Editing Prion (section)

=== Transmission ===
It has been recognized that prion diseases can arise in three different ways: acquired, familial, or sporadic.<ref>{{cite book | veditors = Groschup MH, Kretzschmar HA | title = Prion Diseases Diagnosis and Pathogeneis | series = Archives of Virology | volume = 16 | location = New York | publisher = Springer | year = 2001 | isbn=978-3-211-83530-2 |doi=10.1007/978-3-7091-6308-5}}</ref> It is often assumed that the diseased form directly interacts with the normal form to make it rearrange its structure. One idea, the "Protein X" hypothesis, is that an as-yet unidentified cellular protein (Protein X) enables the conversion of PrP<sup>C</sup> to PrP<sup>Sc</sup> by bringing a molecule of each of the two together into a complex.<ref>{{cite journal | vauthors = Telling GC, Scott M, Mastrianni J, Gabizon R, Torchia M, Cohen FE, DeArmond SJ, Prusiner SB | title = Prion propagation in mice expressing human and chimeric PrP transgenes implicates the interaction of cellular PrP with another protein | journal = Cell | volume = 83 | issue = 1 | pages = 79–90 | date = October 1995 | pmid = 7553876 | doi = 10.1016/0092-8674(95)90236-8 | s2cid = 15235574 | doi-access = free }}</ref>

The primary method of infection in animals is through ingestion. It is thought that prions may be deposited in the environment through the remains of dead animals and via urine, saliva, and other body fluids. They may then linger in the soil by binding to clay and other minerals.<ref>{{cite journal | vauthors = Johnson CJ, Pedersen JA, Chappell RJ, McKenzie D, Aiken JM | title = Oral transmissibility of prion disease is enhanced by binding to soil particles | journal = PLOS Pathogens | volume = 3 | issue = 7 | pages = e93 | date = July 2007 | pmid = 17616973 | pmc = 1904474 | doi = 10.1371/journal.ppat.0030093 | doi-access = free }}</ref>

A [[University of California]] research team has provided evidence for the theory that infection can occur from prions in manure.<ref>{{cite journal | vauthors = Tamgüney G, Miller MW, Wolfe LL, Sirochman TM, Glidden DV, Palmer C, Lemus A, DeArmond SJ, Prusiner SB | title = Asymptomatic deer excrete infectious prions in faeces | journal = Nature | volume = 461 | issue = 7263 | pages = 529–532 | date = September 2009 | pmid = 19741608 | pmc = 3186440 | doi = 10.1038/nature08289 | bibcode = 2009Natur.461..529T }}</ref> And, since manure is present in many areas surrounding water reservoirs, as well as used on many crop fields, it raises the possibility of widespread transmission. Although it was initially reported in January 2011 that researchers had discovered prions spreading through airborne transmission on [[aerosol]] particles in an [[animal testing]] experiment focusing on [[scrapie]] infection in [[laboratory mice]],<ref name=Haybaeck11>{{cite journal | vauthors = Haybaeck J, Heikenwalder M, Klevenz B, Schwarz P, Margalith I, Bridel C, Mertz K, Zirdum E, Petsch B, Fuchs TJ, Stitz L, Aguzzi A | title = Aerosols transmit prions to immunocompetent and immunodeficient mice | journal = PLOS Pathogens | volume = 7 | issue = 1 | pages = e1001257 | date = January 2011 | pmid = 21249178 | pmc = 3020930 | doi = 10.1371/journal.ppat.1001257 | doi-access = free }}{{Retracted|doi=10.1371/journal.ppat.1012396|pmid=39024193|intentional=yes}}<br />Lay summary: {{cite web | vauthors = Mackenzie D |date=January 13, 2011 |title=Prion disease can spread through air |url=https://www.newscientist.com/article/dn19971-prion-disease-can-spread-through-air |url-access=registration |website=New Scientist}}</ref> this report was retracted in 2024.<ref name=Haybaeck11/> Preliminary evidence supporting the notion that prions can be transmitted through use of urine-derived [[human menopausal gonadotropin]], administered for the treatment of [[infertility]], was published in 2011.<ref name="pmid21448279">{{cite journal | vauthors = Van Dorsselaer A, Carapito C, Delalande F, Schaeffer-Reiss C, Thierse D, Diemer H, McNair DS, Krewski D, Cashman NR | title = Detection of prion protein in urine-derived injectable fertility products by a targeted proteomic approach | journal = PLOS ONE | volume = 6 | issue = 3 | pages = e17815 | date = March 2011 | pmid = 21448279 | pmc = 3063168 | doi = 10.1371/journal.pone.0017815 | doi-access = free | bibcode = 2011PLoSO...617815V }}</ref>

==== Genetic susceptibility ====
The majority of human prion diseases are classified as sporadic Creutzfeldt–Jakob disease (sCJD). Genetic research has identified an association between susceptibility to sCJD and a polymorphism at codon 129 in the PRNP gene, which encodes the prion protein (PrP). A homozygous methionine/methionine (MM) genotype at this position has been shown to significantly increase the risk of developing sCJD when compared to a heterozygous methionine/valine (MV) genotype. Analysis of multiple studies has shown that individuals with the MM genotype are approximately five times more likely to develop sCJD than those with the MV genotype.<ref>{{cite journal |vauthors=Kim YC, Jeong BH |title=The First Meta-Analysis of the M129V Single-Nucleotide Polymorphism (SNP) of the Prion Protein Gene (PRNP) with Sporadic Creutzfeldt-Jakob Disease |journal=Cells |volume=10 |issue=11 |date=November 2021 |page=3132 |pmid=34831353 |pmc=8618741 |doi=10.3390/cells10113132 |doi-access=free}}</ref>

==== Prions in plants ====
In 2015, researchers at [[The University of Texas Health Science Center at Houston]] found that plants can be a vector for prions. When researchers fed hamsters grass that grew on ground where a deer that died with [[chronic wasting disease]] (CWD) was buried, the hamsters became ill with CWD, suggesting that prions can bind to plants, which then take them up into the leaf and stem structure, where they can be eaten by herbivores, thus completing the cycle. It is thus possible that there is a progressively accumulating number of prions in the environment.<ref>{{cite news |vauthors=Beecher C |url=http://www.foodsafetynews.com/2015/06/researchers-make-surprising-discovery-about-spread-of-chronic-wasting-disease/ |title=Surprising' Discovery Made About Chronic Wasting Disease |work=[[Food Safety News]] |date=June 1, 2015 |access-date=2016-04-08 |archive-date=2016-04-28 |archive-url=https://web.archive.org/web/20160428055600/http://www.foodsafetynews.com/2015/06/researchers-make-surprising-discovery-about-spread-of-chronic-wasting-disease/ |url-status=live }}</ref><ref>{{cite journal | vauthors = Pritzkow S, Morales R, Moda F, Khan U, Telling GC, Hoover E, Soto C | title = Grass plants bind, retain, uptake, and transport infectious prions | journal = Cell Reports | volume = 11 | issue = 8 | pages = 1168–75 | date = May 2015 | pmid = 25981035 | pmc = 4449294 | doi = 10.1016/j.celrep.2015.04.036 }}</ref>