Can Alzheimer’s be transmitted?

Nature follows a researcher who noticed typical Alzheimer’s lesions in very untypical patients – young people who died after receiving contaminated growth hormone injections:

For [John] Collinge, this led to a worrying conclusion: that the plaques might have been transmitted, alongside the prions, in the injections of growth hormone — the first evidence that Alzheimer’s could be transmitted from one person to another. If true, that could have far-reaching implications: the possibility that ‘seeds’ of the amyloid-? protein involved in Alzheimer’s could be transferred during other procedures in which fluid or tissues from one person are introduced into another, such as blood transfusions, organ transplants and other common medical procedures.

“Our study does not mean that Alzheimer’s is actually contagious,” he stresses. Carers won’t catch it on the job, nor family members, however close. “But it raises concern that some medical procedures could be inadvertently transferring amyloid-? seeds.”

More-conclusive evidence would come from checking whether the original growth hormone and dura-mater preparations contained infectious amyloid seeds, by injecting them into animals and seeing whether this triggers disease. Most of these preparations, however, have long since disappeared. Collinge has access to some original samples of growth hormone stored by the UK Department of Health, and he is planning to analyse them for the presence of amyloid seeds and then inject them into mice. That work will take a couple of years to complete, he says.

If the transmissibility hypothesis proves true, the implications could be severe. Amyloids stick like glue to metal surgical instruments, and normal sterilization does not remove them, so amyloid seeds might possibly be transferred during surgery. The seeds might sit in the body for years or decades before spreading into plaques, and perhaps enabling the other pathological changes needed to induce Alzheimer’s disease.

It means that researchers studying prion diseases and neurodegenerative diseases, who until recently had considered their disciplines to be separate, now find themselves tackling shared questions.