Fine-mapping analysis of the MHC region for vitiligo based on a new Han-MHC reference panel

Update on the pathogenesis of vitiligo

Vitiligo is a complex disease whose pathogenesis results from the interaction of genetic components, metabolic factors linked to cellular oxidative stress, melanocyte adhesion to the epithelium, and immunity (innate and adaptive), which culminate in aggression against melanocytes. In vitiligo, melanocytes are more sensitive to oxidative damage, leading to the increased expression of proinflammatory proteins such as HSP70. The lower expression of epithelial adhesion molecules, such as DDR1 and E-cadherin, facilitates damage to melanocytes and exposure of antigens that favor autoimmunity. Activation of the type 1-IFN pathway perpetuates the direct action of CD8+ cells against melanocytes, facilitated by regulatory T-cell dysfunction. The identification of several genes involved in these processes sets the stage for disease development and maintenance. However, the relationship of vitiligo with environmental factors, psychological stress, comorbidities, and the elements that define individual susceptibility to the disease are a challenge to the integration of theories related to its pathogenesis.

Fine Mapping Analysis of the MHC Region to Identify Variants Associated With Chinese Vitiligo and SLE and Association Across These Diseases

The important role of MHC in the pathogenesis of vitiligo and SLE has been confirmed in various populations. To map the most significant MHC variants associated with the risk of vitiligo and SLE, we conducted fine mapping analysis using 1117 vitiligo cases, 1046 SLE cases and 1693 healthy control subjects in the Han-MHC reference panel and 1000 Genomes Project phase 3. rs113465897 (P=1.03×10^-13, OR=1.64, 95%CI =1.44–1.87) and rs3129898 (P=4.21×10^-17, OR=1.93, 95%CI=1.66–2.25) were identified as being most strongly associated with vitiligo and SLE, respectively. Stepwise conditional analysis revealed additional independent signals at rs3130969(p=1.48×10^-7, OR=0.69, 95%CI=0.60–0.79), HLA-DPB1*03:01 (p=1.07×10^-6, OR=1.94, 95%CI=1.49–2.53) being linked to vitiligo and HLA-DQB1*0301 (P=4.53×10^-7, OR=0.62, 95%CI=0.52-0.75) to SLE. Considering that epidemiological studies have confirmed comorbidities of vitiligo and SLE, we used the GCTA tool to analyse the genetic correlation between these two diseases in the HLA region, the correlation coefficient was 0.79 (P=5.99×10^-10, SE=0.07), confirming their similar genetic backgrounds. Our findings highlight the value of the MHC region in vitiligo and SLE and provide a new perspective for comorbidities among autoimmune diseases.

Fine-Mapping of the Major Histocompatibility Complex Region Linked to Leprosy in Northern China

Background: Leprosy is a chronic infectious skin and neurological disease, and genetic background is considered to be one of the major factors of risk. The major histocompatibility complex (MHC) region not only affects susceptibility to leprosy but also its development and outcome. Given the complex traits of the MHC region, variants and the potential mechanism by which HLA influences leprosy development need to be further explored.

Methods: We extracted previous genome-wide association study data from the Northern Han Chinese population to perform HLA fine-mapping. Using the 1,000 Genome Project Phase 3 dataset as the reference panel, single-nucleotide polymorphisms (SNP), insertion and deletion (INDEL) and copy number variant (CNV) imputation were carried out. HLA classical alleles and amino acids in the MHC region were imputed using the HAN-MHC database. Further stepwise regression analysis was conducted to analyze independent signals of variants related to leprosy.

Results: We identified four independent variants: esv3608598, rs7754498, rs3130781 and rs144388449. Among them, esv3608598 is a CNV and the first HLA CNV associated with leprosy risk. SNP annotation using RegulomeDB, HaploReg, and rVarBase showed that three SNPs are likely to affect the pathogenesis of leprosy.

