Epidemiology and genetics of granulomatosis with polyangiitis.

Granulomatosis with polyangiitis (GPA) previously known as Wegener's granulomatosis (WG) is a rare rheumatic disease affecting subjects of all ages. Prevalence and incidence of this systemic disease greatly varies across different ethnic groups. GPA is the commonest form of ANCA-associated vasculitis (AAV) with PR3 positivity among 85-95% of the cases. Scientific investigations of GPA is warranted because its severity, clinical heterogeneity, fast disease manifestation and end-organ damage. The etiology of GPA is still unknown. Major role of HLA and non-HLA genes with immune functions were identified, however, very limited replication was observed in different ethnic populations. In the present review, we have discussed the updates on the global epidemiology and contribution of HLA and major non-HLA genes/loci in GPA. We have also highlighted the cross disease association of GPA associated genes that may help in better disease management and predictive medicine. We proposed that high-resolution HLA typing and development of genetic risk model would help in early disease diagnosis and understanding the prognosis.

Relevance of HLA gene polymorphisms in Romanian patients with chronic renal insufficiency undergoing renal transplantation.

BACKGROUND: Chronic renal insufficiency (CRI) is a global public health problem with a high incidence in the Romanian population. In this study, we aimed to investigate genomic HLA polymorphisms in Romanian patients with CRI waiting for kidney transplantation. To determine the existence of a potential strong link between certain HLA polymorphisms and CRI, we also looked at HLA specificity combinations within the same locus or even different loci, referring to randomly inherited allelic combinations rather than potential haplotypes. METHODS: A total of 2199 patients with CRI on the kidney transplantation waiting list were included. A total of 2786 healthy individuals were included as controls. Both patients and controls were assessed for both HLA I and class II genes. HLA genes were typed using the low-resolution method polymerase chain reaction sequence-specific primer. RESULTS: Certain class I and class II HLA allele groups, genotypes and haplotypes were significantly more frequent in patients with CRI than in the control individuals (eg B* 40 (p ≤ .001, pc ≤ .001), C* 12 (p ≤ .001, pc ≤ .001), DRB1*14 (p = .0022, pc = .04), C*12,- (p < .001, pc < .001), A*01-C*15 (p = .0003, pc = .03) and A*02-C*12 (p = .0005, pc = .0486)). CONCLUSIONS: HLA gene polymorphisms could be clinically relevant CRI-associated genetic profiles in Romanian patients with CRI.

Dense genotyping of immune-related loci identifies HLA variants associated with increased risk of collagenous colitis.

OBJECTIVE: Collagenous colitis (CC) is a major cause of chronic non-bloody diarrhoea, particularly in the elderly female population. The aetiology of CC is unknown, and still poor is the understanding of its pathogenesis. This possibly involves dysregulated inflammation and immune-mediated reactions in genetically predisposed individuals, but the contribution of genetic factors to CC is underinvestigated. We systematically tested immune-related genes known to impact the risk of several autoimmune diseases for their potential CC-predisposing role. DESIGN: Three independent cohorts of histologically confirmed CC cases (N=314) and controls (N=4299) from Sweden and Germany were included in a 2-step association analysis. Immunochip and targeted single nucleotide polymorphism (SNP) genotype data were produced, respectively, for discovery and replication purposes. Classical human leucocyte antigen (HLA) variants at 2-digit and 4-digit resolution were obtained via imputation from single marker genotypes. SNPs and HLA variants passing quality control filters were tested for association with CC with logistic regression adjusting for age, sex and country of origin. RESULTS: Forty-two markers gave rise to genome-wide significant association signals, all contained within the HLA region on chromosome 6 (best p=4.2×10-10 for SNP rs4143332). Among the HLA variants, most pronounced risk effects were observed for 8.1 haplotype alleles including DQ2.5, which was targeted and confirmed in the replication data set (p=2.3×10-11; OR=2.06; 95% CI (1.67 to 2.55) in the combined analysis). CONCLUSIONS: HLA genotype associates with CC, thus implicating HLA-related immune mechanisms in its pathogenesis.

Role of HLA-DP and HLA-DQ on the clearance of hepatitis B virus and the risk of chronic infection in a multiethnic population.

