RELATIONSHIP BETWEEN RESPONSE TO INTERFERON THERAPY AND DETECTION OF HEPATITIS-C VIRUS-RNA BY DIFFERENTIAL FLOTATION CENTRIFUGATION

Circulating hepatitis C virus (HCV) particles can be fractionated by m eans of differential flotation centrifugation. It is reported that in the bottom fraction HCV is in the form immune complexes, whereas in th e top, it is free of antibodies. We evaluated the significance of circ ulating complex and free HCV in chronic hepatitis C, and assessed the relationship in terms of the response to interferon (IFN) therapy. We examined sera before, just after, and 1 year after administering IFN t o 18 patients with chronic hepatitis C, 10 of whom responded (group CR ), and 8 did not (group NR). The amounts of virus were similar between both groups before therapy. After differential flotation centrifugati on with 1.063 g/ml of NaCl, the top and bottom fractions were assayed for HCV RNA. Before therapy, HCV RNA was detected in the top fraction in 1 of 10 in group CR, and in 6 of 8 in group NR (P < 0.05, chi-squar e test). HCV RNA was positive in the bottom fraction of all samples. I n a follow-up study of group NR, HCV RNA was detected in the top fract ion in 3 of 8 just after IFN therapy, and in 7 of 8 after 1 year. This study suggests that the presence of HCV in the top fraction can predi ct a poor response to IFN therapy.