Ated with different culture supernatant samples. After three washes with PBS containing 0.05 Tween 20, the plates were incubated with rabbit anti-mouse Ig-HRP Cucurbitacin I chemical information AN-3199 conjugate (DAKO, Glostrup, Denmark) for 1 h. The bound-peroxidase activity was detected using tetramethylbenzidine (TMB) and 0.03 H2O2. The reaction was stopped with 1 M H2SO4, and absorption at 450 nm was measured in an ELISA plate reader (Spectramax; Molecular Devices).(ii) Western BlottingHCV-LPs were electrophoresed on 10 polyacrylamide 
gel under reducing conditions and transferred onto nitrocellulose membranes. After blocking the non-specific sites with 0.5 BSAMonoclonal Antibodies Inhibiting HCV InfectionFigure 2. Inhibition of HCV-LP and Huh7 cell binding by mAbs. HCV-LPs of both genotypes 1b and 3a were incubated with increasing concentrations of mAbs as indicated. The Y-axis depicts the percentage activity representing both the percent binding (dark grey) and percent inhibition HCV-LP attachment (light grey). doi:10.1371/journal.pone.0053619.gin PBS, the membranes were incubated with mouse antibodies specific to the HCV-LP, followed by rabbit anti-mouse Ig-HRP conjugate. The blot was developed with diaminobenzidine (1 mg/ ml in citrate buffer, pH 5.0, containing 0.05 H2O2) or Enhanced Chemiluminescence.Inhibition of Binding of HCV-LP to Huh7 Cells by Monoclonal Antibodies against Genotypes 1b and 3aHCV-LPs were pre-incubated with different concentrations of purified individual monoclonal antibodies and the complexes were allowed to react with Huh 7 cells. The binding of the labeled VLPs was monitored by flow cytometry analysis as described above.Monoclonal Antibodies Inhibiting HCV InfectionTable 2. Percentage inhibition of HCV-LP genotype 3a binding to Huh 7 cells using monoclonal antibodies.Table 3. Percentage inhibition of HCV-LP genotype 1b binding to Huh 7 cells using monoclonal antibodies.Percentage inhibition of binding mAb G2C7 E8G9 H1H10 D2H3 E1B11 Non-specific 10 mg 1 66 30 3 0 0 5 mg 0 45 26 6 0 0 2.5 mg 0 26 12 0 0 0 mAb G2C7 E8G9 H1H10 D2H3 E1B11 Non-specificPercentage inhibition of binding 10 mg 0 25 29 12 0 0 5 mg 0 24 23 2 0 0 2.5 mg 0 14 23 2 0doi:10.1371/journal.pone.0053619.tdoi:10.1371/journal.pone.0053619.tIdentification of the Epitopic Regions Recognized by the mAbsA set of five overlapping E2 gene fragments were generated by PCR amplification followed by restriction enzymes (Bam HI and Hind III) digestion of the different regions of E2 gene and subcloned. The corresponding protein fragments were expressed in E. coli., purified and used for western blot analysis. The fragments R1 (16.94 kDa), R2 (10.78 kDa) R4 (11.44 kDa) and R5 (11.11 kDa) were cloned in pRSET B vector, whereas R3 (12.65 kDa) was cloned in pRSET A vector. In the fragment R3, a part of the vector sequences (,2.5 kDa) was included in the expressed protein, however that part did not contribute to the reactivity to the mAb E8G9 (data 23388095 not shown).Revert-Aid (Thermo Scientific). Resulting cDNA was amplified for HCV IRES and GAPDH (internal control) using the ABI real time RT-PCR System (Applied Biosystems).Results Characterization of HCV-LPs of Genotypes 1b and 3aHCV-LPs corresponding to genotypes 1b and 3a (comprising of core-E1 2) have been generated using the baculovirus expression system in insect cells. The purified HCV-LPs of both genotypes were tested for immunoreactivity with polyclonal antibody to recombinant E1 2 (Fig. 1A). The particles were further examined under electron.Ated with different culture supernatant samples. After three washes with PBS containing 0.05 Tween 20, the plates were incubated with rabbit anti-mouse Ig-HRP conjugate (DAKO, Glostrup, Denmark) for 1 h. The bound-peroxidase activity was detected using tetramethylbenzidine (TMB) and 0.03 H2O2. The reaction was stopped with 1 M H2SO4, and absorption at 450 nm was measured in an ELISA plate reader (Spectramax; Molecular Devices).