A study published in Science confirms that the virus, which in some people causes mononucleosis, is one of the risk factors for neurological disease
For decades, researchers have suspected that people become infected with an extremely common virus called Epstein-Barr (EBV), they were more likely to develop multiple sclerosis, an autoimmune degenerative neurological disease (i.e. characterized by an improper immune attack against nerve fibers) which in Italy affects 113 people for every 100,000 inhabitants. In our country it is estimated, according to data from Epicenter, that people with multiple sclerosis are between 68,000-75,000 for a total of 1800-2000 cases each year.
A new study published in Science, which follows other work published since 2000, confirms that the Epstein-Barr virus is one of the causes that can trigger multiple sclerosis. Analyzing data from approximately 10 million US military personnel collected over the course of two decades, the research team led by Alberto Ascherio, an epidemiologist at the Harvard TH Chan School of Public Health, found that the risk of developing multiple sclerosis increases 32 times following an EBV infection. The same researchers warn that the Epstein-Barr virus is not the only known risk factor for people who develop the disease, but it would be the most obvious of all.
EBV is a very widespread herpesvirus in the population and it is estimated that in Italy it infects 97% of people. Although few are aware that they are infected, some develop the mononucleosis (the kissing disease). The virus remains in the body for life. Despite being a very common virus, very few develop multiple sclerosis.
As mentioned in the research the scientists looked at the data of 10 million US military who were controlled for twenty years with tests every two years to check for antibodies against EBV, a sign of the infection. By studying the medical records the researchers identified 801 military who developed multiple sclerosis during the study period finding that 35 of these 801 had tested negative for EBV-specific antibodies during initial serum sampling, but over time all but one people were exposed to the virus. So 800 out of 801 contracted EBV before developing multiple sclerosis.
The team ran several tests to see if other viruses shared such a strong correlation with the disease, discovering why EBV was the only one to stand out in this way. The strength of the study, lead author Dr. Alberto Ascherio, which has been possible to follow the volunteers for years and verify whether Epstein-Barr infections preceded multiple sclerosis.
In multiple sclerosis, still a disabling disease orphan of a definitive cure the immune system mistakenly attacks the myelin, an insulating sheath that surrounds many nerve fibers, and this damage impairs the ability of nerve cells to transmit signals and progressively the patient loses muscle control. The first signs of this nerve cell damage can appear up to six years before the onset of multiple sclerosis.
One question still remains unanswered: why since most people contract EBV, only a few, a very small number, develop multiple sclerosis? We invert the data – he proposes Roberto Furlan, neurologist expert in multiple sclerosis, director of the neurology institute at the San Raffaele hospital in Milan – and we see out of just under a thousand people with EBV, only one develops multiple sclerosis. The virus is a necessary but not sufficient condition.
The Harvard team also identified a another clue on the hypothesis that EBV can trigger multiple sclerosis: in the serum of those who developed the disease, signs of nerve damage which occurred after exposure to EBV but before the official diagnosis of MS. Specifically, they looked for a protein called neurofilament light chain, whose concentrations increase in the blood following damage to nerve cells. This protein increased in the serum of those who developed multiple sclerosis, but only after they were exposed to EBV. For those in the control group, who never developed multiple sclerosis, the concentration of the neurofilament light chain in the blood remained the same before and after contracting EBV; this is in line with the idea that exposure to EBV does not trigger multiple sclerosis in everyone, but rather only in susceptible people.
Because as mentioned, most people contract EBV, but only very few develop multiple sclerosis, what are the others risk factors?
As with all autoimmune diseases more contributing causes come into play. There are other genetic and environmental co-factors, Furlan explains. Not a genetic disease, in fact we do not advise patients to have children. Suffice it to say that the disease concordance in homozygous, identical twins is relatively low, below 7%. It means that in 93% of cases having the same DNA does not cause the disease, in addition to the fact that the twins share the environment. However, they have been identified so far 140 genes in patients with multiple sclerosis who alone have a very small impact but taken together contribute to the predisposition to the disease. Smoking and low vitamin D levels are other predisposing factors in addition to gender: for every male with multiple sclerosis there are 3.8 females.
According to the authors within a genetic and environmental context EBV could ignite the fuse that triggers the development of multiple sclerosis. But perhaps in the future, an EBV vaccine could prevent that fuse from igniting:Epstein-Bar like all herpes viruses are very complex because they change a lot and so far it was not possible to create specific vaccines despite the efforts of scientists. Now let’s see if the new mRNA technology can make a valid contribution to the research, concludes Furlan.
January 14, 2022 (change January 14, 2022 | 18:22)
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