Infectious Proteins Could Cause Two Neurological Diseases

Research has uncovered a new misfolded protein which triggers crippling neurodegenerative disease in humans. It's infectious, difficult to destroy and can even spread through surgical instruments. 

Many readers may have heard of ‘mad cow disease’. This neurodegenerative disease was first identified in 1986. The disease hit the hardest in the UK where during its peak in 1992 three out of every thousand cows were sick. When humans eat meat from sick animals, especially when the meat is contaminated by brain matter, there’s a chance of catching the disease. The human form is known as Creutzfeldt-Jakob disease (CJD). The transmission of this disease is not caused by the traditional infectious agents (viruses, bacteria, fungi or parasites) but by a misfolded protein called a prion. Many proteins can form prions, the term prion refers to the strange property that can cause normal forms of the protein to become prions themselves just by coming in contact with them. Thus prions are self-replicating.     

Several other prion diseases are known such as scrapie in sheep and kuru in humans. In a new paper published in the journal PNAS brain extracts were prepared from patients who suffer from multiple system atrophy (MSA) or progressive supranuclear palsy (PSP), to find out if they were caused by prions. MSA is a rare degenerative disease commonly misdiagnosed as Parkinson's, but patients usually die within 5 to 10 years. If these diseases are caused by prions then exposing brain cells in the lab to brain extracts from these patients would cause formation of prion deposits.

Typical sterilization methods don't destroy prions

Brain extracts from both diseases led to prion deposits.

Next the researchers tested brain extracts from patients with Parkinson’s disease. This disease leads to the formation of protein deposits made of a protein called alpha-synuclein, the same protein that leads to the prion deposits in patients with MSA. People familiar with Parkinson’s disease may notice that this same protein is known to accumulate in the brain of Parkinson's disease patients where it forms little clots called Lewy bodies. So, alpha-synuclein can give rise to two different diseases both caused by the accumulation of abnormal protein deposits, but only in MSA did these abnormal forms of alpha-synuclein act as infectious particles  

This new study also has big consequences for the surgical field. Commonly used methods to sterilize surgical instruments, such as autoclaving, do not destroy prions and so use of instruments that have previously been used on a patient with a prion disease can transmit this disease to all patients operated afterwards. This was first observed in 1976 when the Swiss physician Christopher Bernoulli operated on two young patients suffering from epilepsy. Both died from CJD. The culprit? The electrodes used in the surgery had two years earlier been used in a CJD patient and despite having been cleaning with benzene, alcohol and formaldehyde still contained intact prions.    

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