THURSDAY, Oct 30, 2003 (HealthDayNews) -- A British research team has halted a mad cow-like disease in lab animals, pointing the way to new hope for preventing the progression of the disease in humans as well.
"No one else has reported this, not that we are aware," says Dr. Giovanna Mallucci, a member of the research team at the Institute of Neurology in London. The team's report appears in the Oct. 31 issue of Science.
Called mad cow disease in cattle and Creutzfeldt-Jakob disease (CJD) in humans, the neurological disorders studied occur when normal nerve cell proteins, called prions, change for unknown reasons into a disease-causing form.
Both are fatal brain diseases and there is no known cure. In CJD, patients may have failing memory, behavioral changes, coordination problems, and visual disturbances. Mental deterioration hastens as the disease progresses, and 90 percent of those who have it die within a year, according to the National Institutes of Health.
Since 1996, according to the U.S. Centers for Disease Control and Prevention, there has been accumulating evidence of a causal relationship between outbreaks of bovine spongiform encephalopathy (BSE, the technical name for mad cow disease), in European cattle and CJD in humans. CJD is also known as human BSE.
While the CDC says the specific foods that could transmit the agent from cattle to humans isn't known, the presence of the BSE agent has been located in cattle's brain, spinal cord, retina and other body parts.
A prion is often harmless, but sometimes events such as a mutation change the prion into a form that makes it deadly or infective. The normal form is called PrPc and the abnormal PrPSc.
Mallucci's team generated mutant mice, in which they stripped the nerve cells of normal prions. Then they induced the disease in mice. Once that was done, they then depleted the normal prions in the nerve cells, which successfully reversed the early brain damage and halted the illness.
Even though the neurotoxic prions continued to build up in cells other than nerve cells, the mice stayed healthy because the team had arrested the conversion in the nerve cells of PrPc to PrPSc.
In the process, the team concluded that it is not the PrPSc prions themselves that are toxic, but that some intermediate substance generated by the conversion process is to blame for the disease.
"It appears that the conversion of PrPc to disease-related forms must occur within the neurons to be pathogenic [disease-causing]," the team writes, "consistent with the possibility that a toxic intermediate is generated within neurons during the conversion process."
As to whether the same technique will work in other animals, Mallucci says, "in theory, yes, but it is very difficult to achieve at present."
"Quite unbelievable," says Graham Steel, vice chair of the Human BSE Foundation, a support group for families who have lost members to human BSE. He couches his reaction with caution. "Doing things in mice is a long way off from doing things in humans," he says.
Still, he adds, "until this, there was no hope once people developed CJD. This may be an important step to finding a cure."
More information
Learn about the disorder from the Creutzfeldt-Jakob Foundation, Inc. or the National Institute of Neurological Disorders and Stroke.
