People treated with an immunotherapy known as IVIg–a blood product that contains antibodies from donated blood–had a 42 percent lower risk of developing Alzheimer’s disease than their untreated counterparts, according to a study published today in the journal Neurology. IVIg is currently used to treat patients with inflammatory and immune conditions.

Scientists analyzed the health records of about 85,000 people age 65 or older, including about 850 who had been treated with IVIg for immune deficiencies, leukemia, anemia, and other conditions, and compared Alzheimer’s rates in both groups. According to the American Academy of Neurology (AAN), only 2.8 percent of those treated with IVIg developed Alzheimer’s disease, compared with 4.8 percent of those not treated with immune-based therapy.

“IVIg has been used safely for more than 20 years to treat other diseases,”said Howard Fillit, a physician with the Mount Sinai School of Medicine in New York, who was quoted in the AAN press release. It “is thought to have an indirect effect on Alzheimer’s disease by targeting beta-amyloid, or plaques in the brain.”

The study has limitations–patients were treated with IVIg for other conditions, not specifically to prevent Alzheimer’s. A large clinical trial, sponsored by the National Institute on Aging, is now under way to test the drug’s power to prevent Alzheimer’s. (And it’s important to note that the Neurology study was supported by Baxter International, the pharmaceutical company that makes IVIg.)

A previous trial of another potential Alzheimer’s vaccine was not successful, as I wrote in a TR piece in 2006:

An early clinical trial of an active vaccine, sponsored by the Ireland-based Elan Corporation, was stopped in 2002 after four patients developed encephalitis, an inflammation of the brain. Later, autopsies of these patients’ brains showed that despite the inflammation, the vaccine did clear the toxic protein from the brain.

However, the IVIg is a different type of treatment. Because it contains antibodies, it does not require activation of the immune system, as the earlier Elan vaccine did.