Hiroto Kojima

New susceptibility variants to narcolepsy identified in HLA class II region

Narcolepsy, a sleep disorder characterized by excessive daytime sleepiness, cataplexy and rapid eye movement sleep abnormalities, is tightly associated with human leukocyte antigen HLA-DQB1*06:02. DQB1*06:02 is common in the general population (10-30%); therefore, additional genetic factors are needed for the development of narcolepsy. In the present study, HLA-DQB1 in 664 Japanese narcoleptic subjects and 3131 Japanese control subjects was examined to determine whether HLA-DQB1 alleles located in trans of DQB1*06:02 are associated with narcolepsy. The strongest association was with DQB1*06:01 (P = 1.4 × 10(-10), odds ratio, OR = 0.39), as reported in previous studies. Additional predisposing effects of DQB1*03:02 were also found (P = 2.5 × 10(-9), OR = 1.97). A comparison between DQB1*06:02 heterozygous cases and controls revealed dominant protective effects of DQB1*06:01 and DQB1*05:01. In addition, a single-nucleotide polymorphism-based conditional analysis controlling for the effect of HLA-DQB1 was performed to determine whether there were other independent HLA associations outside of HLA-DQB1. This analysis revealed associations at HLA-DPB1 in the HLA class II region (rs3117242, P = 4.1 × 10(-5), OR = 2.45; DPB1*05:01, P = 8.1 × 10(-3), OR = 1.39). These results indicate that complex HLA class II associations contribute to the genetic predisposition to narcolepsy.

Understanding of HLA-conferred susceptibility to chronic hepatitis B infection requires HLA genotyping-based association analysis

Associations of variants located in the HLA class II region with chronic hepatitis B (CHB) infection have been identified in Asian populations. Here, HLA imputation method was applied to determine HLA alleles using genome-wide SNP typing data of 1,975 Japanese individuals (1,033 HBV patients and 942 healthy controls). Together with data of an additional 1,481 Japanese healthy controls, association tests of six HLA loci including HLA-A, C, B, DRB1, DQB1, and DPB1, were performed. Although the strongest association was detected at a SNP located in the HLA-DP locus in a SNP-based GWAS using data from the 1,975 Japanese individuals, HLA genotyping-based analysis identified DQB1*06:01 as having the strongest association, showing a greater association with CHB susceptibility (OR = 1.76, P = 6.57 × 10−18) than any one of five HLA-DPB1 alleles that were previously reported as CHB susceptibility alleles. Moreover, HLA haplotype analysis showed that, among the five previously reported HLA-DPB1 susceptibility and protective alleles, the association of two DPB1 alleles (DPB1*09:01, and *04:01) had come from linkage disequilibrium with HLA-DR-DQ haplotypes, DRB1*15:02-DQB1*06:01 and DRB1*13:02-DQB1*06:04, respectively. The present study showed an example that SNP-based GWAS does not necessarily detect the primary susceptibility locus in the HLA region.

Immune-related pathways including HLA-DRB1(∗)13:02 are associated with panic disorder.

Panic disorder (PD) is an anxiety disorder characterized by panic attacks and anticipatory anxiety. Both genetic and environmental factors are thought to trigger PD onset. Previously, we performed a genome-wide association study (GWAS) for PD and focused on candidate SNPs with the lowest P values. However, there seemed to be a number of polymorphisms which did not reach genome-wide significance threshold due to their low allele frequencies and odds ratios, even though they were truly involved in pathogenesis. Therefore we performed pathway analyses in order to overcome the limitations of conventional single-marker analysis and identify associated SNPs with modest effects. Each pathway analysis indicated that pathways related to immunity showed the strongest association with PD (DAVID, P=2.08×10(-6); i-GSEA4GWAS, P<10(-3); ICSNPathway, P<10(-3)). Based on the results of pathway analyses and the previously performed GWAS for PD, we focused on and investigated HLA-B and HLA-DRB1 as candidate susceptibility genes for PD. We typed HLA-B and HLA-DRB1 in 744 subjects with PD and 1418 control subjects. Patients with PD were significantly more likely to carry HLA-DRB1(∗)13:02 (P=2.50×10(-4), odds ratio=1.54). Our study provided initial evidence that HLA-DRB1(∗)13:02 and genes involved in immune-related pathways are associated with PD. Future studies are necessary to confirm these results and clarify the underlying mechanisms causing PD.

