Association of beta-defensin 1 single nucleotide polymorphisms with atopic dermatitis

When the microbiome shapes the host: immune evolution implications for infectious disease

The microbiome includes both 'mutualist' and 'pathogen' microbes, regulated by the same innate immune architecture. A major question has therefore been: how do hosts prevent pathogenic infections while maintaining beneficial microbes? One idea suggests hosts can selectively activate innate immunity upon pathogenic infection, but not mutualist colonization. Another idea posits that hosts can selectively attack pathogens, but not mutualists. Here I review evolutionary principles of microbe recognition and immune activation, and reflect on newly observed immune effector-microbe specificity perhaps supporting the latter idea. Recent work in Drosophila has found a surprising importance for single antimicrobial peptides in combatting specific ecologically relevant microbes. The developing picture suggests these effectors have evolved for this purpose. Other defence responses like reactive oxygen species bursts can also be uniquely effective against specific microbes. Signals in other model systems including nematodes, Hydra, oysters, and mammals, suggest that effector-microbe specificity may be a fundamental principle of host-pathogen interactions. I propose this effector-microbe specificity stems from weaknesses of the microbes themselves: if microbes have intrinsic weaknesses, hosts can evolve effectors that exploit those weaknesses. I define this host-microbe relationship as 'the Achilles principle of immune evolution'. Incorporating this view helps interpret why some host-microbe interactions develop in a coevolutionary framework (e.g. Red Queen dynamics), or as a one-sided evolutionary response. This clarification should be valuable to better understand the principles behind host susceptibilities to infectious diseases. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Overview of Atopic Dermatitis in Different Ethnic Groups

Atopic dermatitis (AD) is a common chronic inflammatory skin disease with a high prevalence worldwide, including countries from Asia, Africa, and Latin America, and in different ethnic groups. In recent years, more attention has been placed on the heterogeneity of AD associated with multiple factors, including a patient's ethnic background, resulting in an increasing body of clinical, genetic, epidemiologic, and immune-phenotypic evidence that delineates differences in AD among racial groups. Filaggrin (FLG) mutations, the strongest genetic risk factor for the development of AD, are detected in up to 50% of European and 27% of Asian AD patients, but very rarely in Africans. Th2 hyperactivation is a common attribute of all ethnic groups, though the Asian endotype of AD is also characterized by an increased Th17-mediated signal, whereas African Americans show a strong Th2/Th22 signature and an absence of Th1/Th17 skewing. In addition, the ethnic heterogeneity of AD may hold important therapeutic implications as a patient's genetic predisposition may affect treatment response and, thereby, a tailored strategy that better targets the dominant immunologic pathways in each ethnic subgroup may be envisaged. Nevertheless, white patients with AD represent the largest ethnicity enrolled and tested in clinical trials and the most treated in a real-world setting, limiting investigations about safety and efficacy across different ethnicities. The purpose of this review is to describe the heterogeneity in the pathophysiology of AD across ethnicities and its potential therapeutic implications.

Human beta-defensin 1 circulating level and gene polymorphism in non-segmental vitiligo Egyptian patients

BACKGROUND

Vitiligo is an acquired depigmented skin disorder. It has a genetic and autoimmune background. Human beta defensin-1(HBD-1) plus its gene polymorphism were linked to some autoimmune disorders.

OBJECTIVE

To elucidate the possible role of HBD-1 in the pathogenesis of non-segmental vitiligo (NSV) through evaluation of HBD-1 serum levels and its single nucleotide polymorphism (SNP) in patients having NSV, in addition, to correlating the results with the extent of vitiligo in those patients.

METHODS

A current case-control study included 50 patients having NSV and 50 controls. The authors used Vitiligo Area Scoring Index (VASI) score to assess vitiligo severity and laboratory investigations to assess serum HBD-1 level using ELISA and defensin-beta1 (DEFB1) SNP using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

There were significantly lower HBD-1 serum levels in NSV cases than in controls (p < 0.001). There was a significant predominance of GG DEFB1 genotype and G allele in NSV patients in comparison to controls (p < 0.001). The levels of serum HBD-1 and DEFB1 genotypes were not associated or correlated significantly with any of the personal and clinical parameters of vitiligo patients.

STUDY LIMITATION

The small sample size.

CONCLUSIONS

DEFB1 gene polymorphism (GG genotype and G allele) may modulate vitiligo risk and contribute to vitiligo development in Egyptian populations. Decreased circulating HBD-1 levels might have an active role in vitiligo etiopathogenesis that could be mediated through its possible anti-inflammatory effects.

Drosophila immunity: the Drosocin gene encodes two host defence peptides with pathogen-specific roles

Antimicrobial peptides (AMPs) are key to defence against infection in plants and animals. Use of AMP mutations in Drosophila has now revealed that AMPs can additively or synergistically contribute to defence in vivo. However, these studies also revealed high specificity, wherein just one AMP contributes an outsized role in combatting a specific pathogen. Here, we show the Drosocin locus (CG10816) is more complex than previously described. In addition to its namesake peptide 'Drosocin', it encodes a second mature peptide from a precursor via furin cleavage. This peptide corresponds to the previously uncharacterized 'Immune-induced Molecule 7'. A polymorphism (Thr52Ala) in the Drosocin precursor protein previously masked the identification of this peptide, which we name 'Buletin'. Using mutations differently affecting Drosocin and Buletin, we show that only Drosocin contributes to Drosocin gene-mediated defence against Enterobacter cloacae. Strikingly, we observed that Buletin, but not Drosocin, contributes to the Drosocin gene-mediated defence against Providencia burhodogranariea, including an importance of the Thr52Ala polymorphism for survival. Our study reveals that the Drosocin gene encodes two prominent host defence peptides with different specificity against distinct pathogens. This finding emphasizes the complexity of the Drosophila humoral response and demonstrates how natural polymorphisms can affect host susceptibility.

