Parent-of-origin of HLA-DRB1*1501 and age of onset of multiple sclerosis

Macrophages and HLA-Class II Alleles in Multiple Sclerosis: Insights in Therapeutic Dynamics

Antigen presentation is a crucial mechanism that drives the T cell-mediated immune response and the development of Multiple Sclerosis (MS). Genetic alterations within the highly variable Major Histocompatibility Complex Class II (MHC II) have been proven to result in significant changes in the molecular basis of antigen presentation and the clinical course of patients with both Adult-Onset MS (AOMS) and Pediatric-Onset MS (POMS). Among the numerous polymorphisms of the Human Leucocyte Antigens (HLA), within MHC II complex, HLA-DRB1*15:01 has been labeled, in Caucasian ethnic groups, as a high-risk allele for MS due to the ability of its structure to increase affinity to Myelin Basic Protein (MBP) epitopes. This characteristic, among others, in the context of the trimolecular complex or immunological synapsis, provides the foundation for autoimmunity triggered by environmental or endogenous factors. As with all professional antigen presenting cells, macrophages are characterized by the expression of MHC II and are often implicated in the formation of MS lesions. Increased presence of M1 macrophages in MS patients has been associated both with progression and onset of the disease, each involving separate but similar mechanisms. In this critical narrative review, we focus on macrophages, discussing how HLA genetic alterations can promote dysregulation of this population's homeostasis in the periphery and the Central Nervous System (CNS). We also explore the potential interconnection in observed pathological macrophage mechanisms and the function of the diverse structure of HLA alleles in neurodegenerative CNS, seen in MS, by comparing available clinical with molecular data through the prism of HLA-immunogenetics. Finally, we discuss available and experimental pharmacological approaches for MS targeting the trimolecular complex that are based on cell phenotype modulation and HLA genotype involvement and try to reveal fertile ground for the potential development of novel drugs.

The age at onset of relapsing-remitting multiple sclerosis has increased over the last five decades

BACKGROUND

Patients with relapsing-remitting multiple sclerosis (RRMS) most commonly experience their first symptoms between 20 and 40 years of age. The objective of this study was to investigate how the age at which the first symptoms of RRMS occur has changed over the past decades.

METHODS

Patients who were followed up in our unit after an initial diagnosis of RRMS using the Poser or McDonald criteria and who experienced their first symptoms between January 1970 and December 2019 were included in the study. The cohort was divided into five groups according to the decade in which the first symptoms appeared. The age at disease onset was compared across decades. Changes in age were also determined after excluding patients with early-onset disease (<18 years of age) and those with late-onset disease (>50 years of age) to avoid bias.

RESULTS

The cohort included 1,622 patients with RRMS, 67.6% of whom were women. Among them, 5.9% and 4% had early-onset and late-onset disease, respectively. The mean age ± standard deviation at onset was 31.11 ± 9.82 years, with no differences between men and women. The mean ages at onset were 23.79 ± 10.19 years between 1970 and 1979, 27.86 ± 9.22 years between 1980 and 1989, 30.07 ± 9.32 years between 1990 and 1999, 32.12 ± 9.47 between 2000 and 2009, and 34.28 ± 9.83 years between 2010 and 2019. The ages at disease onset were progressively higher in the later decades; this trend was statistically significant (p < 0.001), with a Pearson linear correlation coefficient R of 0.264 and R² of 0.070 (p < 0.001). The results were similar when analysing men and women separately. We conducted an analysis of 1,460 patients (mean age at onset: 31.10 ± 7.99 years), after excluding patients with early-onset and late-onset disease. In this specific subgroup, the mean ages at disease onset were 28.38 ± 8.17 years between 1970 and 1979, 29.22 ± 7.51 years between 1980 and 1989, 30.06 ± 8.02 years between 1990 and 1999, 31.46 ± 7.77 years between 2000 and 2009, and 33.37 ± 7.97 years between 2010 and 2019. The trend was also statistically significant (p < 0.001), with a Pearson linear correlation coefficient R of 0.193 and R² of 0.037 (p < 0.001).

