The prion's progress

Article Abstract:

Prions are particles of proteins that do not contain nucleic acids, which combine to make up the genetic information necessary for replication. Genetic mutation in the prion gene is proposed as the cause of degenerative brain diseases known as spongiform encephalopathies, such as scrapie in sheep, Creutzfeldt-Jakob disease and Gerstmann-Straussler-Scheinker (GSS) syndrome in humans. Recent studies provide further evidence that these particles are associated with infectivity. One study showed that purified prion proteins isolated from the brains of sheep with scrapie are infectious to other animals. Another study showed the genetic linkage of a particular mutation to GSS. Other mutations have been found in other families with histories of GSS and Creutzfeldt-Jakob diseases. Previous studies have shown that prions from one animal species can be infectious in another animal species, and that transgenic mice, which had been given the hamster prion gene at the embryonic stage, developed that disease at a much faster rate than if simply inoculated with the proteins. Transgenic mice given the mutated prion gene developed the degenerative disease. However, injections of brain extracts from the diseased transgenic mice have not caused disease in other mice, up to eight months after inoculation, which would have confirmed the infectious nature of the particles. How the prion protein becomes infectious is not certain. It is thought that the mutated form is shaped differently from the normal protein and this difference causes the disease state. From the results available so far, it can be concluded that prions are involved in the development of spongiform encephalopathies and a modified form of the prion protein is a part of, if not the complete, infectious agent. (Consumer Summary produced by Reliance Medical Information, Inc.)

Causes of, Central nervous system diseases, Creutzfeldt-Jakob disease

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A crucial role for B cells in neuroinvasive scrapie

Article Abstract:

Prion proteins are effectively propagated via intracerebral inoculation, but peripheral administration has caused the diseases iatrogenic Creutzfeldt-Jakob disease (CJD), bovine spongiform encephalopathy (BSE), new variant CJD and kuru. The identity of cells of the lymphoreticular system was investigated using immune-deficient mice inoculated with prions intraperitoneally. Defects affecting only T lymphocytes had no obvious effect, but mutations disrupting the differentiation and response of B lymphocytes prevented the development of clinical scrapie. Scrapie was found to develop after peripheral inoculation in mice expressing immunoglobulins solely of the M subclass.

Research, B cells

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PrP-expressing tissue required for transfer of scrapie infectivity from spleen to brain

Article Abstract:

There is evidence that a pathological isoform of PrP, a prion protein, is the infectious agent causing transmissible spongiform encephalopathies. It has previously been shown that mice not expressing PrP are resistant to prion infection. Further studies show that PrP-expressing neruografts in Prnp mice do not develop scrapie histopathology following intraperitoneal inoculation with scrapie prions. It is concluded that transfer of infection from the spleen to the central nervous system depends on PrP expression in tissue compartments unable to to be reconstituted by bone marrow transfer.

Diseases, Disease transmission

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