Protective effect of the HLA-DRB1*13:02 allele in Japanese rheumatoid arthritis patients

Human leucocyte antigens and Japanese patients with polymyalgia rheumatica: the protective effect of DRB1*09:01

OBJECTIVE

The hallmarks of the chronic inflammatory disease polymyalgia rheumatica (PMR) include pain, and morning stiffness in areas of the neck, shoulder and pelvic girdle. The human leucocyte antigen (HLA) gene was reported to be an important risk factor for PMR, but it has not been analysed precisely, especially in populations other than Europeans.

METHODS

Genotyping of DRB1 and DQB1 was performed in Japanese PMR patients (n=270) and controls (n=413). Associations between allele carrier and genotype frequencies were determined for PMR.

RESULTS

DRB1*04:05 was associated with a predisposition to PMR (p=0.0006, Pc=0.0193, OR 1.85, 95% CI 1.31 to 2.62). DRB1*09:01 was associated with protection against PMR (p=1.46×10-5, Pc=0.0004, OR 0.40, 95% CI 0.26 to 0.61). A shared epitope (SE) associated with PMR (p=3.07×10-6, OR 2.11, 95% CI 1.54 to 2.88). DQB1*03:03 (p=0.0010, Pc=0.0140, OR 0.52, 95% CI 0.35 to 0.77) was associated with protection against PMR and DQB1*04:01 (p=0.0009, Pc=0.0140, OR 1.82, 95% CI 1.28 to 2.58) was associated with predisposition to PMR. A gene dosage effect was observed for DRB1*09:01 and DQB1*03:03, but not for DRB1*04:05, SE or DQB1*04:01. Haplotype and logistic regression analyses suggested a protective effect for DRB1*09:01.

CONCLUSION

This study is the first to demonstrate predisposing associations of DRB1*04:05, SE, and DQB1*04:01, and protective associations of DRB1*09:01 and DQB1*03:03 with PMR in Japanese patients. Our data indicate HLA has predisposing and protective effects on the pathogenesis of PMR.

MHC-DRB alleles with amino acids Val11, Phe13, and the shared epitopes promote collagen-induced arthritis and a rapid IgG1 response in Filipino cynomolgus macaques

Macaques are useful animal models for studying the pathogenesis of rheumatoid arthritis (RA) and the development of anti-rheumatic drugs. The purpose of this study was to identify the major histocompatibility complex (MHC) polymorphisms associated with the pathology of collagen-induced arthritis (CIA) and anti-collagen IgG induction in a cynomolgus macaque model, as MHC polymorphisms affect the onset of CIA in other animal models. Nine female Filipino cynomolgus macaques were immunized with bovine type II collagen (b-CII) to induce CIA, which was diagnosed clinically by scoring the symptoms of joint swelling over 9 weeks. MHC polymorphisms and anti-b-CII antibody titers were compared between symptomatic and asymptomatic macaques. Four of 9 (44%) macaques were defined as the CIA-affected group. Anti-b-CII IgG in the affected group increased in titer approximately 3 weeks earlier compared with the asymptomatic group. The mean plasma IgG1 titer in the CIA-affected group was significantly higher (p < 0.05) than that of the asymptomatic group. Furthermore, the cynomolgus macaque MHC (Mafa)-DRB1*10:05 or Mafa-DRB1*10:07 alleles, which contain the well-documented RA-susceptibility five amino acid sequence known as the shared epitope (SE) in positions 70 to 74, with valine at position 11 (Val11, V11) and phenylalanine at position 13 (Phe13, F13), were detected in the affected group. In contrast, no MHC polymorphisms specific to the asymptomatic group were identified. In conclusion, the presence of V11 and F13 along with SE in the MHC-DRB1 alleles seems essential for the production of IgG1 and the rapid induction of severe CIA in female Filipino cynomolgus macaques.

Associations between HLA class II alleles and IgE sensitization to allergens in the Qatar Biobank cohort

Background

Allergic disorders are the consequence of IgE sensitization to allergens. Population studies have shown that certain human leukocyte antigen (HLA) alleles are associated with increased or decreased risk of developing allergy.

Objective

We aimed to characterize the relationship between HLA class II allelic diversity and IgE sensitization in an understudied Arab population.

Methods

We explored associations between IgE sensitization to 7 allergen mixes and mesquite (comprising 41 food or aeroallergens) and 45 common classical HLA class II alleles in a well-defined cohort of 797 individuals representing the general adult population of Qatari nationals and long-term residents. To do so, we performed HLA calling from whole genome sequencing data at 2-field resolution using 2 independent algorithms. We then applied 3 different regression models to assess either each allergen mix independently, in the context of IgE sensitization to other allergens tested, or polysensitization.

Results

More than half (n = 447) of the study participants showed IgE sensitization to at least 1 allergen, most of them (n = 400) to aeroallergens (Phadiatop). We identified statistically significant negative and positive associations with 24 HLA class II alleles. These have been reported to confer risk or protection from variety of diseases; however, only a few have previously been associated with allergy in other populations.

Conclusions

Our study reveals several new risk and protective genetic markers for allergen-specific IgE sensitization. This is a first and essential step toward a better understanding of the origins of allergic diseases in this understudied population.

The Association of Human Leukocyte Antigen Genotyping Among Sudanese Patients With Rheumatoid Arthritis: Reference to Ethnicity

INTRODUCTION

 Human leukocyte antigens (HLA) account for up to one-half of the total genetic contribution to rheumatoid arthritis (RA) risk. The study investigated the association of HLA class II genotyping with RA susceptibility in Sudanese ethnic groups.

METHODS

 The DRB1 and DQB1 alleles and haplotypes were determined in 122 RA patients (i.e., Gaalia = 54, Johayna = 24, Baggara = 17, Nile Nubian = 12, and others = 15) and 120 healthy controls of ethnic groups (i.e., Gaalia = 44, Johayna = 11, Baggara = 15, Nile Nubian = 9, and others = 21) using a polymerase chain reaction with sequence-specific primers method.

RESULTS

Susceptibility to RA was associated with a high frequency of DRB1*04 (P = 0.04), DRB1*10 (P = 0.04), and DQB1*03 (P = 2.2 x 10-8/Pc = 6.6 x 10-8) between study ethnic groups, while protective effects were shown with DRB1*07 (P = 0.01), DQB1*02 (P = 0.02), and DQB1*06 (P = 2.2 x 10-6/Pc = 6.6 x 10-6), with an inconsistent frequency between study ethnic groups. The HLA haplotypes that were high in frequency among RA ethnic groups and showed susceptibility associations were DRB1*03-DQB1*03, DRB1*04-DQB1*03, DRB1*08-DQB1*03, DRB1*13-DQB1*02, and DRB1*13-DQB1*03 (P = 0.00003/Pc = 0.0003, P = 0.0001/Pc = 0.0001, P = 0.03, P = 0.004/Pc = 0.03, and P = 3.79x10-8/Pc = 3.3x10-9, respectively). On the contrary, DRB1*03-DQB1*02, DRB1*07-DQB1*02, and DRB1*13-DQB1*06 were lower in frequency in the ethnic groups with RA and may confer protection (P = 0.004/Pc = 0.032, P = 0.002/Pc = 0.02, and P = 0.01, respectively).

