Tests for possible prion infectivity in beef or other meat products currently rely on sampling brain tissue from the animal for abnormally folded prion proteins Photo: Aurileide Alves

Rapid diagnostic tests for prion diseases may fail to identify some infectious samples, a study has suggested.

Tests for possible prion infectivity in beef or other meat products currently rely on sampling brain tissue from the animal for abnormally folded prion proteins, or PrP. However, researchers at the UK's Roslin Institute believe that levels of abnormal PrP in brain tissue may not be a reliable indicator of disease.

They injected mice with two different strains of prion-infected tissue and measured the degree of infection in the mice. An examination of the amount of misfolded PrP in the brains of the sick mice showed no correlation between prions and the infectivity of the disease strain. In some cases, highly infectious tissue samples had nearly undetectable levels of abnormal PrP.

The findings suggest that not all abnormal PrP found in diseased tissues is infectious, and may instead be a by-product of disease. Some other agent, or a particular form of misfolded PrP, may therefore be responsible for prion disease, said the researchers, and tests relying solely on abnormal PrP detection could underestimate the frequency of infection.

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