Stanley Prusiner has added prions to the list of well known infectious agents including bacteria, viruses, fungi and parasites. Prions exist normally as innocuous cellular proteins, however, prions possess an innate capacity to convert their structures into highly stabile conformations that ultimately result in the formation of harmful particles, the causative agents of several deadly brain diseases of the dementia type in humans and animals. Prion diseases may be inherited, laterally transmitted, or occur spontaneously. Regions within diseased brains have a characteristic porous and spongy appearance, evidence of extensive nerve cell death, and affected individuals exhibit neurological symptoms including impaired muscle control, loss of mental acuity, memory loss and insomnia. Stanley Prusiner's discovery provides important insights that may furnish the basis to understand the biological mechanisms underlying other types of dementia-related diseases, for example Alzheimer's disease, and establishes a foundation for drug development and new types of medical treatment strategies.
Prions are much smaller than viruses.
The immune response does not react to prions since they are present as natural proteins from birth. They are not poisonous, but rather become deleterious only by converting into a structure that enables disease causing prion proteins to interact with one another forming thread-like structures and aggregates that ultimately destroy nerve cells. The mechanistic basis underlying prion protein aggregation and their cumulative destructive mechanism is still not well understood. In contrast to other infectious agents, prion particles are proteins and lack nucleic acid. The ability to transmit a prion infection from one species to another varies considerably and is dependent upon what is known as a species barrier.