Entry efficiency, PSC-RANTES and sCD4 sensitivity of R5 viruses evolving over time in DE86 and DG08. Entry of luciferase reporter viruses expressing CCR5-using envelopes into TZM-bl cells expressed as relative light unit (RLU) (A), and susceptibility of the reporter viruses to neutralization with PSC-RANTES (B) and sCD4 (C) were determined. The dashed vertical line indicates time of tropism switch in DE86 (12 wpi), and DG08 (13 wpi). The numbers in the brackets indicate the number of clones analyzed at each time point. Absolute CD4+ T cell count in the animal over the course of infection is shown in (C) for reference and values above the bars indicate fold increase in sCD4 sensitivity relative to that of the w2 viruses. * P<0.05 (Mann-Whitney U test). Data are representative of 2-3 independent experiments (error bars, s.d.).