Analytical performance of a sandwich enzyme immunoassay for preβ1-HDL in stabilized plasma

Abstract

We have established an immunoassay for preβ1-HDL (the initial acceptor of cellular cholesterol) using a monoclonal antibody, MAb55201. Because preβ1-HDL is unstable during storage, fresh plasma must be used for preβ1-HDL measurements. In this study, we describe a method of stabilizing preβ1-HDL, and evaluate the analytical performance of the immunoassay for preβ1-HDL. Fresh plasma was stored under various conditions with or without a pretreatment consisting of a 21-fold dilution into 50% (v/v) sucrose. Preβ1-HDL concentration was measured by immunoassay. In nonpretreated samples, preβ1-HDL decreased significantly from the baseline after 6 h at room temperature. Although preβ1-HDL was more stable at 0°C than at room temperature, it increased from 30.2 ± 8.5 (SE) to 56.5 ± 5.5 mg/l apolipoprotein A-I (apoA-I) (P < 0.001) in hyperlipidemics, and from 18.4 ± 1.2 to 37.9 ± 3.3 mg/l apoA-I (P < 0.001) in normolipidemics after 5-day storage. After 30-day storage at −80°C, preβ1-HDL increased from 29.0 ± 4.0 to 38.0 ± 5.7 mg/l apoA-I (P < 0.001) in hyperlipidemics, whereas it did not change in normolipidemics. In pretreated samples, preβ1-HDL concentration did not change significantly under any of the above conditions. Moreover, preβ1-HDL concentrations determined by immunoassay correlated with those determined by native two-dimensional gel electrophoresis (n = 24, r = 0.833, P < 0.05).An immunoassay using MAb55201 with pretreated plasma is useful for clinical measurement of preβ1-HDL.

Keywords

• hyperlipidemia
• lecithin:cholesterol acyltransferase
• apolipoprotein A-I
• two-dimensional gel electrophoresis