Study finds that virus naturally found in human genes to be active on immune cells in some people with active MS
March 21, 2012
A new study by Dr. Magdalena Laska (Aarhuis University, Denmark) and colleagues suggests that components of a virus called HERV-Fc1 (for human endogenous retrovirus), which are derived from genes normally found in the DNA of all humans, are present at higher levels in plasma and on immune cells in people with active MS. The study, published recently online in the Journal of Virology, provides an intriguing lead to a factor may either cause or result from immune attacks in MS or other disorders. Further research will be needed to better define the unknown role of this factor and its possible implications for people with MS.
Background: The cause of MS has been long debated, but likely includes both environmental and genetic risk factors. Among environmental factors, viruses have been frequently associated with MS. A retrovirus called HERV-Fc1 was previously shown to have a genetic association with MS. Components of this HERV have been found in the brain and blood of people with MS. Human DNA from all people contains genes for parts of retroviruses. Normally, these genes remain mostly silent, and few viral components are found in the body. This research group looked at whether components of HERV-Fc1 are increased in the circulating immune cells in people with active MS compared to healthy controls and people with inactive MS.
The study: To look for components of HERV, the researchers obtained blood samples from three groups: 30 healthy volunteers, 19 people with inactive MS (no relapses for an average of 36 months), and 22 people with active MS (relapses within an average of 3.2 months). Although all three groups had the same number of copies of the HERV component in their DNA, there were distinct differences in their RNA. (RNA is the first step in making virus from the gene.) HERV levels were four times higher in plasma samples from people with active MS compared to healthy people and people with inactive MS.
The team then looked at a protein related to the HERV, examining white blood cells that are known to be important in MS immune attacks. In these white blood cells, more HERV-related protein was found in samples from people with active MS compared to the other two groups. The team also explored whether disease-modifying therapies made a difference in HERV levels in the active MS group, and found no difference between those on therapy versus those who were not on therapy.
Comment: This study strengthens a previously suggested link between MS and HERV-Fc1, and suggests that the HERV-related gene components are “switched on” at a higher level in immune cells of people with active MS. It is not yet know whether HERV components play a role in launching or worsening the immune attacks on the central nervous system in people with MS, or whether they are a result of those attacks. Further studies are required to address these and other questions about these intriguing findings, and their possible implications for people with MS or other disorders.