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Health/ScienceStudy challenges mad cow research
BLOOMBERG NEWS
January 31, 2007
Researchers have found more evidence that a virus may cause mad cow disease and a related brain disorder in humans, threatening to overturn 25 years of research focusing on malformed proteins called prions.
Nerve cells infected with the human form of mad cow disease contained a virus-sized particle that doesn't appear in uninfected cells, said Laura Manuelidis, a neuropathologist at Yale Medical School in New Haven, Conn. Cells infected with scrapie, a sheep disorder related to mad cow disease, contained the same germ.
The findings raise the possibility of vaccines against the diseases and challenge research showing the disorders are spread by prions, abnormal proteins that have also been detected in the brains of infected humans and animals.
Some scientists have questioned the prion research performed by Stanley Prusiner of the University of California, San Francisco, since he won the Nobel Prize in 1997, Manuelidis said.
"If you don't look for something, you're not going to find it," she said in a telephone interview. "If everyone believes the world is flat, no one will go out and try to find the end."
Mad cow disease, otherwise known as bovine spongiform encephalopathy, is one of a family of rare infections that cause slow, relentless brain damage in humans and animals. The disease often takes years to appear and develop, making research especially time-consuming.
Questions about whether prions cause the infections have arisen because people and animals are thought to catch the diseases by eating tainted meat. The human stomach and intestines would quickly break down any protein, normal or abnormal, before it reached the blood or brain, said Sheldon Penman, an emeritus professor of biology at Massachusetts Institute of Technology.
Proteins, the building blocks of cells and tissues, aren't normally considered carriers of infections, like bacteria and viruses, he said. The Nobel Prize-winning work by the University of California's Prusiner lacked the precision to show that injections of prions transmitted the disease, Penman said.
"He injected stuff that had prions in it, including a million other things," Penman said in an interview. "He never did the crucial experiment of injecting prion protein and inducing disease."
Prusiner won the Nobel in physiology or medicine in 1997 "for his discovery of prions - a new biological principle of infection." He declined an interview through a university spokeswoman.
Scientists have been trying to gain a better understanding of mad cow disease, or BSE, since it struck United Kingdom herds in the late 1980s. About 153 people have developed the human form, called variant Creutzfeldt-Jakob disease, or vCJD, and health officials have put restrictions on animal feeding practices to prevent infections.
Manuelidis published research in 2005 showing that infections with a mild form of vCJD protected mice against more severe infections with the same disease. The findings suggested that vaccines against such human and animal diseases might be possible, she said at the time.
In the study published Monday, she and her colleagues studied colonies of cells with and without the human and sheep infections. They found that only infected cells contained a particle at the smaller end of the range associated with viruses.
The particles were configured in rows and groupings that appear similar to the way viruses sometimes congregate in cells, Manuelidis said. Using immune proteins called antibodies, the Yale team determined that the particles are not made of prion protein. The findings appear online in the Proceedings of the National Academy of Sciences.
BLOOMBERG NEWS
January 31, 2007
Researchers have found more evidence that a virus may cause mad cow disease and a related brain disorder in humans, threatening to overturn 25 years of research focusing on malformed proteins called prions.
Nerve cells infected with the human form of mad cow disease contained a virus-sized particle that doesn't appear in uninfected cells, said Laura Manuelidis, a neuropathologist at Yale Medical School in New Haven, Conn. Cells infected with scrapie, a sheep disorder related to mad cow disease, contained the same germ.
The findings raise the possibility of vaccines against the diseases and challenge research showing the disorders are spread by prions, abnormal proteins that have also been detected in the brains of infected humans and animals.
Some scientists have questioned the prion research performed by Stanley Prusiner of the University of California, San Francisco, since he won the Nobel Prize in 1997, Manuelidis said.
"If you don't look for something, you're not going to find it," she said in a telephone interview. "If everyone believes the world is flat, no one will go out and try to find the end."
Mad cow disease, otherwise known as bovine spongiform encephalopathy, is one of a family of rare infections that cause slow, relentless brain damage in humans and animals. The disease often takes years to appear and develop, making research especially time-consuming.
Questions about whether prions cause the infections have arisen because people and animals are thought to catch the diseases by eating tainted meat. The human stomach and intestines would quickly break down any protein, normal or abnormal, before it reached the blood or brain, said Sheldon Penman, an emeritus professor of biology at Massachusetts Institute of Technology.
Proteins, the building blocks of cells and tissues, aren't normally considered carriers of infections, like bacteria and viruses, he said. The Nobel Prize-winning work by the University of California's Prusiner lacked the precision to show that injections of prions transmitted the disease, Penman said.
"He injected stuff that had prions in it, including a million other things," Penman said in an interview. "He never did the crucial experiment of injecting prion protein and inducing disease."
Prusiner won the Nobel in physiology or medicine in 1997 "for his discovery of prions - a new biological principle of infection." He declined an interview through a university spokeswoman.
Scientists have been trying to gain a better understanding of mad cow disease, or BSE, since it struck United Kingdom herds in the late 1980s. About 153 people have developed the human form, called variant Creutzfeldt-Jakob disease, or vCJD, and health officials have put restrictions on animal feeding practices to prevent infections.
Manuelidis published research in 2005 showing that infections with a mild form of vCJD protected mice against more severe infections with the same disease. The findings suggested that vaccines against such human and animal diseases might be possible, she said at the time.
In the study published Monday, she and her colleagues studied colonies of cells with and without the human and sheep infections. They found that only infected cells contained a particle at the smaller end of the range associated with viruses.
The particles were configured in rows and groupings that appear similar to the way viruses sometimes congregate in cells, Manuelidis said. Using immune proteins called antibodies, the Yale team determined that the particles are not made of prion protein. The findings appear online in the Proceedings of the National Academy of Sciences.