BACKGROUND & AIMS: HBV infection exhibits geographical variation in its distribution in South America. While HBV rates are low in central Argentina, the north-western region exhibits intermediate HBV rates. Unfortunately, the reasons that could explain this difference are still unknown. METHODS: A total of 1440 Argentines were recruited and grouped into HBV patients, HBV-resolved individuals and healthy controls. Genetic ancestry was assessed by analysis of biparental lineages and ancestry autosomal typing. SNPs of HLA-DPA1 (rs3077), HLA-DPB1 (rs9277542), HLA-DQB1 (rs2856718) and HLA-DQB2 (rs7453920) were determined, and HBV genotyping was performed by phylogenetic analysis in HBV patients. RESULTS: Native American ancestry prevailed in the north-western region when compared with central Argentina (P<.0001). However, no differences were observed among the three groups of each region. The distribution of HBV genotypes revealed significant differences (P<.0001). Three SNPs (rs3077, rs9277542 and rs7453920) showed a significant association with protection against chronic HBV and viral clearance in both regions. The remaining SNP showed a significant association with susceptibility to chronic HBV. The frequency rates of rs3077-T, related to protection against chronic HBV and viral clearance, were lower in north-western Argentina when compared with central Argentina. The same uneven frequency rates were observed for SNP rs9277542. CONCLUSIONS: This is the first study addressing the associations between the HLA-DP and HLA-DQ loci and the protection against chronic HBV and viral clearance in a multiethnic South American population. The uneven distribution of HLA-DP and HLA-DQ supports the HBV epidemiological differences observed in these two regions of Argentina with dissimilar ancestry genetic background.

[Experience with a rheumatoid arthritis biobank: analysis of biological samples and clinical data of 204 patients]. / Rheumatoid arthritises biobankkal szerzett tapasztalataink: 204 beteg biológiai mintáinak és klinikai adatainak összevetése.

INTRODUCTION: A biobank is a registry, which is suitable for the storage of biological samples (e.g. tissues, DNA, protein), genetical abnormalities and clinical data. Several biobanks have been created worldwide, which contribute to research and the better understanding of disease pathogenesis, genetical polymorphisms. Biobanking also helps to improve the efficacy of therapies. AIM: Our purpose was to create an internet-based biobank, in which laboratory test results, genetic alterations and related disorders of rheumatoid arthritis (RA) patients can be registered. This biobank would be able to make the research easier and it can help to improve our knowledge about diseases and it can inhibit loss of data. PATIENTS AND METHOD: We have biological samples from 204 RA patients and we have entered their data in the biobank which can be found on the website http://rheuma.biobank.eu . Statistical analysis was performed by SPSS20 statistical programme. RESULTS: By the creation of biobank that contains clinical data and biological samples of 204 RA patients, we have a database which can help to improve our knowledge about the disease and help to develop new treatment strategies. CONCLUSION: Biobanking is suitable to analyze blood samples and clinical data together. Orv. Hetil., 2017, 158(7), 270-277.

Single-cell transcriptome profiling reveals cell type-specific variation and development in HLA expression of human skin.

Skin, the largest organ of body, is a highly immunogenic tissue with a diverse collection of immune cells. Highly polymorphic human leukocyte antigen (HLA) molecules have a central role in coordinating immune responses as recognition molecules. Nevertheless, HLA gene expression patterns among diverse cell types within a specific organ, like the skin, have yet to be thoroughly investigated, with stromal cells attracting much less attention than immune cells. To illustrate HLA expression profiles across different cell types in the skin, we performed single-cell RNA sequencing (scRNA-seq) analyses on skin datasets, covering adult and fetal skin, and hair follicles as the skin appendages. We revealed the variation in HLA expression between different skin populations by examining normal adult skin datasets. Moreover, we evaluated the potential immunogenicity of multiple skin populations based on the expression of classical HLA class I genes, which were well represented in all cell types. Furthermore, we generated scRNA-seq data of developing skin from fetuses of 15 post conception weeks (PCW), 17 PCW, and 22 PCW, delineating the dynamic expression of HLA genes with cell type-dependent variation among various cell types during development. Notably, the pseudotime trajectory analysis unraveled the significant variance in HLA genes during the evolution of vascular endothelial cells. Moreover, we uncovered the immune-privileged properties of hair follicles at single-cell resolution. Our study presents a comprehensive single-cell transcriptomic landscape of HLA genes in the skin, which provides new insights into variation in HLA molecules and offers a clue for allogeneic skin transplantation.

