Crystal structure reveals conservation of amyloid-β conformation recognized by 3D6 following humanization to bapineuzumab
© Feinberg et al.; licensee BioMed Central Ltd. 2014
Received: 24 January 2014
Accepted: 23 April 2014
Published: 2 June 2014
Immunotherapy targeting amyloid-β peptide is under active clinical investigation for treatment of Alzheimer’s disease (AD). Among the hypotheses being investigated for impact on clinical outcome are the preferred epitope or conformation of amyloid-β to target for treatment, and the mechanism of action underlying immunotherapy. Bapineuzumab (humanized 3D6), a neo-epitope specific antibody recognizing amyloid-β1-5 with strong preference for an exposed Asp residue at the N-terminus of the peptide, has undergone advanced clinical testing for treatment of AD.
To gain further insight into the epitope conformation, we interrogated structural details of amino-terminal epitopes in amyloid-β using x-ray crystallography of 3D6Fab:amyloid-β complexes. Humanization of 3D6 was carried out using standard procedures integrating recombinant methods, sequence informatics, and homology modeling predictions to identify important mouse framework residues for retention in the finished humanized product.
Here we report the crystal structure of a recombinant Fab fragment of 3D6 in complex with amyloid-β1-7 solved at 2.0 Å resolution. The N-terminus of amyloid-β is bound to 3D6 as a 310 helix. The amino-terminal Asp residue is buried deepest in the antibody binding pocket, with the Cβ atom of residue 6 visible at the entrance to the binding pocket near the surface of the antibody. We further evaluate homology model based predictions used to guide humanization of 3D6 to bapineuzumab, with actual structure of the Fab. The structure of the Fab:amyloid-β complex validates design of the humanized antibody, and confirms the amyloid-β epitope recognized by 3D6 as previously mapped by ELISA.
The conformation of amyloid-β antigen recognized by 3D6 is novel and distinct from other antibodies recognizing N-terminal epitopes. Our result provides the first report demonstrating structural conservation of antigen contact residues, and conformation of antigen recognized, between the parent murine antibody and its humanized version.
Immunotherapy targeting amyloid beta (Aβ) peptide has been demonstrated to prevent or reverse a range of Alzheimer’s disease (AD) related pathologies, in both transgenic mouse models and AD patients [1–5]. Efficacy against Aβ related behavioral deficits has also been reported in transgenic mouse models of AD [6–9]. Despite the failure of initial efforts with immunotherapy to meet primary endpoints in pivotal clinical trials [10, 11], the preponderance of successful pre-clinical studies targeting Aβ provide support for ongoing clinical trials with Aβ immunotherapy for treatment of AD in humans, evidenced by the multiplicity of approaches continuing clinical testing [12–15] (ClinicalTrials.gov Identifier: NCT01760005).
A number of important questions regarding efficacy following Aβ immunotherapy remain under investigation. These include: 1) the mechanisms of action; 2) preferred Aβ epitope to target; and 3) the specific form of Aβ recognized by a given antibody. In our hands, antibody isotypes with maximal effector function targeting amino-terminal epitopes provided the greatest efficacy across a number of end-points in preclinical studies [5, 16, 17]. Fine mapping the epitope specificity among antibody responders from an active vaccination phase 2 trial in AD patients immunized with AN1792 (Aβ1-42 peptide) revealed exquisite specificity for the amino-terminus of Aβ peptide , providing some clinical support for targeting the amino-terminus of Aβ for AD immunotherapy.
Among the efficacious in vivo amino-terminal epitope targeting antibodies we characterized and humanized for clinical development, the antibody 3D6 presented an attractive candidate due to its neo-epitope specificity for the amino-terminus of Aβ, namely a strong preference for a free Asp residue at position 1 of Aβ. This unique specificity of 3D6 precludes recognition of unprocessed amyloid precursor protein (APP) (hypothesized to be a desirable attribute in a clinical candidate), and is preserved in bapineuzumab (humanized 3D6, version 2), as reported below. Furthermore, the 3D6 epitope is detectable in all forms of Aβ tested , from compacted β-amyloid plaques in AD and platelet-derived growth factor (PDGF) promoter driven APP transgenic mouse model of AD (PDAPP) brain, to soluble oligomeric species. The latter are thought to be a primary mediator of neurotoxicity, and have also been postulated to underlie behavioral impairments in AD Tg mice . In summary, the properties of 3D6 most closely reflected the antibody response mapped in AN1792 treated AD patients , supporting advancement of bapineuzumab (humanized 3D6v2) for clinical development [3, 20–22].
