Serum levels of HCV RNA and core protein before and after incubation at 37°C for 24 h

The kinetics of HCV during interferon (IFN) therapy have recently been described and the estimated virion half-life is an average of 2.7 h, suggesting that HCV infection is highly dynamic. The aim of this study was to evaluate serum levels of HCV-RNA and HCV core protein (HCV-Ag) before and after incubation at 37°C for 24 h. We also evaluated the viral kinetics during IFN treatment by determining their serum levels at 0, 24 and 48 h, and day 8 after the start of treatment. The decay slope was calculated as the logarithm of the ratio of HCV-RNA levels at 0 and 24 h of incubation: log(virus load) 24 h-log(virus load) 0 h and the estimated half-life was also calculated. The decay slope was - 1.66 ± 0.75 ( - 4.12 to - 0.18) (mean ± S.D. (range) and the estimated virion half-life was 6.2 ± 6.9 h (1.8-39.3). The HCV-RNA level was rapidly decreased to 6.8 ± 13.1% of the initial load after incubation independently of the serotype. In contrast, the HCV-Ag level after incubation for 24 h was 98.7 ± 12.2% of the initial level. The synthesized naked HCV-RNA (equivalent to 10⁷ copy/ml) was not detected after 1-min incubation. These data suggested that HCV virions are very unstable and collapsed rapidly and that HCV-RNA; existing outside of virions, is immediately degraded in serum, whereas HCV-Ag remains stable. IFN treatment caused a rapid decrease in the levels of both HCV-RNA and HCV-Ag. The HCV-RNA decay slope was - 1.95 ± 0.96 (range: - 3.48 to - 0.50) and was similar to that seen in the incubation study. Our result suggested the significance of measuring HCV-Ag during clinical management independently of HCV-RNA, especially because of its high stability.