EXPRESSION OF RECOMBINANT HUMAN THYROID PEROXIDASE BY THE BACULOVIRUSSYSTEM AND ITS USE IN ELISA SCREENING FOR DIAGNOSIS OF AUTOIMMUNE THYROID-DISEASE

The cDNAs coding for human full-length and soluble thyroid peroxidase (TPO) were constructed, cloned into a baculovirus transfer vector and used for infection of Spodoptera frugiperda (Sf9) cells. The soluble T PO lacking 87 amino acids of the C-terminal transmembrane and intracis ternal domains was designed as a fusion protein with a histidine-hexap eptide as an affinity ligand at its C-terminus. Whereas the recombinan t full-length TPO was expressed mainly in an insoluble form in Sf9 cel ls, the recombinant soluble TPO was almost completely secreted into th e culture medium. Both the full-length and the soluble TPO were purifi ed by convential methods and by a specific affinity chromatography usi ng metal chelating matrix respectively, and tested for their autoantig enicity towards anti-TPO autoantibodies. The ELISA established with th e purified recombinant soluble TPO as antigen demonstrated its specifi city, practicability and reproducibility in screening of anti-TPO auto antibodies in sera of autoimmune thyroid patients. High correlation (r = 0.89, n = 175) was obtained between the soluble TPO and natural TPO prepared from human thyroid glands. Pathological sera (n = 200) were positively assayed with a significance of 91%.