IgG1 anti-P2 as a marker of response to interferon in patients with chronic hepatitis C

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Abstract
To study the relations of antibody production to long‐term outcomes after interferon (IFN) treatment in patients with chronic hepatitis C (CH‐C), we used ELISA to measure the levels of antibodies against HCV core protein and peptides. Samples from 21 complete responders and 36 non‐responders were collected before IFN therapy, soon after the end of IFN therapy and 6 months later. Using a set of 19 synthesized HCV core peptide antigens, we found that anti‐P2 (11–25a.a.) was the most prevalent of all IgG antibodies (93%: 39/42). Among complete responders, IgG1 anti‐P2 levels had fallen by the end of IFN therapy (from 79·8 ± 60·4–46·1 ± 44·2: P < 0·01), and were lower still 6 months after the end of IFN therapy (31·0 ± 35·2: P < 0·001); this change was the greatest of all antibodies studied. Among the non‐responders, there was no change within the follow‐up period. Soon after the end of IFN therapy, IgG1 anti‐P2 levels were more than 30% lower than the initial value in more than two‐thirds of the complete responders, but in only one‐third of the non‐responders (14/20 vs. 8/25: P < 0·05). Six months after the end of IFN therapy, IgG1 anti‐P2 levels were more than 30% lower than the initial value in more than 85% of the complete responders, but in only 12% of the non‐responders (17/20 vs. 3/25: P < 0·001). In conclusion, the changes in levels of IgG1 anti‐P2 paralleled the activity of chronic hepatitis C after IFN therapy, and IgG1 anti‐P2 levels may be markers of the efficacy of IFN therapy.