Polyspecificity of antimicrosomal thyroid antibodies in hepatitis C virus - Related infection

OBJECTIVES: The outcome of dysthyroidism and the presence of antithyroid an tibodies in patients with chronic hepatitis C virus (HCV) infection receivi ng interferon-alpha therapy is clearly established. However, the prevalence and the specificity of antithyroid antibodies in HCV patients before inter feron-alpha therapy remain controversial. The aim of the present study is t o clarify within a large population of HCV patients the prevalence of antit hyroid antibodies before interferon-alpha therapy and to determine whether their immunodominant antigen is the same as described in autoimmune thyroid itis. METHODS: Sera from 99 patients with chronic hepatitis C before (n = 99) and after (n = 37) interferon-alpha treatment were investigated for the presen ce of antimicrosomal and antithyroperoxidase antibodies assessed by indirec t immunofluorescence and ELISA, respectively. Dot blotting on human thyroid lysate was designed to further characterize these autoantibodies. Data wer e compared to those obtained with sera of patients with autoimmune thyroidi tis (n = 75) and healthy subjects (n = 96). RESULTS: In HCV patients, antimicrosomal antibodies were found with a highe r 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 wi th chronic hepatitis C before interferon-alpha therapy. Thyroperoxidase may not be their main target. Further studies are required to determine whethe r HCV infection leads to a breakdown of tolerance to a thyroid self-protein other than thyroperoxidase. (Am J Gastroenterol 2001;96:2978-2983. (C) 200 1 by Am. Coll. of Gastroenterology).