CONCLUSIONS

Our findings indicate an association between HLA-DRB1 and DQB1 genotypes and the susceptibility to RA in the Sudanese population, with a moderate frequency between our ethnic groups.

Associations of HLA Polymorphisms with Chronic Kidney Disease in Japanese Rheumatoid Arthritis Patients

OBJECTIVES

The prevalence of chronic kidney disease (CKD) was reported to be higher in rheumatoid arthritis (RA) patients than in normal healthy individuals. Human leukocyte antigen (HLA) was associated with RA or CKD. Few studies on the association of HLA with CKD in RA have been reported. Here, we investigated the association of HLA polymorphisms with CKD in Japanese RA patients.

METHODS

HLA-DRB1 genotyping was conducted in 351 Japanese RA patients with CKD (estimated glomerular filtration rate [eGFR] lower than 60 [mL/min/1.73 m²]) and 959 without CKD (eGFR equal to or higher than 60 [mL/min/1.73 m²]). Associations of allele carrier frequencies of DRB1 with CKD were examined in the RA patients.

RESULTS

There was an association of DRB1*13:02 with CKD in RA, but this did not achieve statistical significance (p = 0.0265, odds ratio [OR] 1.70, pc = 0.7412, 95% confidence interval [CI] 1.09-2.64). The DR6 serological group was associated with CKD in RA (p = 0.0008, OR 1.65, 95% CI 1.24-2.20). A gene-dosage effect of DR6 was not detected. Logistic regression analysis showed that the association of DR6 with CKD in RA was independent of clinical characteristics.

CONCLUSIONS

The present study first revealed the independent predisposing association of DR6 with CKD in Japanese RA patients, although DR6 is known to be protective against RA. Our data suggest direct or indirect roles of HLA for the development of CKD in RA, but the mechanisms are not clear.

Development of ANCA-associated vasculitis followed by SARS-CoV-2 vaccination in a patient with HLA-DRB1*09: 01 allele

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), presents with severe pneumonia and fatal systemic complications. Currently, SARS-CoV-2 vaccines are effective in reducing the risk of new onset and getting worse of the disease. However, autoimmune diseases such as antineutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) have been reported to develop after COVID-19 vaccine administration. Case presentation: A 71-year-old woman presented with fever, malaise, urinary abnormalities and renal dysfunction after receiving the COVID-19 vaccine (Pfizer-BioNTech). We clinically diagnosed AAV with her manifestations and serological test (MPO-ANCA positive). Her clinical findings were improved after immunosuppressive therapy. We examined her genetic susceptibility to AAV and we found that her allele was HLA-DRB1*09:01, which is a risk allele of MPO-AAV. Mechanistically, SARS-CoV-2 vaccines would activate immunity, including neutrophils, and trigger AAV onset in this patient with a genetic risk to develop AAV. The pathophysiology of this case would share with that of autoimmune/inflammatory syndrome induced by adjuvants (ASIA) in the absence of external adjuvants.

Predisposition of HLA-DRB1*04:01/*15 heterozygous genotypes to Japanese mixed connective tissue disease

Mixed connective tissue disease (MCTD) is a rare systemic autoimmune disease characterized by the production of anti-U1 ribonucleoprotein antibodies and systemic symptoms similar to those of some other autoimmune diseases. HLA-DRB1 polymorphisms are important genetic risk factors for MCTD, but precise associations of DRB1 genotypes with MCTD have not been reported in Japanese people. Genotyping of HLA-DRB1 and -DQB1 was performed in Japanese MCTD patients (n = 116) and controls (n = 413). Associations of specific allele carriers and genotype frequencies with MCTD were analyzed.The following alleles were found to be associated with predisposition to MCTD: HLA-DRB1*04:01 (P = 8.66 × 10^–6, Pc = 0.0003, odds ratio [OR] 7.96, 95% confidence interval [CI] 3.13‒20.24) and DRB1*09:01 (P = 0.0189, Pc = 0.5468, OR 1.73, 95% CI 1.12‒2.67). In contrast, the carrier frequency of the DRB1*13:02 allele (P = 0.0032, Pc = 0.0929, OR 0.28, 95% CI 0.11‒0.72) was lower in MCTD patients than in controls. The frequencies of heterozygosity for HLA-DRB1*04:01/*15 (P = 1.88 × 10^–7, OR 81.54, 95% CI 4.74‒1402.63) and DRB1*09:01/*15 (P = 0.0061, OR 2.94, 95% CI 1.38‒6.25) were also higher in MCTD patients. Haplotype and logistic regression analyses suggested a predisposing role for HLA-DRB1*04:01, DQB1*03:03, and a protective role for DRB1*13:02. Increased frequencies of HLA-DRB1*04:01/*15 and DRB1*09:01/*15 heterozygous genotypes were found in Japanese MCTD patients.

Biomarkers for interstitial lung disease and acute-onset diffuse interstitial lung disease in rheumatoid arthritis

Interstitial lung disease (ILD) is frequently a complication of rheumatoid arthritis (RA) as an extra-articular manifestation which has a poor prognosis. Acute-onset diffuse ILD (AoDILD) occasionally occurs in RA and includes acute exacerbation of ILD, drug-induced ILD, and Pneumocystis pneumonia. AoDILD also confers a poor prognosis in RA. Previously-established biomarkers for ILD include Krebs von den lungen-6 and surfactant protein-D originally defined in patients with idiopathic pulmonary fibrosis; the sensitivity of these markers for RA-associated ILD (RA-ILD) is low. Although many studies on ILD markers have been performed in idiopathic pulmonary fibrosis, only a few validation studies in RA-ILD or AoDILD have been reported. Biomarkers for RA-ILD and AoDILD are thus still required. Recently, genomic, cytokine, antibody, and metabolomic profiles of RA-ILD or AoDILD have been investigated with the aim of improving biomarkers. In this review, we summarize current preliminary data on these potential biomarkers for RA-ILD or AoDILD. The development of biomarkers on RA-ILD has only just begun. When validated, such candidate biomarkers will provide valuable information on pathogenesis, prognosis, and drug responses in RA-ILD in future.

Influence of HLA Class II Alleles and DRB1-DQB1 Haplotypes on Rheumatoid Arthritis Susceptibility and Autoantibody Status in the Chinese Han Population

Human leukocyte antigen (HLA) class II alleles are considered to play a key role in the progress of rheumatoid arthritis (RA). This study was carried out to investigate the presence of HLA class II alleles and their influence on disease risk and autoantibody status in Chinese Han patients with RA. Here, HLA-DRB1, DQB1 and DPB1 genotyping was performed in 125 RA patients and 120 healthy controls by using the next-generation sequencing (NGS). Strong positive associations were shown between high-resolution typed HLA-DRB1*04:05:01, DRB1*10:01:01, DQB1*04:01:01, DPB1*02:01:02 and RA patients. Moreover, the haplotypes HLA-DRB1*04:05:01~ DQB1*04:01:01 and HLA-DRB1*10:01:01~ DQB1*05:01:01 were found to be more frequent in RA populations than in healthy controls. These possible susceptible HLA alleles (HLA-DRB1*04:05:01, DRB1*10:01:01, DQB1*04:01:01 and DPB1*02:01:02) also showed higher frequencies in seropositive RA patients as compared to normal controls. The present study provided evidence that alleles HLA-DRB1*04:05:01, DRB1*10:01:01, DQB1*04:01:01 and DPB1*02:01:02 constituted RA risk alleles, and haplotypes HLA-DRB1*04:05:01~ DQB1*04:01:01, HLA-DRB1*10:01:01~ DQB1*05:01:01 also showed prevalence in Chinese Han patients with RA. Serological results preliminary demonstrated patients carrying RA-risk HLA alleles might elevate the serum level of anti-citrullinated protein antibodies and rheumatoid factor and affect RA progression.

