Density gradient analysis of mutant viruses.

Huh7.5 cells were electroporated with in vitro transcripts of WT or the indicated virus mutants. Concentrated culture medium was fractionated using 10–40% iodixanol density-gradient centrifugation. For each fraction, HCV RNA (A) and infectivity (B) were plotted against the buoyant density (n = 3), and Core protein in each fraction was detected by western blot (C). 1 to 12 in (C) indicated the fractions collected from top to bottom with the buoyant density indicated in (A) and (B). The result of a representative of three independent experiments is shown.