IgM antibody response to hepatitis C virus in end-stage renal disease

BACKGROUND: In HBV infection, as in other viral diseases, antibodies of the IgM class are associated with acute or ongoing infection. In contrast, the significance of this antibody in HCV infection is unclear and data regarding end-stage renal disease (ESRD) patients are lacking. METHODS: We tested sera from 78 ESRD patients (66 chronic dialysis patients, 12 renal allograft recipients) showing anti-HCV IgG antibody, for serum anti-HCV IgM core antibody. A specific solid-phase enzyme-linked immunoassay (HCV IgM EIA, Abbot) was used. In all patients serum HCV RNA was detected by RT-PCR technique, with primers from the 5' untranslated region of the viral genome. RESULTS: Prevalence of anti-HCV IgM core antibody was 22% (17/78). We observed association between prevalence of anti-HCV IgM core antibody and frequency of HCV RNA in the serum. Thus 15 of 45 (33%) sera containing HCV RNA also contained anti-HCV IgM, while two of 33 (6%) HCV RNA negative sera showed anti-HCV IgM core antibody (P = 0.01). There was a significant relationship between absorbance values of anti-HCV IgM core antibody and NS3 (P = 0.01), NS5 (P = 0.04), and core (P = 0.0001) reactivity in RIBA-2 and RIBA-3 assays. Optical density values of anti-HCV IgM were significantly associated with the number of reactive bands in RIBA-2 (P = 0.04) and RIBA-3 (P = 0.03) assays. CONCLUSIONS: 22% of ESRD patients with anti-HCV IgG activity showed anti-HCV IgM core antibody in the serum. Anti-HCV IgM activity seems to correlate positively with HCV viraemia in ESRD population. Testing for this antibody may be useful as a serological marker to indicate the presence of ongoing HCV infection.