CXCR4 and infection: Infections by Env proteins of the ecotropic MLV [6], amphotropic MLV [6], xenotropic MLV (XMRV) [19], vesicular stomatitis virus (VSV) [20], and CXCR4-tropic HIV-1 HXB2 strain [21] were significantly reduced in the wild type GILT-expressing cells compared to the pcDNA3.1-transfected cells (Figures 4A and S1A), but not in the GILT DCS mutant-expressing cells (Figure S1B), showing that the thiolreductase activity of GILT expressed in the target cells confers the resistance to the infections.