White blood cells could play a critical role in the development of Creutzfeld-Jakob disease (CJD), the fatal human version of so-called "mad cow disease," Swiss scientists report in tomorrow's Nature. The news--based on a related condition in mice and first presented at a closed meeting in November--has prompted calls for British blood banks to cull white blood cells from donated blood.
Neuropathologist Adriano Aguzzi of the University of Zurich in Switzerland and his colleagues did not set out to show that infected blood can transmit CJD. Trying to understand how spongiform infections reach the brain--where they kill cells, leaving the tissue full of holes--the researchers had begun to suspect that cells of the immune system might be unwitting collaborators. In their latest work, the researchers attempted to narrow down the list of suspects by infecting different strains of immune-compromised mice with scrapie, a disease related to CJD. The team found that mice lacking T cells or interferon gamma could be infected as easily as controls, but mice lacking B cells, which help produce antibodies, resisted infection. If B cells abet the disease, the authors reason, they may also carry the infectious agent.
Because no one knows what causes CJD--many believe that it is due to misfolded proteins that propagate themselves, while others think a slow-acting virus is to blame--it has been difficult to nail down how the disease [infection] travels through the body. But few researchers are surprised by the latest news. Neuroscientist Paul Brown of the National Institute of Neurological Diseases and Stroke says it builds on decades of previous research, including studies in the 1960s and '70s suggesting that blood can transmit these diseases, although it is less infectious than tissue from the brain or nervous system.
CJD clearly can be transmitted by transfusion in lab animals, Brown says. But both Aguzzi and Brown point out that no human case of CJD has been traced to a blood transfusion. There is a "tremendous amount of epidemiology that all speaks against the possibility of blood-borne transmission of the agent," Aguzzi says. However, he cautions, the new variant (ScienceNOW 23 October 1996), "could be a totally different story."