Anti-HCV immunoglobulin M antibody in patients with acute and fulminant hepatitis C.

To determine whether detection of IgM type antibody (Ab) to hepatitis C virus (HCV) antigens would be useful in the early diagnosis of type C acute hepatitis (AH) or fulminant hepatitis (FH), we assayed serum IgM and IgG type Abs to nonstructural (C100-3) and core (AR 142) antigens of HCV in patients with type C hepatitis. Of 8 patients with AH, anti-C100-3 IgM and anti-AR 142 IgM were positive in 1 and 6 patients, respectively. Early appearance of Anti-AR 142 IgM was observed in all of these 6 patients, and in 4 anti-AR 142 IgM was the sole serological marker of HCV infection during the acute-phase. However, the anti-AR 142 IgM response was rather persistent, not transient in AH. Only 1 patient with AH was positive for anti-C100-3 IgM, and this patient became positive for anti-AR 142 IgM 3 months before the appearance of anti-C100-3 IgM. The titre of anti-AR 142 IgM in AH was not dependent on the activity of hepatitis or on the duration. Anti-AR 142 IgM was also positive in 30-75% cases with chronic HCV carriers. Thus it is suggested that the detection of anti-AR 142 IgM may contribute to the early diagnosis of type C AH, although the appearance of this marker in chronic HCV carriers limits its usefulness as the sole serological marker of acute HCV infection.