Identification of TSH receptor autoantibodies using affinity-purified antibodies
The present invention relates to the use of affinity-purified polyclonal human autoantibodies against the TSH receptor (TSHR-Auto-Ab), obtained from the serum of Graves' disease patients and which have been purified to obtain biochemical homogeneity and comprise a specific activity of at least 1 IU/mg protein (human immunoglobulin). Also disclosed is the use of animal antibodies, which compete with the former for the binding sites of a functional human TSH receptor, as a specific binding reagent in an immunological determination method for the clinical identification of autoantibodies against the TSH receptor (TSHR-Auto-Ab) in a sample of a biological fluid of a patient to be examined for Graves' disease.
1. A method for determining the amount of thyroid stimulating hormone (TSH) receptor autoantibodies in a human serum or plasma sample comprising:
a) contacting said human serum or plasma sample with a functional TSH receptor (TSHr) that is immobilized on a solid support in the presence of labeled autoantibodies against the TSH receptor for a time sufficient for the autoantibodies in said human or plasma sample to competitively bind to the TSH receptor;
b) removing unbound labeled TSH receptor autoantibodies; and
c) determining the amount of TSH receptor autoantibodies in the human serum or plasma sample by measuring the amount of labeled autoantibodies bound to the TSH receptor,
wherein the labeled autoantibodies against the TSH receptor are polyclonal human autoantibodies from a pool of sera from human Graves' disease patients that are affinity purified using a recombinant human TSH receptor that is immobilized to a solid support by a selective monoclonal antibody that:
(i) recognizes a conformational epitope of the functional human TSH receptor;
(ii) does not bind to peptides representing short sequences of human TSH receptor but binds strongly to complete functional recombinant human TSH receptor; and
(iii) is obtained by immunizing an animal with a DNA construct that encodes the human TSH receptor.
2. The method of claim 1 , wherein the affinity-purified polyclonal human autoantibodies against the TSH receptor are purified to biochemical homogeneity and have a specific activity of at least 1 IU/mg of protein.
3. The method of claim 1 , wherein the affinity-purified polyclonal human autoantibodies against the TSH receptor are obtained by purification by affinity chromatography, from a pool of sera of Graves' disease patients, wherein said autoantibodies are bound to an affinity material having a functional human recombinant TSH receptor bound thereto, washed to remove unbound autoantibodies and then eluted from the affinity material.
4. The method of claim 1 , wherein said affinity-purified polyclonal human autoantibodies against the TSH receptor are labeled with a radioisotope, a chemiluminescent label or a fluorescent label.
5. The method of claim 4 , wherein said affinity-purified polyclonal human autoantibodies against the TSH receptor are directly or indirectly labeled.