. Transmission of amyloid-β protein pathology from cadaveric pituitary growth hormone. Nature. 2018 Dec;564(7736):415-419. Epub 2018 Dec 13 PubMed.


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  1. This is an important control and confirmation of the previous human transmission observations by this group. I am not surprised that Aβ in the hormone extracts seeded cerebral amyloidosis in these mice, since it is exactly what transmission studies in mouse models had predicted (Meyer-Lühmann et al., 2006; Eisele et al., 2010). APP transgenic mouse models can be rightly criticized for many things, but their amyloid deposition aspect has nearly always translated faithfully to human observation.

    From my lab’s perspective, having done many transmission studies in mouse models, the present results do not change anything; however, for others who did not believe that such transmission to humans is real, it may be yet another wakeup call.

    What are the real-word implications of this?  It may be a good idea to use separate sets of medical surgical instruments for young and for aged patients. Given the long incubation time, this may minimize the risk of transmission. I was struck that Purro et al. report Aβ concentrations in the hormone extracts almost as high as in AD brain extract. This is somewhat unexpected. It makes me curious about the nature of the Aβ species in the hormone extracts, since the seeding of the hormone extract was much less than that of the AD tissue.

    I believe Aβ assemblies in AD brain behave like prions. Lary Walker and I summarized the state of current knowledge in a very recent review (Jucker and Walker, 2018).


    . Exogenous induction of cerebral beta-amyloidogenesis is governed by agent and host. Science. 2006 Sep 22;313(5794):1781-4. PubMed.

    . Peripherally applied Abeta-containing inoculates induce cerebral beta-amyloidosis. Science. 2010 Nov 12;330(6006):980-2. PubMed.

    . Propagation and spread of pathogenic protein assemblies in neurodegenerative diseases. Nat Neurosci. 2018 Oct;21(10):1341-1349. Epub 2018 Sep 26 PubMed.

    View all comments by Mathias Jucker
  2. Purro et al. have published an important study. There is much scientific value in this work, but I will focus on the nature of the “proteopathic seeds” that template Aβ amyloidosis, and why this question is critical to human health.

    Three sobering studies from Mathias Jucker and Lary Walker directly address the magnitude of the problem. First, initial work revealed that AD brain homogenate inoculated into mutant APP mice can induce a spreading Aβ amyloidosis; this seeding activity is sensitive to Aβ immune-depletion and formic acid treatment (Meyer-Luehmann et al., 2006). Thus, the seeds must be non-covalent aggregates of Aβ, but likely not the free Aβ peptides detected in the HWP vials by Purro et al.

    Second, the most efficient Aβ-seeding species activity is small and soluble—i.e., oligomeric (Langer et al., 2011).  Finally, stainless steel wires provide an excellent fomite in transmission of Aβ amyloidosis to mice (Eisele et al., 2009), in a manner that is sensitive to plasma sterilization, but not boiling.

    Given the frequency of preclinical AD in aging, the suggestion that the most difficult species of aggregated Aβ to detect and sterilize is also the most “seeding” in animal models poses major challenges—to develop assays and techniques to obviate the unwitting transmission of Aβ proteopathic seeds in iatrogenic settings, particularly via neurosurgical instruments.


    . Exogenous induction of cerebral beta-amyloidogenesis is governed by agent and host. Science. 2006 Sep 22;313(5794):1781-4. PubMed.

    . Soluble Aβ seeds are potent inducers of cerebral β-amyloid deposition. J Neurosci. 2011 Oct 12;31(41):14488-95. PubMed.

    . Induction of cerebral beta-amyloidosis: intracerebral versus systemic Abeta inoculation. Proc Natl Acad Sci U S A. 2009 Aug 4;106(31):12926-31. PubMed.

    View all comments by Neil Cashman
  3. This paper proves that the hGH preparation contained Aβ contaminants that have seeding properties, and confirms the concept of iatrogenic CAA. We had also found Aβ and tau contaminants in the French hGH preparations (Duyckaerts et al., 2018). It will be interesting to compare the amounts of Aβ that have been injected in the French and British cases, and to evaluate the effect on the incubation period. This will help determine the effect of the inoculum dose on the transmission of amyloid pathology.

    Quite intriguing is the absence of Alzheimer-type tau pathology in the injected cases. The authors suggest that it may be a question of time. We have published a case of symptomatic iatrogenic CAA (Hervé et al., 2018) in which the incubation period was longer than four decades; no tau pathology was detected. It is, for us, very unlikely that incubation time was the key determinant of the absence of tau seeding. In our view, it also suggests that Aβ accumulation does not cause initiation of tau pathology in this context.

    I think that evidence is now sufficient to be quite sure that Aβ pathology has been transmitted. Precautions that have been taken to prevent the prion risk in neurosurgery are probably sufficient to prevent the risk of transmission of Aβ pathology, but new studies are required to test their effectiveness specifically on Aβ aggregates. 


    . Neuropathology of iatrogenic Creutzfeldt-Jakob disease and immunoassay of French cadaver-sourced growth hormone batches suggest possible transmission of tauopathy and long incubation periods for the transmission of Abeta pathology. Acta Neuropathol. 2018 Feb;135(2):201-212. Epub 2017 Nov 22 PubMed.

