Abstract
Genetic and environmental factors leading to Alzheimer's disease (AD) converge in a pathogenic pathway that leads to the accumulation of misโfolded amyloid peptide (Aฮฒ) in the brain. Removal of Aฮฒ from the brain has thus been the focus of academic and industrial research in the last decade. The concept of immunization therapy could be proven in animal models mimicking amyloid pathology but a multicenter clinical trial in which AD patients were vaccinated with aggregated Aฮฒ has resulted in somewhat unanticipated and partially conflicting results. The occurrence of meningoencephalitis in 6% of vaccinated individuals forced the discontinuation of the clinical study, preventing the generation of sufficient data for an unequivocal statement about the effectiveness of such a therapy approach. This study, however, clearly showed that vaccination induced the production of antibodies against Aฮฒ in some immunized patients. Moreover, circulating antiโAฮฒ antibodies are found in healthy humans suggesting a protective role of such physiological antibodies. Nonetheless, the physiological role of the immune system in preventing AD is not fully understood. This article summarizes crucial animal and clinical data underscoring the potential of the immune system for AD treatment. BioEssays 29:927โ932, 2007. ยฉ 2007 Wiley Periodicals, Inc.