HLA-DRB1*15 allele influences the later course of relapsing remitting multiple sclerosis.

Most of the published works so far have aimed at finding genes associated with multiple sclerosis (MS) susceptibility. Very few studies have attempted to correlate disease features with DNA variants. In a well-characterized sample (651 patients) representative of multiple sclerosis natural history, we engaged a comprehensive study of the role of human leukocyte antigen (HLA) in the course of the disease. We investigated the role of HLA-DRB1*15 allele in samples stratified according to severity evaluated by the Multiple Sclerosis Severity Score (MSSS), time to reach EDSS 6.0 and disease type. We found that HLA-DRB1*15 genotype does not influence MS severity even among patients presenting with a given type of the disease. However, we show for the first time that HLA-DRB1*15 allele modulates the course of MS for relapsing-remitting (RR) onset patients likely by precipitating the secondary progressive (SP) phase.