Illustration by LadyofHats, public domain license
Multiple sclerosis or MS is a demyelinating disorder. Myelin is a fatty material that covers and insulates the nerves. For an unknown reason, in MS patients the immune system destroys myelin surrounding the nerve cells in the brain and spinal cord. This disrupts the flow of nerve impulses through the body and can cause a wide variety of debilitating symptoms, including muscle weakness, coordination problems when moving, and problems with sensation.
As long ago as 2003, researchers found latent HHV-6 in the brain cells of people with severe multiple sclerosis. HHV-6 may not be a direct cause of MS, but it’s thought that the virus prevents the body from repairing loss of myelin. When myelin is damaged in our body, oligodendrocyte progenitor cells normally migrate to the injured area and produce oligodendrocytes. These cells then make myelin to repair the injury. This process may not happen in someone with MS.
HHV-6 becomes latent by incorporating its own DNA into the DNA of its host. The virus then produces a protein called U94. This protein helps the virus to remain in the DNA and prevents it from being detected by the immune system. Researchers from the University of Rochester in the United States have discovered that when the HHV-6 virus is present in the DNA of human oligodendrocyte progenitor cells placed in lab animals, the U94 protein that’s made prevents the cells from migrating to nerves with injured myelin. As a result, the myelin of the animals disappears and the nerves are damaged.
Possible symptoms of multiple sclerosis
Illustration by Mikael Haggstrom, public domain license
The discovery about the possible relationship between the virus and MS is interesting, but there are some questions that need to be answered.
- One question is whether the inability of oligodendrocyte progenitor cells to migrate when they are infected by the virus is true in human cells as well as in the cells of lab animals.
- Another is whether the latent virus is harmful in people with MS or whether it needs to become active in order to be harmful.
- Yet another topic to investigate is the location of the virus in the bodies of healthy people and in the bodies of those with MS.
- We also need to know how the body of people with MS responds to the latent and active virus compared to the body of someone without MS.
The possible role of HHV-6 in multiple sclerosis
Facts about multiple sclerosis