Caderno Técnico: encefalopatia espongiforme transmissível

A nova variante da Doença de Creutzfeld-Jakob, cuja origem é atribuida à ingestão de produtos de origem animal - especialmente bovino - contendo a proteína priônica, traz novos desafios a cientistas e profissionais de saúde pública

Caderno técnico: encefalopatia espongiforme transmissível / Technical notebook: TSE

A nova variante da Doença de Creutzfeld-Jakob, cuja origem é atribuida à ingestão de produtos de origem animal - especialmente bovino - contendo a proteína priônica, traz novos desafios a cientistas e profissionais de saúde pública.

Prion diseases. An overview.

Prion disease is the new designation of a group of spongiform encephalopathies, all invariably fatal, which show similar clinical and neuropathological changes. They comprise a range of distinct diseases in both animals and man, and spontaneous, hereditary and transmissible forms are recognized. Until the sudden occurrence in the mid-1980s of an epizootic of a formerly unknown disease, popularly named 'mad cow disease', in cattle in the UK, very little attention had been paid to these rather obscure diseases. Concurrently it was asserted that the disease-causing agent appeared to be a ubiquitous mammalian brain constituent, and the disease mechanism a conformational change of its structure. These events have not only led to a new understanding of these extraordinary diseases, but have also provided insight into both neurodegeneration and disease mechanisms at the molecular level. Moreover, in 1997 the prion concept earned its originator the second Nobel price for medicine within this scientific field. In this introduction and overview of prion diseases, historical and philosophical perspectives are presented along with descriptions of the diseases in both animals and man. Epidemiology, genetics and transmissibility are also covered.

Los priones, un nuevo desafío evolutivo / Prions: a new evolutionary defiance

El objetivo de esta reseña es actualizar información ya publicada sobre los priones y las patologías que éstos transmiten. La existencia de una nueva variante de la enfermedad de Creutzfeld-Jakob y la confirmación experimental de que es causada por la misma cepa de priones que la encefalopatía espongiforme bovina (BSE), ha incrementado dramáticamente la necesidad de una precisa comprensión de las bases moleculares de la propagación priónica. El agente infeccioso es una proteína cuya conformación se encuentra alterada, que se reproduce a sí misma convirtiendo una proteína normal en una proteína con conformación priónica. La observación de que los priones se replican en los órganos linfoides en estadios muy tempranos de la infección lleva a cuestionar sobre cuáles son los requerimientos de tipo celular a ser infectado en el sistema linforreticular. Las células dendríticas foliculares serían el sitio de elección para la replicación y el reservorio de priores. El diagnóstico de las enfermedades producidas por priones presenta una serie de problemas debido a las peculiaridades de este tipo de patologías. Considerando que los priones se replican en el sistema linforreticular y posteriormente migran al sistema nervioso central, existe un lapso durante el cual podría propagarse este agente infeccioso por medio de la sangre, sus componentes o sus derivados. De esta forma representaría una nueva patología con la potencial capacidad de transmisión transfusional. Esta nueva forma de herencia independiente de los ácidos nucleicos obliga a replantear el axioma de transferencia de la información genética, hasta el momento, y con concordancia con la teoría evolutiva de Darwin, sólo pensando mediante moléculas constituidas por nucleótidos. ¿Será tiempo de cambiar el paradigma?

Encefalopatías espongiformes bovinas / Bovine spongiform encephalopathy

Durante la exposición se revisaron diferentes aspectos normativos en el país respecto a este tipo de encefalopatías, y su posible transmisión a humanos, según el enfoque de ANMAT (Administración Nacional de Medicamentos, Alimentos y Tecnología Médica), y especialmente en alimentos

[Epidemiology of the animal prion diseases]. / Epidemiología de las enfermedades priónicas animales.

The authors review the epidemiology of spongiform encephalitis, discussing the possible mechanism of appearance of the epidemic bovine spongiform encephalitis epidemic, leaving aside to another publication the epidemiology of the human spongiform encephalitis and its pathogeny.

[Prions, infections and confusions in the "transmissible" spongiform encephalopathies. The other evidence-based science. III. Review]. / Priones, infecciones y confusiones en las encefalopatías espongiformes "trasmisibles". Ciencia basada en la otra evidencia III. Revisión.

There are some neurological disorders with a pathological hallmark called spongiosis which include Creutzfeld-Jakob disease and its new variant, the Gertsmann-Straussler-Scheinker Syndrome and the Fatal Familial Insomnia in humans; and Scrapie and Bovine Spongiform Encephalopathy, among others, in animals. The etiological agent has been considered either transmissible or hereditary or both. Curiously, this agent has no nucleic acids, is impossible to filter, is resistant to inactivation by chemical means, has not been cultured and is unobservable at electron microscopy. All of these facts have led to some researches to claim that these agents are similar to viruses appearing in computers. However, after almost fifty years of research, is still not possible to explain why and how such elements produce the diseases commented about. On the contrary, during these years have been possible to know that these entities called slow viral infections, transmissible amyloidosis, transmissible dementia, transmissible spongiform encephalopathies or prion diseases appear in individuals with genetical predispositions exposed to several worldwide immunological stressors. The possibility that prions are the consequence and not the cause of these diseases in animals and man is day by day more reliable, and supports the suggestion that a systematic intoxication due to pesticides as well as mycotoxin ingestion, produced mainly by different molds such as Aspergillus, Penicillium or Fusarium, seem to be the true etiology of these neurodegenerative disorders.