Conclusion: In summary, this is the first study to assess the association between HLA CNV and leprosy susceptibility in a Northern Han Chinese population. By fine mapping of the MHC region in this population, our findings provide evidence for the contribution of HLA to leprosy susceptibility.

Efficacy of topical calcipotriol betamethasone dipropionate as a new adjuvant therapy to follicular unit extraction technique in treatment of stable vitiligo: clinical, dermoscopic and immunohistological study

BACKGROUND

Follicular unit extraction (FUE) grafting is a surgical procedure which provides the vitiliginous patches with undifferentiated stem cells of the hair follicles. It has been postulated that adjuvant therapy enhances the results. This is the first study to assess two different adjuvant therapies vs FUE alone.

AIMS

To study the efficiency of FUE alone or combined with either topical calcipotriol betamethasone dipropionate (CBD) or NB-UVB phototherapy in cases of nonsegmental stable vitiligo. To assess the role of dermoscopy in monitoring the pattern and degree of repigmentation.

PATIENTS/ METHODS

53 patients with 94 lesions with stable nonsegmental vitiligo were divided into three groups. Group 1 (n = 16) with 30 lesions received FUE alone. Group 2 (n = 18) with 32 lesions received FUE plus topical CBD. Group 3 (n = 19) with 32 lesions received FUE plus NB-UVB phototherapy. Assessment was done by grades of repigmentation, color match, percent of size reduction, and immunohistochemical evaluation of perilesional CD8+T lymphocytes.

RESULTS

The fastest onset of repigmentation was observed in both groups 2 and 3 in the second week (16.7%, 10.5%, respectively).Group 2 achieved the best response by all methods of assessment. Perifollicular diffuse repigmentation was the commonest dermoscopic pattern in 60 lesions (63.8%). There was a statistically significant decrease in perilesional CD8+T lymphocytes after 4 months.

CONCLUSION

FUE is an effective method of surgical treatment of stable vitiligo, and topical CBD as a new adjuvant therapy is successful in targeting the immunological background of vitiligo. Dermoscopy has an essential role in monitoring the repigmentation response.

Vitiligo Skin Biomarkers Associated With Favorable Therapeutic Response

Vitiligo is an acquired depigmentation skin disease caused by immune-mediated death of melanocytes. The most common treatment for vitiligo is narrow band ultraviolet B phototherapy, which often is combined with topical therapies such as tacrolimus. However, patients' responses to these treatments show large variations. To date, the mechanism for this heterogeneity is unknown, and there are no molecular indicators that can predict an individual patient's response to therapy. The goal of this study is to identify clinical parameters and gene expression biomarkers associated with vitiligo response to therapy. Six patients with segmental vitiligo and 30 patients with non-segmental vitiligo underwent transcriptome sequencing of lesional and nonlesional skin at baseline before receiving combined UBUVB and tacrolimus therapy for 6 month, and were separated into good response and bad response groups based on target lesion achieving > 10% repigmentation or not. Our study revealed that treatment-responsive vitiligo lesions had significantly shorter disease duration compared with non-responsive vitiligo lesions (2.5 years vs 11.5 years, p=0.046, t-Test), while showing no significant differences in the age, gender, ethnicity, vitiligo subtype, or disease severity. Transcriptomic analyses identified a panel of 68 genes separating the good response from bad response lesions including upregulation of immune active genes, such as CXCL10, FCRL3, and TCR, Further, compared with vitiligo lesions with long disease duration, the lesions with short duration also have much higher level of expression of immune-active genes, including some (such as FCRL3 and TCR genes) that are associated with favorable therapeutic response. In conclusion, our study has identified clinical parameters such as short disease duration and a panel of immune active and other gene expression biomarkers that are associated with favorable response to immune suppressive NBUVB + tacrolimus therapy. These markers may be useful clinically for individualized therapeutic management of vitiligo patients in the future.

