Early appearance and biphasic kinetics of IgG antibody against hepatitis C virus protein C100-3.

Antibody to recombinant hepatitis C virus (HCV) protein C100 (anti-C100) was measured for a period of 6 months by enzyme immunoassay in nine prospectively followed non A-nonB (NANBH) cases which occurred after cardiac surgery at a hospital in Rio de Janeiro (Brazil). At least seven cases were infected with HCV; four of these developed chronic hepatitis as shown in liver biopsy at the 6th month after transfusion. The first elevation of alanine aminotransferase (ALT) occurred between 15 and 45 days after transfusion and ALT values remained elevated for 45 days in resolving hepatitis, whereas in chronic cases fluctuation levels were observed until the end of the study. Anti-C100 appeared after 15 to 30 days, decreased after some weeks, and rose finally to high concentrations except in one resolving case where it disappeared. We conclude that both in acute and chronic hepatitis C an early antibody response occurs which may, however, be undetectable in some cases. After several months all chronic and some resolving cases develop a second stronger response.