CONCLUSION

Our data showed that the age at RRMS onset has increased over the past decades.

The role of sex and pregnancy in multiple sclerosis: what do we know and what should we do?

INTRODUCTION

Multiple sclerosis (MS) is more prevalent in women than in men. The sex of the patient, and pregnancy, are reported to be associated with the clinical features of MS. The mechanism of this is unclear.

AREAS COVERED

This review summarizes data about sex differences in MS and the role of pregnancy. Possible mechanisms for the effects of sex and pregnancy are summarized, and practical suggestions for addressing these issues are provided.

EXPERT OPINION

There is considerable interdependence of the variables that are associated with MS. Men have a worse outcome of MS, and this could be due to the same factors that lead to greater incidence of neurodegenerative disease in men. The possible role of parity on the long-term outcome of MS is of interest. Future studies that look at the mechanisms of the effects of the sex of the patient on the outcome of MS are required. However, there are some actions that can be taken without further research. We can concentrate on public health measures that address the modifiable risk factors for MS and ensure that disease is controlled in women who intend to become pregnant and use appropriate disease modifying agents during pregnancy.

The global prevalence of familial multiple sclerosis: an updated systematic review and meta-analysis

BACKGROUND

Considering that many recent studies have reported the prevalence of familial multiple sclerosis (FMS), we performed an updated meta-analysis of the worldwide prevalence of FMS by the addition of recent publications.

METHODS

A search in PubMed, Scopus, the ISI Web of Science, and Google Scholar was undertaken up to 20 December 2020. The inclusion criteria were based on the CoCoPop approach (condition, context, and population). Meta-analysis of the qualified studies was conducted by comprehensive meta-analysis ver. 2 software.

RESULTS

The pooled prevalence of MS in relatives of 16,179 FMS cases was estimated to be 11.8% (95% CI: 10.7-13) based on a random-effects model. The pooled mean age of disease onset in adult probands was calculated to be 28.7 years (95% CI: 27.2 ± 30.2). Regarding 13 studies that reported the data of FMS in pediatrics (n = 877) and adults (n = 6636), the FMS prevalence in pediatrics and adults was 15.5% (95% CI: 13.8-17.4) and 10.8% (95% CI: 8.1-14.2), respectively. The prevalence of FMS in affected males (n = 5243) and females (n = 11,503) was calculated to be 13.7% (95% CI: 10.1-18.2) and 15.4% (95% CI: 10.3-22.4), respectively. The odds ratio of male/female in FMS cases was not statistically significant (OR = 0.9; 95% CI: 0.6-1.2, P = 0.55). Subgroup analysis demonstrated a significant difference in the prevalence of FMS between the geographical areas (P = 0.007). The meta-regression model indicated that the prevalence of FMS is lower with higher latitude and higher MS prevalence (P < 0.001). In contrast, meta-regression based on prevalence day was not statistically significant (P = 0.29).

CONCLUSIONS

The prevalence of FMS is higher in the pediatric group than that of adults, distinct between geographical areas, and diminishes with the increment of MS prevalence and latitude. Also, the symptoms initiate relatively at younger ages in the FMS cases. Interestingly, our analysis unveiled that FMS is not more prevalent in men than women and the risk of MS development in relatives is not higher when the affected proband is male.

The Contribution of Major Histocompatibility Complex Class II Genes to an Association with Autoimmune Diseases

Genetic studies of patients with autoimmune diseases have shown that one of the most important roles in the developing of these diseases is played by a cluster of genes of the major histocompatibility complex (MHC), as compared with other genome areas. Information on the specific contribution of MHC alleles, mostly MHC class II ones, to the genetic predisposition to autoimmune diseases is crucial for understanding their pathogenesis. This review dwells on the most relevant aspects of this problem: namely, the correlation between carriage of certain MHC II alleles and an increased (positively associated allele) or reduced (negatively associated allele) probability of developing the most common autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, autoimmune thyroiditis, etc. The most universal haplotypes, DR3-DQ2 and DR4-DQ8, are positively associated with many of these diseases, while the universal allele HLA-DRB1*0701 is protective.