The Keratinocyte as a Crucial Cell in the Predisposition, Onset, Progression, Therapy and Study of the Atopic Dermatitis

The keratinocyte (KC) is the main functional and structural component of the epidermis, the most external layer of the skin that is highly specialized in defense against external agents, prevention of leakage of body fluids and retention of internal water within the cells. Altered epidermal barrier and aberrant KC differentiation are involved in the pathophysiology of several skin diseases, such as atopic dermatitis (AD). AD is a chronic inflammatory disease characterized by cutaneous and systemic immune dysregulation and skin microbiota dysbiosis. Nevertheless, the pathological mechanisms of this complex disease remain largely unknown. In this review, we summarize current knowledge about the participation of the KC in different aspects of the AD. We provide an overview of the genetic predisposing and environmental factors, inflammatory molecules and signaling pathways of the KC that participate in the physiopathology of the AD. We also analyze the link among the KC, the microbiota and the inflammatory response underlying acute and chronic skin AD lesions.

New Biologics for the Treatment of Atopic Dermatitis: Analysis of Efficacy, Safety, and Paradoxical Atopic Dermatitis Acceleration

Atopic dermatitis (AD) is a chronic, inflammatory skin disease with an eczematous rash and itching. Due to undesired adverse effects of traditional systemic treatment, there is still an unmet need for safe and effective long-term therapy for refractory AD. As our understanding of the pathogenesis underlying AD grows, novel treatments targeting specific molecules have been developed. Here, we discuss the efficacy and safety profiles of these drugs in recent clinical trials. Among their adverse effects, of particular note is AD acceleration. Although there is still debate about whether certain adverse reactions can be said to be paradoxical adverse events (PAEs), a wide range of PAEs have been reported during biological treatment for chronic immune-mediated diseases. Close surveillance of novel biologics is crucial to detect new undescribed paradoxical reactions and to shed light on the convoluted pathogenesis of AD.

Acne Vulgaris is Associated with the Human β-Defensin 1-Gene Polymorphisms in Han Chinese Ethnic Group Patients

Objective

To study the relationship between the single nucleotide polymorphisms (SNPs) of the human β-defensin 1-gene (DEFB1) and the genetic susceptibility of acne vulgaris in the Han Chinese ethnic group.

Methods

A total of 104 patients with acne vulgaris and 126 healthy participants were included in our study. We analyzed the association between acne vulgaris and the polymorphisms in the DEFB1 G-52A, C-44G, and G-20A gene. We then analyzed the relationship between the different genotypes and the susceptibility to acne vulgaris.

Results

The frequency of DEFB1 C-44G genetic polymorphisms between the acne vulgaris group and the control group was significantly different (P < 0.05). The frequency of DEFB1 G-20A genetic polymorphisms between the acne vulgaris group and the control group was also significantly different (P < 0.05).

Conclusion

The −44G or −20A allele showed a low expression in acne vulgaris, which has already been shown to correlate with the low risk of acne vulgaris among Chinese Han patients. This further supports the contribution of the DEFB1 gene to the pathogenesis of acne.

Association of systemic beta-defensin-1 and -20G/A DEFB1 gene polymorphism with Behçet's disease

BACKGROUND

Behçet's disease (BD) is a multisystem inflammatory disease of unknown etiology. Beta-defensins are antimicrobial peptides involved in epithelial host defense. To explore whether beta-defensins might be involved in BD pathogenesis, we examined plasma human beta-defensin-1 (hBD-1) and DEFB1 -20G/A polymorphism in BD patients.

METHODS

This case-control study included 106 BD patients fulfilling the criteria of the International Study Group for BD and 156 controls. The -20G/A genotypes were determined by PCR-RFLP analysis in all participants, and plasma hBD-1 was assessed by ELISA in 77 BD patients and 44 controls, only. Stepwise multiple regression models were applied to determine independent predictors for plasma hBD-1 in BD patients.

RESULTS

Distribution of -20G/A genotypes was different between BD patients and controls. Compared to GG genotype, "GA" genotype [OR (95% CI), 3.12 (1.56-6.16); p = .001] and "AA" genotype [2.57 (1.10-5.96); p = .027)] were associated with increased risk for BD. Plasma hBD-1 concentrations were significantly higher in BD patients than controls (9.81 ± 3.52 ng/mL vs. 5.30 ± 3.02 ng/mL; p < .001), and in BD patients with neurological involvement than those without (11.1 ± 4.12 ng/mL vs. 9.19 ± 3.10 ng/mL; p = .040). No variation was noted according to other clinical features, treatment received or -20G/A genotypes. In multivariate analysis, neurological involvement was the only predictor for plasma hBD-1 (β, 0.274; p = .029).

CONCLUSIONS

Findings suggest that hBD-1 and its encoding gene DEFB1 could modulate the risk for BD, especially for BD neurological involvement. Further work is needed for a better understanding of role of hBD-1 and its genetic variants in the pathogenesis of BD.

Racial differences in atopic dermatitis

OBJECTIVE

To summarize studies investigating ethnical and racial differences in atopic dermatitis (AD) epidemiology, clinical features, and skin and blood phenotypes.

DATA SOURCES

PubMed literature review (years 2000-2018).

STUDY SELECTIONS

Articles discussing primarily human disease.

RESULTS

Higher overall rates of AD were found in Africa and Oceania as opposed to India and Northern and Eastern Europe. In the United States, AD prevalence was found to be higher in African American (19.3%) compared with European American (16.1%) children. Although several studies have consistently found FLG loss-of-function mutations in up to 50% of European and 27% of Asian patients with AD, FLG mutations were 6 times less common in African American than in European American patients, even in patients with severe AD. Thus, FLG mutations seem to play less a pathogenic role in patients of African origin than in individuals of European or Asian ancestry. The immune phenotype of all ethnic groups was characterized by strong TH2 activation, but important differences in immune polarization exist among the different ethnicities. Asian patients with AD had stronger TH17/TH22 activation than African American and European American patients with AD, whereas African American patients had the highest serum IgE levels among all groups, while largely lacking TH1 and TH17 activation.

CONCLUSION

AD is a heterogeneous disease that has differences among various ethnic and racial groups, which might be important for the development of future, targeted treatments and for personalized medicine approaches.