Biomarkers of Innate Immunity and Immunological Susceptibility to Viral Infection in Patients with Alcoholic Cirrhosis.

BACKGROUND: The harmful effect of alcohol on the immune system may be due to both a direct action of the alcohol or its metabolites on immune cells as an indirect action modifying the different mechanisms of intercellular interaction. The interplay between stimulatory (aKIR) and inhibitory (iKIR) natural killer (NK) cell receptors and their corresponding human leukocyte antigen (HLA) ligands influences the outcome of virus infection. The aim was to analyze the influence of the KIR/HLA pair genetic profile in male alcoholic cirrhosis (AC) patients with and without viral infections to find susceptibility biomarkers that can help establish the risks and prevent viral infections. METHODS: A total of 281 male AC patients were analyzed. The sociodemographic characteristics, viral hepatitis C (HCV), hepatitis B (HBV), and cytomegalovirus (CMV) infections were analyzed. Genomic DNA was extracted, and genetic the KIR/HLA profiles were investigated. A total of 6 KIR genes and their corresponding ligands (HLA-C) were analyzed. Patients were grouped into two groups: with and without associated viral infection. RESULTS: A statistically significant increase in the combination of KIR2DL2+/C1C1 was observed in male AC patients with viral infection compared to those without viral infection (45.9% vs. 24.5%, p = 0.021). The analysis of KIR2DL3+/C1+ showed a high frequency comparing healthy controls and male AC patients without virus infection (85% vs. 76.4%; p = 0.026). The analysis of KIR2DL3+/C2C2 frequency showed a statistically significant increase comparing male AC patients without viral infection and healthy controls (23.6% vs. 15%; p = 0.026). CONCLUSIONS: The genetic KIR2DL2+/C2C2 profiles may play a significant role in determining the vulnerability of male AC patients to viral infections, providing valuable insights for future research and potential therapeutic interventions.

Preliminary Data on SNP of Transplantation-Related Genes after Haploidentical Stem Cell Transplantation.

Background: Hematopoietic stem cell transplantation (HSCT) is one of the mainstream treatments for patients with hematologic malignancies. The matching status of human leukocyte antigen (HLA) between the donor and recipient is highly related to the outcomes of HSCT. Haploidentical HSCT (haplo-HSCT) has emerged as a type of HSCT for patients who cannot find a fully HLA-matched donor. In this study, we investigated whether the single nucleotide polymorphisms (SNPs) of the HLA-related genes and the genes encoding co-stimulatory molecules located on the non-HLA region are related to the outcomes of haplo-HSCT. Methods: The genomic DNAs of 24 patients and their respective donors were isolated from the peripheral blood obtained before performing haplo-HSCT. A total of 75 SNPs of the HLA-related genes (HCP5, NOTCH4, HLA-DOA, LTA, HSPA1L, BAG6, RING1, TRIM27, and HLA-DOB) and the genes located in the non-HLA genes involved in co-stimulatory signaling (CTLA4, TNFSF4, CD28, and PDCD1) were selected to explore their relationship with the outcomes after haplo-HSCT, including graft-versus-host disease, survival status, and relapse. Results: Our data revealed that specific donor or patient SNPs, including rs79327197 of the HLA-DOA gene, rs107822 and rs213210 of the RING1 gene, rs2523676 of the HCP5 gene, rs5742909 of the CTLA4 gene, rs5839828 and rs36084323 of the PDCD1 gene, and rs1234314 of the TNFSF4 gene, were significantly related to the development of adverse outcomes post-haplo-HSCT. Conclusions: These SNPs may play important roles in post-transplant immune response that can be considered during the selection of suitable donors.

HLA Genes: A Hallmark of Functional Genetic Variation and Complex Evolution.

The major histocompatibility complex (MHC) with its highly polymorphic HLA genes represents one of the most intensely studied genomic regions in the genome. MHC proteins play a key role in antigen-specific immunity and are associated with a wide range of complex diseases. Despite decades of research and many advances in the field, the characterization and interpretation of its genetic and genomic variability remain challenging. Here an overview is provided of the MHC, the nature of its exceptional variability, and the complex evolutionary processes assumed to drive this variability. Highlighted are also recent advances in the field that promise to improve our understanding of the variability in the MHC and in antigen-specific immunity more generally.

