Faculty Bibliography

The seminal finding that immunization with amyloid-beta 1-42 in Alzheimer's disease (AD) mouse model prevented formation of and/or cleared amyloid plaques has led to numerous studies exploring related approaches for AD and other conformational degenerative disorders. While clinical trials in AD patients were discouraging because of serious side effects, this approach remains promising in light of recent findings in animal models, in which refinements aimed at reducing potential adverse reactions continue to lead to cognitive improvements. In addition to AD and its models, this type of therapy has primarily been assessed in prion disease with positive results, further supporting the potential of immunotherapy for a variety of protein-related diseases in which clearance of the pathogenic agent is likely to alleviate symptoms

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-beta (Abeta) 1-42, and the adjuvant, QS-21. To avoid this toxicity, we have been using Abeta 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-Abeta burden, Abeta levels and associated pathology was assessed. The therapy started at the cusp of amyloidosis reduced cortical Abeta deposit burden by 31% and Abeta 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 Abeta burden or improve cognition. Significantly, the immunotherapy in the 11-24 months treatment group, that reduced Abeta burden, did not increase cerebral bleeding or vascular Abeta deposits in contrast to several Abeta antibody studies. These findings indicate that our approach age-dependently improves cognition and reduces Abeta burden when used with an adjuvant suitable for humans, without increasing vascular Abeta deposits or microhemorrhages

The first experimental vaccine against Alzheimer's disease caused encephalitis in some patients, which led to termination of the clinical trial and dealt a serious blow to this therapeutic approach. With second-generation vaccines that are likely to circumvent this side effect, this type of therapy remains promising, although more extensive animal studies are likely to be required before approval of other clinical trials. Another potential side effect, microhemorrhages within the brain vasculature, has been observed in mouse models following passive immunization, but has not been assessed in reports of active vaccination. Together, these serious adverse reactions emphasize the need to test potential Alzheimer's immunotherapy in large cohorts of primate models prior to, or at least concurrently with, human trials, as no effective therapy exists for the disease

The increased availability of transgenic mouse models for studying human diseases is shifting the focus of many laboratories from in vitro to in vivo assays. The purpose of this chapter is to provide investigators with methods that will allow them to obtain well-preserved mouse brain sections to be stained with the standard histological dyes for amyloid, Congo red and thio-flavin-S. These sections can as well be used for immunohistological procedures that allow detection of amyloid-beta plaques as well as pre-amyloid deposits

Transgenic mice are used increasingly to model brain amyloidosis, mimicking the pathogenic processes involved in Alzheimer's disease (AD). In this chapter, a strategy is described that has been successfully used to map amyloid deposits in transgenic mouse models of AD with magnetic resonance imaging (MRI), utilizing molecular targeting vectors labeled with MRI contrast agents to enhance selectively the signal from amyloid plaques. To obtain sufficient spatial resolution for effective and sensitive mouse brain imaging, magnetic fields of 7-Tesla (T) or more are required. These are higher than the 1.5-T field strength routinely used for human brain imaging. The higher magnetic fields affect contrast agent efficiency, and determine the choice of pulse sequence parameters for in vivo MRI, all addressed in this chapter. Ex vivo imaging is also described as an important step to test and optimize protocols prior to in vivo studies. The experimental setup required for mouse brain imaging is explained in detail, including anesthesia, immobilization of the mouse head to reduce motion artifacts, and anatomical landmarks to use for the slice alignment procedure to improve image co-registration during longitudinal studies, and for subsequent matching of MRI with histology

We demonstrate herein that human macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine expressed in the brain and not previously considered to be amyloidogenic, forms amyloid fibrils similar to those derived from the disease associated amyloidogenic proteins beta-amyloid and alpha-synuclein. Acid denaturing conditions were found to readily induce MIF to undergo amyloid fibril formation. MIF aggregates to form amyloid-like structures with a morphology that is highly dependent on pH. The mechanism of MIF amyloid formation was probed by electron microscopy, turbidity, Thioflavin T binding, circular dichroism spectroscopy, and analytical ultracentrifugation. The fibrillar structures formed by MIF bind Congo red and exhibit the characteristic green birefringence under polarized light. These results are consistent with the notion that amyloid fibril formation is not an exclusive property of a select group of amyloidogenic proteins, and contribute to a better understanding of the factors which govern protein conformational changes and amyloid fibril formation in vivo

In recent years major outbreaks of prion disease linked to oral exposure of the prion agent have occurred in animal and human populations. These disorders are associated with a conformational change of a normal protein, PrP(C) (prion protein cellular), to a toxic and infectious form, PrP(Sc) (prion protein scrapie). None of the prionoses currently have an effective treatment. A limited number of active immunization approaches have been shown to slightly prolong the incubation period of prion infection. Active immunization in wild-type animals is hampered by auto-tolerance to PrP and potential toxicity. Here we report that mucosal vaccination with an attenuated Salmonella vaccine strain expressing the mouse PrP, is effective at overcoming tolerance to PrP and leads to a significant delay or prevention of prion disease in mice later exposed orally to the 139A scrapie strain. This mucosal vaccine induced gut anti-PrP immunoglobulin (Ig)A and systemic anti-PrP IgG. No toxicity was evident with this vaccination approach. This promising finding suggests that mucosal vaccination may be a useful method for overcoming tolerance to PrP and preventing prion infection among animal and potentially human populations at risk