The landscape of the immunoglobulin repertoire in endemic pemphigus foliaceus.

Introduction: Primarily driven by autoreactive B cells, pemphigus foliaceus (PF) is an uncommon autoimmune blistering skin disease of sporadic occurrence worldwide. However, PF reaches a prevalence of 3% in the endemic areas of Brazil, the highest ever registered for any autoimmune disease, which indicates environmental factors influencing the immune response in susceptible individuals. We aimed to provide insights into the immune repertoire of patients with PF living in the endemic region of the disease, compared to healthy individuals from the endemic region and a non-endemic area. Methods: We characterized the B-cell repertoire in i) nontreated patients (n=5); ii) patients under immunosuppressive treatment (n=5); iii) patients in remission without treatment (n=6); and two control groups iv) from the endemic (n=6) and v) non-endemic areas in Brazil (n=4). We used total RNA extracted from peripheral blood mononuclear cells and performed a comprehensive characterization of the variable region of immunoglobulin heavy chain (IGH) in IgG and IgM using next-generation sequencing. Results: Compared to individuals from a different area, we observed remarkably lower clonotype diversity in the B-cell immune repertoire of patients and controls from the endemic area (p < 0.02), suggesting that the immune repertoire in the endemic area is under geographically specific and intense environmental pressure. Moreover, we observed longer CDR3 sequences in patients, and we identified differential disease-specific usage of IGHV segments, including increased IGHV3-30 and decreased IGHV3-23 in patients with active disease (p < 0.04). Finally, our robust network analysis discovered clusters of CDR3 sequences uniquely observed in patients with PF. Discussion: Our results indicate that environmental factors, in addition to disease state, impact the characteristics of the repertoire. Our findings can be applied to further investigation of the environmental factors that trigger pemphigus and expand the knowledge for identifying new targeted and more effective therapies.

Genetic Association and Differential RNA Expression of Histone (De)Acetylation-Related Genes in Pemphigus Foliaceus-A Possible Epigenetic Effect in the Autoimmune Response.

Pemphigus foliaceus (PF) is an autoimmune skin blistering disease characterized by antidesmoglein-1 IgG production, with an endemic form (EPF) in Brazil. Genetic and epigenetic factors have been associated with EPF, but its etiology is still not fully understood. To evaluate the genetic association of histone (de)acetylation-related genes with EPF susceptibility, we evaluated 785 polymorphisms from 144 genes, for 227 EPF patients and 194 controls. Carriers of HDAC4_rs4852054*A were more susceptible (OR = 1.79, p = 0.0038), whereas those with GSE1_rs13339618*A (OR = 0.57, p = 0.0011) and homozygotes for PHF21A_rs4756055*A (OR = 0.39, p = 0.0006) were less susceptible to EPF. These variants were not associated with sporadic PF (SPF) in German samples of 75 SPF patients and 150 controls, possibly reflecting differences in SPF and EPF pathophysiology. We further evaluated the expression of histone (de)acetylation-related genes in CD4+ T lymphocytes, using RNAseq. In these cells, we found a higher expression of KAT2B, PHF20, and ZEB2 and lower expression of KAT14 and JAD1 in patients with active EPF without treatment compared to controls from endemic regions. The encoded proteins cause epigenetic modifications related to immune cell differentiation and cell death, possibly affecting the immune response in patients with PF.

Extracellular vesicle microRNAs in celiac disease patients under a gluten-free diet, and in lactose intolerant individuals.

BACKGROUND: Celiac disease (CD) is an autoimmune disorder triggered by an abnormal immunological response to gluten ingestion and is associated with deregulated expression of cellular microRNAs (miRNAs) of the gut mucosa. It is frequently misdiagnosed as lactose intolerance (LI) due to symptom resemblance. Microvilli loss may be counteracted by a rigorous gluten-free diet (GFD). AIMS: To identify altered extracellular vesicle miRNAs from plasma among CD patients on GFD (n=34), lactose intolerant individuals on restrictive diet (n=14) and controls (n=23), and to predict biological pathways in which these altered miRNAs may play a part. METHODS: Five different small RNA samples of each group were pooled twice and then screened by new-generation sequencing. Four miRNAs were selected to be quantified by RT-qPCR in the entire sample. RESULTS: The levels of four miRNAs - miR-99b-3p, miR-197-3p, miR-223-3p, and miR-374b-5p - differed between CD patients and controls (P<0.05). Apart from miR-223-3p, all these miRNAs tended to have altered levels also between LI and controls (P<0.10). The results for miR-99b-3p and miR-197-3p between CD and controls were confirmed by RT-qPCR, which also indicated different levels of miR-99b-3p and miR-374b-5p between CD-associated LI and LI (P<0.05). CONCLUSIONS: These miRNAs may have targets that affect cell death, cell communication, adhesion, and inflammation modulation pathways. Hence, altered miRNA levels could be associated with CD-related aspects and gut mucosa recovery.

