Researchers Create Viral Model of MS
Newswise — Many researchers believe that seemingly innocuous viruses harbored by most of us since childhood could be critical triggers for causing multiple sclerosis (MS). They will now have a practical way to test this theory.
In a presentation at the 127th annual meeting of the American Neurological Association, October 18 to 22 in San Francisco, Claude P. Genain, MD, reported that he and his colleagues at the University of California, San Francisco have produced an MS-like condition in an animal model by exposing the animals to a common virus that is suspect in MS.
"This is an unprecedented opportunity to understand how infection with a common human virus could lead to MS in a model system that resembles young humans," said Genain.
Most evidence points to MS being an autoimmune disorder wherein the immune system mistakenly targets essential nervous system cells for destruction. But the ultimate causes for this overactive immune system are not understood and may involve both genetic and environmental factors such as viruses, bacteria, or toxins.
A number of studies have suggested that viruses may trigger the onset of the disease, as well as the cycles of relapse that most patients experience. In part because no specific MS virus has been found, some researchers believe that one or more of the common viruses found in most people are to blame.
"Because common viruses such as measles, varicella zoster, Epstein-Barr and others infect virtually everyone during their childhood without adverse consequences, it is difficult to prove a relationship between these viruses and MS," said Genain.
Genain has been studying MS for many years in common marmosets. The marmosets can develop an MS-like illness called experimental allergic encephalomyelitis.
Genain and his colleagues have now discovered that the marmosets are susceptible to infection with the herpes hominis virus 6 (HHV6), which has shown up as a possible suspect in several studies of MS.
"In the infected marmosets, HHV6 infection appears to produce an inflammatory disorder in the central nervous system almost identical to MS in humans," said Genain.
Many of the hallmarks of MS are apparent in the affected marmosets, including the fact that the immune system targets critical nervous system cells.
The researchers hope that their model can be used to tease out how viruses manage to confuse the human immune system, and to suggest therapeutic approaches to correcting this problem.
Genain listed some of the questions that can be probed with the model: "Does it occur more frequently in males or females? Does it occur in younger or older animals? Are there certain predisposing genes? What kind of exposure to HHV6 is required, for example, one or more? Do antiviral drugs help prevent relapses?"
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