    . Fatal Aβ cerebral amyloid angiopathy 4 decades after a dural graft at the age of 2 years. Acta Neuropathol. 2018 May;135(5):801-803. Epub 2018 Mar 5 PubMed.

    View all comments by Charles Duyckaerts
  4. I find this article quite interesting. In this follow-up study, the authors examined aliquots of human-derived growth hormone used decades ago and found they indeed contained Aβ. More importantly, they showed that when these materials were injected into mouse models of Alzheimer’s disease, the animals developed accelerated amyloid deposition in the brain parenchyma and around cerebral vessel walls. This data indicate that the vials used for human treatment indeed contained Aβ material that was competent to seed the accumulation of pathological amyloid. Therefore, this study, added to the previous one, strongly suggests that the Aβ deposition seen in patients was induced in a manner reminiscent to prions.

    I believe these two articles combined provide a very strong case for transmission of Alzheimer’s pathology in a prion-like infectious manner in human beings. However, the question still remains whether transmission of Alzheimer’s pathology is restricted to these rare conditions (use of human-derived products for treatment) or can occur under more common medical practices, such as for example blood transfusion.

    As a precautionary note, I believe we should think seriously of implementing tools to screen medical equipment used in brain surgery or that can in some way act as vectors to transmit amyloid.

    View all comments by Claudio Soto
  5. This is an important study, which provides further support for the hypothesis that Aβ pathology can be transmitted by iatrogenic means. Several correlative studies, including a previous one from this group, showed that patients who had received cadaverically derived human growth hormone (c-hGH) or dura mater grafts, some of whom subsequently developed iatrogenic Creutzfeldt-Jakob disease, displayed parenchymal or vascular Aβ deposition. However, it was not possible to conclude with certainty that Aβ seeds in the c-hGH preparations or grafts were actually the cause of the Aβ pathology. In this paper, Purro and colleagues provide one further link in the chain of proof by showing that several archived, >30-year-old c-hGH preparations used to treat patients do, in fact, contain Aβ peptides based on biochemical assays, as well as seeding activity based on transmission to transgenic mice expressing a mutant APP gene.

    As the authors point out, their results do not suggest that Alzheimer’s disease is contagious, or is transmissible by conventional means like blood transfusion, a fear that has sometimes been stoked by the popular press. Importantly, it should be kept in mind that the appearance of amyloid pathology in the brains of patients exposed to c-hGH or dura mater grafts does not equate with clinically apparent Alzheimer’s disease. However, this paper, in conjunction with other published studies, argues that care should be exercised to prevent the possible transmission of Aβ or tau pathology as a result of contamination of surgical instruments.

    Prion-like propagation has been offered as a mechanism for the spread of misfolded proteins within the CNS in a number of neurodegenerative diseases, including Alzheimer’s, Parkinson’s, and tauopathies. It is important to note that this concept remains a hypothesis that rests largely on cell culture experiments, as well as artificial seeding experiments in animals, but lacks proof in natural disease settings. The paper by Purro et al. does not directly address this question, since it deals with an iatrogenic form of Aβ pathology, rather than a naturally occurring form that would develop during the course of Alzheimer’s disease.

    View all comments by David Harris
  6. I am not surprised by these findings. A recent paper reported propagation of Aβ aggregates after dura mater grafting (Hervé et al., 2018).

    I have no doubt that growth hormone from diseased people, purified as it used to be, contributed to the transmission of diseases other than CJD. Luckily, it looks as if few batches were contaminated. While a number of people were certainly exposed to pathogenic protein assemblies, very few developed disease. We should thank the capacity of our bodies to clear such pathogenic protein aggregates. 

    I think tools used in neurosurgery may transmit disease if they are not cleaned thoroughly. Some colleagues may argue that there is no clear evidence for that. The evidence is difficult to bring. We have every year over 150,000 cases of PD and over 300,000 case of AD in France. Let’s imagine that we have 10 or 100 or even 1,000 surgical procedures that led to contamination of patients—how would we detect those in the midst of hundreds of thousands of new cases? The situation was different for CJD, with an average number of 25 to 30 cases per year in France. When all of sudden within two years, the Ministry of Health noticed a jump to 70 cases, we started worrying and obtained an answer. ​For AD and PD we simply cannot detect changes unless we all of a sudden had a massive increase in case number. Fortunately this will not happen.

    I am convinced that pathogenic protein assemblies found in humans and animal models are pathogenic, as are the Aβ, tau, and α-syn assemblies we generate de novo. I therefore assessed the efficiency of cleaning methods to lower the risk of exposure of my co-workers to those assemblies we manipulate on a daily basis. Our studies show that detergent such as SDS are good at cleaning and capable of disaggregating the aggregates. Our paper contains a roster for selecting the best cleaning procedure depending on the protein aggregate, the contaminated material nature etc. … I further implemented working conditions in my lab that minimize risk.


    . Fatal Aβ cerebral amyloid angiopathy 4 decades after a dural graft at the age of 2 years. Acta Neuropathol. 2018 May;135(5):801-803. Epub 2018 Mar 5 PubMed.

    View all comments by Ronald Melki

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  1. Confirmed: Human Pituitary Extract Linked to Amyloidosis Contains Aβ Seeds