NEW YORK (Reuters Health) – Scientists reported on Wednesday that it may one day be possible to fight fatal brain-wasting disorders–such as those caused by eating mad-cow contaminated meat–using antibodies directed at prions, the proteins which cause the disease.
UK researchers discovered that these antibodies increased survival in mice infected with the prions that cause scrapie–a form of the brain-wasting disease that normally affects sheep.
Mice who received the antibodies before they developed symptoms remained disease-free indefinitely, staying healthy long after untreated mice with scrapie had died, the authors report in the journal Nature.
These findings suggest that a similar approach may be available to humans infected with variant Creutzfeldt-Jakob disease ( news -web sites ) (vCJD), the condition linked to mad cow disease, study author Dr. Simon Hawke of the Imperial College in London told Reuters Health–but likely not before several years from now, he noted.
Hawke explained that he and his colleagues found that the technique did not fight off scrapie in mice who had already developed neurological symptoms of the illness.
This poses a problem when applying a similar approach to humans, Hawke noted, for it is difficult to detect the illness in humans who have eaten infected meat, but whose brains have not yet been infiltrated by the disease-causing prions.
As a result, doctors need to get better at diagnosing the disease before a treatment approach similar to that used in the current study will work, he said.
But given that previous attempts at treating these types of brain-wasting disorders have yielded few positive results, showing that any technique can combat the disease is encouraging, Hawke added.
“We’re showing that this type of strategy may well work,” Hawke said. “We’ve taken it out of a test tube.”
“But it’s definitely not a treatment,” he cautioned.
In an interview, Hawke explained that vCJD, scrapie, and mad cow disease develop when normal, healthy prions take on an abnormal shape and accumulate in the body.
Hawke said that the antibodies used in the current study were engineered to bind to both abnormal prions and normal prions. Animals become ill when they ingest an abnormal prion, he said, which acts as a “template,” interacting with normal prions and causing them to become deadly.
Hawke explained that the antibodies may bind to both the abnormal and the normal forms of prions, preventing the healthy proteins from converting into disease-causing prions.
Indeed, when Hawke and his colleagues injected scrapie-infected mice with the antibodies, the mice experienced an overall reduction in levels of the abnormal prions in their bodies, and stayed healthy for more than 300 days after a comparison group of untreated, infected mice had died.
Hawke explained that these findings deserve some “cautious optimism,” suggesting that treatment for prion diseases in humans may one day be possible.
“It’s something within our grasp, and it’s a significant first step,” Hawke said.
The next step is to develop similar antibodies to those used in the current study that will be safe to give to humans, then to perform preliminary tests to see how well these human antibodies work, he said.
The entire process will likely require at least a few more years of research, Hawke noted.
SOURCE: Nature 2003;422:80-83.