The spectrum of association in HLA region with rheumatoid arthritis in a diverse Asian population: evidence from the MyEIRA case-control study

BACKGROUND

Fine-mapping of human leukocyte antigen (HLA) region for rheumatoid arthritis (RA) risk factors has identified several HLA alleles and its corresponding amino acid residues as independent signals (i.e., HLA-A, HLA-B, HLA-DPB1, and HLA-DQA1 genes), in addition to the well-established genetic factor in HLA-DRB1 gene. However, this was mainly performed in the Caucasian and East Asian populations, and data from different Asian regions is less represented. We aimed to evaluate whether there are independent RA risk variants in both anti-citrullinated protein antibody (ACPA)-positive and ACPA-negative RA patients from the multi-ethnic Malaysian population, using the fine-mapping of HLA region strategy.

METHODS

We imputed the classical HLA alleles, amino acids, and haplotypes using the Immunochip genotyping data of 1260 RA cases (i.e., 530 Malays, 259 Chinese, 412 Indians, and 59 mixed ethnicities) and 1571 controls (i.e., 981 Malays, 205 Chinese, 297 Indians, and 87 mixed ethnicities) from the Malaysian Epidemiological Investigation of Rheumatoid Arthritis (MyEIRA) population-based case-control study. Stepwise logistic regression was performed to identify the independent genetic risk factors for RA within the HLA region.

RESULTS

We confirmed that the HLA-DRB1 amino acid at position 11 with valine residue conferred the strongest risk effect for ACPA-positive RA (OR = 4.26, 95% CI = 3.30-5.49, P_GWAS = 7.22 × 10^-29) in the Malays. Our study also revealed that HLA-DRB1 amino acid at position 96 with histidine residue was negatively associated with the risk of developing ACPA-positive RA in the Indians (OR = 0.48, 95% CI = 0.37-0.62, P_GWAS = 2.58 × 10^-08). Interestingly, we observed that HLA-DQB1*03:02 allele was inversely related to the risk of developing ACPA-positive RA in the Malays (OR = 0.17, 95% CI = 0.09-0.30, P_GWAS = 1.60 × 10^-09). No association was observed between the HLA variants and risk of developing ACPA-negative RA in any of the three major ethnic groups in Malaysia.

CONCLUSIONS

Our results demonstrate that the RA-associated genetic factors in the multi-ethnic Malaysian population are similar to those in the Caucasian population, despite significant differences in the genetic architecture of HLA region across populations. A novel and distinct independent association between the HLA-DQB1*03:02 allele and ACPA-positive RA was observed in the Malays. In common with the Caucasian population, there is little risk from HLA region for ACPA-negative RA.

The genetics of rheumatoid arthritis

RA is a chronic systemic inflammatory disease that primarily affects the small joints of the hands and feet, and results in a mean reduction in life expectancy of 3-10 years. RA is a multigene disorder with a substantial genetic component and a heritability estimate of 60%. Large-scale Genome-Wide Association Studies (GWAS) and meta-analyses have revealed common disease-associated variants in the population that may contribute cumulatively to RA pathogenesis. This review identifies the most significant genetic variants associated with RA susceptibility to date, with particular focus on the contribution of the HLA class II genes across different ethnic groups. Also discussed are the potential applications of pharmacogenomics to RA management by identifying polymorphisms associated with variation in treatment response or toxicity. The use of genetic variants to guide treatment strategy has the potential to not only reduce National Health Service costs, but also drastically improve patient experience and quality of life.

Contribution of HLA-DRB1 * 09: 01 allele to development of minocycline induced antineutrophil cytoplasmic antibody (ANCA)-associated cutaneous vasculitis: report of two cases

We report two cases of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) that developed after long-term oral administration of minocycline and consider the contribution of human leukocyte antigen (HLA)-DRB 1 * 09: 01 allele to its development. Case 1; A 47-year-old man receiving minocycline for palmoplantar pustulosis for 24 months developed fever, arthralgia, and irregular livedo on the bilateral lower legs. Skin biopsy demonstrated vasculitis, while a blood test showed positivity of myeloperoxidase (MPO)-ANCA. Discontinuation of minocycline and oral administration of prednisolone relieved the symptoms promptly. Case 2; A 53-year-old woman developed reddish-brown livedo reticularis with tenderness on the bilateral lower legs after administration of minocycline to treat palmoplantar pustulosis for 24 months. Although skin biopsy did not demonstrate vasculitis, a blood test showed MPO-ANCA positivity. Cessation of minocycline resulted in rapid improvement of the cutaneous lesions and constitutional symptoms. We diagnosed both cases as having Drug-associated ANCA-associated Vasculitis (DAV) caused by minocycline according to the diagnostic criteria proposed by Cluver et al. Further examination revealed the presence of HLA-DRB1 * 09:01 allele in both cases. This allele has been implicated in the genetic background of idiopathic microscopic polyangiitis (MPA) in the Japanese population. Our finding suggests a relationship between the development of MPO-ANCA or DAV caused by minocycline and HLA-DRB1 * 09:01 allele, but will have to confirmed by further studies with larger numbers of patients.

HLA loci predisposing to immune TTP in Japanese: potential role of the shared ADAMTS13 peptide bound to different HLA-DR

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune disorder caused by neutralizing anti-ADAMTS13 autoantibodies. In white individuals, HLA allele DRB1*11 is a predisposing factor for iTTP, whereas DRB1*04 is a protective factor. However, the role of HLA in Asians is unclear. In this study, we analyzed 10 HLA loci using next-generation sequencing in 52 Japanese patients with iTTP, and the allele frequency in the iTTP group was compared with that in a Japanese control group. We identified the following HLA alleles as predisposing factors for iTTP in the Japanese population: DRB1*08:03 (odds ratio [OR], 3.06; corrected P [Pc] = .005), DRB3/4/5*blank (OR, 2.3; Pc = .007), DQA1*01:03 (OR, 2.25; Pc = .006), and DQB1*06:01 (OR,: 2.41; Pc = .003). The estimated haplotype consisting of these 4 alleles was significantly more frequent in the iTTP group than in the control group (30.8% vs 6.0%; Pc &lt; .001). DRB1*15:01 and DRB5*01:01 were weak protective factors for iTTP (OR, 0.23; Pc = .076; and OR, 0.23, Pc = .034, respectively). On the other hand, DRB1*11 and DRB1*04 were not associated with iTTP in the Japanese. These findings indicated that predisposing and protective factors for iTTP differ between Japanese and white individuals. HLA-DR molecules encoded by DRB1*08:03 and DRB1*11:01 have different peptide-binding motifs, but interestingly, bound to the shared ADAMTS13 peptide in an in silico prediction model.

