Methods for quantitation of functional C1 esterase inhibitor (FC1-INH)
Methods for quantitation of fC1-INH from dried blood spot are provided herein. Such methods may comprise spotting and drying a blood sample on a support member, extracting protein from the dried blood sample and measuring the level of fC1-INH in the extracted proteins.
1. A method for determining a level of functional C1-esterase inhibitor (fC1-INH) in a sample, the method comprising:
(i) spotting a blood sample from a subject on a support member;
(ii) drying the blood sample on the support member to form a dried blood spot;
(iii) extracting proteins from the dried blood spot from (ii); and
(iv) measuring the level of fC1-INH in the extracted proteins in (iii), if present;
wherein measuring the level of fC1-INH comprises:
(a) incubating the extracted proteins with a complement component 1s (C1s) and a C1s substrate, to produce a C1s substrate product;
(b) measuring the level of the C1s substrate product produced in step (a); and
(c) determining the level of fC1-INH in the dried blood spot based on the level of the C1s substrate product measured in step (b).
2. The method of claim 1 , wherein step (iv)(a) is performed by incubating the extracted proteins with the C1s and the C1s substrate to produce a reaction mixture.
3. The method of claim 1 , wherein the measuring step of step (iv)(b) is performed by liquid chromatography-mass spectrometry.
4. The method of claim 1 , wherein the C1s substrate is N α -Carbobenzyloxy-Lys-ThioBenzyl ester and the C1s substrate product is N α -Benzyloxycarbonyl-L-lysine (cbz-Lys).
5. The method of claim 1 , wherein the extracting of (iii) is performed by incubating the dried blood spot with a bovine serum albumin (BSA)/phosphate buffered saline (PBS) buffer for at least 3 hours.
6. The method of claim 1 , wherein the support member is a filter paper.
7. The method of claim 1 , wherein the drying of step (ii) is performed for at least 3 hours at room temperature.
8. The method of claim 1 , further comprising obtaining the blood sample from the subject.
9. The method of claim 1 , wherein the blood sample is a whole blood sample.
10. The method of claim 1 , wherein subject is a human subject.
11. The method of claim 10 , wherein the subject has, is suspected of having, or is at risk for having hereditary angioedema (HAE).
12. The method claim 11 , wherein the HAE is Type I HAE or Type II HAE.
13. The method of claim 1 , further comprising determining whether the subject has a C1-INH-deficiency-mediated disorder, wherein a reduced level of fC1-INH product as compared with a control indicates that the subject has the C1-INH-deficiency-mediated disorder.
14. The method of claim 13 , further comprising identifying a suitable treatment for the subject having the C1-INH-deficiency-mediated disorder based on the level of fC1-INH.
15. The method of claim 1 , further comprising identifying the subject as a candidate for treatment of a C1-INH deficiency-mediated disorder based on the level of fC1-INH determined in step (iv)(c) compared to a control level, wherein the control level is the level of fC1-INH in a sample obtained from a healthy subject.
16. The method of claim 1 , further comprising administering a therapeutic agent to the subject, if the subject is identified as being at risk for or having a C1-INH deficiency-mediated disorder based on the level of fC1-INH determined in step (c) compared to a control level, wherein the control level is the level of fC1-INH in a sample obtained from a healthy subject.
17. The method of claim 16 , wherein the therapeutic agent is a plasma kallikrein (pKal) inhibitor, a bradykinin B2 receptor antagonist, or a C1 esterase inhibitor.
18. The method of claim 16 , wherein the therapeutic agent is ecallantide, lanadelumab, icatibant, or a human plasma-derived C1 esterase inhibitor.
19. The method of claim 13 , wherein the C1-INH deficiency-mediated disorder is HAE.
20. The method of claim 19 , wherein the HAE is Type I HAE or Type II HAE.