March 17, 1997
Medical Update Memo
Two scientists in Belgium claimed in an interview on Belgian radio that they had found the cause of MS. One of the researchers, Dr. Ernest Van den Driessche, said MS is caused by antibodies against human herpes virus 6 (HHV-6), which causes a rash and fever-producing disease of children called roseola. According to the researchers, the HHV-6 antibodies cause MS at a later stage in life in approximately one in 1,000 people. The role that viruses -- including HHV-6 -- may have in the development of MS is the subject of research in many parts of the world including Canada, the United States and Europe. The claims by the Belgian researchers that HHV-6 is definitely the "cause" of MS would appear to be premature since their statements do not seem to be supported by any published documentation in peer-reviewed medical journals.
The claim by two scientists in Belgium that they have found the cause of multiple sclerosis is probably premature, however, there is a solid theoretical basis for thinking that exposure to a common virus may be part of the mechanism that triggers multiple sclerosis. For a number of years many researchers have thought that MS may develop if a combination of three factors exists:
HHV-6 is a common virus best known for causing roseola, a rash and fever- producing disease of young children. Like other herpes viruses, HHV-6 can persist in the body in a latent form for long periods of time and may be reactivated later. HHV-6 is present in normal brain tissue of many healthy adults. Rarely, it may cause serious inflammatory disease of the nervous system (encephalitis).
Human herpes virus 6 is one of a number of common viruses that has caught the attention of MS researchers. A possible link with HHV-6 was reported first in 1995 by researchers from PathoGenesis Corporation (Seattle, Wash.). The researchers reported that they found HHV-6 inside oligodendrocytes, the cells that make and maintain myelin, in 12 of 15 MS samples but in none of the 45 non-MS samples. At this time, it is not known whether the presence of HHV-6 in oligodendrocytes - - if actually confirmed by others -- means that the virus causes MS or whether its presence in the cells is a secondary infection. HHV-6 was also found in nerve cells in MS and in people who had Parkinson's disease, stroke and other diseases.
Other viruses under investigation are herpes simplex virus 1 by Drs. Lorne Kastrukoff and Eva Thomas at the University of British Columbia and the coronavirus by Dr. Pierre Talbot at Institut Armand-Frappier in Montreal. Dr. Talbot is investigating whether the structure of the coronavirus might be similar to that of one of the proteins that make up myelin. A theory called "molecular mimicry" speculates that the immune system attacks the invading virus but then is fooled by the similarity between the virus and the myelin protein and starts attacking the myelin. Other investigators are looking at a number of common viruses in relation to molecular mimicry.
It is hoped that the researchers in Belgium will soon provide published documentation of their work for peer review. Depending upon the outcome of such documentation, their work may provide further evidence of a virus involvement in MS, which at the present time, it must be stressed, remains speculative.
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© 2001 Multiple Sclerosis Society of Canada