Figure 3. Relationship between sCD4 sensitivity, CD4-Ig binding, infection of CD4^low cells and sCD4-induced gp120 release of BR24 viruses.

(A) The relationship between sgp120 binding to CD4-Ig, sCD4 sensitivity, infection of RC49 cells and primary macrophages (mΦ) of BR24 dervied viruses is illustrated. Values above the bars indicate fold increase in sCD4 sensitivity of BR24 viruses compared to viruses in the SHIV_SF162P3N inoculum (P3N). (B) Extent of sCD4-induced gp120 from surface of 293T cells transiently expressing BR24-derived envelope glycoproteins. Percentage difference in gp120 release in the presence of sCD4 relative to that in the absence of sCD4 is shown. The data are the means and standard deviations of two independent experiments. The vertical dashed line in (A) and (B) indicates the time of coreceptor switching, and the dotted area highlights the time when the relationship between sCD4 sensitivity, sgp120 binding to CD4-Ig and infection of CD4^low cells dissipates.