HLA-DRB1* Allele Frequencies in Pediatric, Adolescent and Adult-Onset Multiple Sclerosis Patients, in a Hellenic Sample. Evidence for New and Established Associations

Studies in many populations consistently have showed that the human leukocyte antigens (HLA) and especially the DRB1*15 allele has by far the strongest genetic association with multiple sclerosis (MS). The aim of this study was to investigate the role of HLA-DRB1* alleles in MS risk/resistance and onset. A sample of 165 Hellenic MS patients (18 with pediatric-, 24 with adolescent- and 123 with adult-onset MS) and 107 healthy volunteers were examined with molecular techniques. Comparisons were made according to the Benjamini-Yekutieli method for p value correction. Both adult-onset MS patients and early-onset MS patients (age at onset below 20 years-old) had a significantly higher frequency of the DRB1*15 allele and a significantly lower frequency of the DRB1*11 allele compared to controls. For the early-onset vs. healthy group comparison, subgroup analyses revealed that both the pediatric- and the adolescent-onset MS groups contributed to the aforementioned DRB1*15 significant difference, while the DRB1*11 difference was ascribed solely to the adolescent-MS onset vs. healthy group comparison. Within MS patients comparisons revealed that early-onset MS patients had a tendency for higher DRB1*03 allele and a lower DRB1*16 allele frequency frequencies compared to adult-onset MS patients, although both non-significant. Notably, pediatric-onset MS patients showed complete absence of the DRB1*16 allele, along with a non-significant tendency for higher DRB1*15 allele frequency relative to the adult-onset group. Finally, the adolescent-onset MS group was presented with a lower DRB1*11 allele frequencies compared both to the pediatric- and the adult-onset MS group. Our findings confirm previous studies on the role of HLA-DRB1* in MS. New findings that need to be confirmed by further studies are the pathogenetic role of DRB1*03 for early-onset MS and the putative protective role of the DRB1*16 allele in the pediatric-onset MS.