduction, while Foxp3 gene transfer into purified CD4+ cells leads to the acquisition of the Treg-like phenotype. Incorporation of a suicide mechanism within the engineered Treg-like cells, for their in vivo selective deletion, when desired, will ensure the short-term nature of suppression. The functionality of the generated CAR and the specificity of responses elicited by CAR bearing T cells were validated in vitro. In subsequent preliminary in vivo experiments, intravenous injection of C57BL/6 mice with syngeneic mouse MHCII-specific CD4+ T cells, led to GvHD-like toxicity, while no signs of toxicity were observed when Treg-like cells of the same specificity were transferred alone or in 1:1 mix with mouse MHCII specific CD4+ T cells. These data suggest the suppressive potential of the engineered Treg-like cells.