New evidence involves a virus in amyotrophic lateral sclerosis (ALS), the disease that killed the baseball great Lou Gehrig and afflicts cosmologist Stephen Hawking. Researchers do not catch the virus in the act - they can not say with certainty that it causes ALS. But his presence on the scene, the neurons of the spinal cord killed off the disease, in fact a suspect, they wrote in the January issue of Neurology .
ALS strikes about 4,0 people in the United States each year. It destroys the nerves of the spinal cord that control muscles, paralyzing its victims and eventually kill them by making it impossible to breathe. ALS is known to run in families, but in most cases the cause is a mystery, says neurologist W. T. Longstreth of the University of Washington, Seattle. Research has generally failed to point to a virus as a possible culprit, but a previous study reported fragments of viral DNA in the spinal cord of people who had died of ALS. In addition, animal studies have shown that members of the enterovirus family, which includes the polioviruses, can cause ALS syndrome in mice.
A team led by Martina Berger microbiologist at the Rockefeller University in Lyon, France, used a more sensitive version of the polymerase chain reaction that previous studies to drive the viral RNA, and included samples of the spinal cord more in their research. Of the 18 samples from people who had died from ALS, 17 contained RNA resembles that of echovirus 7, an enterovirus that causes meningitis; in a control group of 29 samples of the spinal cord of people who died of other causes, only one contained the same sequence. Virus related SLA could be echoviruses 7 or a close relative, said Berger, now at the University of California, Irvine, but researchers have enough genetic code of the virus has not sequenced to be sure.
The assumption that a virus is to blame "certainly has its appeal," said Longstreth, as enteroviruses are known to attack neurons. Still, many questions must be asked, neurologists caution George Karpati from McGill University in Montreal and Marinos Dalakas National Institutes of Health in Bethesda; it could well be that the new virus does not cause ALS, they point out, but infects the spinal cord after the disease has taken hold.
0 Komentar