C. parvum could induce cell apoptosis by regulating the expression of apoptosis-related factors in host cells, such as inducing downregulation of IFI27, and further regulating the apoptosis of HCT-8 cells to inhibit the infection of C. parvum to host cells through the tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL)-dependent pathway (68). The gene discussed is IFI27; the disease is infection.