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

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 β 2 -microglobulin (β 2 m) gene was disrupted in 129 (H-2 b )-derived ES cells and then expression vectors for the H-2K d or β 2 m-linked form of K d (β2m-K d ) were introduced, thus resulting in two types of genetically engineered ES-DC, TAP1 −/− /K d ES-DC and β 2 m −/− /β 2 m-K d ES-DC. As intended, both of the transfectant ES-DC expressed K d but not the intrinsic H-2 b haplotype-derived MHC class I. β 2 m −/− /β 2 m-K d and TAP1 −/− /K d ES-DC were not recognized by pre-activated H-2 b -reactive CTL and did not prime H-2 b reactive CTL in vitro or in vivo. β 2 m −/− /β 2 m-K d ES-DC and TAP1 −/− /K d ES-DC had a survival advantage in comparison to β 2 m +/− /β 2 m-K d ES-DC and TAP1 +/+ /K d ES-DC, when transferred into BALB/c mice. K d -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-2 b haplotype-encoded MHC class I. β 2 m −/− /β 2 m-K d ES-DC were significantly more efficient in eliciting immunity against RSV M2 protein-expressing tumor cells than β 2 m +/− /β 2 m-K d ES-DC. The modification of the β 2 m 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.