To gain further insight into this specific Aβ epitope for immunotherapy of AD, we investigated antigen conformation recognized by different antibodies targeting amino-terminal epitopes of Aβ using X-ray crystallography of antibody:Aβ co-complexes solved to very high resolution (1.5 to 3 Å for all antibodies) . Previously, we reported that three independently derived antibodies targeting Aβ residues 3–7 recognize antigen in an extended conformation along the surface of the antibody binding site . Here we report that, in contrast, antibody 3D6, targeting Aβ residues 1–5, binds antigen in a 310 helix. The antigen is bound by antibody such that the amino-terminus of the peptide is buried in a cleft in the antibody binding site, and the carboxy-terminus winds out to the surface of the antibody. Taken together, our findings reveal distinct conformations adopted by the amino-terminal epitope of Aβ, consistent with independent reports from other groups [24–26], and offer a testable hypothesis for the combinatorial manipulation of antibody activities targeting Aβ, for example, as bi-specific antibodies (wherein each arm of the Fab recognizes a different epitope/conformation of Aβ), incorporating the appropriate Fc isotype (for desired effector functions).
The high resolution crystal of 3D6 Fab + Aβ reported here, coupled with the structure of 4HIX (an early version of humanized 3D6 containing mouse framework residues deemed dispensable in bapineuzumab, see Results) in complex with Aβ  afforded the opportunity for retrospectively evaluating the humanization design of 3D6 leading to bapineuzumab. Comparison of our structure with 4HIX illustrates conservation of antigen conformation, and all features of antigen recognition by the antibody. This comparative analysis validates the design of bapineuzumab and attests to the robustness of antibody humanization technology as a platform for obtaining clinical development candidates from preclinical leads for disease therapy in humans.
Recombinant 3D6 Fab was expressed and purified from mammalian cell culture supernatant as previously described . Crystallization conditions are summarized in Additional file 1: Table S1. Crystals of 3D6 Fab with either Aβ1-7 peptide or Aβ1-40 peptide were grown at 22 °C and frozen in liquid nitrogen for data collection.
Crystallographic data statistics
Unit cell lengths (Å)
a = 126.8
a = 40.0
b = 69.4
b = 84.9
c = 61.7
c = 175.9
β = 115.4
Resolution Å(last shell)
% completeness (last shell)
Residues in final model (total)
Average B (Å2)
Bond length RMSD (Å)
Angle RMSD (°)
Ramachandran plot: (% in preferred/ allowed/ outliers regions)b
Molecular replacement calculations were performed using the program COMO . Molecular replacement was done in two stages, first finding the rotation and translation solution of the constant domain and later, while fixing the constant domain, finding the solution for the variable domain. Model building was done using the program Coot . The structures were initially refined using Refmac  and at later stages using Phenix  with individual positional and B-factor refinement and five Translation Libration Screw (TLS) groups (the heavy and light chains were split into two groups each, at the hinge between the constant and the variable domains, and the peptide as a separate group).
In the final model of 3D6 + Aβ1-7 the side chain of residue 6 was not visible past Cβ. Only Aβ residues 1–5 are visible in the 3D6 + Aβ1-40 crystal structure. These crystals were grown in the 200 mM Zn2+, and several strong difference electron density peaks were modeled as Zn2+, based on the geometry of the surrounding ligands and the appearance of strong peaks at these positions in an anomalous difference map. One of these Zn2+ ions occupies the same spatial position as Aβ1-40 and hence cannot be present at this site at the same time as the peptide. The peptide and this Zn2+ ion were treated as alternative conformations each with 50% occupancy. The x-ray coordinates of the structures reported here have been deposited in the protein data base (pdb) and are accessible under the pdb identifiers 4ONF (Aβ1-7 complex) and 4ONG (Aβ1-40 complex).
