‘Seeds’ of Alzheimer’s could be transmitted

LONDON: The “seeds” of Alzheimer’s disease may be transmitted from one person to another during certain medical procedures, scientists have found.

A study into people who died of a separate kind of brain disease after receiving injections of human growth hormone suggests that Alzheimer’s may also be a transmissible disease.

The findings have raised questions about the safety of some medical procedures, possibly including blood transfusions and invasive dental treatment, which may involve the transfer of contaminated tissues or surgical equipment.

The investigation has shown for the first time in humans that Alzheimer’s disease may be a transmissible infection which could be inadvertently passed between people. Scientists emphasised that the new evidence is still preliminary and should not stop anyone from having surgery.

They have also stressed that it is not possible to “catch” Alzheimer’s by living with someone with the disease.

However, the findings of a study into eight people who were given growth-hormone injections when they were children have raised the disturbing possibility that Alzheimer’s can be transmitted under certain circumstances, when infected tissues or surgical instruments are passed between individuals.

Until now, it was thought that Alzheimer’s occurred only as a result of inheriting certain genetic mutations causing the familial version of the disease, or from random “sporadic” events within the brain of elderly people, said Professor John Collinge, the head of neurodegenerative diseases at University College London.

“What we need to consider is that in addition to there being sporadic Alzheimer’s disease and inherited or familial Alzheimer’s disease, there could also be acquired forms of Alzheimer’s disease.”

“You could have three different ways you have these protein seeds generated in your brain. Either they happen spontaneously as you age, or you have a faulty gene, or you’ve been exposed to a medical accident. It’s important to emphasise that this relates to a very special situation where people have been injected essentially with extracts of human tissue.”

The eight adults, aged between 36 and 51, all died of Creutzfeldt-Jakob disease (CJD) after receiving contaminated hormone injections as children. But autopsies on their brains also revealed that seven of them harboured the misfolded proteins associated with the early stages of Alzheimer’s disease. It is unheard of for people in this age group to have such proteins.

The scientists did not find the “tau” protein tangles asso- ciated with the later stages of the disease, which means the seven individuals did not have full-blown Alzheimer’s, although they may well have developed it had they not died.

The study eliminated other possible reasons for the presence of these so-called amyloid-beta (A-beta) proteins and came to the conclusion that they were most probably transmitted as protein “seeds” in the growth-hormone injections. Questions remain about whether these protein seeds could also be transmitted on surgical instruments used in other operations. It is wellestablished that the prion proteins behind CJD and Alzheimer’s stick to metal surfaces and can survive extreme sterilisation procedures.

There is also the question of whether Alzheimer’s disease could be passed on in blood transfusions, given that animal experiments have shown this to be possible. – The Independent