DNA structural features and variability of complete MHC locus sequences.

The major histocompatibility (MHC) locus, also known as the Human Leukocyte Antigen (HLA) genes, is located on the short arm of chromosome 6, and contains three regions (Class I, Class II and Class III). This 5 Mbp locus is one of the most variable regions of the human genome, yet it also encodes a set of highly conserved and important proteins related to immunological response. Genetic variations in this region are responsible for more diseases than in the entire rest of the human genome. However, information on local structural features of the DNA is largely ignored. With recent advances in long-read sequencing technology, it is now becoming possible to sequence the entire 5 Mbp MHC locus, producing complete diploid haplotypes of the whole region. Here, we describe structural maps based on the complete sequences from six different homozygous HLA cell lines. We find long-range structural variability in the different sequences for DNA stacking energy, position preference and curvature, variation in repeats, as well as more local changes in regions forming open chromatin structures, likely to influence gene expression levels. These structural maps can be useful in visualizing large scale structural variation across HLA types, in particular when this can be complemented with epigenetic signals.

How HLA diversity is apportioned: influence of selection and relevance to transplantation.

In his 1972 paper 'The apportionment of human diversity', Lewontin showed that, when averaged over loci, genetic diversity is predominantly attributable to differences among individuals within populations. However, selection can alter the apportionment of diversity of specific genes or genomic regions. We examine genetic diversity at the human leucocyte antigen (HLA) loci, located within the major histocompatibility complex (MHC) region. HLA genes code for proteins that are critical to adaptive immunity and are well-documented targets of balancing selection. The single-nucleotide polymorphisms (SNPs) within HLA genes show strong signatures of balancing selection on large timescales and are broadly shared among populations, displaying low FST values. However, when we analyse haplotypes defined by these SNPs (which define 'HLA alleles'), we find marked differences in frequencies between geographic regions. These differences are not reflected in the FST values because of the extreme polymorphism at HLA loci, illustrating challenges in interpreting FST. Differences in the frequency of HLA alleles among geographic regions are relevant to bone-marrow transplantation, which requires genetic identity at HLA loci between patient and donor. We discuss the case of Brazil's bone marrow registry, where a deficit of enrolled volunteers with African ancestry reduces the chance of finding donors for individuals with an MHC region of African ancestry. This article is part of the theme issue 'Celebrating 50 years since Lewontin's apportionment of human diversity'.

Construction of an HLA Classifier for Early Diagnosis, Prognosis, and Recognition of Immunosuppression in Sepsis by Multiple Transcriptome Datasets.

