Hot Proteins: The Prion Collective
Resistance is futile. These words have become the catch phrase of the Borg, an iconic alien race determined to assimilate all life into their collective. With no regard or any compassion, the aliens do what they want to achieve their objective. Being able to quickly adapt, defeating these foes becomes a herculean challenge for the protagonists of Star Trek. In these fictional scenarios, the writers can easily add a happy ending and give the heroes the means for conquering the infamous aliens until they meet again.
Life can imitate art. Very much like the aliens uttering the ominous resistance quote, a biological agent spreads throughout the environment and assimilates others into its collective. This biological agent is called a prion. Originating from the misfolding of the prion protein (PrPC) found in all mammals, prions can aggregate. If the aggregate encounters a normal PrPC, the normal protein misfolds and becomes assimilated into the aggregate. As the aggregate grows, havoc spreads through the infected mammal’s central nervous system until the unfortunate animals dies (Huang, Chen, & Zhang, 2015). The prime directive of the prion collective does not end with the animal’s death.
Prions are remarkably stable and can exist in the environment for several years. If they are released via the decomposition of an infected animal or waste (urine and feces), the prions can reside on the vegetation or be taken into the actual plant tissue as the plant grows in prion-contaminated soil. When another animal comes along and eats the infected plant material, the unsuspecting victim becomes infected with the prion collective (Pritzkow et al., 2015).
Can prions from one species infect a different species? The answer is yes. Should we start panicking? Yes and no. Bovine spongiform encephalopathy (mad cow disease), is well known to have crossed the species barrier to infect humans (Murdoch & Murdoch, 2015). Another transmissible spongiform encephalopathy, chronic wasting disease (CWD), is spreading throughout the herds of deer and other cervids in North America. In fact, one in four deer in Boulder, CO has CWD (Miller et al., 2008). Research indicates that while CWD can affect primates, it has been unable to assimilate human PrPC into the prion collective (Kurt & Sigurdson, 2016). Nevertheless, the Centers for Disease Control and Prevention provides information for hunters on how to handle deer or elk carcasses to minimize exposure to the potentially infectious agent (Centers for Disease Control and Prevention, 2017).
Like the alien race, CWD prions may one day adapt and become infectious in humans. If prions can be passed through animal feces and urine, will the food we consume (grown in areas of the country where a significant percentage of the deer are infected) continue to be safe?
A diagnostic test does exist for those concerned that they may have been infected (Groveman et al., 2017). The outlook is grim if the results are positive. It will be sometime before science can come up with a way to defeat this foe.
Centers for Disease Control and Prevention (2017). Chronic Wasting Disease Prevention https://www.cdc.gov/prions/cwd/prevention.html
Groveman, B. R., Orru, C. D., Hughson, A. G., Bongianni, M., Fiorini, M., Imperiale, D., . . . Caughey, B. (2017). Extended and direct evaluation of RT-QuIC assays for Creutzfeldt-Jakob disease diagnosis. Ann Clin Transl Neurol, 4(2), 139-144. doi:10.1002/acn3.378
Huang, W. J., Chen, W. W., & Zhang, X. (2015). Prions mediated neurodegenerative disorders. Eur Rev Med Pharmacol Sci, 19(21), 4028-4034.
Kurt, T. D., & Sigurdson, C. J. (2016). Cross-species transmission of CWD prions. Prion, 10(1), 83-91. doi:10.1080/19336896.2015.1118603
Miller, M. W., Swanson, H. M., Wolfe, L. L., Quartarone, F. G., Huwer, S. L., Southwick, C. H., & Lukacs, P. M. (2008). Lions and prions and deer demise. PLoS One, 3(12), e4019. doi:10.1371/journal.pone.0004019
Murdoch, B. M., & Murdoch, G. K. (2015). Genetics of Prion Disease in Cattle. Bioinform Biol Insights, 9(Suppl 4), 1-10. doi:10.4137/BBI.S29678
Pritzkow, S., Morales, R., Moda, F., Khan, U., Telling, G. C., Hoover, E., & Soto, C. (2015). Grass plants bind, retain, uptake, and transport infectious prions. Cell Rep, 11(8), 1168-1175. doi:10.1016/j.celrep.2015.04.036