A Colombian study reported finding an increased risk of multiple sclerosis (MS) associated with a particular allele, or gene variant, in a group of patients from the Colombian capital, Bogotá. The study also found a protective allele — HLA-DRB1*14 — that might explain the low rates of MS observed throughout the country.
The study, “HLA-DRB1*14 is a protective allele for multiple sclerosis in an admixed Colombian population,“ was published in the American Academy of Neurology journal, Neuroimmunology & Neuroinflammation.
The allele HLA-DRB1*15 is one of the most frequently reported genetic risk factors for MS and has been found across different populations, including Europeans, African-Americans, and Latin Americans. Other major histocompatibility complex alleles, like HLA-DRB1*14, have been associated with a reduced MS risk. (An allele is a variation of an inherited gene, with a common example being the allele that gives a person brown eyes instead of green eyes.)
When assessing genetic risk inferred by a specific gene, tracking ancestry is important. This can be done by assessing mitochondrial DNA or nuclear ancestry informative markers, and it is particularly important when studying recently mixed populations such as Latin Americans. The Colombian population is composed of differing proportions of people of European, American Indian, and African ancestry, depending on the region. The study, therefore, also investigated ancestry informative markers.
The research team, led by Jaime Toro from El Bosque University, Bogotá, enrolled 100 MS patients and 200 healthy controls. Researchers found that the HLA-DRB1*15 allele was present in 31 percent of the patients and 13.5 percent of controls, and an analysis taking demographic and clinical characteristics into account showed that the allele was associated with a threefold increased risk for MS.
The HLA-DRB1*14 allele was found in 5 percent of the patients and 15.5 percent of controls, and likewise, it was confirmed as a protective factor in the Colombian population. The results also showed that the population of Bogotá had a significant genetic admixture, with a predominance of European and American Indian ancestry.
Compared to other regions — such as Northern Europe and New Zealand, with MS rates of up to 200 per 100,000 inhabitants — Bogotá has a relatively low prevalence of MS, 4.4 cases per 100,000 inhabitants. The finding of a protective allele in the population may, in part, explain the low frequency of MS in Colombia.
Earlier studies have shown that the protective effect of the HLA-DRB1*14 allele is strong enough to counteract the risk of carrying the HLA-DRB1*15 allele.
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