Serum levels of anti-hepatitis C virus IgM core antibodies may predict the response to interferon-alpha therapy in chronic hepatitis C

The presence of rheumatoid factor in sera from anti-HCV positive blood donors interferes with the detection of HCV-specific IgM. Trent HCV Study Group

BACKGROUND/AIMS

IgM anti-HCV has been reported as a useful marker of disease activity and of likely response to interferon therapy in patients with chronic hepatitis C virus infection. Sera from patients with hepatitis C virus infection may contain rheumatoid factor. This study was designed to investigate the possible effect of rheumatoid factor in an IgM anti-HCV assay.

METHODS

Sera from 75 blood donors with chronic hepatitis C virus infection were tested for the presence of IgM anti-HCV using a core-derived peptide as antigen, before and after removal of IgG. These sera and appropriate control sera were also tested for the presence of rheumatoid factor.

RESULTS

Removal of IgG prior to IgM testing resulted in a significant loss of reactivity in the IgM anti-HCV assay in 30/41 sera that were positive in this assay when tested untreated. Seventy per cent of anti-HCV positive sera were also positive for rheumatoid factor.

CONCLUSIONS

Rheumatoid factor causes significant false positive reactivity in IgM anti-HCV detection assays. The results of assays that do not account for this interference should be viewed with caution.

Detectable levels of IgM antibodies to hepatitis C virus core protein predict breakthrough in patients with chronic hepatitis C treated with interferon-alpha

The predictive value of IgM antibodies to hepatitis C virus core antigen (HCcAb) is controversial. We studied 79 patients undergoing interferon-alpha (IFN-alpha) treatment and we found that detectable levels of IgM HCcAb could predict breakthrough on treatment.

Lack of monomeric IgM anti-hepatitis C virus (HCV) core antibodies in patients with chronic HCV infection

Antibodies of the IgM class against the hepatitis C virus core antigen are found in up to 70% of patients with either acute or chronic hepatitis C. The sedimentation rate of such IgM was analyzed by rate-zonal centrifugation of nine sera taken from seven patients, two acutely and five persistently infected with hepatitis C virus. All patients had circulating high-molecular weight (i.e. pentameric) IgM, indicating that the production of low molecular weight IgM, commonly observed in other persistent viral infections, does not apply to hepatitis C virus and cannot be used to distinguish acute from chronic hepatitis C virus infection.

Hepatitis C virus RNA in peripheral blood mononuclear cells: relation with response to interferon treatment

The polymerase chain reaction (PCR) was used to investigate the presence of positive and negative hepatitis C virus (HCV) RNA strands in serum and peripheral blood mononuclear cells (PBMC) of 20 patients with histologically proven HCV-related chronic liver disease. All patients completed a course of interferon (IFN) treatment (6 MU of IFN-alpha 2b three times a week for 24 weeks) and were followed-up for 12 months after treatment was discontinued. Pre-treatment, end-treatment and 6-month follow-up serum and PBMC samples were examined. At enrollment, the positive strand of HCV-RNA was detected in serum of 18 patients (90%), the negative strand in none. Positive-stranded HCV-RNA was detected in PBMC of 15 patients (75%), 13 of whom also had detectable levels of negative-stranded HCV-RNA in PBMC. By the end of the treatment, 12 patients (60%) were responders. The pre-treatment HCV infection of PBMC, indicated by the presence of both RNA strands, was found in 8 (66.7%) responders compared to 5 (62.5%) non-responders (P = n.s.). End-treatment loss of PBMC HCV-RNA correlated significantly with the response since it occurred in all responders compared to 2 non-responders (P = 0.02). However, end-treatment-negative serum and PBMC HCV-RNA did not predict the occurrence of a sustained response, which was observed at month 12 in 5 of 12 responders (P = n.s.). On the other hand, the persistent absence of HCV RNA in serum and PBMC at the end of the 6-month follow-up was significantly associated with the occurrence of a sustained response (P < 0.0001).