Assessment of preeclampsia using assays for free and dissociated placental growth factor
Described herein are methods, compositions, kits, and systems for detecting free and bound PlGF, and using detection of such species to distinguish between pregnant women with or without preeclampsia or related conditions.
1. A method for determining levels of free and dissociated PlGF in a biological sample from a pregnant human female subject, the method comprising:
(a) isolating a first aliquot of the biological sample for the detection of PlGF-f and a second aliquot of the biological sample for the detection of PlGF-d;
(b) determining an amount of PlGF-f in the first aliquot;
(c) applying a treatment to the second aliquot to dissociate PlGF complexes; and
(d) determining an amount of PlGF-d in the second aliquot.
2. The method of claim 1 , further comprising determining a ratio of the amounts of PlGF-f and PlGF-d.
3. The method of claim 1 , wherein the biological sample has not been stored at a temperature above about 20° C.
4. The method of claim 1 , wherein the amount of PlGF-f and the amount of PlGF-d are determined using the same reagents.
5. The method of claim 1 , wherein the PlGF complex comprises PlGF and s-FLT.
6. The method of claim 1 , wherein the treatment is applied for at least 5, 10, 15, 20, 25, 30, 40, 50, 60, 90, or 120 minutes.
7. The method of claim 1 , wherein the treatment comprises increasing the temperature of the second portion of the biological sample.
8. The method of claim 7 , wherein the treatment comprises increasing the temperature to at least 30° C. for at least 1 hour.
9. The method of claim 1 , wherein the treatment comprises increasing or decreasing the pH of the second portion of the biological sample.
10. The method of claim 1 , wherein the treatment comprises contacting the second portion of the biological sample with an agent that prevents PlGF from assembling into a PlGF complex or disables PlGF from a PlGF:sFLT1 complex.
11. The method of claim 10 , wherein the agent is selected from: a surfactant, a detergent, a chaotropic agent, a PlGF-binding protein, and an s-FLT-binding protein.
12. The method of claim 1 , wherein the method has a LLOQ for PlGF of 20 pg/ml or less.
13. The method of claim 1 , wherein the biological sample is blood, serum, plasma, amniotic fluid, or urine.
14. The method of claim 1 , wherein the biological sample is serum or plasma.
15. The method of claim 1 , wherein the pregnant human female has been pregnant for at least 20 weeks.
16. The method of claim 15 , wherein the pregnant human female has been pregnant for no more than 30 weeks.
17. The method of claim 1 , wherein the amount of PlGF-f, PlGF-d, or both is determined by an immunoassay.
18. The method of claim 17 , wherein the immunoassay is selected from a capture ELISA, an indirect ELISA, a TR-FRET assay, a proximity extension assay, an amplified luminescent proximity (LOCI) assay, an electrochemiluminescence immunoassay, a luminescent oxygen channeling assay, or a lateral flow assay.
19. The method of claim 1 , wherein (b) or (d) involve contacting the first aliquot, second aliquot, or both with a capture reagent.
20. The method of claim 19 , wherein the capture agent comprises an antibody or an antigen-binding fragment thereof.