IL-4Rα Blockade by Dupilumab Decreases Staphylococcus aureus Colonization and Increases Microbial Diversity in Atopic Dermatitis

Beneficial effects of coagulase-negative Staphylococci on Staphylococcus aureus skin colonization

Our skin is constantly exposed to a large number of pathogens while at the same time undergoing selective colonization by commensal microorganisms such as coagulase-negative Staphylococci. Staphylococcus aureus, however, is a facultative pathogen that is usually absent from healthy skin but frequently colonizes the inflamed skin of atopic dermatitis patients, where it further promotes inflammation. Enhanced S. aureus skin colonization was shown to correlate with a loss of microbiome diversity indicating a role for skin commensals to shape pathogen colonization. Together, keratinocytes and immune cells in the skin need to discriminate commensals from pathogens and orchestrate subsequent immune reactions in response to colonizing microbes. However, the mechanisms how individual commensals cooperate with keratinocytes and the immune system of the skin to prevent pathogen colonization are barely understood. In this review, we discuss the current knowledge on the functional effects of coagulase-negative staphylococci, the most frequently isolated skin commensals, on S. aureus skin colonization.

EAACI Biologicals Guidelines-dupilumab for children and adults with moderate-to-severe atopic dermatitis

Atopic dermatitis imposes a significant burden on patients, families and healthcare systems. Management is difficult, due to disease heterogeneity, co-morbidities, complexity in care pathways and differences between national or regional healthcare systems. Better understanding of the mechanisms has enabled a stratified approach to the management of atopic dermatitis, supporting the use of targeted treatments with biologicals. However, there are still many issues that require further clarification. These include the definition of response, strategies to enhance the responder rate, the duration of treatment and its regimen (in the clinic or home-based), its cost-effectiveness and long-term safety. The EAACI Guidelines on the use of dupilumab in atopic dermatitis follow the GRADE approach in formulating recommendations for each outcome and age group. In addition, future approaches and research priorities are discussed.

Development of a human skin commensal microbe for bacteriotherapy of atopic dermatitis and use in a phase 1 randomized clinical trial

Staphylococcus aureus colonizes patients with atopic dermatitis (AD) and exacerbates disease by promoting inflammation. The present study investigated the safety and mechanisms of action of Staphylococcus hominis A9 (ShA9), a bacterium isolated from healthy human skin, as a topical therapy for AD. ShA9 killed S. aureus on the skin of mice and inhibited expression of a toxin from S. aureus (psmα) that promotes inflammation. A first-in-human, phase 1, double-blinded, randomized 1-week trial of topical ShA9 or vehicle on the forearm skin of 54 adults with S. aureus-positive AD (NCT03151148) met its primary endpoint of safety, and participants receiving ShA9 had fewer adverse events associated with AD. Eczema severity was not significantly different when evaluated in all participants treated with ShA9 but a significant decrease in S. aureus and increased ShA9 DNA were seen and met secondary endpoints. Some S. aureus strains on participants were not directly killed by ShA9, but expression of mRNA for psmα was inhibited in all strains. Improvement in local eczema severity was suggested by post-hoc analysis of participants with S. aureus directly killed by ShA9. These observations demonstrate the safety and potential benefits of bacteriotherapy for AD.

Interferon-Lambda 1 Inhibits Staphylococcus aureus Colonization in Human Primary Keratinocytes

Atopic dermatitis (AD) is a common inflammatory skin disease. Staphylococcus aureus (S. aureus) colonization in skin lesions occurs in approximately 70% of AD patients. It has been found that IFN-λ1 can inhibit the colonization of S. aureus in normal human nasal mucosa. IFN-λ1 can increase IL-28RA in infected human keratinocytes. In this study, we found that IFN-λ1 can increase mRNA expression of FLG and antimicrobial peptides (AMPs) and inhibit TSLP mRNA expression in infected human keratinocytes. IFN-λ1 can increase intracellular ROS level, decrease STAT1 phosphorylation, and inhibit the colonization of S. aureus in human primary keratinocytes. These effects were attenuated by knocking-down IL-28R and NADPH oxidase inhibitor, suggesting that this function was mediated by JAK-STAT1 signaling pathway. These results suggest that IFN-λ1 might have an inhibitory effect on S. aureus colonization in AD lesions. Our findings might have potential value in the treatment for AD.