(ii) Western BlottingHCV-LPs were electrophoresed on 10 polyacrylamide gel under reducing conditions and transferred onto nitrocellulose membranes. After blocking the non-specific sites with 0.5 BSAMonoclonal Antibodies Inhibiting HCV InfectionFigure 2. Inhibition of HCV-LP and Huh7 cell binding by mAbs. HCV-LPs of both genotypes 1b and 3a were incubated with increasing concentrations of mAbs as indicated. The Y-axis depicts the percentage activity representing both the percent binding (dark grey) and percent inhibition HCV-LP attachment (light grey). doi:10.1371/journal.pone.0053619.gin PBS, the membranes were incubated with mouse antibodies specific to the HCV-LP, followed by rabbit anti-mouse Ig-HRP conjugate. The blot was developed with diaminobenzidine (1 mg/ ml in citrate buffer, pH 5.0, containing 0.05 H2O2) or Enhanced Chemiluminescence.Inhibition of Binding of HCV-LP to Huh7 Cells by Monoclonal Antibodies against Genotypes 1b and 3aHCV-LPs were pre-incubated with different concentrations of purified individual monoclonal antibodies and 
the complexes were allowed to react with Huh 7 cells. The binding of the labeled VLPs was monitored by flow cytometry analysis as described above.Monoclonal Antibodies Inhibiting HCV InfectionTable 2. Percentage inhibition of HCV-LP genotype 3a binding to Huh 7 cells using monoclonal antibodies.Table 3. Percentage inhibition of HCV-LP genotype 1b binding to Huh 7 cells using monoclonal antibodies.Percentage inhibition of binding mAb G2C7 E8G9 H1H10 D2H3 E1B11 Non-specific 10 mg 1 66 30 3 0 0 5 mg 0 45 26 6 0 0 2.5 mg 0 26 12 0 0 0 mAb G2C7 E8G9 H1H10 D2H3 E1B11 Non-specificPercentage inhibition of binding 10 mg 0 25 29 12 0 0 5 mg 0 24 23 2 0 0 2.5 mg 0 14 23 2 0doi:10.1371/journal.pone.0053619.tdoi:10.1371/journal.pone.0053619.tIdentification of the Epitopic Regions Recognized by the mAbsA set of five overlapping E2 gene fragments were generated by PCR amplification followed by restriction enzymes (Bam HI and Hind III) digestion of the different regions of E2 gene and subcloned. The corresponding protein fragments were expressed in E. coli., purified and used for western blot analysis. The fragments R1 (16.94 kDa), R2 (10.78 kDa) R4 (11.44 kDa) and R5 (11.11 kDa) were cloned in pRSET B vector, whereas R3 (12.65 kDa) was cloned in pRSET A vector. In the fragment R3, a part of the vector sequences (,2.5 kDa) was included in the expressed protein, however that part did not contribute to the reactivity to the mAb E8G9 (data 23388095 not shown).Revert-Aid (Thermo Scientific). Resulting cDNA was amplified for HCV IRES and GAPDH (internal control) using the ABI real time RT-PCR System (Applied Biosystems).Results Characterization of HCV-LPs of Genotypes 1b and 3aHCV-LPs corresponding to genotypes 1b and 3a (comprising of core-E1 2) have been generated using the baculovirus expression system in insect cells. The purified HCV-LPs of both genotypes were tested for immunoreactivity with polyclonal antibody to recombinant E1 2 (Fig. 1A). The particles were further examined under electron.