Association of class I and II HLA alleles and haplotypes with susceptibility to vitiligo: a study of patients with vitiligo from southeast Brazil

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.

The Immunogenetics of Vitiligo: An Approach Toward Revealing the Secret of Depigmentation

Vitiligo is a hypomelanotic skin disease and considered to be of autoimmune origin due to breaching of immunological self-tolerance, resulting in inappropriate immune responses against melanocytes. The development of vitiligo includes a strong heritable component. Different strategies ranging from linkage studies to genome-wide association studies are used to explore the genetic factors responsible for the disease. Several vitiligo loci containing the respective genes have been identified which contribute to vitiligo and genetic variants for some of the genes are still unknown. These genes include mainly the proteins that play a role in immune regulation and a few other genes important for apoptosis and regulation of melanocyte functions. Despite the available data on genetic variants and risk alleles which influence the biological processes, only few immunological pathways have been found responsible for all ranges of severity and clinical manifestations of vitiligo. However, studies have concluded that vitiligo is of autoimmune origin and manifests due to complex interactions in immune components and their inappropriate response toward melanocytes. The genes involved in the immune regulation and processing the melanocytes antigen and its presentation can serve as effective immune-therapeutics that can target specific immunological pathways involved in vitiligo. This chapter highlights those immune-regulatory genes involved in vitiligo susceptibility and loci identified to date and their implications in vitiligo pathogenesis.

The relationship between non-segmental Vitiligo, HLA genotype and oxidative stress

BACKGROUND

Vitiligo is an autoimmune disease characterised by acquired loss of melanocytes. Although the pathogenesis of vitiligo remains unknown, oxidative stress and autoimmune dysregulations are considered to play a role.

OBJECTIVE

The aim of this study was to evaluate the HLA profile and total antioxidant capacity (TAC) and their relationship to clinical characteristic of vitiligo patients.

METHODS

Ninety-one vitiligo patients and 100 healthy controls were included in the study. We analysed HLA allele frequencies using sequence-specific oligonucleotide Prob (SSOP) method. Serum total antioxidant capacity (TAC) levels were measured and compared between vitiligo patients and controls.

RESULTS

HLA-A*02 allele frequency was increased (OR = 1.6, CI = 1.12-2.24, P = .009), HLA-A*11 (OR = 0.46, CI = 0.32-0.91, P = .019) and HLA-DRB1*01 (OR = 0.39, CI = 0.16-0.92, P = .029) frequencies were decreased in vitiligo patients. HLA-A*02 allele especially increased the risk of late onset (Vitiligo onset >30 years of age) vitiligo (OR:3.67, 95% CI: 1.63-8.26, P = .002). Serum TAC levels were similar between vitiligo patients and healthy controls but TAC levels were significantly lower in patients who did not have an HLA-DRB1*01 allele (1.52 vs 1.61, P = .033).

CONCLUSION

Our study showed that HLA-A*02 increases, HLA-A*11 and HLA-DRB1*01 decreases vitiligo susceptibility in Turkish patients as well as a possible relationship between HLA and TAC.

Novel findings of HLA association with anti-LGI1 encephalitis: HLA-DRB1*03:01 and HLA-DQB1*02:01

This study was to investigate whether autoimmune encephalitis is associated with the human leukocyte antigen (HLA) genotypes in Chinese Han population. We compared and analyzed the HLA genotypes of 101 patients with autoimmune encephalitis (77 anti-NMDAR, 11 anti-LGI1 and 13 anti-GABA_BR antibody, respectively) to the 200 healthy control groups. Our results showed that the DRB1*03:01 or DQB1*02:01 allele and the extended DRB1*03:01 ~ DQB1*02:01 haplotype represented the strong susceptibility locus for anti-LGI1 encephalitis (OR = 18.84, 95% CI = 5.01-70.89, Pc = 0.004; OR = 18.84, 95% CI = 5.01-70.89, Pc = 0.004; OR = 18.84, 95% CI = 5.01-70.89, Pc = 0.001). Additionally, the DRB1*08:03 ~ DQB1*06:01 or B*08:01 ~ C*07:02 haplotype was likely to be associated with anti-LGI1 encephalitis (OR = 10.23, 95% CI = 2.87-36.42, Pc = 0.039; OR = 74.62, 95% CI = 6.97-799.06, Pc = 0.043). No statistically significant differences were found for HLA association between patients with anti-NMDAR or anti-GABA_BR encephalitis and healthy controls. These results indicated that HLA subtypes were only associated with anti-LGI1 encephalitis.

