Immunohistochemical characterization of novel monoclonal antibodies against the N-terminus of amyloid β-peptide

Amyloid beta-peptide (A beta) is a key molecule in Alzheimer's disease (AD). Reliable immunohistochemical (IHC) methods to detect A beta and A beta-associated factors (AAF) in brain specimens are needed to determine their role in AD pathophysiology. Formic acid (FA) pre-treatment, which is generally used to enable efficient detection of A beta with IHC, induces structural modifications within the A beta, as well as in AAF. Consequently, interpretation of double IHC stainings becomes difficult. Therefore, serial stainings of two newly produced monoclonal antibodies (mAbs) VU-17 and IC16 and two other mAbs (6E10 and 3D6) were performed with four different pre-treatments (no pre-treatment, Tris/EDTA, citrate and FA) and additionally six IHC characteristics were scored: diffuse/compact/classic plaques, arteries with cerebral A beta angiopathy, dyshoric angiopathy, capillaries with dyshoric angiopathy. Subsequently, these stainings were compared with IHC procedures, which are frequently used in a diagnostic setting, employing mAbs 4G8 and 6F/3D with FA pre-treatment. IHC A beta patterns obtained with VU-17 and, IC16 and 3D6 without the use of FA pre-treatment were comparable to those obtained with 4G8 and 6F/3D upon FA pre-treatment. Omission of FA pre-treatment gives the advantage to allow double IHC stainings, detecting both A beta and AAF that otherwise would have been structural modificated upon FA pre-treatment.