Current insights into the role of human β-defensins in atopic dermatitis

Anti-microbial peptides or host defence peptides are small molecules that display both anti-microbial activities and complex immunomodulatory functions to protect against various diseases. Among these peptides, the human β-defensins (hBDs) are localized primarily in epithelial surfaces, including those of the skin, where they contribute to protective barriers. In atopic dermatitis skin lesions, altered skin barrier and immune dysregulation are believed to be responsible for reduced hBD synthesis. Impaired hBD expression in the skin is reportedly the leading cause of increased susceptibility to bacterial and viral infection in patients with atopic dermatitis. Although hBDs have considerable beneficial effects as anti-microbial agents and immunomodulators and may ameliorate atopic dermatitis clinically, recent evidence has also suggested the negative effects of hBDs in atopic dermatitis development. In the current review, we provide an overview of the regulation of hBDs and their role in the pathogenesis of atopic dermatitis. The efforts to utilize these molecules in clinical applications are also described.

The Genetics and Epigenetics of Atopic Dermatitis-Filaggrin and Other Polymorphisms

Atopic dermatitis (AD) is a chronic inflammatory skin disease caused by a combination of genetic and environmental factors. Genetic evidences depict a complex network comprising by epidermal barrier dysfunctions and dysregulation of innate and adaptive immunity in the pathogenesis of AD. Mutations in the human filaggrin gene (FLG) are the most significant and well-replicated genetic mutation associated with AD, and other mutations associated with epidermal barriers such as SPINK5, FLG-2, SPRR3, and CLDN1 have all been linked to AD. Gene variants may also contribute to the abnormal innate and adaptive responses found in AD, including mutations in PRRs and AMPs, TSLP and TSLPR, IL-1 family cytokines and receptors genes, vitamin D pathway genes, FCER1A, and Th2 and other cytokines genes. GWAS and Immunochip analysis have identified a total of 19 susceptibility loci for AD. Candidate genes at these susceptibility loci identified by GWAS and Immunochip analysis also suggest roles for epidermal barrier functions, innate and adaptive immunity, interleukin-1 family signaling, regulatory T cells, the vitamin D pathway, and the nerve growth factor pathway in the pathogenesis of AD. Increasing evidences show the modern lifestyle (i.e., the hygiene hypothesis, Western diet) and other environmental factors such as pollution and environmental tobacco smoke (ETS) lead to the increasing prevalence of AD with the development of industrialization. Epigenetic alterations in response to these environmental factors, including DNA methylation and microRNA related to immune system and skin barriers, have been found to contribute to the pathogenesis of AD. Genetic variants and epigenetic alteration might be the key tools for the molecular taxonomy of AD and provide the background for the personalized management.

Prediction of the impact of coding missense and nonsense single nucleotide polymorphisms on HD5 and HBD1 antibacterial activity against Escherichia coli

Defensins confer host defense against microorganisms and are important for human health. Single nucleotide polymorphisms (SNPs) in defensin gene-coding regions could lead to less active variants. Using SNP data available at the dbSNP database and frequency information from the 1000 Genomes Project, two DEFA5 (L26I and R13H) and eight DEFB1 (C35S, K31T, K33R, R29G, V06I, C12Y, Y28* and C05*) missense and nonsense SNPs that are located within mature regions of the coded defensins were retrieved. Such SNPs are rare and population restricted. In order to assess their antibacterial activity against Escherichia coli, two linear regression models were used from a previous work, which models the antibacterial activity as a function of solvation potential energy, using molecular dynamics data. Regarding only the antibacterial predictions, for HD5, no biological differences between wild-type and its variants were observed; while for HBD1, the results suggest that the R29G, K31T, Y28* and C05* variants could be less active than the wild-type one. The data here reported could lead to a substantial improvement in knowledge about the impact of missense SNPs in human defensins and their world distribution. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 633-644, 2016.

Medium-dose ultraviolet A1 phototherapy improves SCORAD index and increases mRNA expression of interleukin-4 without direct effect on human β defensin-1, interleukin-10, and interleukin-31

BACKGROUND

Effectiveness of ultraviolet (UV)A1 in flares of atopic dermatitis (AD) is thought to influence the expression of cytokines involved in its pathogenesis. The aim of the study was to investigate whether mRNA expression of human β defensin-1 (hβD-1) correlates with that of interleukin (IL)-4, IL-10, and IL-31 in skin lesions in AD before and after UVA1 phototherapy, to determine whether UVA1 decreases the expression of the aforementioned mediators, and to confirm whether changes in mRNA expression correspond with the clinical efficacy of UVA1.

METHODS

Twenty-five patients with AD underwent medium-dose UVA1 phototherapy. Before and after UVA1, biopsies from acute skin lesions were studied using reverse transcription and real-time polymerase chain reaction.

RESULTS

Levels of mRNA hβD-1 correlated with those of IL-10 and IL-31, levels of IL-4 mRNA correlated with those of IL-10 and IL-31, and IL-10 expression correlated with that of IL-31, both before and after UVA1. Phototherapy with UVA1 improved SCORing of Atopic Dermatitis (SCORAD) values, decreased pruritus, and increased expression of IL-4. After UVA1, no difference was found in the mRNA expression of other molecules. The SCORAD index did not correlate with the expression of any examined mRNA either before or after UVA1.

CONCLUSIONS

hβD-1, IL-4, IL-10, and IL-31 are expressed in acute skin lesions in AD, and their levels correlate with each other. UVA1 improves SCORAD and pruritus and increases the expression of IL-4 without direct effect on other molecules.

