FIG. 3.

Relationship between Fr-RBD concentration and infection by Fr-MLV (Epo-env). Infection on 293 cells that express mCAT1 alone (triangles) or in combination with EpoR (squares) of a 1:10 dilution of Fr-MLV (Epo-env) supernatant was measured as a function of the concentration of Fr-RBD (0 to 2,000 nM). The cells were assayed for acquired β-galactosidase expression 48 h postinfection. The effect of each concentration of Fr-RBD on infection was assessed in triplicate wells of a six-well plate; standard errors are indicated. As a reference, the effect of Fr-RBD on Fr-MLV (env ΔH8) infection was replotted from Fig. 2C (circles). In a separate experiment, we observed no detectable difference in the relationship between Fr-RBD concentration and Fr-MLV (env ΔH8) infection on human 293 mCAT1 and human 293 mCAT1-EpoR cells (data not shown).