Determination of apolipoprotein B-48 in plasma by a competitive ELISA

Background: Apolipoprotein B-48 (apoB-48) is produced by the small intestin e, as part of chylomicrons, and appears to be a suitable marker far clinica l studies of postprandial lipoproteins and related cardiovascular risk. Our aim was to develop, for routine analysis,an assay to quantify apoB-48 in p lasma samples. Methods: A microtiter plate was coated with a C-terminal apoB-48-specific h eptapeptide. Plasma samples were incubated with appropriate detergent to al low competition between immobilized antigen and plasma apoB-48, Appropriate calibration curves were obtained in the ELISA, using calibrated lymph and chylomicrons. Results: Treatment of plasma samples with the mild detergent Triton X-100 a llowed an efficient competition between immobilized antigen and plasma apoB -48. No cross-reactivity was found with apoB-100, as checked by ELISA and W estern blot analysis. Intra- and interassay CVs were 5.4% and 5.5%, respect ively. In healthy subjects, apoB-48 concentrations markedly increased in th e postprandial state, in parallel with triglycerides. Conclusions: This new ELISA allows determination of the concentration of ap oB-48 in normolipidemic plasma. (C) 2000 American Association for Clinical Chemistry.