MICROPARTICLE-ENHANCED NEPHELOMETRIC IMMUNOASSAY OF LACTOFERRIN IN HUMAN-MILK

A microparticle-enhanced nephelometric immunoassay was developed for l actoferrin quantitation in human milk. It is based on the nephelometri c measurement of the light scattered during the competitive immuno-agg lutination of a microparticle-lactoferrin conjugate with an antilactof errin antiserum. This immunoassay is sensitive (detection limit in rea ction mixture, 0.2 mg/L) and can be performed in diluted milk (1/3,000 in reaction mixture), excluding any interference or sample pretreatme nt. It allowed the quantification of lactoferrin on a large range of c oncentrations (0.675-21.6 g/L) with accuracy (linear recovery in dilut ion-overloading assay) and precision (within-and between-run coefficie nts of variation from 3% to 6%). Changes in the lactoferrin concentrat ion of human milk during lactation were determined in 190 samples. The concentration and ratio of lactoferrin vs. total protein were found t o be significantly higher in colostrum (5.9 g/l, 29%) than in transiti onal milk (2.9 g/L, 22%) or mature milk (2.5 g/L, 24%). (C) 1997 Wiley -Liss, Inc.