Limitations of the semisynthetic library approach for obtaining human monoclonal autoantibodies to the thyrotropin receptor of Graves' disease

Characteristics of an scFv antibody fragment that binds to immunoglobulin G of Graves' disease patients and inhibits autoantibody-mediated thyroid-stimulating activity

Thyroid-stimulating antibodies (TSAbs) are responsible for hyperthyroid Graves' disease (GD). Although two peptides that bind to GD immunoglobulin G (IgG), and some monoclonal antibodies to the TSH receptor (TSH-R), have been reported to inhibit stimulation of cAMP production by patient serum TSAb, our work is the first to use phage-display technology to produce a mouse single-chain Fv antibody fragment (scFv) that binds to GD IgG and acts as a powerful TSAb (and TSH) antagonist. The specificity characteristics and relative affinity (2.8 mol/L) of T17 were identified by competitive inhibition ELISA and thiocyanate elution. The purified T17 scFv was then tested for its effect on stimulation of cAMP production by Graves' patients' sera in TSH receptor-transfected Chinese hamster ovary (CHO) cells. T17 was an effective antagonist of TSAb activity in 13 of 16 patients with GD. In addition, (125)I-TSH binding to TSH-R was also inhibited by T17 (57% inhibition at 1 mg/mL). This new scFv suggests in vitro applications such as purification of TSAb or diagnosis of GD. In addition, it may have in vivo usefulness such as treatment of TSH-R mediated ophthalmic symptoms of Graves' disease.

Immunoaffinity carrier prepared by immobilization of antibodyvia Co3+-chelate

A method for the immobilization of antibodies to inert matrix represents an important factor that affects results of immunoaffinity chromatography. Binding antibodies to immobilized metal ions is an example of oriented immobilization that avoids a random coupling of a protein. Preparation of a stable immunoaffinity sorbent using immobilized metal ions was described. Antibodies were bound to chelated Co3+ ions that were prepared by oxidation of Co2+-iminodiacetic acid agarose using hydrogen peroxide. The formation of a stable complex of the antibody with immobilized Co3+ ions was proved. Antibodies bound by this way were not released with solutions of 50 mM EDTA, 6 M urea, 3 M NaCl, 20% v/v dioxane, 0.1 M imidazole and buffers of pH 2.5 and pH 11.0. If needed, antibody could be released from the carrier by the reduction of Co3+ ions with a reducing agent (e.g. dithiotreitol or 2-mercaptoethanol). Antibody released from the carrier could be then replaced by another antibody. The method described in this paper was used for the immobilization of polyclonal rabbit anti-ovalbumin antibody or egg yolk antibody (IgY) produced in chicken. In a model experiment, immobilized polyclonal rabbit antibodies were used for the separation of ovalbumin from egg white and conditions of chromatography were described.