The Genetic Basis of Vitiligo

Vitiligo is a complex disease in which autoimmune destruction of epidermal melanocytes results in patches of depigmented white skin. Vitiligo has an estimated prevalence of about 0.2-2% in different populations and approximately 0.4% in the European-derived white (EUR) population. The fraction of disease risk attributable to genetic variation, termed heritability, is high, with estimates from family studies in EUR of 0.75-0.83 and from SNP based studies estimated at 0.78. About 70% of genetic risk comes from common genetic variants and about 30% from rare genetic variants. Through candidate gene, genomewide linkage, and genomewide association studies, over 50 vitiligo susceptibility loci have been discovered. These have been combined into a vitiligo polygenic risk score, which has allowed various aspects of vitiligo genetic architecture in the EUR population to be better understood. Vitiligo has thus proved to be a particularly tractable model for investigation of complex disease genetic architecture. Here, we summarize progress to date including dissection of heritability, discovery of vitiligo susceptibility loci through candidate gene, genomewide linkage, and genomewide association studies, relationships to other autoimmune diseases, polygenic architecture of vitiligo risk, vitiligo triggering, and disease onset, and provide suggestions for future directions.

HLA-G Polymorphisms Are Associated with Non-segmental Vitiligo among Brazilians

(1) Background: Vitiligo is characterized by white patches on the skin caused by loss of melanocyte activity or the absence of these cells. The available treatments minimize the symptoms by retarding the process of skin depigmentation or re-pigmenting the affected regions. New studies are required for a better comprehension of the mechanisms that trigger the disease and for the development of more efficient treatments. Studies have suggested an autoimmune feature for vitiligo, based on the occurrence of other autoimmune diseases in vitiligo patients and their relatives, and on the involvement of genes related to the immune response. (2) Methods: We evaluated, by massive parallel sequencing, polymorphisms of the HLA-G gene in vitiligo patients and control samples, to verify if variants of this gene could influence the susceptibility to vitiligo. (3) Results: We detected an association with non-segmental vitiligo regarding the haplotype Distal-010101a/G*01:01:01:01/UTR-1, adjusting for population stratification by using ancestry-informative markers (AIMs). (4) Conclusions: It remains unclear whether the HLA-G variants associated with vitiligo were detected because of the high linkage disequilibrium (LD) with HLA-A*02, or if the HLA-A variants previously reported as associated with vitiligo were detected because of the high LD with HLA-G*01:01:01:01/UTR-1, or if both genes jointly contribute to vitiligo susceptibility.

Autoreactive T-Lymphocytes in Inflammatory Skin Diseases

The presence of one or several autoantigen(s) and a response by the adaptive immune system are the key criteria to classify a pathology as an autoimmune disease. The list of entities fulfilling this criterion is currently growing in the light of recent advancements in the pathogenetic understanding of a number of important dermatoses. The role of autoreactive T-lymphocytes differs amongst these pathologies. While they are directly involved as effector cells attacking and sometimes killing their respective target in some diseases (e.g., vitiligo), they provide help to B-lymphocytes, which in turn produce the pathogenic autoreactive antibodies in others (pemphigus and pemphigoid). Atopic dermatits is a chimera in this regard, as there is evidence for both functions. Psoriasis is an example for an entity where autoantigens were finally identified, suggesting that at least a subgroup of patients should be classified as suffering from a true autoimmune rather than autoinflammatory condition. Identification of resident memory T-lymphocytes (T_RM) helped to understand why certain diseases relapse at the same site after seemingly effective therapy. Therefore, the in-depth characterization of autoreactive T-lyphocytes goes way beyond an academic exercise and opens the door toward improved therapies yielding durable responses. T_RM are particularly suitable targets in this regard, and the clinical efficacy of some established and emerging therapeutic strategies such as the inhibition of Janus Kinase 3 or interleukin 15 may rely on their capacity to prevent T_RM differentiation and maintenance. Research in this field brings us closer to the ultimate goal in the management of autoimmunity at large, namely resetting the immune system in order to restore the state of tolerance.

