Science - January 19, 2006

Classical prion in ‘new’ CJD strain

Patients suffering from the new form of the deadly Creutzfeldt-Jakob Disease (CJD) have two types of pathogenic prions in their brains. This has been demonstrated in research done on a highly sensitive antibody developed by CIDC-Lelystad.

‘The discovery confirms a suspicion we had already had for a while: that all diseases related to BSE are caused by a combination of prion proteins. This has no immediate implications for fighting the disease, but can help to solve questions about the origins of the disease,’ says Dr Jan Langeveld, researcher at the Central Institute for Animal Disease Control (CIDC-Lelystad). He published the discovery in the January number of the American Journal of Pathology together with colleagues from the British National CJD Surveillance Unit in Edinburgh.

It was already known that classical forms of CJD, from which a few people died before the outbreak of BSE, were caused by one of two types of prion – PrPSc type 1 or type 2 – or a combination of them. The new strain of CJD, probably caused by eating beef contaminated by BSE, is distinguished by the presence of another type of prion: PrPSc type 2B. The diagnosis ‘BSE-related patient’ is done on the basis of this variant prion type.

The recently published research shows, however, that all 21 patients with the new form of CJD who were examined also accumulate type 1 prions in their brains and tonsils. Langeveld: ‘The amount is much smaller, but there are definitely two types active in these patients. You see the same mixtures of prions in cattle with BSE and in sheep that have been infected with BSE. It puts our ideas about the origin and infection in another light. It raises the question, for example, of whether scrapie in sheep, which mostly have type 1 prions, might have played a role in the origin of the epidemic.’

There has been an absolute ban on using animal proteins in animal feed for more than five years in Europe to prevent BSE infection. / GvM