CD8A and viral infectious disease: The HHD mice share the same genetic background with the C57BL/6 mice except for the MHC class I; therefore, the results suggested that the wild type mouse’s MHC class I-restricted (i.e., H-2Db and H-2Kb-restricted) CD8+ T cell responses are important for controlling the virus infection and the HHD mouse’s class I-restricted (HLA-A2.1-restricted) CD8+ T cell responses cannot control the virus.