Yale University researchers published a report in the January 29, 2007, online version of the Proceedings of the National Academy of Sciences suggesting that diseases associated with spongiform encephalopathies may be caused by a virus. The proposed theory contradicts the prevailing assumption that degenerative and fatal brain disorders, known as mad cow disease in animals and variant Creutzfeldt-Jakob disease (vCJD) in humans, are caused by misshapen prion proteins in the brain. vCJD infection has most often been associated with eating the contaminated meat from cows infected by bovine spongiform encephalopathy (BSE).
After infecting cell lines with either scrapie (a BSE-associated disorder in sheep and goats) or CJD agents, investigators discovered large amounts of “virus-like” particles in the cultures. Using an electron microscope, they observed that these particles did not bind to antibodies of the prion protein, signifying that the particles were not made up of the prion protein. Furthermore, infected cells containing a high concentration of particles were linked to higher rates of infectivity, while concentrations of the prion proteins did not show a similar correlation.
“Although much work remains to be done, there is a reasonable possibility these are the long sought viral particles that cause transmissible spongiform encephalopathies,” said lead author Laura Manuelidis, MD, professor and section chief of neuropathology at the Yale School of Medicine. “The abnormal protein is probably not infectious, but is a pathological result of an infectious virus binding to this host protein,” she added.
Source: Manuelidis L, Yu, ZX, Banquero, N and Mullins, B. “Cells Infected with Scrapie and Creutzfeldt–Jakob Disease Agents Produce Intracellular 25-nm Virus-like Particles,” Proceedings of the National Academy of Sciences. 2007; 104:6; 1965-1970.
The study was funded by grants from the National Institutes of Health and the U.S. Department of Defense.
Source: Yale University Office of Public Affairs news release dated February 13, 2007