Molecular biology of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific genetic and immunological mechanisms. The rapid development of new techniques in molecular biology had ushered in new discoveries on the role of cytokines, chemokines, and immune cells in the pathogenesis of AD. New polymorphisms of AD are continually being reported in different populations. The physical and immunological barrier of normal intact skin is an important part of the innate immune system that protects the host against microbials and allergens that are associated with AD. Defects in the filaggrin gene FLG may play a role in facilitating exposure to allergens and microbial pathogens, which may induce Th2 polarization. Meanwhile, Th22 cells also play roles in skin barrier impairment through IL-22, and AD is often considered to be a Th2/Th22-dominant allergic disease. Mast cells and eosinophils are also involved in the inflammation via Th2 cytokines. Release of pruritogenic substances by mast cells induces scratching that further disrupts the skin barrier. Th1 and Th17 cells are mainly involved in chronic phase of AD. Keratinocytes also produce proinflammatory cytokines such as thymic stromal lymphopoietin (TSLP), which can further affect Th cells balance. The immunological characteristics of AD may differ for various endotypes and phenotypes. Due to the heterogeneity of the disease, and the redundancies of these mechanisms, our knowledge of the pathophysiology of the disease is still incomplete, which is reflected by the absence of a cure for the disease.

Relevance of α-defensins (HNP1-3) and defensin β-1 in diabetes

AIM: To investigate the genetic background of human defensin expression in type 1 and 2 diabetes.

METHODS: Associations between DEFA1/DEFA3 gene copy number polymorphism and diabetes as well as between the promoter polymorphisms of DEFB1 and diabetes were studied. The copy number variation of the DEFA1/DEFA3 genes was determined in 257 diabetic patients (117 patients with type 1 and 140 with type 2 diabetes). The control group consisted of 221 age- and gender-matched healthy blood donors. The cumulative copy numbers of the DEFA1/DEFA3 genes were detected by using quantitative PCR analysis. To evaluate the HNP 1-3 (human neutrophil peptide 1-3 or α-defensin) levels in the circulation, plasma HNP 1-3 concentrations were measured by ELISA. The expression of DEFA1/A3 in peripheral leukocytes of the diabetic patients was measured by quantitative RT PCR analysis. Three SNPs of the human DEFB1 (human defensin β-1) gene: DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946) were genotyped by Custom TaqMan^® Real Time PCR assay.

RESULTS: Significant differences were observed in HNP1-3 levels between the healthy subjects and both groups of diabetic patients. The mean ± SE was 28.78 ± 4.2 ng/mL in type 1 diabetes, and 29.82 ± 5.36 ng/mL in type 2 diabetes, vs 11.94 ± 2.96 ng/mL in controls; P < 0.01 respectively. There was no significant difference between patients with type 1 and type 2 diabetes in the high plasma concentrations of HNP1-3. The highest concentrations of α-defensin were found in diabetic patients with nephropathy (49.4 ± 4.8 ng/mL), neuropathy (38.7 ± 4.8 ng/mL) or cardiovascular complications (45.6 ± 1.45 ng/L). There was no significant difference in the cumulative copy numbers of DEFA1/DEFA3 genes between controls and patients, or between patients with the two types of diabetes. Comparisons of HNP 1-3 plasma level and DEFA1/A3 copy number of the same patient did not reveal significant relationship between defensin-α levels and the gene copy numbers (r² = 0.01). Similarly, no positive correlation was observed between the copy numbers and the mRNA expression levels of DEFA1/A3. Regarding the C-44G polymorphism of DEFB1, the GG “protective” genotype was much less frequent (1%-2%) among both groups of patients than among controls (9%).

CONCLUSION: Elevated HNP1-3 levels in diabetes are independent of DEFA1/DEFA3 copy numbers, but GG genotype of C-44G SNP in DEFB1 gene may result in decreased defensin β-1 production.

Skin barrier defects in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin condition with complex etiology that is dependent upon interactions between the host and the environment. Acute skin lesions exhibit the features of a Th2-driven inflammatory disorder, and many patients are highly atopic. The skin barrier plays key roles in immune surveillance and homeostasis, and in preventing penetration of microbial products and allergens. Defects that compromise the structural integrity or else the immune function of the skin barrier play a pivotal role in the pathogenesis of AD. This article provides an overview of the array of molecular building blocks that are essential to maintaining healthy skin. The basis for structural defects in the skin is discussed in relation to AD, with an emphasis on filaggrin and its genetic underpinnings. Aspects of innate immunity, including the role of antimicrobial peptides and proteases, are also discussed.

Esophageal human β-defensin expression in eosinophilic esophagitis

BACKGROUND

Defensins are antimicrobial peptides expressed on mucosal surfaces that contribute to maintaining intestinal homeostasis by providing innate defense mechanisms for the epithelia. Defensin expression is altered in a number of diseases that affect mucosal surfaces, such as atopic dermatitis, allergic rhinitis, and inflammatory bowel disease. Similar to atopic dermatitis, eosinophilic esophagitis (EoE) is a chronic disease in which the squamous epithelial surface is affected by a similar TH2 microenvironment and eosinophil-predominant inflammation. Therefore, we hypothesized that defensin expression would be decreased in EoE.

METHODS

To address this, we measured defensin expression in vitro in cell lines derived from patients with EoE (EoE1-T) or gastroesophageal reflux disease (GERD) (NES-G4T cells) and ex vivo in esophageal mucosal biopsy samples from children with EoE or GERD and control children without esophageal disease.

RESULTS

Interleukin-5 induced a decrease in human β-defensin (hBD) -1 and hBD3 expression in EoE1-T but not in NES-G4T cells. Compared with esophageal biopsy specimens from GERD and control children, specimens from EoE pediatric patients revealed a significant decrease in mRNA and protein expression for hBD1 and hBD3.

CONCLUSION

Diminished expression of hBD1 and hBD3 may make the esophageal epithelium more susceptible to the development and/or perpetuation of EoE.

