The rest six T/F viruses showed a very low efficiency of infection, especially p1059_09.A4.1460, p9012_14.B2.4571, p1058_11.B11.1550 and pWEAUd15.410.5017; the latter two were dual tropic Env clones and exhibited a gaussia luciferase activity approximately 5~20-fold above the background. The gene discussed is ERVW-1; the disease is infection.