Association of HLA-DRB1*04:05 allele with drug-induced interstitial lung disease in Japanese population

Drug-induced interstitial lung disease (DILD) is a life-threatening adverse reaction. The Japanese population is more susceptible to DILD as compared with other populations, suggesting its pathogenesis could vary depending on ethnic genetic background. We conducted case-control studies to elucidate the association between DILD and HLA alleles in the Japanese. The 177 clinically diagnosed DILD patients and 3002 healthy controls for exploration and 55 DILD patients and 201 healthy controls for validation were genotyped for four HLA genes. HLA-DRB1*04:05 was significantly associated with DILD (corrected p = 0.014); this was also validated in the other set of patients/controls. Chemical drugs other than protein therapeutics showed this association (p = 1.7 × 10^-4) . The Japanese population showed a higher HLA-DRB1*04:05 frequency than most other populations. In conclusion, HLA-DRB1*04:05 could be associated with DILD susceptibility in Japanese individuals, and its high general frequency may explain the high reported incidence of DILD in Japanese.

Current Understanding of an Emerging Role of HLA-DRB1 Gene in Rheumatoid Arthritis-From Research to Clinical Practice

Rheumatoid arthritis (RA) is an autoimmune disease with an unclear pathogenic mechanism. However, it has been proven that the key underlying risk factor is a genetic predisposition. Association studies of the HLA-DRB1 gene clearly indicate its importance in RA morbidity. This review presents the current state of knowledge on the impact of HLA-DRB1 gene, functioning both as a component of the patient’s genome and as an environmental risk factor. The impact of known HLA-DRB1 risk variants on the specific structure of the polymorphic HLA-DR molecule, and epitope binding affinity, is presented. The issues of the potential influence of HLA-DRB1 on the occurrence of non-articular disease manifestations and response to treatment are also discussed. A deeper understanding of the role of the HLA-DRB1 gene is essential to explore the complex nature of RA, which is a result of multiple contributing factors, including genetic, epigenetic and environmental factors. It also creates new opportunities to develop modern and personalized forms of therapy.

Comprehensive meta-analysis reveals an association of the HLA-DRB1*1602 allele with autoimmune diseases mediated predominantly by autoantibodies

The human leukocytes antigen (HLA)-DRB1*16:02 allele has been suggested to be associated with many autoimmune diseases. However, a validation of the results of the different studies by a comprehensive analysis of the corresponding meta data is lacking. In this study, we performed a meta-analysis of the association between HLA-DRB1*16:02 allele with various autoimmune disorders. Our analysis shows that HLA-DRB1*16:02 allele was associated with systemic lupus erythematosus, anti-N-Methyl-d-Aspartate receptor (NMDAR) encephalitis, Graves' disease, myasthenia gravis, neuromyelitis optica and antibody-associated systemic vasculitis with microscopic polyangiitis (AASV-MPA). However, no such association was found for multiple sclerosis, autoimmune hepatitis type 1, rheumatoid arthritis, type 1 diabetes and Vogt-Koyanagi-Harada syndrome. Re-analysis of the studies after their categorization into autoantibody-dependent and T cell-dependent autoimmune diseases revealed that the HLA-DRB1*16:02 allele was strongly associated with disorder predominantly mediated by autoantibodies (OR = 1.93; 95% CI = 1.63-2.28, P = 1.95 × 10^-14) but not with those predominantly mediated by T cells (OR = 1.08; 95% CI = 0.87-1.34, P = .474). In addition, amino acid sequence alignment of common HLA-DRB1 subtypes demonstrated that HLA-DRB1*16:02 carries a unique motif of amino acid residues at position 67-74 which encodes the third hypervariable region. Taken together, the distinct pattern of disease association and the unique amino acid sequence of the third hypervariable region of the HLA-DRB1 provide some hints on how HLA-DRB1*16:02 is involved in the pathogenesis of autoimmune diseases.

HLA associations in inflammatory arthritis: emerging mechanisms and clinical implications

Our understanding of the mechanisms underlying HLA associations with inflammatory arthritis continues to evolve. Disease associations have been refined, and interactions of HLA genotype with other genes and environmental risk factors in determining disease risk have been identified. This Review provides basic information on the genetics and molecular function of HLA molecules, as well as general features of HLA associations with disease. Evidence is discussed regarding the various peptide-dependent and peptide-independent mechanisms by which HLA alleles might contribute to the pathogenesis of three types of inflammatory arthritis: rheumatoid arthritis, spondyloarthritis and systemic juvenile idiopathic arthritis. Also discussed are HLA allelic associations that shed light on the genetic heterogeneity of inflammatory arthritides and on the relationships between adult and paediatric forms of arthritis. Clinical implications range from improved diagnosis and outcome prediction to the possibility of using HLA associations in developing personalized strategies for the treatment and prevention of these diseases.

Comparative analysis of human leucocyte antigen between idiopathic and anti-PD-1 antibody induced isolated adrenocorticotropic hormone deficiency: A pilot study

BACKGROUND

Adult-onset idiopathic isolated adrenocorticotropic hormone deficiency (id-IAD) is a rare disease with unknown aetiology. Recently, numerous cases of anti-PD-1 antibody-induced IAD (PD1-IAD) have been reported, but the clinical course, predictive factors and relationship to id-IAD have not been clarified. Moreover, associations of id-IAD and PD1-IAD with human leucocyte antigen (HLA) require elucidation.

METHODS

Clinical characteristics of 13 Japanese patients with id-IAD and eight Japanese patients with PD1-IAD were analysed, and HLA-typing test was performed for each patient. Allele and haplotype frequencies of the patients were compared to those of healthy Japanese controls.

RESULTS

In the HLA allele and haplotype analyses of id-IAD, the frequencies of HLA-C*14:02, HLA-DPB1*05:01, HLA-DRB1*04:05-DQB1*04:01-DPB1*05:01 and HLA-DRB1*09:01-DQB1*03:03-DPB1*05:01 were significantly increased. On the other hand, HLA alleles account for PD1-IAD susceptibility as follows: HLA-DQB1*06:01, HLA-DPB1*09:01 and HLA-DRB5*01:02. Moreover, protective effect for HLA-C*03:03 was suggested in combined id-IAD and PD1-IAD patients. Comparison of the effects of HLA on id-IAD and PD1-IAD revealed some differences. Alleles or haplotypes frequencies increased in id-IAD group were as follows: HLA-DPB1*05:01, HLA-DRB1*09:01, HLA-DRB4*01:03:02, HLA-DQB1*03:03 and HLA-DRB1*09:01-DQB1*03:03. In clinical settings, hyponatremia, disturbance of consciousness and hypoglycaemia were less frequently seen in patients with PD1-IAD than in patients with id-IAD.

CONCLUSIONS

Distinct clinical characteristics and predisposing HLA allele contributions were proposed between id-IAD and PD1-IAD. Further investigations with greater number of cases are warranted to clarify the detailed mechanisms of id-IAD and PD1-IAD.

