Methods of detecting anti-leptin neutralizing antibodies

1. A method of identifying human subjects having neutralizing antibodies to leptin in blood, serum, or plasma from the subject comprising the steps of:

(a) inactivating leptin present in the sample of the subject's blood, serum, or plasma;

(b) adding a known quantity of labeled leptin to the sample;

(c) contacting the sample containing labeled leptin of (b) with a substrate capable of binding the labeled leptin;

(d) washing the substrate to remove unbound labeled leptin;

(e) measuring the label signal produced by the bound labeled leptin;

(f) measuring a positive control signal, said positive control signal produced by completing steps (a)-(e), and further comprising adding a known quantity of anti-leptin antibody at step (b); and

(g) comparing the signal from (e) with the signal from (f), wherein if the level of signal measured in step (e) is equal to or less than the level of signal measured in step (f), then the subject tests positive for anti-leptin neutralizing antibodies.

2. The method of claim 1 , wherein the leptin is labeled with horseradish peroxidase or ruthenium tris-bipyridine.

3. The method of claim 1 , wherein the inactivation step (a) is accomplished by heating the sample.

4. The method of claim 1 , wherein said substrate capable of binding the labeled leptin comprises:

(i) a coated matrix; and

(ii) a tagged leptin receptor bound to the matrix of (i).

5. The method of claim 4 , wherein the coated matrix is a streptavidin-coated matrix.

6. The method of claim 4 , wherein the leptin receptor is tagged with biotin.

7. The method of claim 1 , wherein said substrate capable of binding the labeled leptin comprises:

(i) a coated matrix;

(ii) an antibody bound to the matrix of (i); and

(iii) a tagged leptin receptor bound to the antibody of (ii).

8. The method of claim 7 , wherein the coated matrix is a streptavidin coated matrix.

9. The method of claim 7 , wherein the leptin receptor is tagged with a tag suitable for affinity purification.

10. The method of claim 9 , wherein the leptin receptor is tagged with a hexa-histidine tag.

11. The method of claim 7 , wherein the antibody is labeled with a tag suitable to bind to the coated matrix.

12. The method of claim 11 , wherein the tag is biotin.

13. The method of claim 1 , further comprising the step of decreasing the pH of the inactivated sample (a) by the addition of an acidic solution, wherein labeled leptin added in (b) further comprises a basic solution sufficient to neutralize the pH of the sample after addition.

14. The method of claim 13 , wherein the acidic solution is an acetic acid solution.

15. The method of claim 14 , wherein the acidic solution is 0.8% acetic acid.

16. The method of claim 1 , wherein the labeled leptin comprises recombinant human leptin.

17. The method of claim 1 , wherein the labeled leptin comprises metreleptin.