Affinity determination by Biacore
Interactions between anti-Aβ antibodies and biotinylated DAE10 peptide (Aβ1-10 conjugated to biotin at the carboxy-terminus and immobilized to streptavidin coated chips) were quantitatively analyzed using BIAcore plasmon resonance technology, and apparent kinetic rate constants were derived. Bio DAE-10 peptide was diluted in water at 1.0 mg/ml and kept at -80°C (stock). Following immobilization of the biotinylated DAE10 peptide, varying concentrations of each antibody were applied in triplicate and the binding was measured as a function of time. Affinity measurements chips were performed on chips coated at lower densities, typically 4 to 7 response units (RU) of the bio-peptide ligand. Antibodies were injected in triplicate at 100 nM at a flow rate of 30 μl/minute, injection time two minutes, post-injection time ten minutes, followed by regeneration of chips with 5 μl 0.1% tri-fluro acetic acid (TFA). All the antibodies were run in at least three different chips over three different density surfaces. From these measurements the apparent dissociation (kd) and association (ka) rate constants were derived and used to calculate a KD value for the interaction, corrected for active concentration of antibody. Active concentration of antibody measurements was carried out using chips coated with bio-DAE peptide at high density. All the affinity data presented in this report were analyzed using the bivalent model.
Humanization of 3D6
As the humanization of 3D6 preceded the elucidation of its crystal structure, the variable light and heavy regions of 3D6 were modeled using the most homologous mouse antibodies of solved crystal structure as templates to guide humanization of 3D6 [31–34]. The homology model of 3D6 Fv was built using pdb identifiers 1CR9 VL and 1OPG VH, respectively, (overall VL identity = 94% and VH identity = 72%) using QUANTA (Release dated 1999, Accelrys Software Inc., San Diego, CA, USA). The crystal structures of the selected modeling templates had been solved to high resolution (2 Å), and their primary sequence fulfilled key criteria to facilitate design of the humanized antibody based on the most homologous human VL (Kabat accession #019230) and VH (Kabat accession #045919) frameworks available at the time in public databases . All antibody residue numbering in this report is according to Kabat , with the one exception as noted in the figure legend.
Structure of 3D6 with Aβ peptide
Residues of the antibody contacting A β (that is, within 4 angstroms) in the structure of 3D6 with A β1-7
W89 G91 R96
Y95H S100a S100b
A2 E3 F4
W89 G91 R96
Y95H S100a S100b
A2 E3 F4
G91 T92 H93 F94
D1 E3 F4 R5 H6
G91 T92 H93 F94
D1 E3 F4 R5 H6
W47 S50 R52 Y58
D1 A2 F4 R5
W47 S50 R52 Y58
D1 A2 F4 R5
G33 M34 S50 I51 R52 Y95
D1 A2 E3 R5
G33 M34 S50 I51 R52 Y95
D1 A2 E3 R5
D27d D28 Y32 G91 T92
A2 E3 F4 H6
D27d D28 Y32 G91 T92
A2 E3 F4 H6
Summary of mouse VL and VH framework residues retained in humanized 3D6/bapineuzumab based on predicted interactions (<4 Å) with critical distal intra-chain or inter-chain residues
Mouse VL Fr residue retained in bapineuzumab
Interacting residues revealed from crystal structure of 3D6
Mouse VH Fr residue retained in bapineuzumab
Interacting residue revealed from crystal structure of 3D6
Ser50:H2, Tyr58:H2 Tyr59:H2
Tyr95:H3, Ser100B:H3 Tyr102:H3
Trp35(L), Leu36(L) Asp55:L2, Val58(L)
Tyr95:H3, Asp96:H3 Ser100B:H3, Asp101:H3 Tyr102:H3
Ser99:H3, Ser100a:H3 Ser100b:H3 , Asp101:H3
Several interactions between the peptide and the antibody involve bridging water molecules (also observed in the 4HIX crystal structure . Water molecules are present not only on the surface of the antibody but also inside the deep fissure at the antibody binding site, and interact with residues from the N-terminus of the peptide that are positioned at the bottom of the elongated site. Examples are shown in Additional file 2: Figure S1. As also noted by Miles et al. , a helical conformation of Aβ has been revealed via nuclear magntic resonance (NMR) spectroscopy [39, 40]. Whereas the structure of the amyloidogenic core of Aβ peptide has been extensively characterized (see for example, [41–43]), it is well recognized that the amino-terminus of Aβ does not adopt a single conformation in solution. Coupled with the solution NMR data, our results are consistent with the notion that the amino terminus dynamically samples a helical conformation, and it is this subpopulation of Aβ that is recognized by 3D6. A hypothetical fit of the NMR structure of Aβ with our structure is illustrated in Additional file 3: Figure S2. Given the absence of electron density after residue 5 in the Aβ1-40 complex, it is likely that upon binding the amino-terminal epitope, the antibody can interact with different conformations adopted by the Aβ peptide past residue 5.
