Genetic differences can also play a role, study finds
THURSDAY, April 7 (HealthDay News) -- The common Epstein-Barr virus may increase the risk of lupus in black Americans, researchers report.
Their study also found that genetic variations between individuals may influence immune system responses to the virus in people with lupus.
Almost all adults have been infected with Epstein-Barr at some point in time, which is a member of the herpes family of viruses. Initial infection can cause symptoms ranging from fever and sore throat in children, to mononucleosis in teens and adults. After initial infection, the virus settles into immune system B cells. It remains there for life and is mostly dormant, with occasional bouts of reactivation and replication.
In this study, published in the April issue of Arthritis & Rheumatism, researchers in North and South Carolina compared the prevalence of antibodies in blood samples collected from 230 lupus patients and from a group of healthy individuals.
Among both lupus patients and the control group, blacks had a higher prevalence of EBV-IgG antibodies -- a telltale sign of prior Epstein-Barr infection -- than whites. The researchers also found that 66 of the black participants with lupus had another antibody -- EBV-IgA -- which indicates repeat or reactivated EVB infection.
Among blacks, the presence of EBV-IgA was calculated to increase the odds of lupus by five to six times. This association appeared stronger in older blacks compared to younger blacks. Among whites, the association between EBV-IgA and lupus was found to be modest, although it did greatly increase with age.
In both black and white lupus patients, the researchers identified a genetic variation in the CTLA-4 protein, which significantly increased the risk of lupus associated with EBV-IgA antibodies.
"The racial difference in the association between EBV-IgA and (lupus) is intriguing, especially since African-Americans have a higher risk of (lupus), tend to develop the disease earlier, and often have a more severe course of the disease," study author Christine G. Parks said in a prepared statement.
She conducted the study while a postdoctoral fellow at the U.S. National Institute of Environmental Health Sciences.
"One explanation could be that there are more opportunities for reinfection among African-Americans, given the higher population prevalence of infection and likelihood of encountering and becoming infected with new viral strains," Parks explained.
SOURCE: John Wiley & Sons Inc., news release, March 31, 2005
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