FIG. 3.

Inhibition of virus binding (a), virus-induced cell-cell fusion (b), and virus infectivity (c and d). (a) Purified MV was incubated with either sCD46-C4bpα protein (black circles) or sCD46 protein (triangles) before the addition of CHO-CD46 cells; alternatively MV was incubated with CHO-CD46 cells to which the sCD46-C4bpα protein was added afterwards (open circles). (b) Inhibition of fusion in the presence of sCD46-C4bpα protein (circles), sCD46 protein (triangles), 48Cl6 anti-H (diamonds), Y503 anti-F (squares), or WM1 anti-C3b(C3c) (exes) MAbs. The results are expressed as a percentage of the fusion between HeLa and MV-infected HeLa cells observed in the absence of inhibitor as determined by the level of β-Gal activity. (c) MV (100 PFU) was incubated with sCD46-C4bpα protein (circles), sCD46 protein (triangles), or bovine serum albumin (exes) prior to infection of Vero cells. (d) MV (10⁵, 10⁴, 10³, and 10² TCID₅₀ [black to light grey columns, respectively]) was incubated with the indicated reagent, and the remaining virus was titrated using the TCID₅₀ assay. The results are expressed as the MV fraction not neutralized. Note that no infectious MV was recovered from 10² TCID₅₀ MV incubated with sCD46-C4bpα (i.e., recovery fraction = 0:100).