Peptide quantitation assay for differentiating full-length high molecular weight kininogen (HMWK) and cleaved HMWK

1. A method for detecting cleaved high molecular weight kininogen (HMWK) in a sample, the method comprising:

(i) providing a sample suspected of containing HMWK,

(ii) contacting the sample with a protease to generate a plurality of digested peptides; and

(iii) measuring the level of a signature peptide indicative of the 46 kDa light chain or 56 kDa light chain of cleaved HWMK in the plurality of digested peptides, wherein the signature peptide indicative of the 46 kDa light chain is:

(SEQ ID NO: 1)

KHNLGHGH,

(SEQ ID NO: 2)

KHNLGHGHKHE;

(SEQ ID NO: 3)

KHNLGHGHK;

or

(SEQ ID NO: 4)

KHNLGHGHKHER;

 or,

wherein the signature peptide indicative of the 56 kDa light chain is SSRIGE (SEQ ID NO: 5).

2. The method of claim 1 , wherein the protease is selected from the group consisting of chymotrypsin, endoproteinase Glu-C, endoproteinase Asp-N, cathepsin G, and endoproteinase Lys-C.

3. The method of claim 1 , further comprising measuring the level of a signature peptide that is indicative of full-length HMWK.

4. The method of claim 3 , wherein the signature peptide indicative of full-length HMWK is:

(SEQ ID NO: 6)

GHEKQRKH;

(SEQ ID NO: 7)

KQRKHNLGHGHKHE;

(SEQ ID NO: 17)

DWGHKQRKHNLGHGHKHER;

(SEQ ID NO: 9)

HNLGHGHK;

or

(SEQ ID NO: 10)

SYYFDLTDGLS.

5. The method of claim 3 , wherein the level of the signature peptide indicative of cleaved HMWK, the level of the signature peptide indicative of full-length HMWK, or both are measured by liquid chromatography-mass spectrometry (LC-MS).

6. The method of claim 1 , wherein the sample is a biological sample obtained from a human subject.

7. The method of claim 6 , wherein the human subject has or is suspected of having hereditary angioedema (HAE).

8. The method of claim 6 , wherein the biological sample is a plasma sample collected in an evacuated blood collection tube, which comprises a liquid formulation that comprises a mixture of protease inhibitors.

9. The method of claim 1 , wherein step (ii) is performed in the presence of a reducing agent.

10. The method of claim 6 , further comprising determining whether the human subject has hereditary angioedema (HAE), wherein an elevated level of cleaved HMWK in the biological sample obtained from the human subject as compared with a predetermined reference value indicates that the human subject has HAE.

11. The method of claim 6 , further comprising determining whether the human subject is at risk for hereditary angioedema (HAE) attack; wherein an elevated level cleaved HMWK in the biological sample obtained from the human subject as compared with a predetermined reference value indicates that the human subject is at risk for HAE attack.

12. The method of claim 6 , wherein the biological sample is a blood sample or a plasma sample.

13. The method of claim 8 , wherein the evacuated blood collection tube is a SCAT tube.

14. The method of claim 1 , wherein step (ii) is performed in the absence of a protease inhibitor, an anticoagulant, or both the absence of a protease inhibitor and an anticoagulant.