Vaccination of Alzheimer's model mice with Aβ derivative in alum adjuvant reduces Aβ burden without microhemorrhages

Abstract

Immunotherapy holds great promise for Alzheimer's disease (AD) and other conformational disorders but certain adverse reactions need to be overcome. The meningoencephalitis observed in the first AD vaccination trial was likely related to excessive cell-mediated immunity caused by the immunogen, amyloid-β (Aβ) 1-42, and the adjuvant, QS-21. To avoid this toxicity, we have been using Aβ derivatives in alum adjuvant that promotes humoral immunity. Other potential side effects of immunotherapy are increased vascular amyloid and associated microhemorrhages that may be related to rapid clearance of parenchymal amyloid. Here, we determined if our immunization strategy was associated with this form of toxicity, and if the therapeutic effect was age-dependent. Tg2576 mice and wild-type littermates were immunized from 11 or 19 months and their behaviour evaluated prior to killing at 24 months. Subsequently, plaque-and vascular-Aβ burden, Aβ levels and associated pathology was assessed. The therapy started at the cusp of amyloidosis reduced cortical Aβ deposit burden by 31% and Aβ levels by 30-37%, which was associated with cognitive improvements. In contrast, treatment from 19 months, when pathology is well established, was not immunogenic and therefore did not reduce Aβ burden or improve cognition. Significantly, the immunotherapy in the 11-24 months treatment group, that reduced Aβ burden, did not increase cerebral bleeding or vascular Aβ deposits in contrast to several Aβ antibody studies. These findings indicate that our approach age-dependently improves cognition and reduces Aβ burden when used with an adjuvant suitable for humans, without increasing vascular Aβ deposits or microhemorrhages.

A non-toxic ligand for voxel-based MRI analysis of plaques in AD transgenic mice

“…In the current study we used K6-A␤1-30 chelated to gadolinium via incorporation of DPTA at the amino terminus. In our previously published studies we used K6-A␤1-30 as a vaccine therapy in AD model mice and have shown that this peptide is both non-toxic and non-fibrillogenic (Sigurdsson et al, 2001;Asuni et al, 2006). In the current study we have also demonstrated that this A␤ homologous peptide is nontoxic when labeled with chelated Gd (Fig.…”

“…We designed these homologous peptides so that they still have a high binding affinity to wild-type A␤ peptides and also have a similar BBB permeability. In prior studies we have shown that these A␤ homologous peptides do not self-assemble or promote the fibrillization of endogenous A␤ peptides (Asuni et al, 2006;Sigurdsson et al, 2001Sigurdsson et al, , 2004a). In the current study we used K6-A␤1-30 chelated to gadolinium via incorporation of DPTA at the amino terminus.…”

Specific Amyloid β Clearance by a Catalytic Antibody Construct

“…The A␤ species mass (monomers, oligomers, and proteolytic fragments) was computed by comparison with reference proteins (1.4 -27 kDa and 14 -97 kDa ladders; Bio-Rad). Oligomer disappearance was monitored by densitometry of the SDS-stable trimer, tetramer, and high mass oligomer bands (45 kDa band, 64 -84 kDa smear) following staining of gel blots with a mixture of mouse anti-A␤ monoclonal IgG 6E10, IgG 4G8 (both from Covance, Princeton, NJ), and IgG 6D4 (MyBioSource, San Diego, CA) (directed to A␤ (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), A␤ (17)(18)(19)(20)(21)(22)(23)(24), and the A␤ C terminus, respectively). Freshly dissolved A␤42 without prior oligomerization was mixed immediately with the nIgVs (3 g/ml) to test the nIgV effect on oligomer accumulation over 24 h of incubation at 4°C.…”

“…The analyzed neocortical area was dorsomedial from the cingulate cortex and extended ventrolaterally to the rhinal fissure within the right hemisphere (measured field 700 ϫ 700 m). Left brain hemispheres after removing the olfactory bulb were homogenized as described (24). The hemispheres were weighed and homogenized (10%, w/v) in 20 mM Tris base, 250 mM sucrose, 1 mM EDTA, 1 mM EGTA, 100 mM phenylmethylsulfonyl fluoride, 5 g/ml pepstatin A, and a 25-fold dilution of cOmplete protease inhibitor mixture as recommended by the supplier (Roche Applied Science).…”

“…Another age-matched mouse group received similar PBS injections. Coronal brain sections of the right and left hemispheres obtained 7 days thereafter were stained with a mixture of anti-A␤ monoclonal IgGs 6E10 and 4G8, and the A␤ deposits were quantified (BIOQUANT Image Analysis Corp., Nashville, TN) (24). The A␤ plaque burden is defined as the percentage area occupied by the stained reaction product in a 640 ϫ 480-m rectangle surrounding the injection site (estimated in five 40-m sections spaced 200 m apart).…”