Histone deacetylase (HDAC) 1 controls the expression of beta defensin 1 in human lung epithelial cells

Deregulation of the expression human beta defensin 1 (DEFB1), an antimicrobial peptide, has been implicated in the pathogenesis of COPD and asthma. Since the molecular mechanisms that regulate DEFB1 gene expression are widely unknown, the epigenetic processes involved in the regulation of the constitutive expression of DEFB1 in lung epithelial cells (A549) were investigated. The data demonstrate that histone deacetylases (HDACs) participate in the regulation of DEFB1 gene expression. Inhibition of the class I HDACs, HDACs 1-3, increases DEFB1 gene expression in A549 cells. Chromatin immunoprecipitation (ChIP) assays revealed that the inhibition of the class I HDACs also results in modifications of the chromatin at the DEFB1 promoter. Histone modifications, histone H3 acetylation and H3K4 trimethylation, that are associated with transcriptional activation, were found to increase after inhibition of HDACs 1-3. Finally, RNAi knockdown experiments identified HDAC1 as the sole HDAC responsible for maintaining the constitutive level of DEFB1 transcription. Taken together, our data reveal epigenetic mechanisms which are the basis of the maintenance of the constitutive gene expression of human beta defensin 1.

Antimicrobial peptide elicitors: New hope for the post-antibiotic era

Antimicrobial peptides or host defense peptides are fundamental components of human innate immunity. Recent and growing evidence suggests they have a role in a broad range of diseases, including cancer, allergies and susceptibility to infection, including HIV/AIDS. Antimicrobial peptide elicitors (APEs) are physical, biological or chemical agents that boost human antimicrobial peptide expression. The current knowledge of APEs and their potential use in the treatment of human infectious diseases are reviewed, and a classification system for APEs is proposed. The efficient use of APEs in clinical practice could mark the beginning of the urgently needed post-antibiotic era, but further trials assessing their efficacy and safety are required.

Clinical application of human β-defensin and CD14 gene polymorphism in evaluating the status of chronic inflammation

Background

Periodontitis is a common disease that affects the periodontal tissue supporting the teeth. This disease is attributed to multiple risk factors, including diabetes, cigarette smoking, alcohol, pathogenic microorganisms, genetics and others. Human beta-defensin-1 (hBD-1) is a cationic antimicrobial peptide with cysteine-rich ß-sheets and broad-spectrum antimicrobial activity. CD14 is a protein involved in the detection of bacterial lipopolysaccharide (LPS) and has also been associated with periodontitis. This study investigates the single nucleotide polymorphic (SNP) region, -1654(V38I), of the human beta-defensin-1 (hBD-1) gene as well as the -159 region of the CD14 gene in subjects with chronic periodontitis.

Methods

Blood samples from periodontally healthy subjects and periodontitis patients were obtained. DNA was extracted from the blood and was used to perform restriction digest at the polymorphic G1654A site of DEFB1 with the enzyme HincII. The polymorphic site 159TT of CD14 was digested with the enzyme AvaII. Enzyme-linked immunosorbent assay (ELISA) was performed on soluble samples to determine the protein expressions.

Results

The control and patient groups expressed 35% and 38% 1654 A/A genotype of DEFB1, respectively. The A allele frequency of the control group was 40%, while the patient blood group was 54%. The mean hBD-1 protein levels of the control and patient samples were 102.83 pg/mL and 252.09 pg/mL, respectively. The genotype distribution of CD14 in healthy subjects was 16% for C/C, 26% for T/T and 58% for C/T. The genotype frequencies of CD14 in periodontitis patients were 10% for C/C, 43% for T/T and 47% for C/T. The CD14 protein expression determined by ELISA showed a mean protein level of the control samples at 76.28ng/mL and the patient blood samples at 179.27ng/mL with a p value of 0.001.

Our study demonstrated that patients suffering from chronic periodontitis present more commonly with the 1654A/A genotype on the DEFB1 gene and the 159T/T genotype on the CD14 gene.

Conclusions

This study purely investigated the association between periodontitis and one polymorphic site on both DEFB1 and CD14 gene, with the purpose of expanding knowledge for the future development in diagnostic markers or therapeutic interventions to combat this disease.

Functional single-nucleotide polymorphisms in the DEFB1 gene are associated with systemic lupus erythematosus in Southern Brazilians

Systemic lupus erythematosus (SLE) is an autoimmune disease that results in inflammation and tissue damage. The etiology of SLE remains unknown, but recent studies have shown that the innate immune system may have a role in SLE pathogenesis through the secretion of small cationic peptides named defensins. The aim of the study was to determine the possible involvement in SLE of three functional single nucleotide polymorphisms (SNPs) (c.−52G>A, c.−44C>G and c.−20G>A) in the 5’UTR region of DEFB1 gene, by analyzing them in a population of 139 SLE patients and 288 healthy controls. The c.−52G>A SNP showed significant differences in allele and genotype frequency distribution between SLE patients and controls ( p = 0.01 and p = 0.02 respectively) indicating protection against SLE (A allele, OR = 0.68, AA genotype OR = 0.51). Significant differences were also observed for c.−44C>G SNP, the C/G genotype being associated with susceptibility to SLE (OR = 1.60, p = 0.04). Moreover , statistically significant differences between patients and controls were found for two DEFB1 haplotypes (GCA and GGG, p = 0.01 and p = 0.02 respectively). When considering DEFB1 SNPs and SLE clinical and laboratory manifestations, significant association was found with neuropsychiatric disorders, immunological alterations and anti-DNA antibodies. In conclusion, our results evidence a possible role for the c.−52G>A and c.−44C>G DEFB1 polymorphisms in SLE pathogenesis, that can be considered as possible risk factors for development of disease and disease-related clinical manifestations. Additional studies are needed, to corroborate these results as well as functional studies to understand the biological role of these SNPs in the pathogenesis of SLE.

Human polymorphisms as clinical predictors in leprosy

Genetic and serum markers in human host can predict leprosy susceptibility per se as well as be useful in classification and/or prediction of clinical variants and immunological responses in leprosy. Adequate and timely assessment of potential risks associated with these 38 host leprosy genes could diminish epidemiological burden and improve life quality of patients with this still prevalent mycobacterial disease.

Beta defensin-1 gene (DEFB1) polymorphisms are not associated with atopic dermatitis in children and adolescents from northeast Brazil (Recife, Pernambuco)

BACKGROUND

Atopic dermatitis (AD) is a common inflammatory skin disease resulting from the interplay between environmental, immunological and genetic factors. In our study, we investigated the role of three single nucleotide polymorphisms (SNPs) at 5'-UTR of DEFB1 gene, encoding for the human beta defensin-1, on the susceptibility to develop AD in a group of Brazilian children and adolescents.