Anti-Myelin Oligodendrocyte Glycoprotein and Human Leukocyte Antigens as Markers in Pediatric and Adolescent Multiple Sclerosis: on Diagnosis, Clinical Phenotypes, and Therapeutic Responses

Early-onset (pediatric and adolescent) multiple sclerosis (MS) is a well-established demyelinating disease that accounts for approximately 3-5% of all MS cases. Thus, identifying potential biomarkers that can reflect the pathogenic mechanisms, disease course and prognosis, and therapeutic response in such patients is of paramount importance. Myelin oligodendrocyte glycoprotein (MOG) has been regarded as a putative autoantigen and autoantibody target in patients with demyelinating diseases for almost three decades. However, recent studies have suggested that antibodies against MOG represent a distinct clinical entity of dominantly humoral profile, with a range of clinical phenotypes closely related to the age of onset, specific patterns of disease course, and responses to treatment. Furthermore, the major histocompatibility complex (MHC)—which has been regarded as the “gold standard” for attributing genetic burden in adult MS since the early 1970s—has also emerged as the primary genetic locus in early-onset MS, particularly with regard to the human leukocyte antigen (HLA) alleles DRB1⁎1501 and DRB1⁎0401. Recent studies have investigated the potential interactions among HLA, MOG, and environmental factors, demonstrating that early-onset MS is characterized by genetic, immunogenetic, immunological, and familial trait correlations. In this paper, we review recent evidence regarding HLA-genotyping and MOG antibodies—the two most important candidate biomarkers for early-onset MS—as well as their potential application in the diagnosis and treatment of MS.

Genetic risk factors for pediatric-onset multiple sclerosis

BACKGROUND

Strong evidence supports the role of both genetic and environmental factors in pediatric-onset multiple sclerosis (POMS) etiology.

OBJECTIVE

We comprehensively investigated the association between established major histocompatibility complex (MHC) and non-MHC adult multiple sclerosis (MS)-associated variants and susceptibility to POMS.

METHODS

Cases with onset <18 years (n = 569) and controls (n = 16,251) were included from the United States and Sweden. Adjusted logistic regression and meta-analyses were performed for individual risk variants and a weighted genetic risk score (wGRS) for non-MHC variants. Results were compared to adult MS cases (n = 7588).

RESULTS

HLA-DRB1*15:01 was strongly associated with POMS (odds ratio (OR)_meta = 2.95, p < 2.0 × 10^-16). Furthermore, 28 of 104 non-MHC variants studied (23%) were associated (p < 0.05); POMS cases carried, on average, a higher burden of these 28 variants compared to adults (OR_avg = 1.24 vs 1.13, respectively), though the difference was not significant. The wGRS was strongly associated with POMS (OR_meta = 2.77, 95% confidence interval: 2.33, 3.32, p < 2.0 × 10^-16) and higher, on average, when compared to adult cases. Additional class III risk variants in the MHC region associated with POMS were revealed after accounting for HLA-DRB1*15:01 and HLA-A*02.

CONCLUSION

Pediatric and adult MS share many genetic variants suggesting similar biological processes are present. MHC variants beyond HLA-DRB1*15:01 and HLA-A*02 are also associated with POMS.

The Role of HLA in MS Susceptibility and Phenotype

One of the most consistent findings in multiple sclerosis (MS) is that development of MS is linked with carriage of the class II human leucocyte antigen (HLA) molecule HLA-DRB1*15:01; around 60 % of Caucasian MS patients carry this allele compared to 25-30 % of ethnically matched healthy individuals. However, other HLA molecules have also been linked to the development of MS. In this chapter, the association between different HLA types and susceptibility to MS will be reviewed, and other linkages between the carriage of specific HLA molecules and clinical and experimental findings in MS will be considered.

