New data confirm link between Epstein-Barr virus and multiple sclerosis

Over the last 40 years, Epstein-Barr virus (EBV) has been repeatedly associated with multiple sclerosis and other autoimmune diseases. During the 2nd European Congress of Immunology ECI 2009 held in Berlin, Francesca Aloisi, Istituto Superiore di Sanità, Rome, will present new data that further support the link. In the brain lesions of patients with multiple sclerosis her team found abnormal accumulation of EBV infected B lymphocytes. Similar findings were made in the pathological tissues of patients with other autoimmune diseases.

Multiple sclerosis is the most common inflammatory disease of the central nervous system affecting young adults. Similarly to other chronic inflammatory diseases, like rheumatoid arthritis and systemic lupus erythematosus, multiple sclerosis is thought to result from an inappropriate attack of the immune system toward selected body components, a process named autoimmunity. In the case of multiple sclerosis, the immune system is thought to attack myelin, the lipid-rich sheath coating our nerves.

To date neither the causes nor the cure of this highly disabling disease have been identified. A detailed knowledge of the cause(s) and the pathogenesis is needed to develop effective new options for therapy and prevention. Viruses have always attracted the interest of immunologists as possible triggers of autoimmune diseases due to their ability to interfere with the host's immune system. One of the most ubiquitous viruses, EBV, which infects up to 95 % of the human population worldwide, has been repeatedly associated with multiple sclerosis through epidemiological and serological studies, but direct proof of its involvement was missing. The virus has the ability to hide in a particular population of immune cells, the B lymphocytes, remaining in a relatively dormant state for the entire life of the host. However, when not properly controlled by the immune system, EBV can reactivate causing tumours.

At the end of 2007, Aloisi and co-workers showed that EBV is present in brain lesions of patients with multiple sclerosis and that the virus is brought into the central nervous system by B lymphocytes, which behave as Trojan horses for the virus. They also showed that the infected B cells present in the brain become the target of an immune attack, thus promoting the chronic inflammation which leads to tissue destruction. „This raises the suspicion that EBV and its Trojan horses are the main cause of brain damage in multiple sclerosis", Aloisi says.

The scientists demonstrated that abnormal accumulation of EBV infected B lymphocytes is also found in pathological tissues in other autoimmune diseases. „These findings reinforce the long-held view that EBV might be involved in several autoimmune diseases and represent a step forward in the effort to understand the mechanisms underlying the development of autoimmunity. One of the main challenges for the future will be to understand whether preventing or counteracting EBV infection will have a beneficial impact on autoimmune diseases."