HLA diversity in Brazil

Brazil is the fifth largest country in the world in area and the fifth most populous. The Brazilian voluntary Bone Marrow Donor Registry is the third largest in terms of number of donors in the world, being a valuable source of HLA genetics to characterize the donor population of Brazil as well. The genetic background of the Brazilian population is quite heterogeneous, resulting from 5 centuries of admixture among Native Americans, Europeans and Africans, making the Brazilian population unique in terms of genetic ancestry. The unique characteristics of populations in different Brazilian regions make them an exciting focus for genetic diversity studies. Studies on HLA genetic diversity of Brazilian populations have been conducted since the late 1980s and, in this review, we highlight the main findings from studies carried out in Brazil based on classical HLA. In addition, we calculated the genetic distance from the molecular data of the studies included in this review in order to have a broader view of the HLA diversity in Brazilian populations. We emphasize that characterization of HLA diversity is not only important for transplantation programs, but can shed a light on ancestry, history and other demographic patterns with or without association with autoimmune disease.

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.

Evaluation of treatment response to autologous transplantation of noncultured melanocyte/keratinocyte cell suspension in patients with stable vitiligo

Background

Vitiligo is a chronic disease characterized by the appearance of achromic macules caused by melanocyte destruction. Surgical treatments with melanocyte transplantation can be used for stable vitiligo cases.

Objectives

To evaluate treatment response to the autologous transplantation of noncultured epidermal cell suspension in patients with stable vitiligo.

Methods

Case series study in patients with stable vitiligo submitted to noncultured epidermal cell suspension transplantation and evaluated at least once, between 3 and 6 months after the procedure, to observe repigmentation and possible adverse effects. The maximum follow-up period for some patients was 24 months.

Results

Of the 20 patients who underwent 24 procedures, 25% showed an excellent rate of repigmentation, 50% good repigmentation, 15% regular, and 10% poor response. The best results were observed in face and neck lesions, while the worst in extremity lesions (88% and 33% of satisfactory responses, respectively). Patients with segmental vitiligo had a better response (84%) compared to non-segmental ones (63%). As side effects were observed hyperpigmentation of the treated area and the appearance of Koebner phenomenon in the donor area.

Study limitations

Some limitations of the study included the small number of patients, a subjective evaluation, and the lack of long-term follow-up on the results. CONCLUSION: Noncultured epidermal cell suspension transplantation is efficient and well tolerated for stable vitiligo treatment, especially for segmental vitiligo on the face and neck.

Meta-Analysis of the Association between Vitiligo and Human Leukocyte Antigen-A

Objective. The objective of this study was to systematically evaluate the association between vitiligo and human leukocyte antigen- (HLA-) A. Methods. PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure, and reference lists were searched for relevant original articles. Results. Nineteen case-control studies comprising 3042 patients and 5614 controls were included, in which 33 HLA-A alleles were reported. Overall, three alleles (HLA-A^⁎02, A^⁎33, and Aw^⁎31) were significantly associated with increased risk of vitiligo, two (HLA-A^⁎09 and Aw^⁎19) were associated with decreased risk, and the remaining 28 were unassociated. Twelve alleles, seven alleles, and 19 alleles were common to three ethnicities, both types of vitiligo, and both typing methods, respectively. In the subgroup analysis by ethnicity and typing methods, the association of six alleles and five alleles was inconsistent in three populations and both typing methods, respectively. In the subgroup analysis by clinical type, the association of all seven alleles was consistent in both types of vitiligo. Conclusion. The meta-analysis suggests that HLA-A^⁎02, A^⁎33, and Aw^⁎31 are associated with increased risk of vitiligo, while HLA-A^⁎09 and Aw^⁎19 are associated with decreased risk of vitiligo. The association of some alleles varies in terms of ethnicity and typing methods.