METHODS

Three SNPs, -20 G/A (rs11362), -44 C/G (rs1800972), and -52 G/A (rs1799946) at 5'-UTR of DEFB1 gene were genotyped in two groups of children and adolescents, one affected by AD (96 subjects), the other healthy (191 individuals), from northeast Brazil.

RESULTS

-44 C/G frequencies were comparable between the two groups. The -20 GG genotype was more frequent in AD subjects than in healthy controls; the -52 GG, conversely, was more frequent in healthy controls than in AD. However, both these differences did not reach statistical significance. Also, association between SNPs and AD severity has been shown. The analysis of DEFB1 haplotypes did not highlight any association of the three SNPs with AD development or disease severity.

CONCLUSIONS

Our results seem to exclude a role for the -44 C/G DEFB1 SNPs on the pathogenesis and severity of AD, while for the -20 C/G and -52 G/A, even if not statistically significant, we evidenced a slight trend for susceptibility (-20 GG) and protection (-52 GG) for the development of AD. However, as controversial findings have been reported in the literature, the role of DEFB1 in the development of AD and in the severity of the phenotype deserves further investigation.

Polymorphisms of beta defensins are associated with the risk of severe acute pancreatitis

AIMS

Bacterial translocation from the intestinal tract plays an important role in severe acute pancreatitis (AP). Human β-defensins are a family of antimicrobial peptides present at the mucosal surface. The aim of this study was to investigate the relevance of single nucleotide polymorphisms (SNPs) in the DEFB1 gene and copy number polymorphisms of the DEFB4 genes in AP.

METHODS

124 AP patients (30 with mild and 94 with severe disease) and 100 healthy controls were enrolled in the study. Three SNPs of the DEFB1 gene [G-20A (c.-20G→A), C-44G (c.-44C→G) and G-52A (c.-52G→A)] were genotyped by Custom TaqMan assay. The DEFB4 gene copy number was determined by means of a TaqMan real-time PCR assay.

RESULTS

Significantly higher frequencies of the AA genotype of G-20A (c.-20G→A) and the AA genotype of G-52A (c.-52G→A) were observed among the patients with severe AP (SAP) compared with the healthy controls (38 vs. 20 and 41 vs. 18%, respectively). The GG protective genotype of C-44G (c.-44C→G) SNP was much less frequent (1%) among the patients than among the controls (9%). A higher frequency of a lower (<4) copy number of the DEFB4 gene was observed in the patients with SAP compared with the healthy controls (62 vs. 24%, respectively).

CONCLUSIONS

The variations in the genes encoding human β-defensin-1 and -2 may be associated with the risk of SAP. and IAP.

Defensin-barbed innate immunity: clinical associations in the pediatric population

Defensins and related antimicrobial peptides serve a central role in innate immunity in all species of plants and animals. In humans, defensins are widely expressed, including in neutrophils, skin, and mucosal epithelia. Most defensins are potent antibiotics, and some have chemotactic and toxin-neutralizing activities. Results of recent studies on the homeostatic and disease-fighting activities of human defensins point to a key relevance in several pediatric disorders. Inherited variation in defensin gene expression may contribute to susceptibility to several diseases, including psoriasis and Crohn disease. We review here the recent discoveries in innate immunity that shed light on the potential roles of defensins, and other antimicrobial molecules, in the pathophysiology of common pediatric diseases such as atopic dermatitis, necrotizing enterocolitis, cystic fibrosis, and otitis media.

In vitro antimicrobial efficacy of β-defensin 3 against Staphylococcus pseudintermedius isolates from healthy and atopic canine skin

β-Defensins (BDs) are highly conserved antimicrobial peptides important in innate defence against bacteria. β-Defensin 3 has a specific role in protecting the skin. This study quantified the minimal inhibitory concentration (MIC) of human (h)BD3 against Staphylococcus pseudintermedius isolates from atopic and healthy dogs. Single colony isolates (1 × 10(5) colony-forming units/mL log phase) were cultured with doubling dilutions of hBD3 in sodium phosphate buffer from 0.8 to 50 μg/mL at 37 °C for 2 h, before adding 100 μL of tryptone soy broth and incubating for a further 20 h. Bacterial growth was assessed as the mean optical density at 540 nm corrected for background. The median MIC was 12.5 μg hBD3/mL (range 3.125-25 μg/mL; n=22). Forty-five percent of the isolates were inhibited at ≤ 6.25 μg hBD3/mL, and 90% were inhibited at ≤ 12.5 μg hBD3/mL. Bacterial growth was not inhibited at ≤ 1.6 μg hBD3/mL. There were no significant differences in the inhibition by hBD3 of isolates from atopic (median MIC 12.5 μg/mL, range 6.25-25 μg/mL, n=14) and healthy dogs (median MIC 9.4 μg/mL, range 3.125-12.5 μg/mL, n = 8); from noninfected colonized sites (median MIC 12.5 μg/mL, range 3.125-25 μg/mL, n=16) and infected lesions (median MIC 9.4 μg/mL, range 6.25-12.5 μg/mL, n=6); or between sample sites (nose median MIC 12.5 μg/mL, range 6.25-25 μg/mL, n=5; perineum median MIC 12.5 μg/mL, range 3.125-25 μg/mL, n=7; ear median MIC 6.25 μg/mL, range 6.25-12.5 μg/mL, n=4; lesions median MIC 9.4 μg/mL, range 6.25-12.5 μg/mL, n=6). In conclusion, hBD3 inhibited the growth of canine S. pseudintermedius isolates in vitro irrespective of origin.

