Past infection with the Epstein-Barr virus (EBV) has been reported to increase the risk for multiple sclerosis (MS). Now, researchers have found a link between EBV and MS in three racial-ethnic groups, with African-Americans and Latinos showing a higher risk for MS than Caucasians.
The research study, “Epstein-Barr virus, cytomegalovirus, and multiple sclerosis susceptibility,” was published in the journal Neurology.
Previous studies have suggested that EBV infection, which causes mononucleosis, also known as mono or the kissing disease, increases the risk for MS. More recently, infection with another virus, the cytomegalovirus (CMV), also has been linked to increased risk of MS, although the data remain controversial.
Now, researchers further investigated the potential link between EBV and CMV infections and the risk for MS. The team studied the prevalence of each virus in populations from different racial-ethnic backgrounds, including African-Americans, Latinos, and Caucasians, because it has been reported that these populations have a natural variation on the prevalence for these infections.
“Previous studies that have found a link between mononucleosis and MS have looked primarily at white populations, so for our study, we examined whether there was a similar link for other racial groups as well,” Annette Langer-Gould, MD, PhD, of Kaiser Permanente Southern California in Pasadena, a study author, said in a press release. “Indeed, we did find a strong biological link for all three racial groups.”
Researchers recruited 1,090 people from the three groups from Kaiser Permanente Southern California (KPSC), a large health maintenance organization (HMO) with more than 4 million members. The participants were a representative sample of the general population in Southern California.
Included in each racial-ethnic group were healthy, matched controls and participants with established MS or early phases of the disease, a condition known as clinically isolated syndrome. All subjects underwent blood test analysis for antibodies for each of the infections and were asked if they had ever had mono.
The results showed that those who had mono had a significantly greater risk for MS or its precursor, clinically isolated syndrome. This association was observed in all three racial-ethnic groups and was independent of any other potential factors that could affect MS risk, including sex, age, smoking, and genetic ancestry.
Specifically, the data showed that black and Latino participants who had mononucleosis presented about four times the increased risk for MS compared with those without the disease. In white subjects, the risk was two times higher.
“While many people had Epstein-Barr virus antibodies in their blood, we found among all three groups, people who also developed mono in their teen years or later had a greater risk of MS,” said Langer-Gould, a member of the American Academy of Neurology. “This implies that delaying Epstein-Barr virus infection into adolescence or adulthood may be a critical risk factor for MS.”
EBV usually causes few, if any, symptoms in individuals infected at a young age.
For CMV, an inconsistent association was found across racial-ethnic groups. Antibodies against CMV were found to be associated with a lower risk of MS or clinically isolated syndrome in Latinos, but not in African-Americans or Caucasians.
Overall, the results point to a strong biological link between EBV infection and MS and highlight how our understanding of the factors underlying MS can be greatly improved by multiethnic studies.
“Studies like ours that include participants from multiple racial groups can be a strong tool to test for biological risk factors, especially when the frequency of exposures to biological factors like Epstein-Barr virus and mononucleosis differ between groups. If the findings were not the same across all groups, it would be less likely that a link would be biological,” Langer-Gould concluded.