Assays for determining levels of plasma protease C1 inhibitor
View Patent ↗The invention provides assay methods of detecting plasma protease CI inhibitor (Cl-INH) that binds plasma kallikrein, Factor XII, or both, and uses thereof for identifying subjects at risk for or suffering from a pKal-mediated or bradykinin-mediated disorder. Provided methods permit analysis of patients with plasma kallikrein-mediated angioedema (KMA), or other diseases mediated by pKal useful in the evaluation and treatment.
1. A method, comprising:
contacting a sample containing plasma protease C1 inhibitor (C1-INH) with a capture reagent, and
measuring a level of the C1-INH in the sample that binds to the capture reagent;
wherein the capture reagent comprises:
i) an active form of Factor XII,
ii) an active form of plasma kallikrein, or
iii) a combination of i) and ii);
wherein the active form of plasma kallikrein retains protease activity of a naturally occurring plasma kallikrein and the active form of Factor XII retains blood coagulation activity of a naturally occurring Factor XII.
2. The method of claim 1 , wherein the capture reagent is immobilized on a substrate.
3. The method of claim 1 , wherein the capture reagent comprises the active form of Factor XII.
4. The method of claim 1 , wherein the level of C1-INH that binds to the capture agent is measured by an enzyme-linked immunosorbent assay (ELISA).
5. The method of claim 1 , wherein the sample containing C1-INH is obtained from a subject.
6. The method of claim 5 , wherein the sample is a blood sample or a plasma sample.
7. The method of claim 5 , wherein the subject has a symptom of a pKal-mediated disorder.
8. The method of claim 7 , wherein the subject is resistant to an anti-histamine therapy, a corticosteroid therapy, or both.
9. The method of claim 7 , wherein the symptom is edema.
10. The method of claim 7 , wherein the symptom is:
recurrent attacks of swelling;
swelling wherein said swelling is completely or predominantly peripheral;
hives;
redness, pain, and swelling in the absence of evidence of infection; or
non-histamine-mediated edema.
11. The method of claim 5 , wherein the subject has no symptom of a pKal-mediated disorder at the time the sample is collected, has no history of a symptom of a pKal-mediated disorder, or no history of a pKal-mediated disorder.
12. The method of claim 1 , wherein the active form of Factor XII is of a naturally-occurring Factor XII and the active form of plasma kallikrein is of a naturally-occurring plasma kallikrein.
13. The method of claim 12 , wherein the naturally-occurring Factor XII is human Factor XII and the naturally-occurring plasma kallikrein is human plasma kallikrein.
14. The method of claim 1 , wherein the measuring step is performed by an immunoassay.
15. The method of claim 14 , wherein the immunoassay is a Western blot assay, an enzyme linked immunosorbent assay, a radioimmunoassay, or an electrochemiluminescence-based detection assay.