ABSTRACT
Prion diseases are a group of diseases that are caused by prions; the term prion is an abbreviation of “proteinaceous infectious particles.” Prions are proteins that occur in cells but can fold abnormally and become misshapen. These misshapen prions have the ability to cause similar proteins to fold abnormally and turn into misshapened prions. Hence, a few misshapened prions in a cell can develop into many, and their accumulation in brain tissue causes cell death. Prions are absorbed by adjacent nerve cells, and the process is repeated. When enough nerve cells die in the brain, tiny holes develop, which give brain tissue the appearance of a sponge when viewed through a microscope (Figure 27.1). Thus, the name for this group of diseases is transmissible spongiform encephalopathy (TSE), which means a disease of the brain that causes it to appear in the form of a sponge. The process of converting normal proteins into prions is very slow, and it can take years between when an animal or human is infected and when it rst exhibits symptoms; ultimately, however, enough nerve cells are destroyed that normal brain function is impaired. Prion diseases are always fatal providing
that the infected animal or person lives long enough. Yet, prions do not produce a response by the immune system because they are not recognized as a foreign agent (Londhe et al. 2012).
