FIG. 4.
HVR1 deletion from JFH1-based viruses with Core-NS2 of different genotypes resulted in increased sensitivity to neutralizing antibodies. Viruses of genotypes 1a, 2a, 3a, 5a, and 6a with HVR1 (closed symbols) and without HVR1 (open symbols) (Table 1) were neutralized by incubation for 1 h at 37°C with heat-inactivated chronic-phase patient serum H06 (genotype 1a virus-infected patient H) previously shown to contain cross-genotype-reactive neutralizing antibodies (18, 29). The number of FFUs/well was visualized following 48 h of infection by HCV-specific immunostaining. Neutralization data are shown as the means of three replicates with the standard error of the mean (SEM) (error bars) related to the mean of 6 replicates with virus only. Variable-slope dose-response curve regression was used to fit the data points. Due to the relatively low infectious titer of the 1aΔHVR1,H261R,Q444R recombinant, this virus was concentrated ∼50-fold using Amicon centrifugation columns. Mutations are annotated based on the H77 reference sequence (GenBank accession no. AF009606).