VitiVar: A locus specific database of vitiligo associated genes and variations

Vitiligo is the most common skin pigmentation disorder which affects around 1% of the population worldwide. The disease has complex pathogenesis and is of multifactorial etiology, that finally culminates in patchy depigmentation of skin. Genetic contribution to the disease is well studied, however the information about multiple associated genes and contributing variations are scattered across the literature. To address this complex disorder affecting the skin, we systematically cataloged the genes and variations by creating a Locus Specific Database for vitiligo called, “VitiVar”. This comprehensive resource houses manually curated 322 genes and 254 variations, from 202 articles indexed in PubMed. We applied an integrative approach to stratify genes and variations to facilitate dissection of vitiligo pathogenesis by layering it with expression status in specific constituent cell types of skin and in-house vitiligo expression data. Finally, we were able to demonstrate the utility of VitiVar by generating a vitiligo interactome using GeneMANIA and overlaying the vitiligo and cell type specific information. This interaction network yielded 20 new genes (apart from 322 VitiVar genes) of which we were able to prioritize IFI27 and IFI6 for further validation. This, thereby makes VitiVar a comprehensive integrative platform in unravelling disease biology by providing meaningful leads for functional interrogation. VitiVar is freely accessible to the research community for prioritizing and validating the candidate genes and variations (http://vitivar.igib.res.in/).

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We developed a Vitiligo centric web resource cataloguing the associated genes and variations

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Overlaid the information of cell type specificity and expression status in Vitiliginous skin

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Utilizing the network approach, we prioritized IFI6 & IFI27 which could be functionally interrogated in disease pathology

HLA Class II Genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 Are Associated With the Antibody Response to Inactivated Japanese Encephalitis Vaccine

Aim: The objective of this study was to evaluate the association of the human leukocyte antigen (HLA) class II genes HLA-DRB1, HLA-DPB1, and HLA-DQB1 with the humoral immune response elicited by inactivated Japanese encephalitis (JE) vaccine (IJEV).

Methods: A total of 373 individuals aged 3–12 years in the Inner Mongolia Autonomous Region in China, who received two doses of IJEV at 0 and 7 days, were enrolled in the current study. Based on the individuals' specific JE virus (JEV)-neutralizing antibodies (NAbs), they were divided into a seropositive and a seronegative group. HLA-DRB1, HLA-DPB1, and HLA-DQB1 were genotyped using a sequencing-based typing method. Next, the association of the HLA class II genes and their haplotypes with antibody response was evaluated.

Results: Based on NAbs, a total of 161 individuals were classified as seropositive and 212 as seronegative. DQB1^*02:01 was significantly associated with JEV seropositivity (P < 0.001, OR = 0.364, 95% CI: 0.221–0.600), while DQB1^*02:02 was significantly associated with JEV seronegativity (P = 5.03 × 10⁻⁶, OR = 7.341, 95% CI: 2.876–18.736). The haplotypes DRB1^*07:01-DPB1^*04:01-DQB1^*02:01, DRB1^*15:01-DPB1^*02:01-DQB1^*06:02, DRB1^*07:01-DQB1^*02:01, and DPB1^*02:01-DQB1^*06:02 were very frequent in the seropositive group, while DRB1^*07:01-DPB1^*17:01-DQB1^*02:02, DRB1^*07:01-DQB1^*02:02, and DPB1^*17:01-DQB1^*02:02 were very frequent in the seronegative group. The presence of DRB1^*01:01, DRB1^*04:05, DRB1^*09:01, DRB1^*12:02, DRB1^*13:02, and DRB1^*14:01 was associated with a higher geometric mean titer (GMT) of NAbs than that of DRB1^*11:01 at the DRB1 locus (P < 0.05). At the DPB1 locus, the presence of DPB1^*05:01 was associated with higher GMTs than that of DPB1^*02:01 and DPB1^*13:01 (P < 0.05), and the presence of DPB1^*04:01 and DPB1^*09:01 was associated with higher GMTs than that of DPB1^*13:01 (P < 0.05).

Conclusions: The present study suggests that HLA class II genes may influence the antibody response to IJEV.