Polyspecificity of antimicrosomal thyroid antibodies in hepatitis C virus-related infection.

OBJECTIVES

The outcome of dysthyroidism and the presence of antithyroid antibodies in patients with chronic hepatitis C virus (HCV) infection receiving interferon-alpha therapy is clearly established. However, the prevalence and the specificity of antithyroid antibodies in HCV patients before interferon-alpha therapy remain controversial. The aim of the present study is to clarify within a large population of HCV patients the prevalence of antithyroid antibodies before interferon-alpha therapy and to determine whether their immunodominant antigen is the same as described in autoimmune thyroiditis.

METHODS

Sera from 99 patients with chronic hepatitis C before (n = 99) and after (n = 37) interferon-alpha treatment were investigated for the presence of antimicrosomal and antithyroperoxidase antibodies assessed by indirect immunofluorescence and ELISA, respectively. Dot blotting on human thyroid lysate was designed to further characterize these autoantibodies. Data were compared to those obtained with sera of patients with autoimmune thyroiditis (n = 75) and healthy subjects (n = 96).

RESULTS

In HCV patients, antimicrosomal antibodies were found with a higher proportion before interferon-alpha therapy (12.1%) than after therapy (8%). Thyroperoxidase constitutes the main antigen in only 4% before treatment, a prevalence similar to that observed in healthy controls.

CONCLUSIONS

The prevalence of antithyroid antibodies is low in patients with chronic hepatitis C before interferon-alpha therapy. Thyroperoxidase may not be their main target. Further studies are required to determine whether HCV infection leads to a breakdown of tolerance to a thyroid self-protein other than thyroperoxidase.