Tracing the Distribution of European Lactase Persistence Genotypes Along the Americas.

In adulthood, the ability to digest lactose, the main sugar present in milk of mammals, is a phenotype (lactase persistence) observed in historically herder populations, mainly Northern Europeans, Eastern Africans, and Middle Eastern nomads. As the -13910∗T allele in the MCM6 gene is the most well-characterized allele responsible for the lactase persistence phenotype, the -13910C > T (rs4988235) polymorphism is commonly evaluated in lactase persistence studies. Lactase non-persistent adults may develop symptoms of lactose intolerance when consuming dairy products. In the Americas, there is no evidence of the consumption of these products until the arrival of Europeans. However, several American countries' dietary guidelines recommend consuming dairy for adequate human nutrition and health promotion. Considering the extensive use of dairy and the complex ancestry of Pan-American admixed populations, we studied the distribution of -13910C > T lactase persistence genotypes and its flanking haplotypes of European origin in 7,428 individuals from several Pan-American admixed populations. We found that the -13910∗T allele frequency in Pan-American admixed populations is directly correlated with allele frequency of the European sources. Moreover, we did not observe any overrepresentation of European haplotypes in the -13910C > T flanking region, suggesting no selective pressure after admixture in the Americas. Finally, considering the dominant effect of the -13910∗T allele, our results indicate that Pan-American admixed populations are likely to have higher frequency of lactose intolerance, suggesting that general dietary guidelines deserve further evaluation across the continent.

Genetic association and differential expression of HLAComplexGroup lncRNAs in pemphigus.

BACKGROUND: Pemphigus is a group of bullous diseases characterized by acantholysis and skin blisters. As for other autoimmune diseases, the strongest genetic associations found so far for pemphigus foliaceus (PF) and vulgaris (PV) are with alleles of HLA genes. However, apart from protein-coding genes, the MHC region includes a set of poorly explored long non-coding RNA (lncRNA) genes, the HLA complex group (HCG). OBJECTIVES: To investigate if HCG lncRNA alleles are associated with pemphigus susceptibility. METHODS AND RESULTS: We analyzed SNPs in 13 HCG lncRNA genes, both in PV (Germany: 241 patients; 1,188 controls) and endemic PF (Brazil: 227 patients; 194 controls), applying multivariate logistic regression. We found 55 associations with PV (pcorr < 0.01) and nine with endemic PF (pcorr < 0.05), the majority located in TSBP1-AS1 (which includes HCG23) and HCG27 lncRNA genes, independently of HLA alleles previously associated with pemphigus. The association of TSBP1-AS1 rs3129949*A allele was further replicated in sporadic PF (p = 0.027, OR = 0.054; 75 patients and 150 controls, all from Germany). Next, we evaluated the expression levels of TSBP1-AS1, TSBP1, HCG23, and HCG27 in blood mononuclear cells of Brazilian patients and controls. HCG27 was upregulated in endemic PF (p = 0.035, log2 FC = 1.3), while TSBP1-AS1 was downregulated in PV (p = 0.029, log2 FC = -1.29). The same expression patterns were also seen in cultured keratinocytes stimulated with IgG antibodies from patients and controls from Germany. TSBP1 mRNA levels were also decreased in endemic PF blood cells (p = 0.042, log2 FC = -2.14). TSBP1-AS1 and HCG27 were also observed downregulated in CD19+ cells of endemic PF (p < 0.01, log2 FC = -0.226 and -0.46 respectively). CONCLUSIONS: HCG lncRNAs are associated with susceptibility to pemphigus, being TSBP1-AS1 and HCG27 also differentially expressed in distinct cell populations. These results suggest a role for HCG lncRNAs in pemphigus autoimmunity.

Lack of Association between LCT_rs140433552*CA>del Indel Polymorphism and Lactose Intolerance in a Southern Brazilian Population.

BACKGROUND/AIMS: Polymorphisms in the enhancer of the lactase gene (LCT) are strongly associated with lactase persistence, but not always predictive of the phenotype. We investigated a possible association between the regulatory rs140433552*CA>del variant of LCT and lactose intolerance (LI). METHODS: We genotyped 122 individuals for rs140433552 and rs4988235 (-13910*C>T). RESULTS: Associations of rs140433552*CA>del with LI depend on -13910*C>T. Homozygous individuals for the C-CA haplotype, as well as C-CA+/C individuals, seem more likely to manifest LI (OR 3.33 [95% CI 1.32-8.35], p = 0.011, and OR 3.93 [95% CI 1.61-9.61], p = 0.003, respectively), while homozygous individuals for the T-CA haplotype seem more likely to be lactose tolerant (OR 0.04 [95% CI 0.002-0.70], p = 8 × 10-4). CONCLUSIONS: rs140433552*CA>del is not independently associated with LI.