IgM antibody to a hepatitis C virus core peptide (CP14) for monitoring activity of liver disease in patients with acute or chronic hepatitis C

Antibodies to the hepatitis C virus (HCV) core of various immunoglobulin classes were determined by enzyme immunoassays with three synthetic peptides, CP14 (amino acids 5‐40 of the core protein), CP10 (5‐23), and CP9 (39‐74). In 135 patients with chronic type C liver disease, anti‐CPU, anti‐CP10, and anti‐CP9 of IgG class were detected in 99%, 94%, 82%, respectively; those of IgM class in 86%, 69%, and 39%; and those of IgA class in 56%, 40%, and 4%. Thus anti‐CP14 was more prevalent than anti‐CPlO or anti‐CP9 in every immunoglobulin class. The prevalence of IgM anti‐CP14 was much higher (P < 0.001) in patients (116/135 or 86%) than in asymptomatic carriers of HCV (13/39 or 33%). In seven patients with acute hepatitis C, IgM anti‐CP14 continued to decrease in two in whom hepatitis resolved, but increased in five in whom hepatitis once resolved and then exacerbated. IgM anti‐CP14 was followed in 30 patients with chronic hepatitis C during 24 weeks while they received recombinant interferon α‐2a. IgM anti‐CP14 decreased remarkably within 8 weeks in all of them. Thereafter, it continued to decrease in nine patients who responded to interferon and lost HCV RNA from circulation, but started to increase in five non‐responders who continued to have high titers of HCV RNA. In the remaining 16 patients in whom HCV RNA decreased once and then increased, IgM anti‐CP14 continued to decrease till 20 weeks and then increased. These results indicate that IgM anti‐CP14 reflects the activity of liver disease, and is useful in following the outcome of patients with acute hepatitis C and in monitoring the response to interferon in patients with chronic hepatitis C. © 1994 Wiley‐Liss, Inc.