The amyloid beta peptide is derived from the cleavage of the Amyloid precursor protein (APP) and varies in length from 39 to 43 amino acids. However, the form(s) of amyloid-beta peptide (Aβ) associated with the pathology characteristic of Alzheimer’s disease (AD) remains unclear. In particular, the neurotoxicity of intraneuronal Aβ accumulation is an area of considerable research and controversy principally because antibodies thought to be specific for Aβ have been shown to actually detect intraneuronal APP and not Aβ exclusively.
MOAB-2 (mouse IgG2b) is a pan-specific, high-titer antibody to Aβ residues 1-4 as demonstrated by biochemical and immunohistochemical analyses (IHC), and is highly specific just to amyloid beta peptide. MOAB-2 did not detect APP or APP-CTFs in cell culture media/lysates (HEK-APPSwe or HEK APPSwe/BACE1) or in brain homogenates from transgenic mice expressing 5 familial AD (FAD) mutation (5xFAD mice).
Using IHC on 5xFAD brain tissue, MOAB-2 immunoreactivity co-localized with C-terminal antibodies specific for Aβ40 and Aβ42. MOAB-2 did not co-localize with either N- or C-terminal antibodies to APP. In addition, no MOAB-2-immunreactivity was observed in the brains of 5xFAD/BACE-/- mice, although significant amounts of APP were detected by N- and C-terminal antibodies to APP, as well as by 6E10. In both 5xFAD and 3xTg mouse brain tissue, MOAB-2 co-localized with cathepsin-D, a marker for acidic organelles, further evidence for intraneuronal Aβ, distinct from Aβ associated with the cell membrane. MOAB-2 demonstrated strong intraneuronal and extra-cellular immunoreactivity in 5xFAD and 3xTg mouse brain tissues.
Biosensis now offers biotinylated MOAB-2 antibody allowing more flexibility in experimental design by using the biotin-avidin/streptavidin detection method. Biotinylated MOAB-2 antibody may also help to reduce background staining in difficult-to-stain tissues and increase detection sensitivity. The ability of biotinylated MOAB-2 antibody to detect amyloid beta has been validated by IHC.
The biotinylated MOAB-2 antibody has been tested by IHC (1:500 – 1:2,000 dilution) and is also expected to work in applications validated for the unlabelled antibody (M-1586-100) at same or higher dilutions: Western Blotting (WB), Immunohistochemistry (IHC), Immunohistochemistry/paraffin embedded IHC(P), Immunoprecipitation (IP), Immunofluorescence (IF), ELISA.
Western Blotting:
MOAB-2 has been tested in WB using purified synthetic beta-amyloid preparations and from transgenic mouse brain formic acid extracts (see Figure 1). Formic acid extraction/concentration is required for western blot detection from extracts. Suggested dilution of 1:2000-1:5,000 for WB, standard ECL detection systems.
Tissue samples for the detection of beta-amyloid should be prepared as detailed in Youmans KL et al., 2011 (Journal of Neuroscience Methods 196: 51–59) for best results. Detection of beta-amyloid 40/42 in direct westerns can be difficult; Dot-blots of prepared samples are recommended as detailed in Youmans KL et al., 2012.
Immunohistochemistry:
Suggested dilution for biotinylated MOAB-2 in IHC is 1:500-1:2,000. Fresh frozen, 4% paraformaldehyde fixed frozen, or formalin fixed paraffin embedded tissues are all suitable. Antigen retrieval is required in fixed tissues for optimal staining.
Antibody was tested on 4% paraformaldehyde/0.1% glutaraldehyde fixed frozen tissue from 3xTg and 5xFAD mice. MOAB-2 antibody detects intraneuronal and extracellular beta-amyloid in IHC and does not detect APP (Youmans KL et al., 2012).
The antibody also reacts with archival formalin-fixed, paraffin-embedded tissue samples with antigen Heat Induced Epitope Retrieval (HIER). Recommended buffer for HIER is citrate, pH 6.0. Signal was weak without antigen retrieval. Immunoreactivity was observed in intraneural-amyloid deposition (plaque) in Alzheimer’s brain. MOAB-2 was found to be extremely clean and with an excellent signal to noise ratio with no neuro-cellular diffusive staining.
In addition, MOAB-2 demonstrated no significant differences in Aβ detection using paraffin fixed, free-floating sections (Youmans KL et al., 2012). Formic acid (FA) treatment resulted in optimal detection of both intraneuronal and extracellular Aβ compared to without FA (incubated in 88% FA 8 min, Youmans KL et al., 2012). Free floating tissue sections were permeabilized in TBS containing 0.25% Triton X-100 (TBSX; 3 × 10 min), blocked with 3% horse serum in TBSX (3 × 10 min) followed by 1% horse serum in TBSX (2 ×10 min) and incubated with appropriate primary antibodies diluted in TBSX containing 1% horse serum overnight. See Youmans KL et al., 2012, for full IHC(P) protocol and method details.
Immunofluorescence:
For IF, suggested dilution is 1:100-1:500. The antibody was tested on 4% PFA fixed frozen tissue. Fixed tissues were washed in TBS (3 × 10 min), then incubated in 88% FA (8 min), and then permeabilized in TBSX (3 × 10 min), and blocked in TBSX containing 5% bovine serum albumin (BSA; 1 hr). Sections were subsequently incubated with appropriate primary antibodies diluted in TBSX containing 2% BSA overnight on an oscillatory rotator. Detection was via fluorescently labelled absorbed secondary antibodies (Youmans KL et al., 2012).
Immunoprecipitation:
For IP, the suggested dilution is 1:200 to 1:1,000 for labelled beta-amyloid using SA-coated beads as the capture vehicle, similar to the protocols employed by Youmans KL et al., 2012.
ELISA:
In an ELISA, a dilution of 1:50-1:1,000 is suggested. The antibody has been tested in ELISAs on synthetic beta-amyloid and tissue homogenates from beta-amyloid-Tg mice.
Biosensis recommends optimal dilutions/concentrations should be determined by the end user for all applications. Dilutions provided are only meant to serve as a basic guide.
Type: Primary
Antigen: APP
Clonality: Monoclonal
Clone: MOAB-2
Conjugation: Biotinylated
Epitope: Recombinant human amyloid beta protein 42 (Aβ42): DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA
Host: Mouse
Isotype: IgG2b, lambda light chain
Reactivity: Human;Rat
