What characterizes an infectious agent such as a prion?

An infectious agent such as a prion is characterized by being composed entirely of protein. Prions are misfolded forms of normal proteins that can induce other normal proteins to also misfold, leading to a chain reaction that results in disease. Unlike traditional infectious agents such as bacteria or viruses, which contain nucleic acids (DNA or RNA), prions lack any genetic material and are solely made up of protein. This unique structure is crucial for their ability to cause neurodegenerative diseases, as it allows them to propagate by converting normal proteins into the abnormal prion form without the need for nucleic acid replication or cellular machinery. This is a defining aspect that distinguishes prions from other infectious agents.