It is thus possible that the superiority of HIV-1NL4–3 over HIV-1BH10 in replicating in IFITM1-expression SupT1 cells, despite that both viruses are equally impaired by IFITM1 in the one-round infection, might be a result of the greater ability of HIV-1NL4–3 to transmit between cells. This evidence concerns the gene IFITM1 and infection.