HLA-DRB1 and DQB1 Allelic Polymorphism and Multiple Sclerosis in a Moroccan Population

Introduction: Multiple sclerosis (MS) is a chronic immune-mediated disease of the central nervous system (CNS) that leads to inflammation and demyelination, manifesting in either a relapsing-remitting or progressive form. As a multifactorial disease, MS involves both genetic and environmental factors, with a known significant contribution from human leukocyte antigen (HLA) genes, mainly represented by the HLA-DRB1 and HLA-DQB1 loci, which have been linked to either susceptibility or protection, but variably across populations and ethnic groups. We aimed to study the distribution and polymorphism of HLA-DRB1 and HLA-DQB1 alleles in a population with MS from the southern Moroccan region, in comparison with healthy controls. Materials and Methods: A cross-sectional study was conducted over a period of 2 years (2022-2024) in a MS cohort including 40 patients and 100 healthy controls. DRB1 and DQB1 HLA genotyping was performed using a high-resolution reverse sequence-specific oligonucleotide (SSO) method, based on the Luminex system (xMAP technology, One lambda^®). Data were analyzed using SPSS 26; differences in allele frequencies were evaluated by the Chi-square test and Fisher's exact test. OR (95% CI) was calculated, and FDR corrections were applied for multiple testing. Results: Among the various HLA-DRB1 and DQB1 alleles studied, including those considered as predisposing to MS, the DQB1*02:01 and DRB1*15:01 alleles were more prevalent in MS patients, with 40% and 8.8% vs. 16% and 4.08% in controls respectively, although these differences were not statistically significant (p = 0.06 and p = 0.12). Likewise, the DRB1*15:01-DQB1*06:02 association was significantly more prevalent in the MS group (9%, p = 0.004). In contrast, the DRB1*07:01 allele, linked to protection against MS in many populations, was significantly predominant in controls (17%, p = 0.004). Similarly, the DRB1*07:01-DQB*02:01 combination was rather more frequent in controls (12%, p = 0.01). Confronted to MS clinical forms, we remarkably noted that the DRB1*13:03 allele was found only among relapsing-remitting MS (RRMS) patients (6%, p = 0.003), while DQB1*02:01 was significantly associated with RRMS (42.1%) and primary progressive MS (41%, p = 0.001), with an intermediate Expanded Disability Status Scale (EDSS) score, which may indicate a possible link with disease progression and severity. Conclusions: The results of our study highlighted particular HLA alleles, DRB1 and DQB1, alone or in combination, as potential immunogenic factors of susceptibility to MS in a population from southern Morocco, while other alleles seem rather to protect against the disease. This HLA polymorphism is also reflected in the clinical forms of the disease, showing a tendency toward severity for certain alleles. However, such preliminary results need to be consolidated and confirmed by studies carried out on a larger population sample, and compared with others on a national scale.