Association of HLA-DRB1 genotype with younger age onset and elder age onset rheumatoid arthritis in Japanese populations

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by joint destructions and human leukocyte antigen (HLA)-DRB1 is an important genetic risk factor for RA and influences the phenotype of RA. The clinical features of elder age onset RA (EORA) were known to be different from those of younger age onset RA (YORA). Previous studies reported the different association pattern of DRB1 alleles with YORA or EORA. The associations of DRB1 genotype with these RA subsets remained almost unknown. We investigated the genotype association of DRB1 with YORA or EORA in Japanese populations.HLA genotyping was performed in Japanese RA patients and the association of allele or genotype carrier frequencies were analyzed.The genotype frequency of DRB104:05/DRB104:06 (P = .0204, OR 7.69, 95%CI 1.39-42.72), DRB104:05/DRB112:01 (P = .0050, OR 5.53, 95%CI 1.71-17.88), and DRB104:05/DRB115:01 (P = .0124, OR 3.34, 95%CI 1.39-8.02) in YORA was higher than EORA. However, the frequencies of DRB101:01/DRB104:05 in YORA was tended to be lower than EORA (P = .0784, OR 0.14, 95%CI 0.01-2.42). The gene dosage effect of the shared epitope alleles was detected in EORA, but not in YORA. Trans-complementing DQ heterodimer molecules, formed by DQA1 and DQB1 of the haplotypes with and without shared epitope alleles, might explain the higher genotype frequencies of "shared epitope /not shared epitope". Linear regression analyses showed the primary role of DQB104:01 allele for the age at onset of RA.This is the first report for the associations of DRB1 genotype with YORA or EORA in the Japanese population and the differential distribution of the genotypes was noted between these RA subsets. The involvement of DQ molecules for the age at onset of RA was suggested.

Reference Grade Characterization of Polymorphisms in Full-Length HLA Class I and II Genes With Short-Read Sequencing on the ION PGM System and Long-Reads Generated by Single Molecule, Real-Time Sequencing on the PacBio Platform

Although NGS technologies fuel advances in high-throughput HLA genotyping methods for identification and classification of HLA genes to assist with precision medicine efforts in disease and transplantation, the efficiency of these methods are impeded by the absence of adequately-characterized high-frequency HLA allele reference sequence databases for the highly polymorphic HLA gene system. Here, we report on producing a comprehensive collection of full-length HLA allele sequences for eight classical HLA loci found in the Japanese population. We augmented the second-generation short read data generated by the Ion Torrent technology with long amplicon spanning consensus reads delivered by the third-generation SMRT sequencing method to create reference grade high-quality sequences of HLA class I and II gene alleles resolved at the genomic coding and non-coding level. Forty-six DNAs were obtained from a reference set used previously to establish the HLA allele frequency data in Japanese subjects. The samples included alleles with a collective allele frequency in the Japanese population of more than 99.2%. The HLA loci were independently amplified by long-range PCR using previously designed HLA-locus specific primers and subsequently sequenced using SMRT and Ion PGM sequencers. The mapped long and short-reads were used to produce a reference library of consensus HLA allelic sequences with the help of the reference-aware software tool LAA for SMRT Sequencing. A total of 253 distinct alleles were determined for 46 healthy subjects. Of them, 137 were novel alleles: 101 SNVs and/or indels and 36 extended alleles at a partial or full-length level. Comparing the HLA sequences from the perspective of nucleotide diversity revealed that HLA-DRB1 was the most divergent among the eight HLA genes, and that the HLA-DPB1 gene sequences diverged into two distinct groups, DP2 and DP5, with evidence of independent polymorphisms generated in exon 2. We also identified two specific intronic variations in HLA-DRB1 that might be involved in rheumatoid arthritis. In conclusion, full-length HLA allele sequencing by third-generation and second-generation technologies has provided polymorphic gene reference sequences at a genomic allelic resolution including allelic variations assigned up to the field-4 level for a stronger foundation in precision medicine and HLA-related disease and transplantation studies.

Independent association of HLA-DPB1*02:01 with rheumatoid arthritis in Japanese populations

Objective

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized with joint destructions; environmental and genetic factors were thought to be involved in the etiology of RA. The production of anti-citrullinated peptide antibodies (ACPA) is specifically associated with RA. DRB1 is associated with the susceptibility of RA, especially ACPA-positive RA [ACPA(+)RA]. However, a few studies reported on the independent associations of DPB1 alleles with RA susceptibility. Thus, we investigated the independent association of DPB1 alleles with RA in Japanese populations.

Methods

Association analyses of DPB1 were conducted by logistic regression analysis in 1667 RA patients and 413 controls.

Results

In unconditioned analysis, DPB1*04:02 was nominally associated with the susceptibility of ACPA(+)RA (P = 0.0021, corrected P (Pc) = 0.0275, odds ratio [OR] 1.52, 95% confidence interval [CI] 1.16–1.99). A significant association of DPB1*02:01 with the susceptibility of ACPA(+)RA was observed, when conditioned on DRB1 (P_adjusted = 0.0003, Pc_adjusted = 0.0040, OR_adjusted 1.47, 95%CI 1.19–1.81). DPB1*05:01 was tended to be associated with the protection against ACPA(+)RA, when conditioned on DRB1 (P_adjusted = 0.0091, Pc_adjusted = 0.1184, OR_adjusted 0.78, 95%CI 0.65–0.94). When conditioned on DRB1, the association of DPB1*04:02 with ACPA(+)RA was disappeared. No association of DPB1 alleles with ACPA-negative RA was detected.

Conclusion

The independent association of DPB1*02:01 with Japanese ACPA(+)RA was identified.

Association of a single nucleotide polymorphism in TNIP1 with type-1 autoimmune hepatitis in the Japanese population

Several studies reported that autoimmune diseases share a number of susceptibility genes. Of these genes, a SNP rs7708392 in TNIP1 was reported to be associated with systemic lupus erythematosus (SLE). Autoimmune hepatitis (AIH), a rare chronic progressive liver disease, shares some clinical features with SLE. Therefore, we investigated whether the SNP is associated with Japanese AIH. An association study of rs7708392 was conducted in 343 Japanese AIH patients and 828 controls. We found that rs7708392 is associated with AIH (P = 0.0236, odds ratio (OR) 1.26, 95% confidence interval (CI): 1.03-1.54), under the allele model for C allele. Significant differences of clinical characteristics of the AIH patients with or without G allele of rs7708392 were not detected. Of interest, the association was stronger in AIH without HLA-DRB1*04:05 allele (P = 0.0063, Q = 0.0127, OR 1.48, 95% CI: 1.12-1.96), though the association was not detected in AIH with DRB1*04:05. The C allele of rs7708392 was associated with AIH, especially AIH without DRB1*04:05, an already established risk factor.

HLA-DRB1 and DQB1 alleles in Japanese type 1 autoimmune hepatitis: The predisposing role of the DR4/DR8 heterozygous genotype

OBJECTIVE

Autoimmune hepatitis (AIH) is a chronic progressive liver disease. AIH is composed predominantly of type 1 in Japanese populations. The genetic and environmental factors are associated with the pathogenesis of AIH. HLA-DRB1*03:01 and *04:01 are associated with type 1 AIH in European and *04:05 in Japanese populations. Here, we conducted an HLA association study in order to find HLA alleles or haplotypes predisposing or protective for Japanese AIH.

