A woman who has died of vCJD, varient Creutzfeldt-Jakob disease aka mad cow disease, did not have the same type of the protein/prion that most victims have.
Her brain was examined by researchers at the Institute of Neurology, at University College London, who found it had an unusual pattern of disease and carried out a genetic analysis. This showed that her version of the prion protein was different from all other previous victims of the infection. In vCJD it is the patients' own prion protein that is subverted by the infection; it alters shape, forming clumps that fatally clog up the brain. About 40% of the population carry the so-called MM variant, found in all victims so far identified, but her VV type is shared by around 10% of the population.
I don't know what exactly is the difference between the VV and MM genotypes or how that changes the resulting structure of the prion protein. But if another genotype can contract vCJD from having eaten contaminated, there maybe a few more people that will suffer. It also means that whatever makes MM different from VV is not enough to stop a prion from changing the original protein to another prion.
There is a precedent for prion diseases affecting people with MM and VV prion-types differently. Kuru, a brain-wasting disease similar to BSE which struck a cannibalistic tribe in Papua New Guinea, had different incubation times according to people's genes. The word kuru means "trembling with fear".
Now that is interesting. It could be that people with different genotypes will suffer differently. A different time scale could be one way that it could manifest. A slightly different change in the brain tissue could be another part of that.
Its sad that people have to suffer because we turned herbivorous cattle into cannibals. At the same time it has spurred research into what otherwise may have languished in the annals of biochemistry as another strange way proteins act. Creutzfeldt-Jakob and scrapies are rather rare, as are other prion diseases such as Fatal Familial Insomnia, and while curious, they probably wouldn't have lead to the funding that this outbreak in the UK has lead to. Squeaky wheels getting oil and stories that bleed, lead.