Quantification of human plasma phospholipid transfer protein (PLTP): relationship between PLTP mass and phospholipid transfer activity

Measurement of Human Plasma Phospholipid Transfer Protein by Sandwich ELISA

Background: Plasma phospholipid transfer protein (PLTP) plays a central role in the remodeling of HDLs. Reliable and accurate methods for assaying PLTP concentration are required.

Methods: A sandwich ELISA for PLTP has been developed, using two monoclonal antibodies against recombinant human PLTP (rhPLTP) expressed in Chinese hamster ovary cells. The ELISA allows for the quantification of PLTP in the range 0.625–15.0 ng/assay (1.2–30.0 mg/L). Intra- and interassay CVs were <3.0% and <4.2% respectively. The assay was used to quantify plasma PLTP concentrations in 132 Japanese subjects (75 males and 57 females).

Results: PLTP concentrations were 12.0 ± 3.0 mg/L (mean ± SD; range, 4.9–20.5 mg/L). No sex difference was observed. Plasma PLTP concentration was positively correlated with HDL-cholesterol (r = 0.72; P <0.001), apolipoprotein (apo) A-I (r = 0.62; P <0.001) and HDL2-cholesterol (r = 0.72; P <0.001), and was negatively correlated with triacylglycerol (r = −0.45; P <0.001). There was no correlation with plasma apo A-II. These results agree with other evidence that plasma PLTP is associated with large apo A-I-containing lipoproteins. There was no correlation (r = −0.01) between plasma PLTP and plasma phosphatidylcholine transfer activity (range, 3.5–10.5 μmol · mL−1 · h−1), suggesting that PLTP may exist in active and inactive forms.

Conclusion: This new ELISA will be of value for further studies of PLTP in health and disease.