Comparison of 3D6 and 12A11 binding to Aβ peptide
Structure of 3D6 Fab:Aβ complex supports design considerations in humanization to bapineuzumab
Humanization of 3D6 was effected by a combination of CDR grafting of mouse residues from 3D6 VL and VH into human frameworks, and homology model guided retention of select mouse framework residues in the initial humanized version of the monoclonal antibody (mAb) [31, 32, 35, 44, 45]. Superposition of the model with the solved crystal structure of 3D6 gives an RMSD 0.74 Å for the VL domain, and 1.93 Å for VH (primarily attributable to expected deviation in CDR-H3). The overall RMSD for Fv is 2.35 Å, arising from a difference in the orientation of VL and VH with respect to each other. Two versions of humanized 3D6 were expressed and tested (detailed below), and both versions were demonstrated to retain all desired in vitro and in vivo properties of the parent murine mAb , for example, retention of affinity for antigen, stimulation of plaque phagocytosis by microglia in a frozen section ex-vivo assay, ability to recognize β-amyloid in plaque by histology of PDAPP and AD brain in frozen section, brain localization in PDAPP and epitope specificity.
Binding kinetics of murine, recombinant chimeric, and two versions of humanized 3D6 to Aβ1-10 peptide
3.61E + 05
3.43E + 05
Hu 3D6 v1
1.89E + 05
Hu 3D6 v2
1.50E + 05
The murine VL framework residues Val2, Leu36 and Arg46 were retained in bapineuzumab based on the model, which predicted interactions of Val2 with residues in CDR L1 and L3 (see Additional file 4: Figure S3). Leu36 was retained based on its predicted role for inter-chain packing, while Arg46 was predicted to be involved in interactions with H3, in addition to multiple contacts with non-contiguous VL Fr residues. These predictions were confirmed in the crystal structure of 3D6 as summarized in Table 3, and detailed in Additional file 5 ‘Structural observations in 3D6 regarding mouse VL Fr residues retained during humanization, confirming predictions based on homology model’.
The three mouse VH framework residues retained in humanized 3D6 VHv1 (Ala49, Val93, and Arg94) are all revealed by the crystal structure of 3D6 to mediate contacts with CDR residues, contributing to preservation of CDR conformation, and by extension, contributing to antibody:antigen contacts (Table 3, and Additional file 5 ‘Structural observations in 3D6 regarding mouse VL Fr residues retained during humanization, confirming predictions based on homology model’).
Finally, three human VH Fr residues in v1 of humanized 3D6 were converted to germline A75S, S78T and L93V based on the sequence of the closest human germline VH region (V3-23), leading to version two of humanized 3D6 (bapineuzumab). The germline changes were incorporated in bapineuzumab to minimize potential Fr changes in the human VH (KABID 045919) arising from somatic hypermutation during affinity maturation. The crystal structure of 3D6 reveals that the methyl side chain of Ala75 is exposed to solvent on a β-turn. Conversion to germline of human Ser78 to Thr actually restores the residue at this position in 3D6, and preserves intra-chain cross β-strand interactions between T78 and residues on β-strand 1 of VH. The Leu93Val germline change is a conservative mutation that would preserve local interactions of the original Fr Leu residue. These germline changes in bapineuzumab VH were not incorporated into the molecule crystallized by Miles et al.  (pdb identifier 4HIX). Version two of humanized 3D6 was advanced for clinical development as bapineuzumab. The integrity of the sequence of bapineuzumab was confirmed by mass spectroscopy, and amino acid analysis (AAA) (data not shown, reported in the chemistry, manufacture, and controls (CM and C) section of the investigative new drug (IND) application submitted to the US Food and Drug Administration (FDA) in support of the clinical development of bapineuzumab).
While the contribution of individual light and heavy chain framework residues described in this section to antibody activity (particularly affinity) must await confirmation via systematic site directed mutation analyses in future studies, the activity of bapineuzumab was compared with 3D6 in vitro as well as in vivo in a number of different assays . Binding kinetics and affinity (a primary criteria in antibody humanization) measurements comparing 3D6 with bapineuzumab were carried out by surface plasmon resonance. The data comparing 3D6 versus two versions of humanized 3D6 binding to an Aβ1-10 peptide antigen, summarized in Table 4, revealed that both versions of humanized 3D6 retained binding affinity for antigen within the target 2-3X of parent mouse antibody, although this relative difference in affinity measures appears insignificant when referenced to the chimeric antibody. (See Additional file 6: Figure S4 for representative surface plasmon resonance binding curves underlying the data in Table 4.) The conformation of CDR loops, conformation of antigen binding residues, as well as the conformation of bound antigen, reveals excellent conservation of structure between 3D6 and 4HIX (Figure 4), supporting the design algorithm employed in the humanization of 3D6 to bapineuzumab.
