Epitope mapping of human thyroid peroxidase defined seven epitopes recognized by sera from patients with thyroid pathologies.

Human thyroid peroxidase (hTPO) is the major component of the microsomal antigen. In almost cases, antibodies against this protein are found in sera from patients with autoimmune thyroid diseases. Overlapping cDNAs which correspond to the complete hTPO mRNA obtained from a thyroid library or by polymerase chain reaction were cloned and expressed as fusion proteins in a prokaryotic vector. Seven antigenic determinants between 21 and 49 amino acids were defined by cloning, subcloning of the immunoreactive regions and screenings with the two rabbit polyclonal anti hTPO antibodies. This study confirms the antigenic nature of the sequences 70-160 and 590-675 but above all refines the localization of three shorter distinct antigenic peptides corresponding to the sequences 68-105, 106-126 and 574-621. Moreover, four other determinants were characterized on the sequences 233-277, 467-515, 641-685 and 701-730. Analysis of sera from patients with autoimmune thyroid diseases (AITD) against the seven immunoreactive peptides confirms the heterogeneous nature of autoantibodies to hTPO.