IFITM1 and HIV-1 infection: Indeed, we have observed that FLAG-tagged IFITMs are approximately 25–30% more potent than their WTs to inhibit HIV-1 infection; however, the order of potency in inhibition for the untagged WT IFITMs and FLAG-IFITMs remains the same, that is, IFITM3 > IFITM2 > IFITM1.