One of the most intriguing new areas of research in neuroscience has to do with the discovery that proteins involved with Alzheimer's, Parkinson's and other neurodegenerative illnesses can contort into the wrong shape. The misshapen molecules can spread throughout the brain in a manner akin to prion diseases—the most notorious of which is variant Creutzfeldt-Jakob disease, better known as Mad Cow.
Misfolded proteins can lead to a buildup of cellular gunk that then causes damage inside or outside cells. If the process of misfolding observed in Alzheimer's and Parkinson's is similar to the one in Mad Cow, the next question is whether these misshapen proteins are transmissible from one organism to another.
Last month, an article appeared in Acta Neuropathologica Communications from researchers at the Centre for Biological Threats and Special Pathogens at the Robert Koch-Institut in Berlin that raised questions about whether medical instruments need to be decontaminated if they come into contact with post-mortem brain tissue from Alzheimer's or Parkinson's patients.
The case for putting in place such prophylaxis is rooted in lab studies that show that injecting deposits of these proteins into an animal brain can initiate a "seeding" process in which one protein causes another to misfold. "Whether those harmful effects can be also caused by transmitted protein particles in humans who express mutated or normal alpha-synuclein, A-beta or tau is still unknown," the article says. But then it goes on: "...the ability to decontaminate medical instruments from aggregated A-beta, tau and alpha-synuclein may potentially add to patient safety."
The article describes previous research that developed procedures for decontaminating medical instruments that contained residues of variant Creutzfeldt-Jakob disease. It found that they seemed to work for the proteins implicated in neurodegenerative diseases as well. "When we assessed the activity of prion-effective reprocessing procedures against amyloid-beta, tau and alpha-synuclein we found that these were simultaneously reduced up to 100-fold, and below the threshold of detection, by alkaline formulations applied at RT [room temperature] such as 1 M NaOH [one mole of sodium hydroxide]..."
On the face of it, questions about transmissibility might provoke low-level hypochondriasis. But contaminated lab instruments are not about to become the next Ebola crisis. Most people don't get many chances to play around with brain samples—and even contact with these tissues in the lab has not really been shown to pose a threat.
Lary C. Walker of Emory University, who wrote a great article for Scientific American in 2013 about the prion-like nature of misfolded proteins involved in Parkinson's and Alzheimer's, sent me an e-mail about research looking at the prospects for contamination:
The transmission of Alzheimer’s, tauopathy, or synucleinopathy by contaminated surgical instruments currently seems unlikely, based on existing evidence. Even the transmission of prion disease [variant Creutzfeldt-Jakob, for instance] via contaminated instruments is quite rare (four known instances) and with the introduction of more stringent decontamination procedures, iatrogenic transmission [transmission in a lab] appears to have ceased.
"The Penn group evaluated the risk of Alzheimer’s and Parkinson’s in persons who had been treated earlier in life with peripheral injections of growth hormone that had been prepared from human pituitary glands. A significant number of these patients later developed prion disease. However, in those who are now reaching old age, there is no detectable increase in risk for Alzheimer’s or Parkinson’s disease (at least so far).
That being said, one lesson from studies of prion infectivity is that extremely small doses of infectious prions can induce disease when they are delivered directly to the brain (much larger doses are needed when administered peripheral to the CNS). For this reason, it is prudent to ensure that neurosurgical instruments are as clean as possible. Thomzig and colleagues indicate that decontamination protocols that are effective against prions also destroy Aβ, tau, and α-synuclein seeds. In my opinion, rigorous decontamination should be standard for all instruments that are re-used in neurosurgical procedures, if only to minimize the risk of prion transmission.
Panic is not the order of the day. The observation that major neurodegenerative illnesses display prion-like properties is not only a fascinating new line of research. It also may yield new clues to how to treat these diseases by finding ways to halt the pathological chain of events in which one protein causes another to bend out of shape.
Image Source: CDC/ Teresa Hammett Photo Credit: Sherif Zaki; MD; PhD; Wun-Ju Shieh; MD; PhD; MPH