As shown in Figure 4A, EKL1C could effectively inhibit HIV-1-Env-mediated cell–cell fusion with an IC50 of 7 nM, which is 2.5-fold more potent than that of T20, confirming that EKL1C inhibits HIV-1 infection through the suppression of viral Env-mediated fusion between viral and target cell membranes. The gene discussed is ERVW-1; the disease is HIV-1 infection.