Floating density of hepatitis C virus particles and response to interferon treatment.

Hepatitis C virus (HCV) particles can be classified into two major fractions according to their floating density in serum. However, the genomic heterogeneity of each fraction and the relationship between this viral characteristic and interferon (IFN) response in patients with chronic hepatitis are not known. In this study, floating density and single strand conformation polymorphism (SSCP) of the hypervariable region 1 (HVR1) of HCV were examined in 16 patients with chronic hepatitis prior to IFN treatment. The ratio of HCV RNA titers in the top (T) and bottom (B) fractions, or T:B ratio, was 10:1 in 4 patients, 1:1 in 7, and 1:10 in 5. Three of the 4 patients with a 10:1 ratio showed a sustained response to IFN, while none of the 5 patients with a 1:10 ratio demonstrated a sustained response (P < 0.05). All 4 patients with a 10:1 ratio had 1 or 2 SSCP bands, and 4 of the 5 patients with a 1:10 ratio had 4 or 5 bands (P < 0.01). Furthermore, the number of SSCP bands in the top fraction from 6 sustained responders (1.8 +/- 0.3) was significantly smaller than from 10 non sustained responders (4.1 +/- 0.8) (P < 0.05). Thus, patients with a high T:B ratio and low heterogeneity in HVR1 demonstrated sustained responses to IFN, while those with low T:B ratios and high heterogeneity did not.