Multiple groups have reported the structural features of antigen recognition and antigen conformation from anti-Aβ antibodies targeting an amino-terminal epitope of the peptide [23–26, 37, 38]. The neo-epitope specificity of 3D6 combined with conformation of the bound epitope, elucidated here at 2 Å resolution and in the structure 4HIX , is clearly unique among the antibodies studied to date, as well as among clinical candidates under current investigation. Gantenerumab  binds Aβ in a manner that overlaps the epitope recognized by 3D6 and offers an interesting comparison. Although gantenerumab recognizes two discontinuous epitopes on Aβ by pepspot analysis, the crystal structure revealed binding to Aβ residues 1–11. The reported crystal structure for gantenerumab crystals soaked with Aβ1-11 is not publicly available, limiting a detailed comparison with our structure of 3D6 with Aβ. However, in contrast with the 310 helical conformation captured by 3D6, Aβ is described as binding gantenerumab in an extended conformation with antibody residues from H1, H2, H3 and L3 contributing sites of contact with antigen. This further contrasts with our observations with antibody 3D6 CDRs, where CDRs H1, H2, H3, L1 and L3 contribute sites of contact with Aβ (Table 2). Thus, available evidence suggests that the conformation of Aβ recognized by gantenerumab is distinct from 3D6, and apart from a reversed amino to carboxy terminal orientation, is more similar to WO2 , 12A11  and PFA1 . Hence, the amino-terminal conformation of Aβ recognized by 3D6, and most likely also bapineuzumab as evidenced by 4HIX, comprises a third conformation adopted by this non-amyloidogenic and relatively unstructured domain of the peptide.
In conjunction with the wealth of biophysical studies of the structure of the core amyloidogenic region of Aβ in fibrils (see for example, [41–43]), the combined data sets from antibody crystallization studies provide a structural snapshot of the amino-terminal conformations adopted by one of the two important pathologic determinants of AD. Based on the distinct conformations of Aβ recognized by 3D6 (helical) versus 12A11, gantenerumab, WO2, PFA1 (extended), it is reasonable to speculate that 12A11 and 3D6 target different amino-terminal conformations of Aβ peptide presented in its multiple states. Consequently, one could envision a scenario whereby antibody binding to the amino terminal epitope of Aβ alone could skew the equilibrium distribution of total Aβ species (soluble monomer to amyloid plaque deposited forms) toward the antibody bound state, and thereby potentially affect the overall steady-state distribution of the different forms in which Aβ may exist at any given point in time.
Although the structure of 3D6:Aβ reported here is in very close agreement with its humanized version 4HIX , the discrepancy between our reports in the affinity of humanized 3D6 v1 (equivalent to 4HIX) merits comment. We observed low nanomolar affinity for Aβ with both versions of humanized 3D6 and a 2-3X loss of affinity between murine or chimeric 3D6 and humanized (Table 4). Miles et al. reported an affinity of 76 nM for Aβ1-40, 150 nM for Aβ1-28, and low μM for Aβ1-7, from their synthetic Fab of humanized 3D6 (equivalent to our version 1). These values reflected a 15 to 30 fold loss of affinity in the humanized mAb when compared to a 5 nM affinity of 3D6 for Aβ1-40 reported by DeMattos et al. . Our measure of the affinity of 3D6 for Aβ1-10 is in closer agreement with that reported by DeMattos et al. The discrepancy between affinity measurements reported here (and by DeMattos et al.), versus the affinity reported by Miles et al. can be attributed primarily to the use of whole antibody (this report and DeMattos et al.) versus Fab (Miles et al.). A secondary contributor to our discrepant affinity measures may be attributable to differences in methodology for affinity determination (surface plasmon resonance in our report and microscale thermophoresis by Miles et al. ). The structural details for antigen recognition by antibody provide insight toward modulating affinity via site directed mutagenesis.
