FIG. 3.
HVR1 was critical for infectivity of low-density HCVcc irrespective of genotype. Equilibrium gradient density centrifugation was done in iodixanol comparing a single JFH1-based Core-NS2 genotype virus with and without HVR1 (Table 1) (genotypes 2a, 3a, 5a, and 6a). After centrifugation, ∼550-μl gradient fractions were harvested from the bottom of the tube, and 400-μl portions were weighed to calculate fraction densities. HCV RNA titration (the lower cutoff was 20,000 IU/ml and is shown as a dotted line in each graph) and infectivity titration (the lower cutoff was 500 FFUs/ml) was performed for each fraction (samples were diluted at least 1:10). Mutations are annotated based on the H77 reference sequence (GenBank accession no. AF009606).