Background: Sepsis is a clinical syndrome, due to a dysregulated inflammatory response to infection. Accumulating evidence shows that human leukocyte antigen (HLA) genes play a key role in the immune responses to sepsis. Nevertheless, the effects of HLA genes in sepsis have still not been comprehensively understood. Methods: A systematical search was performed in the Gene Expression Omnibus (GEO) and ArrayExpress databases from inception to 10 September 2021. Random forest (RF) and modified Lasso penalized regression were conducted to identify hub genes in multi-transcriptome data, thus we constructed a prediction model, namely the HLA classifier. ArrayExpress databases, as external validation, were utilized to evaluate its diagnostic, prognostic, and predictive performance. Immune cell infiltration score was calculated via CIBERSORTx tools and single-sample gene set enrichment analysis (ssGSEA). Gene set variation analysis (GSVA) and ssGSEA were conducted to determine the pathways that are significantly enriched in different subgroups. Next, we systematically correlated the HLA classifier with immunological characteristics from multiple perspectives, such as immune-related cell infiltration, pivotal molecular pathways, and cytokine expression. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to validate the expression level of HLA genes in clinical samples. Results: A total of nine datasets comprising 1,251 patients were included. Based on RF and modified Lasso penalized regression in multi-transcriptome datasets, five HLA genes (B2M, HLA-DQA1, HLA-DPA1, TAP1, and TAP2) were identified as hub genes, which were used to construct an HLA classifier. In the discovery cohort, the HLA classifier exhibited superior diagnostic value (AUC = 0.997) and performed better in predicting mortality (AUC = 0.716) than clinical characteristics or endotypes. Encouragingly, similar results were observed in the ArrayExpress databases. In the E-MTAB-7581 dataset, the use of hydrocortisone in the HLA high-risk subgroup (OR: 2.84, 95% CI 1.07-7.57, p = 0.037) was associated with increased risk of mortality, but not in the HLA low-risk subgroup. Additionally, immune infiltration analysis by CIBERSORTx and ssGSEA revealed that B cells, activated dendritic cells, NK cells, T helper cells, and infiltrating lymphocytes (ILs) were significantly richer in HLA low-risk phenotypes, while Tregs and myeloid-derived suppressor cells (MDSCs) were more abundant in HLA high-risk phenotypes. The HLA classifier was significantly negatively correlated with B cells, activated dendritic cells, NK cells, T helper cells, and ILs, yet was significantly positively correlated with Tregs and MDSCs. Subsequently, molecular pathways analysis uncovered that cytokine-cytokine receptor (CCR) interaction, human leukocyte antigen (HLA), and antigen-presenting cell (APC) co-stimulation were significantly enriched in HLA low-risk endotypes, which was significantly negatively correlated with the HLA classifier in multi-transcriptome data. Finally, the expression levels of several cytokines (IL-10, IFNG, TNF) were significantly different between the HLA subgroups, and the ratio of IL-10/TNF was significantly positively correlated with HLA score in multi-transcriptome data. Results of qRT-PCR validated the higher expression level of B2M as well as lower expression level of HLA-DQA1, HLA-DPA1, TAP1, and TAP2 in sepsis samples compared to control sample. Conclusion: Based on five HLA genes, a diagnostic and prognostic model, namely the HLA classifier, was established, which is closely correlated with responses to hydrocortisone and immunosuppression status and might facilitate personalized counseling for specific therapy.

Single-Nucleotide Polymorphisms Within Non-HLA Regions Are Associated With Engraftment Effectiveness for Patients With Unrelated Cord Blood Transplantation.

Clinically, stem cells with matched human leukocyte antigens (HLAs) must be selected for allogeneic transplantation to avoid graft rejection. However, adverse reactions still occur after cord blood transplantation (CBT). It was inferred that the HLA system is not the only regulatory factor that may influence CBT outcomes. Therefore, we plan to investigate whether the single-nucleotide polymorphisms (SNPs) located in non-HLA genes are associated with the effectiveness of CBT. In this study, the samples of 65 donors from CBT cases were collected for testing. DNA sequencing was focused on the SNPs of non-HLA genes, cytotoxic T-lymphocyte-associated protein 4 (CTLA4), CD28, tumor necrosis factor ligand superfamily 4 (TNFSF4), and programmed cell death protein 1 (PDCD1), which were selected in regard to the literatures published in 2017 and 2018, which indicated that they were related to stem cell transplantation. Then, in combination with the detailed follow-up transplantation tracking database, these SNPs were analyzed with the risk of mortality, relapse, cytomegalovirus (CMV) infection, and graft-versus-host disease (GVHD). We found that there were 2 SNPs of CTLA4, 1 SNP of TNFSF4, and 2 SNPs of PDCD1 associated with the effectiveness of unrelated CBT. These statistically significant SNPs and haplotypes would be used in clinical to choose the best donor for the patient receiving CBT. Moreover, the polygenic risk scores (PRSs) with these SNPs could be used to predict the risk of CBT adverse reactions with an area under the receiver operating characteristic curve (AUC) of 0.7692. Furthermore, these SNPs were associated with several immune-related diseases or cancer susceptibility, which implied that SNPs play an important role in immune regulation.

The gut microbiome molecular mimicry piece in the multiple sclerosis puzzle.

The etiological complexity of multiple sclerosis, an immune-mediated, neurodegenerative disease with multifactorial etiology is still elusive because of an incomplete understanding of the complex synergy between contributing factors such as genetic susceptibility and aberrant immune response. Recently, the disease phenotypes have also been shown to be associated with dysbiosis of the gut microbiome, a dynamic reservoir of billions of microbes, their proteins and metabolites capable of mimicring the autoantigens. Microbial factors could potentially trigger the neuroinflammation and symptoms of MS. In this perspective article, we discussed how microbial molecules resulting from a leaky gut might mimic a host's autoantigen, potentially contributing to the disease disequilibrium. It further highlights the importance of targeting the gut microbiome for alternate therapeutic options for the treatment of MS.