An update on the genetics of atopic dermatitis: scratching the surface in 2009

A genetic basis for atopic dermatitis (AD) has long been recognized. Historic documents allude to family history of disease as a risk factor. Before characterization of the human genome, heritability studies combined with family-based linkage studies supported the definition of AD as a complex trait in that interactions between genes and environmental factors and the interplay between multiple genes contribute to disease manifestation. A summary of more than 100 published reports on genetic association studies through mid-2009 implicates 81 genes, in 46 of which at least 1 positive association with AD has been demonstrated. Of these, the gene encoding filaggrin (FLG) has been most consistently replicated. Most candidate gene studies to date have focused on adaptive and innate immune response genes, but there is increasing interest in skin barrier dysfunction genes. This review examines the methods that have been used to identify susceptibility genes for AD and how the underlying pathology of this disease has been used to select candidate genes. Current challenges and the potential effect of new technologies are discussed.

Susceptibility to infectious diseases based on antimicrobial peptide production

In the last few years, the great impact of antimicrobial peptides on infectious disease susceptibility and natural resistance has been reported. In some cases, susceptibility to diseases is related to antimicrobial peptide polymorphisms and gene copy numbers, but for the vast majority of infectious diseases, these phenomena need to be elucidated. This review is focused on the current knowledge about susceptibility and resistance conferred by genetic variations in antimicrobial peptide expression in infectious diseases.

A 3' UTR transition within DEFB1 is associated with chronic and aggressive periodontitis

Periodontal diseases are complex inflammatory diseases and affect up to 20% of the worldwide population. An unbalanced reaction of the immune system toward microbial pathogens is considered as the key factor in the development of periodontitis. Defensins have a strong antimicrobial function and are important contributors of the immune system toward maintaining health. Here, we present the first systematic association study of DEFB1. Using a haplotype-tagging single nucleotide polymorphism (SNP) approach, including described promoter SNPs of DEFB1, we investigated the associations of the selected variants in a large population (N=1337 cases and 2887 ethnically matched controls). The 3' untranslated region SNP, rs1047031, showed the most significant association signal for homozygous carriers of the rare A allele (P=0.002) with an increased genetic risk of 1.3 (95% confidence interval: 1.11-1.57). The association was consistent with the specific periodontitis forms: chronic periodontitis (odds ratio=2.2 (95% confidence interval: 1.16-4.35), P=0.02), and aggressive periodontitis (odds ratio=1.3 (95% confidence interval 1.04-1.68), P=0.02). Sequencing of regulatory and exonic regions of DEFB1 identified no other associated variant, pointing toward rs1047031 as likely being the causative variant. Prediction of microRNA targets identified a potential microRNA-binding site at the position of rs1047031.

Association of a genetic polymorphism (-44 C/G SNP) in the human DEFB1 gene with expression and inducibility of multiple beta-defensins in gingival keratinocytes

Background

Human β-defensins (hBDs) are antimicrobial peptides with a role in innate immune defense. Our laboratory previously showed that a single nucleotide polymorphism (SNP) in the 5' untranslated region of the hBD1 gene (DEFB1), denoted -44 (rs1800972), is correlated with protection from oral Candida. Because this SNP alters the putative mRNA structure, we hypothesized that it alters hBD1 expression.

Methods

Transfection of reporter constructs and evaluation of antimicrobial activity and mRNA expression levels in keratinocytes from multiple donors were used to evaluate the effect of this SNP on constitutive and induced levels of expression.

Results

Transfection of CAT reporter constructs containing the 5' untranslated region showed that the -44 G allele yielded a 2-fold increase in CAT protein compared to other common haplotypes suggesting a cis effect on transcription or translation. The constitutive hBD1 mRNA level in human oral keratinocytes was significantly greater in cells from donors with the -44 GG genotype compared to those with the common CC genotype. Surprisingly, the hBD3 mRNA level as well as antimicrobial activity of keratinocyte extracts also correlated with the -44 G allele. Induced levels of hBD1, hBD2, and hBD3 mRNA were evaluated in keratinocytes challenged with Toll-like receptor 2 and 4 ligands, interleukin-1β, TNFα, and interferon-γ (IFNγ). In contrast to constitutive expression levels, IFNγ-induced keratinocyte hBD1 and hBD3 mRNA expression was significantly greater in cells with the common CC genotype, but there was no clear correlation of genotype with hBD2 expression.

Conclusion

The DEFB1 -44 G allele is associated with an increase in overall constitutive antimicrobial activity and expression of hBD1 and hBD3 in a manner that is consistent with protection from candidiasis, while the more common C allele is associated with IFNγ inducibility of these β-defensins and is likely to be more protective in conditions that enhance IFNγ expression such as chronic periodontitis. These results suggest a complex relationship between genetics and defensin expression that may influence periodontal health and innate immune responses.

Potential role of human beta-defensin 1 in Helicobacter pylori-induced gastritis

OBJECTIVE

Helicobacter pylori-induced gastric inflammation is dependent on the persistence of the microorganism in the gastric epithelium. Modulation of the host epithelial antimicrobial responses may be a critical determinant in H. pylori-induced gastritis. Human beta-defensins (hBDs) are important components of the host defence at mucosal surfaces. The aim of the present study was to investigate the relevance of three single nucleotide polymorphisms (SNPs) of the human beta defensin-1 (hBD-1) gene in H. pylori-induced gastritis and to assess the mRNA expression of hBD-1 in H. pylori-infected AGS cells.

MATERIAL AND METHODS

Three SNPs of the beta defensin DEFB1 gene, DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946), were genotyped either by Custom TaqMan SNP genotyping assays or by restriction fragment length polymorphism (RFLP) in 150 patients with chronic active gastritis; 100 serologically H. pylori-positive subjects without gastric or duodenal symptoms served as controls. hBD-1 mRNA expression in AGS cells was measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Significant differences in frequencies of the GA and AA genotypes of G-52A SNPs were observed between patients with chronic active gastritis and healthy controls. The maximum level of hBD-1 mRNA expression in AGS cells was observed at 24 h after infection with H. pylori, this not being dependent on the presence of the cag pathogenicity island (PAI).

CONCLUSIONS

The results of these genetic and in vitro experiments suggest that not only the inducible, but also the constitutive form of hBD may be important in the pathogenesis of H. pylori-induced gastritis.

