An organism is considered to have an infection when a disease-causing agent, called a pathogen, establishes a viable presence in the organism. This can occur only if the pathogenic agent is able to reproduce itself in the host organism. …
This assumption has been challenged, however, by scientists seeking to identify the pathogen that causes Creutzfeldt-Jakob disease (CJD), a degenerative form of dementia in humans. CJD causes the brain to become riddled with tiny holes, like a sponge (evidence of extensive nerve cell death). Its symptoms include impaired muscle control, loss of mental acuity, memory loss, and chronic insomnia. Extensive experiments aimed at identifying the pathogen responsible for CJD have led surprisingly to the isolation of a disease agent lacking nucleic acid and consisting mainly, if not exclusively, of protein. Researchers coined the term "prion" for this new type of protein pathogen.
Upon further study, scientists discovered that prions normally exist as harmless cellular proteins in many of the body's tissues, including white blood cells and nerve cells in the brain; however, they possess the capability of converting their structures into a dangerous abnormal shape. Prions exhibiting this abnormal conformation were found to have infectious properties and the ability to reproduce themselves in an unexpected way, by initiating a chain reaction that induces normally shaped prions to transform themselves on contact, one after another, into the abnormal, pathogenic conformation. This cascade of transformations produces a plaque, consisting of thread-like structures, that collects in the brain and ultimately destroys nerve cells. …
Although the discovery of the link between prions and CJD was initially received with great skepticism in the scientific community, subsequent research has supported the conclusion that prions are an entirely new class of infectious pathogens. Furthermore, it is now believed that a similar process of protein malformation may be involved in other, more common degenerative neurological conditions such as Alzheimer's disease and Parkinson's disease. …
It can be inferred from the passage that the author would be least likely to agree with which one of the following?
The presence of certain abnormally shaped prions in brain tissue is a sign of neurological disease.
Some patients currently infected with CJD will recover from the disease.
Not supported (which makes this answer correct). The author notes that CJD is
Prions do not require nucleic acid for their reproduction.
The body has no natural defense against CJD.
Scientists have only a partial understanding of the mechanism by which prions reproduce.
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