CCR5 and infection: Infection of TZM-bl and P4-CCR5 reporter cells with these viral constructs showed that mutation of Y86F alone or in combination with Y87F strongly impaired the ability of SIVcol Nef to enhance virion infectivity, whereas alterations in Y residues at positions 28, 30, 46, 64, 80 and 87 had no significant effect (Fig 2B).