Pharmacogenetic and Association Studies on the Influence of HLA Alleles and Rivastigmine on the Iranian Patients with Late-Onset Alzheimer's Disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting cognitive function. A number of allelic genes from HLA complex have shown variable associations with AD in different populations. In this study, we investigated the association of DQB1*06:00/x, DRB1*04:00/x, DRB1*15:00/x, and B*07:00/x genotypes with AD and their relevance to the efficacy of rivastigmine treatment in the Iranian population. Our findings suggest that DQB1*06:00/x genotype offers strong protection against AD (P = 0.0074), while B*07:00/x genotype imposes a significant susceptibility for sporadic Alzheimer's disease (SAD) (P = 0.009). Interestingly, B*07:00/x genotype does not show any apparent associations with familial Alzheimer's disease (FAD). Our studies also suggest a pharmacogenetic relationship between drug treatment and presence of a particular genotype in the Iranian LOAD patient population. The Clinical Dementia Rating analysis showed that LOAD patients carrying DRB1*04:00/x genotype tend to display a downward trend in the disease severity and symptoms after 2-year follow-up with rivastigmine treatment. Moreover, in our total patient population, the carriers of DQB1*06:00/x and B*07:00/x alleles have better and worse responses to rivastigmine respectively. We also measured the clinical relevance of the testing for these genotypes employing prevalence-corrected positive predictive value (PcPPV) formula. The PcPPV of testing for DQB1*06:00/x in the Iranian LOAD patients was 1.17% which means that people carrying this genotype have half of the probability of the absolute risk for developing LOAD, whereas the PcPPV of testing for B*07:00/x was 4.45% for SAD, which can be interpreted as a doubling chance for developing LOAD among the Iranian population carrying this genotype. These results also suggest that DQß1 peptide containing positively charged AAs histidine30 and arginine55 and HLA class I ß chain containing negatively charges aspartic acid114 and glutamic acid45,152 in their binding groove plays important roles in protection against and susceptibility for LOAD respectively.

Identical twins with idiopathic membranous nephropathy.

The pathogenesis of idiopathic membranous nephropathy is associated with autoantibodies, most often against the phospholipase A2 receptor (PLA2R) and with genetic factors, especially those involving human leukocyte antigen (HLA) genes. Idiopathic membranous nephropathy is not a typical inherited Mendelian disorder. Reports of idiopathic membranous nephropathy in twins are rare. Herein, we report on two twin sisters diagnosed with PLA2R-associated idiopathic membranous nephropathy. We identified the HLA-DRB1*0301, HLA-DRB1*1501, and HLA-DQB1*0602 alleles in the twin sisters, which were reported as independent risk alleles for idiopathic membranous nephropathy in the Asian population. This case report provides novel evidence for the role of predisposing HLA alleles in the pathogenesis of idiopathic membranous nephropathy.

TNF-α and α-synuclein fibrils differently regulate human astrocyte immune reactivity and impair mitochondrial respiration.

Here, we examine the cellular changes triggered by tumor necrosis factor alpha (TNF-α) and different alpha-synuclein (αSYN) species in astrocytes derived from induced pluripotent stem cells. Human astrocytes treated with TNF-α display a strong reactive pro-inflammatory phenotype with upregulation of pro-inflammatory gene networks, activation of the nuclear factor κB (NF-κB) pathway, and release of pro-inflammatory cytokines, whereas those treated with high-molecular-weight αSYN fibrils acquire a reactive antigen (cross)-presenting phenotype with upregulation of major histocompatibility complex (MHC) genes and increased human leukocyte antigen (HLA) molecules at the cell surface. Surprisingly, the cell surface location of MHC proteins is abrogated by larger F110 fibrillar polymorphs, despite the upregulation of MHC genes. Interestingly, TNF-α and αSYN fibrils compete to drive the astrocyte immune reactive response. The astrocyte immune responses are accompanied by an impaired mitochondrial respiration, which is exacerbated in Parkinson's disease (PD) astrocytes. Our data provide evidence for astrocytic involvement in PD pathogenesis and reveal their complex immune reactive responses to exogenous stressors.