Disrupting FCRN-albumin interactions

1. A method of identifying a candidate compound for decreasing the concentration of an albumin-binding toxin in a subject, the method comprising:

contacting (a) a test compound, (b) an FcRn polypeptide or albumin-binding fragment thereof, and (c) an albumin polypeptide or FcRn-binding fragment thereof, under conditions and for a time sufficient to allow binding between the FcRn polypeptide or fragment thereof and the albumin polypeptide or fragment thereof and

detecting whether the test compound inhibits binding between the FcRn polypeptide or fragment thereof and the albumin polypeptide or fragment thereof

wherein a test compound that inhibits binding between the FcRn polypeptide or fragment thereof and the albumin polypeptide or fragment thereof is a candidate compound for decreasing the concentration of an albumin-binding toxin in a subject.

2. The method of claim 1 , wherein the test compound is selected from the group consisting of: a polypeptide, a small molecule, a nucleic acid, an antibody, an antibody fragment, and combinations thereof.

3. The method of claim 1 , wherein the albumin polypeptide is a wild type albumin polypeptide.

4. The method of claim 1 , wherein the albumin polypeptide or fragment thereof is a human, mouse or rat albumin polypeptide.

5. The method of claim 1 , wherein the FcRn polypeptide is a wild type FcRn polypeptide.

6. The method of claim 1 , wherein the FcRn polypeptide or fragment thereof is a human FcRn polypeptide.

7. The method of claim 1 , wherein either one or both of the FcRn polypeptide or fragment thereof and the albumin polypeptide or fragment thereof are fluorescently labeled.

8. The method of claim 1 , further comprising:

selecting a test compound that inhibits binding between the FcRn polypeptide or fragment thereof and the albumin polypeptide or fragment thereof,

administering the test compound to a test animal expressing an FcRn polypeptide or albumin-binding fragment thereof and an albumin polypeptide or FcRn-binding fragment thereof; and

determining a level of the albumin polypeptide or fragment thereof in a body fluid of the test animal;

wherein a change in the level of the albumin polypeptide or fragment thereof in the body fluid of the animal in the presence of the test compound as compared to in the absence of the test compound indicates that the test compound is a candidate compound for decreasing the concentration of an albumin-binding toxin in a subject.

9. The method of claim 8 , wherein the body fluid is selected from the group consisting of bile, urine, and feces, and wherein the change in the level of the albumin polypeptide or fragment thereof is an increase in the level in the body fluid.

10. The method of claim 8 , wherein the body fluid is blood or lymph, and wherein the change in the level of the albumin polypeptide or fragment thereof is a decrease in the level in the blood or lymph.

11. The method of claim 1 , further comprising:

selecting a test compound that inhibits binding between the FcRn polypeptide or fragment thereof and the albumin polypeptide or fragment thereof,

administering the test compound and an albumin-binding toxin to a test animal expressing an FcRn polypeptide or albumin-binding fragment thereof and an albumin polypeptide or FcRn-binding fragment thereof; and

determining an effect of the albumin-binding toxin in the test animal; wherein a change in the effect of the albumin-binding toxin in the presence of the test compound as compared to in the absence of the test compound indicates that the test compound is a candidate compound for decreasing the concentration of the albumin-binding toxin in a subject.

12. The method of claim 8 , wherein the test animal expresses a human FcRn polypeptide or a fragment thereof.

13. The method of claim 8 , wherein the test animal expresses a human albumin polypeptide or a fragment thereof.

14. A method of reducing levels of an albumin-binding toxin in a subject, the method comprising administering to the subject a therapeutically effective amount of an antibody or antigen-binding portion thereof that binds specifically to FcRn and disrupts binding between FcRn and albumin.

15. The method of claim 14 , wherein the step of administering is selected from the group consisting of: intravenous administration, intradermal administration, subcutaneous administration, oral administration, transdermal administration, transmucosal administration, rectal administration, and combinations thereof.

16. The method of claim 1 , wherein the albumin-binding toxin is selected from the group consisting of copper, hematin, long-chain fatty acid, zinc, bilirubin, thyroxine, eicosanoids, tryptophan, vitamin D3, bile acids, calcium, magnesium, chloride, indomethacin, bromphenol blue, salicylate, warfarin, phenylbutazone, digoxin, furosemide, phenytoin, chlorpropamide, benzylpenicillin, Evans blue, diazepam, ibuprofen, naproxen, clofibrate, chlorpromazine, imipramine, quinidine, ricin, and acetaminophen.

17. The method of claim 14 , wherein the albumin-binding toxin is selected from the group consisting of copper, hematin, long-chain fatty acid, zinc, bilirubin, thyroxine, eicosanoids, tryptophan, vitamin D3, bile acids, calcium, magnesium, chloride, indomethacin, bromphenol blue, salicylate, warfarin, phenylbutazone, digoxin, furosemide, phenytoin, chlorpropamide, benzylpenicillin, Evans blue, diazepam, ibuprofen, naproxen, clofibrate, chlorpromazine, imipramine, quinidine, ricin, and acetaminophen.

18. The method of claim 11 , wherein the test animal expresses a human FcRn polypeptide or a fragment thereof.

19. The method of claim 11 , wherein the test animal expresses a human albumin polypeptide or a fragment thereof.