Virus yang menyebabkan 'mono' dalam beberapa kasus dapat menyebabkan multiple sclerosis

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Scientists have long linked the Epstein-Barr virus and multiple sclerosis.

Epstein-Barr virus infection has been linked to the onset of multiple sclerosis, an inflammatory illness affecting the brain and spinal cord (EBV).

According to the clinical resource UpToDate, EBV, also known as human herpesvirus 4, infects 90 to 95 percent of people by the time they reach adulthood. Even though EBV can cause infectious mononucleosis (often known as "mono") in youngsters, it is more common among adolescents and young adults. EBV is a common virus, but research suggests that it may be a risk factor for multiple sclerosis, which is far less prevalent.

People with multiple sclerosis, for example, have greater amounts of EBV-specific antibodies—immune molecules that bind to the virus—compared to those without the condition. Additionally, the previous study has shown an increased risk of acquiring multiple sclerosis in the future for those who contract mono throughout childhood. The difficulty in proving that EBV infections cause multiple sclerosis is because most persons encounter EBV at some point.

New evidence for this theory was published in the journal Science on Thursday (Jan. 13) . Over two decades, more than 10 million U.S. military personnel were studied and have an increased risk of multiple sclerosis after being infected with EBV. They discovered no evidence of a link between the autoimmune disease and other viral infections, and no other risk variables showed a significant increase in the probability of developing the condition.

According to Dr. Lawrence Steinman, a Stanford University School of Medicine professor who was not involved in the study, EBV is linked to multiple sclerosis, but other viruses are not. Another problem is that the research does not explain exactly how EBV might be driving the disease, but other recent studies have provided strong clues.

'Indisputable proof'

Scientists at the Harvard T.H. Chan School of Public Health's Neuroepidemiology Research Group have been studying the possibility that EBV may be a risk factor for M.S. for more than two decades, according to to study co-author and senior research scientist Kassandra Munger. When looking for people who had never been exposed to the virus, the team decided to monitor their EBV status throughout time to see if their risk of developing multiple sclerosis rose after exposure.

Munger reported that "about 95 percent of the population is infected with EBV by the time they reach maturity." People who hadn't previously been exposed to EBV were found by combing through a dataset managed by the U.S. Department of Defense.

Serum, the yellowish fluid portion of blood, is kept in a repository by the Department of Defense. Active-duty military personnel supply HIV screening serum at the start of their service and every two years after that. Any remaining serum from the testing is stored in the repository. It is possible to detect antibodies against the virus in serum, which is why these serum samples allowed the researchers to track each individual's EBV status over time.

Finally, they investigated whether there was a connection between EBV status and M.S. onset. Their data only looked at people exposed in their early twenties rather than those who were told as children.

They found 801 people with multiple sclerosis who were diagnosed during the study period and had submitted at least three serum samples. At the outset, 35 of the 801 people were negative for EBV-specific antibodies, but the virus was eventually transmitted to all but one. As a result, 800 of the 801 people tested positive for EBV before being diagnosed with M.S.

Many studies were done to discover if any other viruses had such a high association with the disease, but only EBV stood out.

According to the research team, multiple sclerosis may be brought on by exposure to the EBV virus, which found evidence of nerve damage in the serum of people who acquired the condition but had not yet been officially diagnosed with M.S.

When the immune system targets the insulating sheath that covers numerous nerve fibers by mistake, it causes damage to the nerve cells' ability to transfer impulses, which causes multiple sclerosis. To check for symptoms of nerve cell injury earlier than six years before the development of multiple sclerosis, the team examined serum samples from people who had not yet developed multiple sclerosis.

Neurofilament light chain, a protein that is elevated in the blood when nerve cells are damaged, was the focus of their research. Multiple sclerosis patients' serum levels of this protein spiked after exposure to Epstein-Barr virus (EBV). There was no change in the neurofilament light chain concentration in the blood of those in the control group who did not acquire multiple sclerosis, which supports the hypothesis that EBV exposure does not cause multiple sclerosis in everyone but instead just in those who are vulnerable. In Munger's opinion, "the infection appears to occur before any sign of nervous system involvement.

"This is really, we think, convincing evidence of causality," she told Live Science when combining her findings with those of the other studies.

According to Robinson, who echoed the sentiment, EBV infection and M.S. development are linked irrevocably. However, a recent study by Robinson and Steinman sheds some light on why this association exists.

There has been no peer-review or publication of this paper, which was published on Research Square on Jan. 11. People with multiple sclerosis appear to have a large number of particular antibody-producing cells floating about their brains and spinal cords, according to this study. These cells produce two kinds of antibodies: one that attacks an EBV protein called EBNA-1, and the other that attacks the cells that produce myelin.

In several other studies, EBV-specific antibodies have also been shown to target components of nerve cells and the myelin sheath. According to Robinson, this striking resemblance triggers the immune system to target myelin. "I think that would be the leading view," he added.

Yet, even with all of this data, there is still a significant mystery: Why do just a tiny percentage of persons who contract EBV go on to acquire M.S.? At the very least, their ancestry has something to do with it.

According to Robinson, a researcher in the field, multiple sclerosis may be linked to a person's immune system. EBV may then serve as the spark that ignites the onset of multiple sclerosis in those genetically predisposed to it. He speculated that an EBV vaccine or treatments to block the virus's lasting effects on the immune system might one day stop multiple sclerosis in its tracks, thus preventing the fuse from ever being lighted.

Steinman and Robinson noted in a remark that "maybe M.S. could be eradicated now that the primary trigger for M.S. has been recognized."

Reference : https://www.livescience.com/epstein-barr-virus-multiple-sclerosis-link

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