Determination of apolipoprotein B-48 in serum by a sandwich ELISA

Background: Apolipoprotein B-48 (apoB-48) is produced by the small intestine, as a part of chylomicrons (CMs), and appears to be a suitable marker for clinical studies of postprandial lipoproteins and related cardiovascular risk factors. We have developed an assay for routine analysis to quantify apoB-48 in serum or plasma. Methods: A microtiter plate was coated with monoclonal antibody (4C8) raised against apoB-48 C-terminal specific decapeptide. Serum samples were diluted 100-fold with 0.05 mol/l Tris-HCl buffer (with or without 0.1% Triton X-100). Appropriate calibration curves were obtained in the ELISA by using apoB-48 recombinant antigen. Results: No cross-reactivity (<0.001%) was found with apoB-100, as verified by ELISA and Western blot analyses. Intra- and inter-assay CVs were 4.8% and 5.4%, respectively. Recovery of added recombinant apoB-48 in serum was within 94-105%. The assay linearity was intact >5-fold dilution of serum by dilution buffer. ApoB-48 levels in healthy controls (n=18) at fasting were within the range of 2.69-6.56 mug/ml (mean +/- S.D.: 4.60 +/- 1.54 mug/ml). In healthy subjects, serum apoB-48 concentrations markedly increased in the postprandial state, in parallel with serum triglycerides. Conclusion: This method for measuring apoB-48 using the monoclonal antibody 4C8 is simple, reliable and suitable for routine analyses. (C) 2004 Elsevier B.V. All rights reserved.