Scientists have succeeded in eradicating many deadly diseases through vaccination and some day this same approach might prevent or cure Alzheimer’s disease.
Researchers generally agree that a build up of beta amyloid protein in the brain plays an important role in Alzheimer’s disease. Thus, prevention or clearing of the protein accumulation could be an effective treatment. In 1999, studies revealed that injection of the beta amyloid itself, called active immunization, caused laboratory mice to produce antibodies against the protein and reduced its accumulation.
Spurred on by the potential of immunotherapy, some pharmaceutical companies started human clinical trials. In 2001, Elan and Wyeth began actively immunizing over 300 Alzheimer’s patients with beta amyloid. The trials were halted in 2002 when about six percent of participants developed a potentially serious side effect, acute encephalitis (inflammation in the brain). Several participants later died from other causes. Autopsies revealed that a large amount of beta amyloid had been cleared from their brains, their brain volume was lower, and lower levels of tau, another protein related to Alzheimer’s disease, were found in their spinal fluid. Further, for the living trial participants who developed antibodies, there was evidence of better memory, attention and concentration.
These encouraging results have led researchers like Dr. Gunnar K. Gouras of Weill Medical College at Cornell University to continue testing beta amyloid antibodies in the laboratory. In a paper that appeared June 29 in the Journal of Biological Chemistry, Dr. Gouras’ team describes investigations in which antibodies reduced the levels of beta amyloid in mouse nerve cells and helped restore cell communications. This renewal of communication between cells means that memory could actually be improved. Dr. Gouras and his colleagues have discovered that the beta amyloid build up occurs within nerve cells in the brain, and they will continue to study this process.
Some pharmaceutical companies are also initiating further human trials using passive immunotherapy, in which antibodies to a protein rather than the protein itself are given to the recipient. Elan and Wyeth are currently conducting two Phase II studies with an antibody called bapineuzumab. One study is assessing its safety as well as cognition and function in participants, and the second is imaging beta amyloid. Phase II data will be released in 2008, but based on data already gathered, Elan and Wyeth plan to begin Phase III clinical trials of bapineuzumab later this year.
Continued research is needed to better understand how beta amyloid aggregates in the brain and to enhance drug therapy.