Nonsense mutation in HLA‐B*40:02 in a case with acquired aplastic anaemia: a possible origin of clonal escape from autoimmune insult

The cause of idiopathic aplastic anaemia (AA) has not been clarified, but some evidence supports the role of T cell-mediated autoimmune destruction of haematopoietic stem/progenitor cells (HSPCs; Young & Maciejewski, 1997). The condition of approximately 70% of patients with idiopathic AA has been observed to improve after immunosuppressive therapy (IST; Bacigalupo et al, 2000; Kojima et al, 2000). In vitro monoclonal or oligoclonal expansion of CD8 T-cells has been noted in patients with idiopathic AA (Risitano et al, 2004). However, the target antigens of T cells have not been clearly identified. Katagiri et al (2011) reported that a considerable proportion of Japanese patients with idiopathic AA acquired copy number-neutral loss of heterozygosity of the 6p arms (6pLOH), leading to loss of one human leucocyte antigen (HLA) haplotype. Moreover, the missing haplotype was concentrated in particular alleles: HLA-A*02:01, HLAA*02:06, HLA-A*31:01 and HLA-B*40:02. Furthermore, Japanese patients with idiopathic AA typically inherited only those four HLA alleles (Katagiri et al, 2011). These findings suggest that these HLA alleles are the target antigens of T cells in the pathogenesis of idiopathic AA and 6pLOH is the mechanism by which HSPCs escape from autoreactive cytotoxic T-lymphocytes (CTL). In this study, we report a patient with idiopathic AA who carried a nonsense mutation in an HLA allele. Tracing the case history with fluctuations in her HLA typing illustrated how HSPCs escape from autoimmune insult. A 2-year-old girl was diagnosed with severe acquired AA. Neither chromosomal abnormalities nor morphological dysplasia was observed in her bone marrow cells. Serological HLA typing was performed using the Terasaki–NIH Standard method, revealing that her phenotypes (A24/-, B55/B61, DR8/DR9) completely matched those of her father. She received immunosuppressive therapy for 20 months, leading to partial remission, but she relapsed with thrombocytopenia 7 months after discontinuing IST. Although she was retreated with IST, regular blood transfusions had been required since the age of 5 years. Therefore, stem cell transplantation was scheduled at the age of 7 years. Confirmation of her HLA type by high-resolution sequencing-based typing of a peripheral blood sample, revealed a nonsense mutation (CAG to TAG) at codon 54 in exon 2 of either HLA-B*40:02 or HLA-B*55:02 (Fig 1A). In contrast, no mutation in HLA-B alleles was found in either of her parents. To resolve the discrepancy, we re-examined the serological HLA typing by the same method. Analysis of her blood sample demonstrated that the HLA-B61 antigen, corresponding to

A case of fulminant type 1 diabetes mellitus, with a precipitous decrease in pancreatic volume, induced by nivolumab for malignant melanoma: analysis of HLA and CTLA-4 polymorphisms.

Nivolumab is a monoclonal antibody directed against PD1 (programmed cell death 1) that can improve survival in patients with metastatic melanoma. Such immune checkpoint inhibitors have been known to induce type 1 diabetes mellitus (T1D) [1, 2].A 54-year-old woman reported enlarging black nodules on her left sole, which had been present for seven months (figure 1A). CT imaging revealed swollen lymph nodes in the left inguinal and pelvic regions (figure 1B). After clinical diagnosis of malignant melanoma [...]

