To evaluate whether the block to HIV-1 infection was envelope dependent, we prepared HIV-1 viruses pseudotyped with the amphotropic murine leukemia virus (A-MLV) envelope glycoprotein, which mediates viral entry through a mechanism that involves caveola-dependent endocytosis or macropinocytosis19, 20. The gene discussed is ERVW-1; the disease is HIV-1 infection.