Fig. 6.

Complement enhances neutralization of NiVpp by soluble EphrinB2 receptor through a C4-dependent pathway. (A) Titration. NiVpp were incubated alone (PBS) or with the indicated concentrations of soluble EphrinB2 receptor in the absence (hatched bars) or presence (black bars) of a 1:20 dilution of NHS from two different donors. The remaining infectivity was determined by infecting Vero cells and assaying luciferase activity. (B) Time course. NiVpp were incubated with a 1:20 dilution of NHS. At the indicated times p.i., the remaining infectivity was determined by infecting Vero cells and assaying luciferase activity. (C) Activation of classical pathway. NiVpp were treated as described for panel A, and samples were assayed for the C4a cleavage product by ELISA. Error bars show standard deviations. #, P < 0.001; α, P < 0.04; *, P < 0.004.