Association between HLA-DRB1*0405, -DQB1*0401 and -DQA1*0303 alleles and lamotrigine-induced cutaneous adverse drug reactions. A pilot case-control study from Japan

BACKGROUND Human leukocyte antigen (HLA) genotypes in lamotrigine -induced (LTG-induced) cutaneous adverse drug reactions (cADRs) have been described in several reports but controversy remains even for a given ethnic group. We attempted to clarify a possible association between LTG-induced cADRs and HLA alleles in Japanese patients. METHOD Sixteen subjects, including eight patients with LTG-induced cADRs and eight LTG-tolerant controls were included in this study. All eight patients with LTG-induced cADRs gave positive results in a drug-induced lymphocyte stimulation test (DLST) with LTG. We performed HLA-typing for HLA-A, -B, -C, -DRB1, -DQA1, -DQB1, -DPA1 and -DPB1, using PCR with sequence-specific oligonucleotide probes and multiple analyte profiling (xMAP) technology (Luminex System; Luminex Corporation, Austin, TX). We examined differences between allele frequencies in our two groups of subjects and the allele frequencies in the general Japanese population. RESULTS The frequencies of HLA-DRB1*0405, and HLA-DQB1*0401 alleles were higher in our LTG-cADRs patients than the reference frequencies in the general Japanese population. We also detected HLA-DQA1*0303 frequently in our LTG-cADRs patients, but data for this allele in the Japanese population was not available. Our observation was presumably due to the linkage disequilibrium among the three alleles. The haplotype frequency of HLA-DRB1*0405, DQB1*0401 and DQA1*0303 in our LTG-cADRs subjects was also different from the corresponding haplotype frequency in the database for the Japanese population and the difference was statistically significant. One patient with the HLA-DRB1*0405, -DQB1*0401 and DQA1*0303 haplotype was safely re-treated with LTG after results of a DLST with LTG ceased to be positive about 4 months after discontinuation of LTG. LIMITATIONS Our analysis included only 16 patients. Associations between LTG-induced cADRs and specific HLA loci will have to be confirmed in larger studies. CONCLUSIONS LTG-induced cADRs are associated with HLA-DRB1*0405, -DQB1*0401 and -DQA1*0303.

An association analysis of HLA-DQB1 with narcolepsy without cataplexy and idiopathic hypersomnia with/without long sleep time in a Japanese population

Narcolepsy without cataplexy (NA w/o CA) (narcolepsy type 2) is a lifelong disorder characterized by excessive daytime sleepiness and rapid eye movement (REM) sleep abnormalities, but no cataplexy. In the present study, we examined the human leukocyte antigen HLA-DQB1 in 160 Japanese patients with NA w/o CA and 1,418 control subjects. Frequencies of DQB1*06:02 were significantly higher in patients with NA w/o CA compared with controls (allele frequency: 16.6 vs. 7.8%, P=1.1×10−7, odds ratio (OR)=2.36; carrier frequency: 31.3 vs. 14.7%, P=7.6×10−8, OR=2.64). Distributions of HLA-DQB1 alleles other than DQB1*06:02 were compared between NA w/o CA and narcolepsy with cataplexy (NA-CA) to assess whether the genetic backgrounds of the two diseases have similarities. The distribution of the HLA-DQB1 alleles in DQB1*06:02-negative NA w/o CA was significantly different from that in NA-CA (P=5.8×10−7). On the other hand, the patterns of the HLA-DQB1 alleles were similar between DQB1*06:02-positive NA w/o CA and NA-CA. HLA-DQB1 analysis was also performed in 186 Japanese patients with idiopathic hypersomnia (IHS) with/without long sleep time, but no significant associations were observed.

NK cell alloreactivity against KIR-ligand-mismatched HLA-haploidentical tissue derived from HLA haplotype-homozygous iPSCs.