Antibody humanization provided the first approach to solving the limiting immunogenicity of mouse antibodies in man [32, 44, 47, 49–51]. Antibody engineering technology has been continuously evolving over that time period, from pioneering work with phage display [52–56] and xeno-mouse based approaches [57–59] to more esoteric recombinant engineering of xenogenic species derived antibodies and yeast display based approaches (for reviews, see [60–62]). The excellent agreement we report between the structures of 3D6:Aβ and that of 4HIX, as summarized in Table 2 and Figure 4, attests to the robustness and continued viability of antibody humanization as a rapid and efficient technology for lead optimization of biological drug candidates. The approaching expiry of the exclusivity period of archetypal humanization patents [63–66] provides an illustrative (but not comprehensive) rationale for the continued value of antibody humanization as an economical platform for drug development going forward.
A bi-specific [67, 68] or dual variable domain  antibody combining recognition of the two conformations of Aβ revealed from crystal structure studies, that is, extended conformation on one arm and helical conformation on the other arm, would offer intriguing dual activity that could be particularly well suited for disaggregation of β-amyloid plaque independent of effector cell engagement. Recent progress with immunotherapy targeting Tau in preclinical models is revealing preferred targets for antibody binding . Structural investigation of the conformation of tau recognized by efficacious anti-Tau antibodies will be informative regarding the mechanisms underlying intercellular transmission of these pathological entities, and furthermore, enable design of bi-specific antibodies capable of recognizing and neutralizing both tau and Aβ.
Disease modifying therapy of AD remains a significant unmet medical need [71–74]. The disease modifying effects of Aβ-targeted immunotherapy  have been widely reproduced in preclinical models. Although the initial clinical trials with bapineuzumab failed to achieve the clinical end-points at the disease stage tested , the continued refinement of Aβ targeted immunotherapy for AD has resulted in numerous follow-on passive and active immunotherapy approaches currently undergoing clinical investigation. The efforts underway target either different epitopes of Aβ, (for example, Solaneuzumab  and Gantenerumab ), different species of Aβ (for example, oligomer specific antibodies discovered via a range of technologies [76–78] versus plaque specific ), or engage different mechanisms to effect clearance or neutralization of Aβ mediated pathologies, for example, effector function (Crenezumab  versus bapineuzumab  and gantenerumab ). The report by Lu et al. demonstrating conformational variation of β-amyloid fibril structure in AD patients  suggests utility as well as limitations of approaches targeting a specific conformation. As we have reported, 3D6 shows the ability to target and neutralize multiple species of Aβ , in an Fc receptor dependent as well as independent manner. Current evidence based on pre-clinical studies suggests that attenuated effector activity may be preferable in an immunotherapeutic targeting Aβ . Hence, a second generation anti-Aβ therapeutic with attenuated effector function, as embodied in crenezumab and AAB-003 (containing humanized 3D6 variable regions), or a bi-specific antibody targeting different Aβ amino-terminal conformations, or both Aβ and Tau (as discussed earlier), which targets all forms of pathogen to neutralize, or promote, its clearance, may prove to be efficacious when applied in a disease stage appropriate manner [71, 74].
Fab 3D6 + Aβ residues 1–40
Fab 3D6 + Aβ residues 1–7
amino acid analysis
amyloid precursor protein
amyloid beta peptide
beta-site APP cleavage enzyme
complementarity determining region
- CM and C:
chemistry, manufacture, and controls
enzyme linked immunosorbent assay
fragment antigen binding, comprising variable and first constant regions of heavy and light chains of an antibody
fragment constant, that is, constant region of antibody comprising the hinge, second and third constant regions of immunoglobulin heavy chain
fragment variable, that is, just the VL and VH fragments of an antibody
CDR1 in VH
CDR2 in VH
CDR3 in VH
investigative new drug
CDR1 in VL
CDR2 in VL
CDR3 in VL
PDGF promoter driven APP transgenic mouse model of AD
protein data base
platelet-derived growth factor
root mean square deviation of atomic position
Translation Libration Screw
variable region, heavy chain
variable region, light chain.
We thank Farshid Oshidari for expert technical assistance in cloning and expression of recombinant 3D6Fab, and Frederique Bard for critical reading of the manuscript. All co-authors with the exception of William Weis and Hadar Feinberg were employees of and shareholders in either Elan Pharmaceuticals, or Wyeth Inc., during the time this work was performed. Jose Saldanha was a consultant to Elan Pharmaceuticals, Inc.. This work was supported by Elan Pharmaceuticals Inc., and Wyeth Inc., and the manuscript was reviewed and approved for publication by Elan, Pfizer, and Janssen Alzheimer Immunotherapy prior to submission. Portions of this work were conducted at the Stanford Synchrotron Radiation Lightsource, supported by the U.S. Department of Energy and the National Institutes of Health.
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