MHC class I trafficking signal improves induction of cytotoxic T lymphocyte using artificial antigen presenting cells.

Inducing antigen peptide-specific cytotoxic T cells is challenging, partly due to the difficulty of maintaining the quality of antigen-presenting cells, such as dendritic cells. Consequently, artificial antigen-presenting cells (aAPCs) derived from the erythroleukemia cell line K562 have been employed for T cell stimulation. K562-based aAPCs can be utilized for both non-specific and antigen-specific T cell stimulation. Antigen peptide-pulsed aAPCs are commonly used to stimulate T cells with known specific antigenic peptides, which require identifying antigenic peptides from cognate antigen proteins. Therefore, antigen gene-overexpressing aAPCs might be useful for detecting unknown antigenic peptides. In this study, we evaluated the efficacy of cytotoxic T lymphocyte (CTL) induction using antigen gene-overexpressing aAPCs. To enhance antigen presentation efficiency, we assessed the signal peptide (SP) fused with MHC class I trafficking signal (MITD) sequences (SP-MITD). SP-MITD, fused with epitopes from the neoantigen AKF9 and the viral antigen CMVpp65, was transduced into aAPCs. We compared the CTL induction ability of peptide-pulsed aAPCs, only mini-gene-overexpressing aAPCs [SP-MITD (-)], and mini-gene fused with SP-MITD overexpressing aAPCs [SP-MITD (+)]. The SP-MITD (+) gene-overexpressing aAPCs exhibited the highest CTL induction efficiency compared to both peptide-pulsed and SP-MITD (-) gene-overexpressing aAPCs. These findings suggest that antigen gene-fused with SP-MITD transduced aAPCs are highly effective for inducing CTLs specific to both known and unknown antigenic peptides.