Summary HLA haplotype-homozygous (HLA-homo) induced pluripotent stem cells (iPSCs) are being prepared to be used for allogeneic transplantation of regenerated tissue into recipients carrying an identical haplotype in one of the alleles (HLA-hetero). However, it remains unaddressed whether natural killer (NK) cells respond to these regenerated cells. HLA-C allotypes, known to serve as major ligands for inhibitory receptors of NK cells, can be classified into group 1 (C1) and group 2 (C2), based on their binding specificities. We found that the T cells and vascular endothelial cells regenerated from HLA-homo-C1/C1 iPSCs were killed by specific NK cell subsets from a putative HLA-hetero-C1/C2 recipient. Such cytotoxicity was canceled when target cells were regenerated from iPSCs transduced with the C2 gene identical to the recipient. These results clarify that NK cells can kill regenerated cells by sensing the lack of HLA-C expression and further provide the basis for an approach to prevent such NK cell-mediated rejection responses.

Genotyping of relapsing polychondritis identified novel susceptibility HLA alleles and distinct genetic characteristics from other rheumatic diseases

OBJECTIVE To uncover the genetic background of relapsing polychondritis (RPC), a rare autoimmune disease with unknown mechanisms characterized by systemic inflammation of the cartilage, to deepen our understanding of the pathophysiology of RPC and show its distinct genetic characteristics from other rheumatic diseases. METHODS A total of 102 patients with RPC and 1000 healthy subjects were recruited for a two-staged genetic association study and genotyped for six HLA classical loci. Haplotype association tests were also performed. The associations of amino acid (AA) residues and positions with susceptibility to RPC were analysed. Frequencies of representative susceptibility HLA alleles to other rheumatic diseases in RPC were also analysed. RESULTS HLA-DRB1*16:02, HLA-DQB1*05:02 and HLA-B*67:01, which are in linkage disequilibrium with each other, were associated with RPC (P = 1.9 × 10(-6), 1.4 × 10(-5) and 0.00024, respectively). AA residue at position 57 in HLA-DQB1, the most significant position in type I diabetes mellitus, showed the strongest association among AA residues. HLA-DR4, a known susceptibility allele in Germans, showed a trend of susceptibility association without significance (P = 0.067). No associations were observed between the three alleles and clinical phenotypes. Representative susceptibility HLA alleles to RA, SLE, Behçet disease and Takayasu arteritis did not show enrichment in RPC in spite of sufficient statistical power. CONCLUSIONS HLA-DRB1*16:02, HLA-DQB1*05:02 and HLA-B*67:01, in linkage disequilibrium with each other, are associated with susceptibility to RPC Importance of HLA-class II loci in RPC susceptibility is suggested. RPC is considered a genetically distinct disease from other rheumatic diseases.

Killer immunoglobulin-like receptor genotype did not correlate with response to anti-PD-1 antibody treatment in a Japanese cohort

Immune checkpoint blockade (ICB) induces a remarkable response in patients with certain cancers. However, the response rate is not yet satisfactory. Biomarkers that help physicians identify patients who would benefit from ICB need to be developed. Killer immunoglobulin-like receptors (KIRs) are a class of receptors that are mainly expressed by natural killer cells. KIR genotypes have been shown to influence the outcomes of patients with neuroblastoma and hematopoietic malignancies. KIRs may thus influence the clinical outcomes of melanoma patients receiving nivolumab. We aimed to identify the KIR genotype, or KIR/KIR-ligand combinations, which influence the outcomes of melanoma patients receiving nivolumab. We genotyped 112 melanoma patients who were treated with nivolumab for KIR and human leukocyte antigen. The clinical records of the patients were analyzed to determine if they showed a response to nivolumab, and whether or not they experienced adverse events. Our analysis showed that no KIR gene was associated with a response to nivolumab. The KIR/KIR-ligand combination did not correlate with a response to nivolumab. KIR genes were not predictive of experiencing adverse events of grade 2 or greater. We conclude that the KIR genotype or KIR/KIR-ligand genotype do not show predictive value in melanoma patients receiving nivolumab.