Single nucleotide polymorphisms and the haplotype in the DEFB1 gene are associated with atopic dermatitis in a Korean population

BACKGROUND

Atopic dermatitis (AD) patients have been recognized to have an increased susceptibility to cutaneous colonization and infection by bacteria, fungi and viruses.

OBJECTIVE

We wanted to evaluate the associations of single nucleotide polymorphism (SNP) and the haplotype in the defensin (DEFA) and defensin (DEFB) genes, and so we performed genotyping for the SNPs in these genes in both AD patients and normal controls.

METHOD

We genotyped 27 SNPs from the DEFA 4, 5 and 6 genes and the DEFB1 gene for 1089 case-control samples (631 AD patients and 458 normal controls). We analyzed the SNPs and haplotypes in each gene.

RESULT

We identified that two SNPs and the haplotype CT in the DEFB1 gene are associated with AD in Koreans. The rs5743399 (-2266T/C) SNP is associated with AD, and especially with the high IgE, extrinsic type, and the rs5743409 (-1241T/G) SNP is associated with AD. On the haplotype analysis of these two SNPs, the haplotype CT is associated with AD, and especially with the allergic, extrinsic type of AD. However, we could not find any significant associations between the SNPs in the three DEFA genes and AD.

CONCLUSION

We found that the rs5743399 SNP, the rs5743409 SNP and the CT haplotype in the DEFB1 gene were significantly associated with the susceptibility to AD. We also found that rs5743399 polymorphism and the haplotype CT in this gene showed a strong association with the allergic, extrinsic type of AD. These results suggest that the DEFB1 gene has a main effect on the skin inflammation and/or skin responsiveness to any kind of allergic reaction.

Increased levels of human beta-defensins mRNA in sexually HIV-1 exposed but uninfected individuals

Protection against HIV-1 infection in exposed seronegative (ESN) individuals likely involves natural resistance mechanisms that have not been fully elucidated. Human beta defensins (HBD) are antimicrobial peptides found primarily in mucosae, the main ports of HIV entry. HBD-2 and 3 mRNA are induced by HIV-1 in human oral epithelial cells and exhibit strong anti-HIV-1 activity; in addition, polymorphisms in the DEFB1 gene, which encodes HBD-1, have been associated with resistance/susceptibility to different infections, including HIV-1. Here, we have assessed the association of HBD expression with the ESN phenotype. Peripheral blood and vaginal/endocervical and oral mucosal samples were taken from 47 ESN, 44 seropositive (SP) and 39 healthy controls (HC). HBD-1, 2 and 3 mRNA copy numbers were quantified by real time RT-PCR and A692G/G1654A/A1836G polymorphisms in the DEFB1 gene were detected by restriction fragment length polymorphisms and confirmed by nucleotide sequencing. ESN expressed significantly greater mRNA copy numbers of HBD-2 and 3 in oral mucosa than HC; p=0.0002 and p=0.007, respectively. mRNA copy numbers of HBD-1, 2 and 3 in vaginal/endocervical mucosa from ESN and HC were similar. Homozygosity for the A692G polymorphism was significantly more frequent in ESN (0.39) than in SP (0.05) (p=0.0002). In summary, ESN exhibited enhanced mucosal expression of the innate defense genes HBD-2 and 3; however, additional studies are required to verify these results and the potential association of the A692G polymorphism to the relative resistance of ESN to HIV-1 infection.

Association of beta-defensin 1 single nucleotide polymorphisms with Crohn's disease

OBJECTIVE

It has been suggested that deficient defensin expression is associated with the chronic inflammation of Crohn's disease. The regional localization of Crohn's disease, ileal or colonic disease can be linked to different defensin profiles. As constitutive beta-defensin 1 has a colonic expression, we considered it of interest to investigate single nucleotide polymorphisms (SNPs) of the beta-defensin 1 gene (DEFB1) in Crohn's disease.

MATERIAL AND METHODS

Three SNPs of the DEFB1 gene, DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946), were genotyped either by Custom TaqMan SNP genotyping assays or by restriction fragment length polymorphisms (RFLP) in 190 patients with Crohn's disease and 95 Hungarian controls.

RESULTS

It was found that the G-20A and C-44G SNPs had a strong association with the colonic and ileocolonic localizations of the disease, respectively, but no association was detected for the ileal localization. A significantly higher frequency of the GA genotype of G-20A was observed among patients with colonic localization (60%) as compared with healthy controls (39%), with an odds ratio (OR) of 2.39. The GG genotype of C-44G SNP, which is regarded as a protective genotype, was much less frequent (4%) among patients than among controls (12%), OR 3.367.

CONCLUSIONS

These results indicate that genetic variations in the DEFB1 gene encoding constitutive human beta-defensin 1 may be associated with the risk for Crohn's disease and may determine disease phenotype, e.g. colonic localization.

Antimicrobial peptides in human skin disease

The skin continuously encounters microbial pathogens. To defend against this, cells of the epidermis and dermis have evolved several innate strategies to prevent infection. Antimicrobial peptides are one of the primary mechanisms used by the skin in the early stages of immune defense. In general, antimicrobial peptides have broad antibacterial activity against gram-positive and negative bacteria and also show antifungal and antiviral activity. The antimicrobial activity of most peptides occurs as a result of unique structural characteristics that enable them to disrupt the microbial membrane while leaving human cell membranes intact. However, antimicrobial peptides also act on host cells to stimulate cytokine production, cell migration, proliferation, maturation, and extracellular matrix synthesis. The production by human skin of antimicrobial peptides such as defensins and cathelicidins occurs constitutively but also greatly increases after infection, inflammation or injury. Some skin diseases show altered expression of antimicrobial peptides, partially explaining the pathophysiology of these diseases. Thus, current research suggests that understanding how antimicrobial peptides modify susceptibility to microbes, influence skin inflammation, and modify wound healing, provides greater insight into the pathophysiology of skin disorders and offers new therapeutic opportunities.