Lp-PLA2 assays and composition with detergent
Provided herein are methods, systems, and compositions for Lp-PLA2 detection assays that employ amounts of detergent to liberate all or nearly all of the Lp-PLA2 molecules from associated lipoprotein particles. In this regard, the true Lp-PLA2 concentration can be detected in a sample, which correlates better with known Lp-PLA2 activity assays.
1. A method of detecting lipoprotein-associated phospholipase A2 (Lp-PLA2) in a sample comprising:
a) contacting a sample with a first amount of a detergent mix and Lp-PLA2 binding molecules,
wherein said detergent mix comprises two or more detergents,
wherein said detergent is not CHAPS,
wherein said sample comprises Lp-PLA2 associated with lipoprotein particles,
wherein said first amount of the detergent mix is sufficient such that at least 95% of all of said Lp-PLA2 in said sample that is associated with said lipoprotein particles is liberated from said lipoprotein particles, and
wherein said Lp-PLA2 binding molecules bind to Lp-PLA2 to form complexes; and
b) detecting said complexes, thereby determining said Lp-PLA2 concentration in said sample.
2. The method of claim 1 , wherein said first amount of the detergent mix is sufficient such that at least 98% of all of said Lp-PLA2 in said sample that is associated with said lipoprotein particles is liberated from said lipoprotein particles.
3. The method of claim 1 , wherein a ratio of Lp-PLA2 concentration, in ng/ml, to Lp-PLA2 activity, in nmol/min/ml, is at least 12:1, and wherein said Lp-PLA2 activity is determined with a mass-spectrometry based activity assay.
4. The method of claim 3 , wherein said ratio is at least 13:1.
5. The method of claim 1 , wherein said sample is from a patient suspected of having, or diagnosed with, cardiovascular disease.
6. The method of claim 1 , wherein said sample is selected from the group consisting of: a serum sample, a plasma sample, and a blood sample.
7. The method of claim 1 , wherein said detergent mix comprises at least an non-ionic detergent.
8. The method of claim 1 , wherein said detergent mix comprises at least a ionic detergent.
9. The method of claim 1 , wherein said detergent mix comprises at least a zwitterionic or a chaotropic detergent.
10. The method of claim 1 , wherein said detergent mix comprises at least one detergent selected from the group consisting of: Triton X-100, Deoxycholate, sodium dodecyl sulfate, cholate, sarkosyl, n-Dodecyl β-D-maltoside (DDM), digitonin, tween 20, tween 80, and urea.
11. The method of claim 1 , wherein said Lp-PLA2 binding molecules are selected from the group of: aptamers, antibodies, and antigen-binding portions of antibodies.
12. The method of claim 1 , wherein the concentration of said first amount of the detergent mix is between 0.05% to 2%.
13. The method of claim 12 , wherein the concentration of said first amount of the detergent mix is between 0.05% to 1%.
14. The method of claim 1 , wherein said two or more detergents are selected from the group consisting of: Triton X-100, Deoxycholate, sodium dodecyl sulfate, cholate, sarkosyl, DDM, digitonin, tween 20, tween 80, and urea.