METHODS

HLA-DRB1 and DQB1 genotyping of 360 type 1 AIH patients and 1026 healthy controls was performed.

RESULTS

The predisposing association of DRB1*04:01 (P = 0.0006, corrected P [Pc] = 0.0193, odds ratio [OR] 2.97, 95% confidence interval [CI] 1.62-5.43), DRB1*04:05 (P = 1.89×10-21, Pc = 5.86×10-20, OR 3.41, 95% CI 2.65-4.38), and DQB1*04:01 (P = 4.66×10-18, Pc = 6.99×10-17, OR 3.89, 95% CI 2.84-5.33) and the protective association of DRB1*13:02 (P = 0.0003, Pc = 0.0080, OR 0.48, 95% CI 0.32-0.72) with Japanese type 1 AIH were observed. An association of the DR4/DR8 heterozygous genotype with Japanese AIH was identified for the first time (P = 3.12×10-9, OR 3.52, 95% CI 2.34-5.29). Susceptible diplotypes were DRB1*04:05-DQB1*04:01/DRB1*08:02-DQB1*03:02 (P = 0.0004, OR 24.77, 95% CI 1.45-424.31) and DRB1*04:05-DQB1*04:01/DRB1*08:03-DQB1*06:01 (P = 1.18×10-6, OR 10.64, 95% CI 3.19-35.46). Serum levels of Immunoglobulin G and Immunoglobulin M, International Autoimmune Hepatitis Group score, positive rate of anti-smooth muscle antibodies, and the rate of definite AIH were higher in AIH patients with DRB1*04:05 than without.

CONCLUSIONS

The important roles of specific combinations of DRB1 and DQB1 alleles or haplotypes in the pathogenesis of type 1 AIH were suggested. The association of DR4/DR8 heterozygous genotype suggested the pathologic importance of trans-complementing DQα-β heterodimer molecules encoded by DQA1 allele of one haplotype and the DQB1 allele of the other haplotype, as it was proposed in the HLA association studies of Type 1 diabetes.

Association of ETS1 polymorphism with granulomatosis with polyangiitis and proteinase 3-anti-neutrophil cytoplasmic antibody positive vasculitis in a Japanese population

ETS proto-oncogene 1, transcription factor (ETS1) is involved in various immune responses. Genome-wide association studies on systemic lupus erythematosus in Chinese populations identified the association of ETS1 polymorphism in 3' untranslated region, rs1128334A, which was associated with lower ETS1 expression. In view of substantial sharing of susceptibility genes across multiple autoimmune diseases, we examined whether ETS1 is associated with a rare autoimmune rheumatic disease, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Association of rs1128334 was tested in 466 Japanese patients with AAV and 1099 healthy controls by logistic regression analysis under the additive model. AAV patients were classified into 285 microscopic polyangiitis (MPA), 92 granulomatosis with polyangiitis (GPA), 56 eosinophilic GPA, and 33 unclassifiable AAV, according to the European Medicines Agency (EMEA) algorithm. Among the patients, 376 were positive for MPO-ANCA and 62 for PR3-ANCA. When the patients were classified according to the EMEA classification, rs1128334A allele was significantly increased in GPA (P = 0.0060, P _c = 0.030, odds ratio (OR), 1.54; 95% confidence interval (CI), 1.13-2.10). With respect to the ANCA specificity, significant association was observed in PR3-ANCA positive AAV (P = 0.0042, P _c = 0.021, OR, 1.72; 95% CI, 1.19-2.49). In conclusion, ETS1 polymorphism was suggested to be associated with GPA and PR3-ANCA positive AAV in a Japanese population.

The role of anticitrullinated protein antibodies in the early stages of rheumatoid arthritis

PURPOSE OF REVIEW

This review provides an update on the recent discoveries on the role of anticitrullinated protein antibodies (ACPA) in early rheumatoid arthritis (RA).

RECENT FINDINGS

RA is characterized by an immune response against posttranslationally modified proteins, in particular citrullinated proteins. Recent studies have found that the ACPA response matures shortly before clinical disease manifests itself and is characterized by an increase in titre, isotype switching, antigen-recognition profile, and a change in the Fc-glycosylation pattern. To date, many citrullinated autoantigens have been identified and novel studies suggest that the human leucocyte antigen class II locus may directly influence the maturation of the ACPA response via antigen-specific T cells. Clinical studies have demonstrated that effective treatment of arthritis can lead to reduced ACPA levels or a change in composition of ACPA. In addition to ACPA, autoantibodies targeting other posttranslational modifications have been identified and may be associated with disease prognosis.

SUMMARY

Key studies have demonstrated that autoimmunity against citrullinated proteins is already present in preclinical RA and matures over time. Future studies are required to reveal whether autoantibodies and the B cells that produce them play a role in disease development or can function as biomarkers for disease maturation.

The role of common protective alleles HLA-DRB1*13 among systemic autoimmune diseases

Associations between human leukocyte antigen (HLA) and susceptibility to systemic autoimmune diseases have been reported. The predisposing alleles are variable among ethnic groups and/or diseases. On the other hand, some HLA alleles are associated with resistance to systemic autoimmune diseases, including systemic sclerosis, systemic lupus erythematosus and rheumatoid arthritis. Interestingly, DRB1*13 alleles are the protective alleles shared by multiple autoimmune diseases. DRB1*13:01 allele is protective in European populations and DRB1*13:02 in Japanese. Because alleles in multiple HLA loci are in strong linkage disequilibrium, it is difficult to determine which of the protective alleles is functionally responsible for the protective effects. Thus far, association studies suggested that DRB1*13:02 represents at least one of the causally associated protective factors against multiple systemic autoimmune diseases in the Japanese population. The protective effect of DRB1*13 alleles appears to overcome the predisposing effect of the susceptible alleles in heterozygous individuals of DRB1*13 and the susceptible allele. A gene dosage effect was observed in the associations of DRB1*13:02 with the protection from systemic autoimmune diseases; thus homozygous individuals are more effectively protected from the systemic autoimmune diseases than heterozygotes. DRB1*13:02 also confers protection against organ-specific autoimmune diseases and some infectious diseases. Several hypotheses can be proposed for the molecular mechanisms of the protection conferred by DRB1*13, some of which can explain the dominant effect of DRB1*13 molecules over the susceptible alleles, but the actual protective function of DRB1*13 requires further study. Understanding of the protective mechanisms of DRB1*13 may lead to the identification of targets for the curative treatment of systemic autoimmune diseases.

Genetic markers as therapeutic target in rheumatoid arthritis: A game changer in clinical therapy?

Rheumatoid arthritis (RA) is a chronic, inflammatory, multi-systemic autoimmune disease unremitted by genetic and environmental factors. The factors are crucial but inadequate in the development of disease; however, these factors can be representative of potential therapeutic targets and response to clinical therapy. Insights into the contribution of genetic risk factors are currently in progress with studies querying the genetic variation, their role in gene expression of coding and non-coding genes and other mechanisms of disease. In this review, we describe the significance of genetic markers architecture of RA through genome-wide association studies and meta-analysis studies. Further, it also reveals the mechanism of disease pathogenesis investigated through the mutual findings of functional and genetic studies of individual RA-associated genes, which includes HLA-DRB1, HLA-DQB1, HLA-DPB1, PADI4, PTPN22, TRAF1-C5, STAT4 and C5orf30. However, the genetic background of RA remains to be clearly depicted. Prospective efforts of the post-genomic and functional genomic period can travel toward real possible assessment of the genetic effect on RA. The discovery of novel genes associated with the disease can be appropriate in identifying potential biomarkers, which could assist in early diagnosis and aggressive treatment.

