FIGURE 5.

Virus entry. DTT concentrations cleaving 2–9 disulfides/E2 (Δ) were present in the medium during incubation of target cells with HCVpp/HCVcc (Coinc DTT). Alternatively, HCVpp/HCVcc were pretreated prior to dilution (>1:100) and infection (Preinc DTT). In some experiments, iodoacetamide (IAA; a 3 m excess versus DTT) was added following DTT preincubation. For infection, cells and virions expressing GFP (HCVpp)/YFP (HCVcc) were co-incubated for 4–5 h before washing and culture for 72 h. GFP/YFP expression resulting from virus entry was quantified by flow cytometry (100%, signal using untreated particles) (n = 3, HCVpps; n = 4, HCVccs); duplicates were performed; means of one experiment are shown). In some assays, DTNB (1–2 mm) was also added during the co-incubation step of cells and HCVpp/HCVcc. Amphotropic MLV 4070A pseudoparticles expressing GFP were used in control infections in parallel to the use of HCVpp. The anti-CD81 JS-81 antibody and an irrelevant antibody were used as controls for HCVcc infections. *, not done.