FIG. 5.

Binding to cells and inhibition of HCVpp entry by anti-CD81 MAbs. (A) Different concentrations of MAbs JS81 (squares) and 1D6 (triangles) ranging over 2 orders of magnitude were added to Huh-7 cells, and binding was quantified by flow cytometry (MFI) after cell labeling with a PE-conjugated anti-mouse IgG. Binding is expressed as a percentage of the MFI at the highest, saturating concentration of MAb, beyond which no further effect was observed. Values are means of three independent experiments ± SD. (B) Different concentrations of MAbs JS81 (squares) and 1D6 (triangles) were added to Huh-7 cells, which were then infected with HCVpp. Luciferase activity was measured in cell lysates 48 h after infection. The percentage of HCVpp entry was calculated relative to entry in the absence of anti-CD81 MAbs. A 100% inhibition of HCVpp entry was set at the MAb concentration beyond which no further effect was observed. Values are means of three independent experiments ± SD. (C) Calculated EC₅₀ and IC₅₀ values for JS81 and 1D6 after nonlinear curve fitting using GraphPad Prism 4 software.