Eating BSE-infected meat could lead to people developing different types of CJD, according to new research.

It had been thought that BSE was only linked to variant CJD, but experts at the Medical Research Council now suspect a link with sporadic CJD, or another form yet to be seen in humans.

The research focused on a gene that makes a normal version of the rogue “prion” protein involved in vCJD by encoding two types of amino acid – methionine (M) or valine (V).  With patients having two copies of the gene, they can prove to be MM, MV or VV.  Scientists had found that only those carrying the MM gene, thought to be 38 per cent of the population, were susceptible to vCJD or sporadic CJD – there has been only one exception where a patient with the MV genes developed the disease after receiving a blood transfusion. But after research using mice, it was found that those with the VV genes  developed a form of the disease with different prions to vCJD, now dubbed “type five”.
Published in Science, the study raises the possibility that a higher proportion of the population is susceptible to CJD than first thought.

“These mouse studies give us vital clues about the behaviour of prions and how they appear to modify and adapt depending on the genetic make-up of the individual they are infecting,” said Professor John Collinge, director of the MRC Prion Unit at University College London.

“We are always cautious about making direct comparison to the human condition, but our work strongly suggests that we can not assume only those with one genetic profile are vulnerable to BSE infection.
“At this stage, it is not possible to say how this should alter estimates of those likely to become ill, but our findings do suggest we should be taking steps to draw up a more sophisticated system of categorising the disease so we don’t mistake BSE related infection for a version of sporadic CJD.”