[The capacity of albumin to bind to beta-amyloid]

Most plasma beta-amyloid peptide (Alphabeta) has been described to circulate bound to albumin (approx. 90%). Moreover, a balance between peripheral and brain Alphabeta seems to exist, so a reduction of Alphabeta levels in blood through plasma exchange with therapeutic albumin should induce a clearance of brain Alphabeta. In this study, content of Alphabeta in therapeutic albumin as well as its binding capacity were characterized.

Levels of Alphabeta(1-40) and Alphabeta(1-42) were determined by means of ELISA technique in therapeutic albumin (human albumin Grifols; n = 18 batches), in normal plasma (n = 8) and in plasma from patients with Alzheimer disease (n = 45). Binding capacity of therapeutic albumin to synthetic peptides containing the primary sequence of human Alphabeta(1-42) was determined by means of surface plasmon resonance (SPR) technique. RESULTS. Both the Alphabeta(1-40) and Alphabeta(1-42) levels in therapeutic albumin were always lower than the last valid point measured in the standard curve (< 25 to < 63 pg/mL). Levels in normal plasma and in plasma from Alzheimer disease patients ranged between < 25 to 312 pg/mL for Alphabeta(1-40), and < 25 to 279,4 pg/mL for Alphabeta(1-42). SPR studies confirmed the high affinity of therapeutic albumin for the experimental Alphabeta peptide.

Human albumin Grifols shows undetectable Alphabeta levels, and lower to those observed in normal plasma and in plasma from patients with Alzheimer disease. Moreover, it was able to bind peptides containing the sequence of human Alphabeta(1-42).