VARIABILITY OF IGM RESPONSE IN HEPATITIS-C VIRUS-INFECTION

The IgM and IgG antibody response to various hepatitis C virus (HCV) a ntigens was studied in 8 patients who acquired posttransfusion HCV inf ection. IgM anti-HCV was detectable in only 4 of these patients, coinc ident with (1 patient) or later than (3 patients) the IgG anti-HCV res ponse. Seven patients had initially decreasing IgG anti-HCV titres, in dicating passive transfer of antibodies from donor to recipient. All 8 patients showed active IgG seroconversion, as demonstrated by increas ing IgG anti-HCV titres, on average, 75 days after infection. Five yea rs after infection, all patients were still reactive for IgG anti-HCV antibodies and 7 were positive for HCV RNA by the polymerase chain rea ction (PCR). Two of these PCR positive patients were also reactive for IgM anti-HCV. It is concluded that the serology of HCV infection does not follow the classical pattern of IgM response preceding detection of IgG. The IgM response may be absent, late, or persistent after HCV infection. The serological diagnosis of recent HCV infection should be based on the polymerase chain reaction or rising IgG titres in at lea st 2 sequential patient blood samples. (C) 1993 Wiley-Liss, Inc.