Masashi Gotoh

Development of HLA-A2402/Kb transgenic mice

HLA‐transgenic mice have been developed to facilitate studies of HLA‐restricted cytotoxic responses, e.g., for the identification of immunodominant HLA‐restricted CTL epitopes and the optimization of peptide or DNA vaccine constructs for human use. We have developed HLA‐A2402/Kb‐transgenic mice expressing chimeric human (α1 and α2 domains of HLA‐A2402) and mouse (α3, transmembrane and cytoplasmic domains of H‐2Kb) class I molecules. Immunization of these HLA‐A2402/Kb‐transgenic mice with various known HLA‐A24‐restricted immunodominant cancer CTL epitope peptides derived from gp100, MAGE‐1, MAGE‐3, Her2/neu, CEA and TERT induced HLA‐A24‐restricted, peptide‐specific CTLs. Using these transgenic mice, we identified a novel HLA‐A24‐restricted CTL epitope, PSA152–160, encoded by human prostate‐specific antigen. Staining with HLA tetramers showed that the cytotoxic activity induced by immunizing with PSA152–160 in HLA‐A2402/Kb transgenic mice was HLA‐A2402‐restricted and CD8‐dependent. Therefore, PSA152–160 might be a candidate peptide for vaccination of HLA‐A24+ patients with prostate cancer. Our results suggest that HLA‐A2402/Kb transgenic mice might be useful in the search for HLA‐A24‐restricted CTL epitopes functioning as human cancer antigens and for the development of peptide‐based cancer immunotherapy.

Sequence Analysis of Genes Encoding Rodent Homologues of the Human Tumor‐rejection Antigen SART‐1

Human SART‐1 (hSART‐1) gene encodes a 125 kD protein with a leucine‐zipper motif expressed in the nucleus of all proliferating cells, and a 43 kD protein expressed in the cytosol of most epithelial cancers. In this study, two rodent genes (rSART‐1 and mSART‐1) homologous to hSART‐1 were cloned from cDNA libraries of murine brain and a rat tumor cell line, respectively. mSART‐1 and rSART‐1 were highly homologous to hSART‐1 with 86% and 84% identity at the nucleotide level, and 95% and 91% at the protein level, respectively. The leucine zipper domain and two basic amino acid portions that bind DNA, as well as peptide sequences recognized by human cyto‐toxic T lymphocytes (CTLs), were all conserved in these rodent genes. Nuclear protein homologous to the 125 kD hSART‐1800 protein, but not to the 43 kD cytosol SART‐1259 protein, was detectable with specific antibody in the nuclear fractions of rodent tumor cell lines, and normal rodent fetal liver and testis. These rodent genes should be a novel tool for studies on the biological roles of the SART‐1 gene, and also in the construction of animal models of specific immuno‐therapy using SART‐1 gene products.