Study: Alzheimer Vaccine Clears Amyloid Beta Clumps from Brains of Monkeys

A new vaccine that clears deposits of amyloid beta protein from the brains of monkeys may prevent or halt the progression of Alzheimer's disease in humans, according to Harvard Medical School researchers.

Many scientists believe that Alzheimer's disease is caused by an accumulation of amyloid beta protein in the brain. As the protein becomes more tightly clumped, it is difficult to clear, diminishing the connections between neurons.

Several groups are exploring the possibility that vaccines can help the brain either lower the production of amyloid beta protein or increase its clearance in Alzheimer patients.

Researchers at Harvard Medical School found that vaccinating monkeys with synthetic amyloid beta peptide enhanced the clearance of amyloid beta protein from around the brain. Although this finding confirms what had already been shown in mice, it is significant because monkeys have the same amyloid beta protein as humans.

Over a nine-month period, five monkeys were given eight injections of the amyloid beta peptide, while five control monkeys did not receive the treatment. All of the immunized monkeys made antibodies to amyloid beta peptide, which were found in blood and, in lower amounts, in the fluid around the brain.

Between 22 and 42 days after immunization, levels of amyloid beta protein dropped in the brain fluid and increased in the blood, suggesting that the antibodies bound to amyloid beta protein and increased its slow release from brain fluid to the blood for clearance. In addition, no plaques were found in the immunized animals.

"Our study is the first to show clearance of amyloid beta by vaccination in a primate model, thus providing further evidence for the potential use of such a vaccine in humans," said lead researcher Cynthia Lemere of Harvard Medical School.

Earlier studies that showed mice had increased amyloid clearance after vaccination led to clinical trials to test the treatment in humans. However, the trials were stopped midway because some patients developed cerebral inflammation.

While no signs of inflammation were found in any of the immunized monkey brains, Lemere and her team are now attempting to make an even safer vaccine by developing new amyloid beta compounds.

Other sources: Society for Neuroscience