Sexual disparities in the incidence and course of MS

Multiple sclerosis (MS) affects three times more women than men and this ratio appears to be increasing. However male patients experience increased disease progression, brain atrophy, and cognitive impairment. Gonadal hormones may modulate these sex differences. For example, female puberty heralds an increased risk of MS, and during pregnancy disease activity is milder, with an increased risk of postpartum relapses. Gonadal hormones likely have complex and inflammatory and neuroprotective effects, and may interact with other disease modulators, such as vitamin D. Sex differences in the heritability of disease susceptibility genes implicate a role for epigenetic modification. Many questions remain, including the impact of sex on treatment response and epigenetic changes, and the modulatory potential of hormonal treatments. This article summarizes what is known about sexual dimorphism in MS onset and course, as well as potential interactions between sex and other factors influencing MS pathogenesis, incidence and severity.

Role of gender in multiple sclerosis: clinical effects and potential molecular mechanisms

Multiple sclerosis (MS) is more prevalent in females than males, and this female predominance is increasing as time goes by. Additionally, gender appears to play critical roles in development, progression and treatment of MS, and is therefore an aspect that should always be considered in the design and interpretation of research and clinical trials for MS. In this review, factors that could potentially explain the gender-biased observations in MS are discussed. These include sex-specific differences between the male and female immune systems and nervous systems, genetic and epigenetic or environmental-related effects, the effects of gonadal hormones, and materno-fetal interactions.

Multiple sclerosis etiology: beyond genes and environment

Multiple sclerosis (MS) is a disorder of the CNS with inflammatory and neurodegenerative components. The etiology is unknown, but there is evidence for a role of both genetic and environmental factors. Among the heritable factors, MHC class II genes are strongly involved, as well as genes coding for others molecules of immunological relevance, genes controlling neurobiological pathways and genes of unknown function. Among nonheritable factors, many infectious agents (mainly viruses) and environmental factors (e.g., smoke, sun exposition and diet) seem to be of etiologic importance. Here, we report and discuss recent findings in MS on largely unexplored fields: the alternative splicing of mRNAs and regulatory noncoding RNAs, the major sources of transcriptome diversity; and epigenetic changes with special attention paid to DNA methylation and histone acetylation, the main regulators of gene expression.

HLA-DRB1*1501 tagging rs3135388 polymorphism is not associated with neuromyelitis optica

Background: Association of the HLA-DRB1*1501 allele with multiple sclerosis is well established, but its association with neuromyelitis optica has only been evaluated in small populations.

Methods: We performed a case-control genetic association study to evaluate the association of HLA-DRB1*1501 with neuromyelitis optica. The single nucleotide polymorphism rs3135388, which tags HLA-DRB1*1501, was genotyped in 164 patients with neuromyelitis optica, 220 patients with multiple sclerosis and 959 controls matched for age, gender and ethnicity. Genotyping for rs3135388 was performed by Taqman-based 5' nuclease assay.

Results: Rs3135388*A was positively associated with multiple sclerosis (OR = 3.93; 95% CI = 2.58—5.97, p = 1.18 × 10-09) but negatively associated with NMO (OR = 0.57; 95% CI = 0.36—0.91, p = 0.01).

Conclusions: Multiple sclerosis and neuromyelitis optica differ in their associations with DRB1*1501.

Modifying effects of HLA-DRB1 allele interactions on age at onset of multiple sclerosis in Western Australia

The contribution of genetic factors to the age at onset in multiple sclerosis is poorly understood. Our objective was to investigate the disease modifying effects of HLA-DRB1 alleles and allele interactions on age at onset of multiple sclerosis. High-resolution four-digit HLA-DRB1 genotyping was performed in a cohort of 461 multiple sclerosis patients from the Perth Demyelinating Diseases Database. Carriage of the HLA-DRB1*1501 risk allele was not significantly associated with age at onset but HLA-DRB1*0801 was associated with a later onset of the disease. The HLA-DRB1*0401 allele was associated with a reduced age at onset when combined with DRB1*1501 but may delay age at onset when combined with DRB1*0801. These findings indicate that epistatic interactions at the HLA-DRB1 locus have significant modifying effects on age at onset of multiple sclerosis and demonstrate the value of high-resolution genotyping in detecting such associations.