Immunization with a vaccine against Alzheimer's disease (AD) doubled the risk of stroke in mice. This finding may help explain the brain inflammation seen recently in human subjects participating in tests of a highly touted vaccine against this dreaded neurodegenerative disease.
A group led by Mathias Jucker at the University of Basel (Switzerland) injected a transgenic mouse model of AD weekly with a monoclonal antibody that recognizes β-amyloid, the peptide that accumulates in the brains of AD patients (Science, 15 November 2002). After five months, the immunized mice exhibited a 23% decrease in amyloid load but were also more than twice as likely to suffer cerebral hemorrhage as were mice in the control group.
These microhemorrhages occurred only in areas of the brain affected by cerebral amyloid angiopathy (CAA), which is characterized by the intravascular deposition of amyloid protein. Researchers believe this accumulation of protein weakens the vessel walls, making them more susceptible to hemorrhage. Although CAA appears in 80% of AD patients, the APP23 mouse strain used in this study is the only model of AD that exhibits this condition, possibly explaining why this is the first mouse study to uncover this potentially fatal side effect of the vaccine.
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Mouse Study Suggests New Risk Associated with Alzheimer's Vaccine. Lab Anim 32, 12 (2003). https://doi.org/10.1038/laban0103-12d