[The influence of anti-interferon-alpha 2a antibodies in initial daily four-week interferon-alpha 2a therapy for chronic hepatitis C].

Thirty-two patients with chronic active hepatitis C were initially treated with 9 million units of interferon (IFN)-alpha 2a daily for 4 weeks and then thrice weekly for 20 weeks. The incidence of development and influence on clinical effectiveness of anti-IFN alpha 2a neutralizing antibodies measured by bioassay were investigated. Thirteen (41%) of the 32 patients developed antibodies, 4 (12.5%) of whom exhibited a high titer of 128 NU or greater. There was a significant difference (p < 0.05) between responders and non-responders in the low viral load group (less than 10(5) copies/50 microliters) in the incidence of antibody development, with antibodies present in 2 of the 9 responders (22%) and 5 of the 7 non-responders (71%). There was also a significant difference between the antibody-negative and antibody-positive patients in circulating HCV-RNA, 2-5AS activity and average ALT levels at the latter half of treatment. In addition, 2-5AS activity was significantly lower (p < 0.05) at completion of treatment in the high antibody titer group (128 NU or greater) than in the low antibody titer group. These results indicate that the development of anti-IFN neutralizing antibodies had a definite influence on the clinical course of IFN treatment for chronic hepatitis C.