Prions

Prions are very peculiar “infectious agents” composed of only one protein genome free. Prions are aggregates of a “normal” prion protein (PrP,) mainly and normally present on the surface of the neuron’s membrane. Aggregation occurs when the normal cellular PrP (PrPc) meets a PrP scrapie (PrPsc) that is a PrPc with a consistent modified conformation (the “seed”) able to induce transformation and aggregation of PrPc.

The PrPc could be:

a) introduced from the outside, for instance as contaminated food or feed causing alimentary transmitted diseases like Kuru in humans or BSE in bovine;
b) sporadically and spontaneously formed in the neuron at old age, presumably for a decreased ability of the cells to carefully control the synthesis process of the proteins.

Prions cause transmissible spongiform encephalopathy (TSE), a degenerative disease of the central nervous system with a very long incubation period lastingly many years. Typical disease in humans is Creutzfeldt-Jakob (CJD), while in animals scrapie in ovine and BSE in bovine. All TSEs are lethal with a relatively short clinical period, with signs typical for each disease.

Starting from 2001, IZSLER examined well over 2 million adult bovines as requested by the European surveillance plan for TSE, finalized to definitively establish the incidence of BSE in all the European countries. In over 10 years of activity the IZSLER laboratories found around one hundredBSE positive cases, most of which in the first three years of control. As expected, cases of BSE rapidly disappeared and the disease could be now considered eradicated in Italy.

The situation for scrapie of goat and sheep is different. The disease is endemic in Italy, although at low levels, and few case each year are still detected.

The IBVR at IZSLER includes part of the original samples resulted BSE or Scrapie positive. They consist in few grams of the brainstem left after the tests (rapid test and confirmatory test carried out at the National Reference Center for TSE at IZS of Torino) and stored at – 72°C.

People interested must know that working with prions (class 3 risk material) requires special safety and dedicated areas, specific equipment and well trained people. In addition, considering the high epidemiological risk and danger represented by BSE prion, the permission to transport and export prion samples must follow a particular procedure that has to directly involve the Health Authorities of all the involved countries.

Quality controls

Samples originated directly from the field (mainly slaughterhouses) and therefore they are carrier of a generic microbiological contamination.

Diagnostic methods

All the samples resulted positive towards UE validated rapid tests. They changed over the time according to the outcomes of a specific national tender and were: Prionics western blotting, LIA Prionics, Priostrip Prionics, ELISA Ideex. All the samples were then confirmed as positive at CEA Torino (histology, immunohistochemistry and western blotting).

Quality management system

IZSLER laboratories, that supply biological resources to IBVR, use testing methods performed according to UNI EN ISO/IEC 17025 quality system.

 

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