HLA-A2.1/Kb Transgenic Murine Dendritic Cells Transduced with an Adenovirus Encoding Human gp100 Process the Same A2.1-Restricted Peptide Epitopes as Human Antigen-Presenting Cells and Elicit A2.1-Restricted Peptide-Specific CTL

HLA-A2.1/Kb transgenic mice (A2.1/Kb mice) were used to investigate the processing of human gp100 melanoma antigen by murine antigen presenting cells (APC). Bone marrow-derived dendritic cells (DC) from A2.1/Kb mice were transduced with adenovirus encoding human gp100 (Ad2/hugp100v2). The Ad2/hugp100v2-transduced DC express human gp100, as documented by immunoperoxidase staining. Flow cytometric analysis demonstrates that Ad vector transduction does not downregulate expression of several markers, including MHC class I. We show that Ad2/hugp100v2-transduced DC are recognized by peptide-specific, A2.1-restricted CTL, suggesting correct processing and presentation of the hugp100 antigen by murine DC. To assess dominance among the various A2.1-restricted epitopes encoded by hugp100, A2.1/Kb transgenic mice were immunized with Ad2/hugp100v2-transduced DC. Resulting effector cytotoxic T lymphocytes (CTL) were assayed for peptide specificity using a panel of six synthetic peptides known to encode A2.1-restricted epitopes of human gp100 (denoted G154, G177, G209, G280, G457, G476). CTL obtained from Ad2/hugp100v2-transduced DC immunized A2.1/Kb mouse lysed target cells presenting five of the six epitopes, supporting the observation that murine cells correctly process the hugp100 antigen. The immunogenicity of individual gp100 epitopes correlates with their binding affinity to A2.1. CTL generated from A2.1/Kb mice immunized with Ad2/hugp100v2-transduced DC also specifically recognize A2.1+/gp100+ human melanoma cells. These data suggest that murine APC process and present the same set of HLA-restricted peptides, similar to human APC. HLA transgenic mice serve as a useful model system to study class I-restricted epitopes of human tumor-associated antigens.