Activation of Antigen-Specific Cytotoxic T Lymphocytes by β2-Microglobulin or TAP1 Gene Disruption and the Introduction of Recipient-Matched MHC Class I Gene in Allogeneic Embryonic Stem Cell-Derived Dendritic Cells

Abstract

A method for the genetic modification of dendritic cells (DC) was previously established based on the in vitro differentiation of embryonic stem (ES) cells to DC (ES-DC). The unavailability of human ES cells genetically identical to the patients will be a problem in the future clinical application of this technology. This study attempted to establish a strategy to overcome this issue. The TAP1 or β2-microglobulin (β2m) gene was disrupted in 129 (H-2b)-derived ES cells and then expression vectors for the H-2Kd or β2m-linked form of Kd (β2m-Kd) were introduced, thus resulting in two types of genetically engineered ES-DC, TAP1−/−/Kd ES-DC and β2m−/−/β2m-Kd ES-DC. As intended, both of the transfectant ES-DC expressed Kd but not the intrinsic H-2b haplotype-derived MHC class I. β2m−/−/β2m-Kd and TAP1−/−/Kd ES-DC were not recognized by pre-activated H-2b-reactive CTL and did not prime H-2b reactive CTL in vitro or in vivo. β2m−/−/β2m-Kd ES-DC and TAP1−/−/Kd ES-DC had a survival advantage in comparison to β2m+/−/β2m-Kd ES-DC and TAP1+/+/Kd ES-DC, when transferred into BALB/c mice. Kd-restricted RSV-M2-derived peptide-loaded ES-DC could prime the epitope-specific CTL upon injection into the BALB/c mice, irrespective of the cell surface expression of intrinsic H-2b haplotype-encoded MHC class I. β2m−/−/β2m-Kd ES-DC were significantly more efficient in eliciting immunity against RSV M2 protein-expressing tumor cells than β2m+/−/β2m-Kd ES-DC. The modification of the β2m or TAP gene may therefore be an effective strategy to resolve the problem of HLA class I allele mismatch between human ES or induced pluripotent stem cells and the recipients to be treated.