ERVW-1 and infection: Two Envs were cloned at 5 and 173 wpi and selected for mutational analysis as they both carried N241, N262, N386, N392 and N448, unlike other clones (Fig. 1a), and these were compared for Env expression and mannosylation as well as PSV entry efficiency, DC-SIGN binding and trans-infection of CD4+ cells.