Protective Role of HLA-DRB1*13:02 against Microscopic Polyangiitis and MPO-ANCA-Positive Vasculitides in a Japanese Population: A Case-Control Study

Among antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV), granulomatosis with polyangiitis (GPA) and proteinase 3-ANCA-positive AAV (PR3-AAV) are prevalent in European populations, while microscopic polyangiitis (MPA) and myeloperoxidase-ANCA-positive AAV (MPO-AAV) are predominant in the Japanese. We previously demonstrated association of DRB1*09:01-DQB1*03:03 haplotype, a haplotype common in East Asians but rare in the European populations, with MPA/MPO-AAV, suggesting that a population difference in HLA-class II plays a role in the epidemiology of this disease. To gain further insights, we increased the sample size and performed an extended association study of DRB1 and DPB1 with AAV subsets in 468 Japanese patients with AAV classified according to the European Medicines Agency algorithm (MPA: 285, GPA: 92, eosinophilic GPA [EGPA]: 56, unclassifiable: 35) and 596 healthy controls. Among these patients, 377 were positive for MPO-ANCA and 62 for PR3-ANCA. The significance level was set at α = 3.3x10-4 by applying Bonferroni correction. The association of DRB1*09:01 with MPO-AAV was confirmed (allele model, P = 2.1x10-4, odds ratio [OR] = 1.57). Protective association of DRB1*13:02 was detected against MPO-AAV (allele model, P = 2.3x10-5, OR = 0.42) and MPA (dominant model, P = 2.7x10-4, OR = 0.43). A trend toward increased frequency of DPB1*04:01, the risk allele for GPA in European populations, was observed among Japanese patients with PR3-AAV when conditioned on DRB1*13:02 (Padjusted = 0.0021, ORadjusted = 3.48). In contrast, the frequency of DPB1*04:01 was decreased among Japanese patients with MPO-AAV, and this effect lost significance when conditioned on DRB1*13:02 (Padjusted = 0.16), suggesting that DRB1*13:02 or other allele(s) in linkage disequilibrium may be responsible for the protection. The differential association of DPB1*04:01 with PR3-AAV and MPO-AAV and difference in DPB1*04:01 allele frequencies between populations supported the hypothesis that the HLA-class II population difference may account in part for these epidemiologic characteristics. Furthermore, taken together with our previous observations, the haplotype carrying DRB1*13:02 was suggested to be a shared protective factor against multiple autoimmune diseases.

Human Leukocyte Antigen and Systemic Sclerosis in Japanese: The Sign of the Four Independent Protective Alleles, DRB1*13:02, DRB1*14:06, DQB1*03:01, and DPB1*02:01

Objective

Several studies on associations between human leukocyte antigen (HLA) allele frequencies and susceptibility to systemic sclerosis (SSc) have been reported. Anti-centromere antibodies (ACA) and anti-topoisomerase I antibodies (ATA) are found in SSc patients. Here, we sought to identify HLA alleles associated with SSc in Japanese, and explored their associations with SSc phenotypes including the presence of autoantibodies.

Methods

Associations of HLA-DRB1, DQB1, and DPB1 were analyzed in 463 Japanese SSc patients and 413 controls.

Results

We found that DRB1*13:02 (P = 0.0011, Pc = 0.0319, odds ratio [OR] 0.46, 95% confidence interval [CI] 0.29–0.73), DRB1*14:06 (P = 6.60X10^-5, Pc = 0.0020, OR 0.05, 95%CI 0.01–0.41), DQB1*03:01 (P = 0.0009, Pc = 0.0150, OR 0.56, 95%CI 0.40–0.79), and DPB1*02:01 (P = 5.16X10^-6, Pc = 8.77X10^-5, OR 0.52, 95%CI 0.39–0.69) were protectively associated with SSc. In addition, these four alleles seemed to be independently associated with the protection against the susceptibility of SSc. On the other hand, we could not find predisposing alleles for overall SSc. With respect to SSc subsets, a tendency for these four alleles to be protectively associated was observed. However, there was a significant association between DRB1*01:01, DRB1*10:01, DQB1*05:01, and DPB1*04:02 and the susceptibility to SSc with ACA. On the other hand, the presence of DRB1*15:02, DQB1*06:01, DPB1*03:01, and DPB1*09:01 was associated with SSc with ATA.

Conclusion

Thus, the present study has identified protective associations of the four HLA class II alleles with overall Japanese SSc and predisposing associations of HLA class II alleles with Japanese SSc subsets.

Protective effect of HLA-DRB1*13 alleles during specific phases in the development of ACPA-positive RA

OBJECTIVE

Human leucocyte antigen (HLA)-DRB1*13 alleles are associated with protection from anticitrullinated protein antibody (ACPA)-positive rheumatoid arthritis (RA). It is, however, unknown at which phase of disease development (seroconversion, ACPA maturation, disease onset or outcome) these alleles are most important. We therefore examined the effect of HLA-DRB1*13 on: ACPA presence (systemic autoimmunity associated with RA) in individuals with and without RA, on ACPA characteristics and on clinical outcome measures.

METHODS

The effect of HLA-DRB1*13 on ACPA presence in subjects with or without RA (non-RA) was assessed in the Swedish twin registry (n=10 748). ACPA characteristics were studied in patients with ACPA-positive RA from the Swedish Epidemiological Investigation of RA (EIRA, n=1224) and the Dutch Leiden Early Arthritis Clinic (EAC, n=441). Disease activity at inclusion and disease outcome (disease-modifying antirheumatic drugs (DMARD)-free sustained remission and radiographic progression) was assessed in patients with RA from the EAC.

RESULTS

HLA-DRB1*13 is associated with protection from ACPA-positive RA (prevalence 16% vs 28% in ACPA-negative non-RA), but not with significant protection from ACPA in individuals without RA (prevalence: 22%, p value 0.09). HLA-DRB1*13 is associated with lower ACPA-levels (EIRA: 447 U/ml versus 691 U/ml, p value= 0.0002) and decreased citrullinated epitope recognition (EIRA: p<0.0001). No association between HLA-DRB1*13 and disease activity or outcome was found.

CONCLUSIONS

These data indicate that HLA-DRB1*13 mainly affects the onset of ACPA-positive RA in ACPA-positive non-RA individuals. In RA, HLA-DRB1*13 influences ACPA characteristics but not the disease course. This implies that therapeutic strategies aimed at emulating the HLA-DBR1*13 protective effect may be most effective in ACPA-positive healthy individuals at risk for RA.

