Parallel infection with a second replication-competent R5 HIV-1 GFP reporter virus, HIV-1NL4-3 92TH014-2 Env GFP, resulted in a productive infection of human T-cells as seen both by an increase in the percentage of GFP-positive cells and p24 antigen in supernatants (Fig. 9A, 9B, right panels). This evidence concerns the gene ERVW-1 and infection.