In order to prevent infection in these cells, one of the promising approaches for gene therapy against HIV infection is to construct EGSs against CCR5 and CXCR4 and to deliver and express these EGSs together in hematopoietic stem/progenitor cells before they differentiate into multilineage progeny cells in vivo, including T cells and macrophages [4, 5, 11, 56, 57]. Here, CCR5 is linked to infection.