The present invention relates to a non-human transgenic mammal which has had an HLA-A24 gene introduced and in which CTLs are induced when stimulated by an HLA-A24-binding antigen. Such a transgenic mammal provides a method of screening therapeutic or preventive agents for tumors or virus infections by administering a test substance to the transgenic animal and evaluating whether CTLs specific for the test substance are induced. An HLA-A24-binding tumor antigen peptide of PSA origin that is selected by this screening method is described, as are a chimera DNA (DNA construct) useful in the generation of a non-human transgenic mammal, and a host cell transformed by the chimera gene and use thereof.