The Protective Role of HLA-DRB1(∗)13 in Autoimmune Diseases

Autoimmune diseases (AIDs) are characterized by a multifactorial aetiology and a complex genetic background, with the MHC region playing a major role. We genotyped for HLA-DRB1 locus 1228 patients with AIDs-213 with Systemic Lupus Erythematosus (SLE), 166 with Psoriasis or Psoriatic Arthritis (Ps + PsA), 153 with Rheumatoid Arthritis (RA), 67 with Systemic Sclerosis (SSc), 536 with Multiple Sclerosis (MS), and 93 with Myasthenia Gravis (MG) and 282 unrelated controls. We confirmed previously established associations of HLA-DRB1^∗15 (OR = 2.17) and HLA-DRB1^∗03 (OR = 1.81) alleles with MS, HLA-DRB1^∗03 with SLE (OR = 2.49), HLA-DRB1^∗01 (OR = 1.79) and HLA-DRB1^∗04 (OR = 2.81) with RA, HLA-DRB1^∗07 with Ps + PsA (OR = 1.79), HLA-DRB1^∗01 (OR = 2.28) and HLA-DRB1^∗08 (OR = 3.01) with SSc, and HLA-DRB1^∗03 with MG (OR = 2.98). We further observed a consistent negative association of HLA-DRB1^∗13 allele with SLE, Ps + PsA, RA, and SSc (18.3%, 19.3%, 16.3%, and 11.9%, resp., versus 29.8% in controls). HLA-DRB1^∗13 frequency in the AIDs group was 20.0% (OR = 0.58). Although different alleles were associated with particular AIDs, the same allele, HLA-DRB1^∗13, was underrepresented in all of the six diseases analysed. This observation suggests that this allele may confer protection for AIDs, particularly for systemic and rheumatic disease. The protective effect of HLA-DRB1^∗13 could be explained by a more proficient antigen presentation by these molecules, favouring efficient clonal deletion during thymic selection.

Coeliac disease and rheumatoid arthritis: similar mechanisms, different antigens

Rheumatoid arthritis (RA) and coeliac disease are inflammatory diseases that both have a strong association with class II HLAs: individuals carrying HLA-DQ2.5 and/or HLA-DQ8 alleles have an increased risk of developing coeliac disease, whereas those carrying HLA-DR shared epitope alleles exhibit an increased risk of developing RA. Although the molecular basis of the association with specific HLA molecules in RA remains poorly defined, an immune response against post-translationally modified protein antigens is a hallmark of each disease. In RA, understanding of the pathogenetic role of B-cell responses to citrullinated antigens, including vimentin, fibrinogen and α-enolase, is rapidly growing. Moreover, insight into the role of HLAs in the pathogenesis of coeliac disease has been considerably advanced by the identification of T-cell responses to deamidated gluten antigens presented in conjunction with predisposing HLA-DQ2.5 molecules. This article briefly reviews these advances and draws parallels between the immune mechanisms leading to RA and coeliac disease, which point to a crucial role for T-cell-B-cell cooperation in the development of full-blown disease. Finally, the ways in which these novel insights are being exploited therapeutically to re-establish tolerance in patients with RA and coeliac disease are described.

Identification of Disease-Promoting HLA Class I and Protective Class II Modifiers in Japanese Patients with Familial Mediterranean Fever

Objectives

The genotype-phenotype correlation of MEFV remains unclear for the familial Mediterranean fever (FMF) patients, especially without canonical MEFV mutations in exon 10. The risk of FMF appeared to be under the influence of other factors in this case. The contribution of HLA polymorphisms to the risk of FMF was examined as strong candidates of modifier genes.

Methods

Genotypes of HLA-B and -DRB1 loci were determined for 258 mutually unrelated Japanese FMF patients, who satisfied modified Tel-Hashomer criteria, and 299 healthy controls. The effects of carrier status were evaluated for the risk of FMF by odds ratio (OR). The HLA effects were also assessed for clinical forms of FMF, subsets of FMF with certain MEFV genotypes and responsiveness to colchicine treatment.

Results

The carriers of B*39:01 were increased in the patients (OR = 3.25, p = 0.0012), whereas those of DRB1*15:02 were decreased (OR = 0.45, p = 0.00050), satisfying Bonferroni’s correction for multiple statistical tests (n = 28, p<0.00179). The protective effect of DRB1*15:02 was completely disappeared in the co-existence of B*40:01. The HLA effects were generally augmented in the patients without a canonical MEFV variant allele M694I, in accordance with the notion that the lower penetrance of the mutations is owing to the larger contribution of modifier genes in the pathogenesis, with a few exceptions. Further, 42.9% of 14 colchicine-resistant patients and 13.5% of 156 colchicine-responders possessed B*35:01 allele, giving OR of 4.82 (p = 0.0041).

Conclusions

The differential effects of HLA class I and class II polymorphisms were identified for Japanese FMF even in those with high-penetrance MEFV mutations.

Genetics of Interstitial Lung Disease: Vol de Nuit (Night Flight)

Interstitial lung disease (ILD) is a chronic, progressive fibrotic lung disease with a dismal prognosis. ILD of unknown etiology is referred to as idiopathic interstitial pneumonia (IIP), which is sporadic in the majority of cases. ILD is frequently accompanied by rheumatoid arthritis (RA), systemic sclerosis (SSc), polymyositis/dermatomyositis (PM/DM), and other autoimmune diseases, and is referred to as collagen vascular disease-associated ILD (CVD-ILD). Susceptibility to ILD is influenced by genetic and environmental factors. Recent advances in radiographic imaging techniques such as high-resolution computed tomography (CT) scanning as well as high-throughput genomic analyses have provided insights into the genetics of ILD. These studies have repeatedly revealed an association between IIP (sporadic and familial) and a single nucleotide polymorphism (SNP) in the promoter region of the mucin 5B (MUC5B). HLA-DRB1*11 alleles have been reported to correlate with ILD in European patients with SSc, whereas in Japanese patients with RA, the HLA-DR2 serological group was identified. The aim of this review is to describe the genetic background of sporadic IIP, CVD-ILD, drug-induced-ILD (DI-ILD), pneumoconiosis, and hypersensitivity pneumonitis. The genetics of ILD is still in progress. However, this information will enhance the understanding of the pathogenesis of ILD and aid the identification of novel therapeutic targets for personalized medicine in future.

Human leukocyte antigen polymorphisms and personalized medicine for rheumatoid arthritis

Human leukocyte antigen (HLA) polymorphisms are the most important genetic risk factors for rheumatoid arthritis (RA), a chronic systemic inflammatory disease of unknown etiology. Certain HLA-DRB1 alleles, known as shared epitope (SE) alleles because they have the same amino-acid sequence at positions 70-74, are associated with susceptibility to RA. A gene dosage effect is present for RA-predisposing SE alleles, and protective alleles show epistasis. An important role of amino-acid polymorphisms at positions 11 and 13 of the HLA-DRβ chain was also reported recently. Rheumatoid factor and anticitrullinated peptide antibodies are present in many RA patients. Similar to extra-articular manifestations, the presence of these autoantibodies is also associated with certain DRB1 alleles. Different frequencies of RA risk alleles in different ethnicities explain the varying prevalence of RA in different populations and suggest genetic heterogeneity of RA with regard to phenotype and population subsets. Some drug-induced hypersensitivity reactions due to disease-modifying antirheumatic drugs are also associated with HLA alleles. Understanding the role of HLA as the most important genetic factor relevant to RA susceptibility may help in determining its pathogenesis and pave the way to personalized medicine.