Background/aims: To analyze the kinetics of the hepatitis C virus and the patterns of resistance to interferon alpha, we assessed HCV RNA levels early during retreatment with high-dose interferon in patients who did not respond to standard treatment.
Methods: Eleven non-responders to previous therapy with 3-6 MU interferon three times a week were retreated with daily 10 MU. Plasma was sampled at days 0, 1, 2, 3, 14 and 28; all samples were prepared within 2 h and stored at -70 degrees C without thawing until analysis. The quantitative HCV RNA level was assessed by the Superquant assay (NGI, USA). The Eurohep reference panel, tested blindly, confirmed the linearity of the assay with a detection limit for genotypes 1 and 3 between 10(2) and 10(3) copies/ml.
Results: All patients showed a fall in viral load between week 0 and week 2 (2.6 log, i.e. 99.7%, range 1.3-4.7 log), whereas no fall was detected after week 2. Closer examination in nine patients revealed that all had a dramatic fall in the first 2 days (first day 1.8 log, 0.8-3.5; second day 0.8 log, -0.2-1.3), without any significant fall thereafter. The calculated half-life of viral decay in plasma was 5 (2-8.9) h, corresponding to a clearance of 2.4 (0.2-13.7) x 10(11) virions per day. Sustained responders showed a significantly greater fall in viral load in the first day (3.2 log, 2.8-3.5) than those who did not respond (1.4 log, 0.8-2.1, p=0.001). All three sustained responders had undetectable plasma HCV RNA at day 14.
Conclusion: In patients without a response to standard interferon, the hepatitis C virus has a high daily turnover rate similar to that reported in naive patients. Our findings suggest that an early clearance of HCV RNA from the circulation is the key to a sustained response, which might be induced in about 25% of these patients by treatment with high (10 MU) daily doses of interferon. These findings have important implications for the concept of treatment of hepatitis C, which should shift its focus from long-term mild treatment towards aggressive therapy aiming at a fast viral disappearance within the first few days.