Latitude line up: EBV joins vitamin D centre stage

13 July 2012

Author: MS Trust

Research published this week sheds further light on why MS is generally more prevalent further away from the equator. For example, the prevalence of MS is higher in Scotland than in England and highest of all in Orkney.

The vast majority of people with MS have antibodies to Epstein Barr virus (EBV) in their blood showing that they have been exposed to the virus at some point in their life. The infection with EBV may have caused them to have glandular fever (also known as infectious mononucleosis) or they may have shown no symptoms at all. People who do not have MS are less likely to have antibodies to EBV.

A study published this week found that people with MS living at higher latitudes (further away from the equator) were more likely to have antibodies to EBV than those living at lower latitudes. At first sight, this seems an exciting result as latitudes with high levels of MS seem to correspond to areas where more people have antibodies to EBV suggesting that EBV is directly involved in causing MS. However, the same study found a similar geographical gradient in EBV antibodies in people who did not have MS. So, anyone living at higher latitudes is more likely to have antibodies to EBV, irrespective of whether they have MS or not.

What does this all mean? Most likely, there is another factor involved in addition to EBV and a strong candidate is vitamin D. It was already known that vitamin D deficiency is associated with a higher risk of MS. Vitamin D is made in the skin when exposed to sunlight so people living at higher latitudes are less able to make enough vitamin D in this way.

The researchers suggest that exposure to EBV and lack of vitamin D may be linked together in causing MS. It is known that vitamin D helps the immune system defend the body from viral infections and previous research has shown that lower vitamin D levels correspond to more copies of EBV in an infected individual.

They suggest that vitamin D deficiency could impair the immune response to EBV leading to increased susceptibility to the virus or to reactivation of the virus later on in life. This means that, if EBV plays a role in causing MS, then vitamin D deficiency could make MS more likely.