We further used CD4+/CD8+ T cell ratio as an indicator for CD4+ T cell depletion because this parameter was always used in clinical setting to diagnose HIV infection (44, 45), and we found a ~10-fold CD4+/CD8+ T cell ratio reduction (p<0.05) in the HIV/Mtb co-infected mice as early as 15 dpi, and this trend remained until the end of the experiment. This evidence concerns the gene CD8A and HIV infectious disease.