A prominent example for the former is engineered resistances against HIV-linked acquired immunodeficiency syndrome (HIV/AIDS), where CD4 co-receptor CCR5 and chemokine receptor CXCR4 mediate infection of different HIV isolates and may be edited or silenced in T cells or HSCs to make HIV target cells resistant to the virus [182,183,184,240]. This evidence concerns the gene CXCR4 and AIDS.