High affinity binding of monoclonal antibodies to the sequential epitope EFRH of beta-amyloid peptide is essential for modulation of fibrillar aggregation

Monoclonal antibodies raised against the N-terminal of Alzheimer's beta-amy loid peptide (beta AP) were found to modulate its fibrillar aggregation. Wh ile mAbs 6C6 and 10D5 inhibit the formation of beta-amyloid fibrils, trigge r disaggregation and reversal to its non-toxic form, mAb 2H3 is devoid of t hese properties. MAb 2H3 binds the sequence DAEFRHD. corresponding to posit ion 1-7 of the beta AP with high affmity (2 x 10(-9)M) similar to its bindi ng with the whole beta AP. The EFRH peptide strongly inhibits binding of mA bs 6C6 and 10D5 to beta AP, whereas it inhibits weakly the interaction of 2 H3 with beta AP. Low affinity binding of mAb 2H3 to EFRH might explain its failure in prevention of beta-amyloid formation. (C) 1999 Elsevier Science B.V. All rights reserved.