Objective: To investigate the HLA-DR associations in relapsing-remitting/secondary progressive multiple sclerosis (RR/SPMS) and primary progressive MS (PPMS). The HLA-DR2 allele (or its split, HLA-DRB1*15) is felt to be a risk factor for MS, rather than a genetic marker for the population of origin. Some studies have indicated a different HLA-DR antigen profile in PPMS patients compared with those having an initially relapsing-remitting course, only those with relapsing disease showing an increase in HLA-DR2. Association of PPMS with DR4 has been suggested. Several DR alleles have also been felt to influence the prognosis in MS.
Methods: Genomic DNA was prepared from peripheral blood of 202 RR/SPMS patients identified in a population-based prevalence study, 102 PPMS patients identified throughout Northern Ireland and 398 normal controls (Nor) matched for the postcode areas of those identified in the prevalence study. Samples were typed for the HLA-DR antigens using polymerase chain reaction (PCR) technology and sequence specific oligonucleotide probes (SSOP).
Results: A high incidence of HLA-DRB1*15 was found in each MS group - PPMS (63.73%), RR/SPMS (66.83%) - compared with normals (32.41%), (PPMS vs. Nor, P<0.0001: RR/SPMS vs. Nor, P<0.0001). HLA-DRB1*04 occurred at a lower incidence in both MS groups compared with controls - RR/SPMS (22%), PPMS (30%), Nor (35%). Overall, highly significant differences existed across the full HLA-DR allele distribution (RR/SPMS vs. Nor, P<0.0001, df=12: PPMS vs. Nor, P=0.0007, df=12). No significant differences existed between PPMS and RR/SPMS (P=0.47, df=12), and the allele distributions in benign and aggressive MS were similar.
Conclusions: These data suggest that in this population, HLA-DRB1*15 is indeed associated with PPMS and that PPMS has a HLA-DR profile distinct from the normal population but not from those with an initially relapsing-remitting course. No single allele is associated with either a good or poor prognosis.