Staphylococcal Communities on Skin Are Associated with Atopic Dermatitis and Disease Severity

The skin microbiota of atopic dermatitis (AD) patients is characterized by increased Staphylococcus aureus colonization, which exacerbates disease symptoms and has been linked to reduced bacterial diversity. Skin bacterial communities in AD patients have mostly been described at family and genus levels, while species-level characterization has been limited. In this study, we investigated the role of the bacteria belonging to the Staphylococcus genus using targeted sequencing of the tuf gene with genus-specific primers. We compared staphylococcal communities on lesional and non-lesional skin of AD patients, as well as AD patients with healthy controls, and determined the absolute abundance of bacteria present at each site. We observed that the staphylococcal community, bacterial alpha diversity, and bacterial densities were similar on lesional and non-lesional skin, whereas AD severity was associated with significant changes in staphylococcal composition. Increased S. aureus, Staphylococcus capitis, and Staphylococcus lugdunensis abundances were correlated with increased severity. Conversely, Staphylococcus hominis abundance was negatively correlated with severity. Furthermore, S. hominis relative abundance was reduced on AD skin compared to healthy skin. In conclusion, various staphylococcal species appear to be important for skin health.

Cutaneous barrier dysfunction in allergic diseases

The fundamental defect(s) that drives atopic dermatitis (AD) remains controversial. "Outside in" proponents point to the important association of filaggrin gene mutations and other skin barrier defects with AD. The "inside out" proponents derive support from evidence that AD occurs in genetic animal models with overexpression of type 2 immune pathways in their skin, and humans with gain-of-function mutations in their type 2 response develop severe AD. The observation that therapeutic biologics, targeting type 2 immune responses, can reverse AD provides compelling support for the importance of "inside out" mechanisms of AD. In this review, we propose a central role for epithelial cell dysfunction that accounts for the dual role of skin barrier defects and immune pathway activation in AD. The complexity of AD has its roots in the dysfunction of the epithelial barrier that allows the penetration of allergens, irritants, and microbes into a cutaneous milieu that facilitates the induction of type 2 immune responses. The AD phenotypes and endotypes that result in chronic skin inflammation and barrier dysfunction are modified by genes, innate/adaptive immune responses, and different environmental factors that cause skin barrier dysfunction. There is also compelling evidence that skin barrier dysfunction can alter the course of childhood asthma, food allergy, and allergic rhinosinusitis. Effective management of AD requires a multipronged approach, not only restoring cutaneous barrier function, microbial flora, and immune homeostasis but also enhancing skin epithelial differentiation.

Gut-Skin Axis: Current Knowledge of the Interrelationship between Microbial Dysbiosis and Skin Conditions

The microbiome plays an important role in a wide variety of skin disorders. Not only is the skin microbiome altered, but also surprisingly many skin diseases are accompanied by an altered gut microbiome. The microbiome is a key regulator for the immune system, as it aims to maintain homeostasis by communicating with tissues and organs in a bidirectional manner. Hence, dysbiosis in the skin and/or gut microbiome is associated with an altered immune response, promoting the development of skin diseases, such as atopic dermatitis, psoriasis, acne vulgaris, dandruff, and even skin cancer. Here, we focus on the associations between the microbiome, diet, metabolites, and immune responses in skin pathologies. This review describes an exhaustive list of common skin conditions with associated dysbiosis in the skin microbiome as well as the current body of evidence on gut microbiome dysbiosis, dietary links, and their interplay with skin conditions. An enhanced understanding of the local skin and gut microbiome including the underlying mechanisms is necessary to shed light on the microbial involvement in human skin diseases and to develop new therapeutic approaches.

Skin microbiome transplantation and manipulation: Current state of the art

Many skin conditions are associated with an imbalance in the skin microbiome. In recent years, the skin microbiome has become a hot topic, for both therapeutic and cosmetic purposes. The possibility of manipulating the human skin microbiome to address skin conditions has opened exciting new paths for therapy. Here we review the skin microbiome manipulation strategies, ranging from skin microbiome transplantation, over skin bacteriotherapy to the use of prebiotics, probiotics and postbiotics. We summarize all efforts undertaken to exchange, manipulate, transplant or selectively apply the skin microbiome to date. Multiple microbial groups have been targeted, since they have been proven to be beneficial for skin health. We focus on the most common skin disorders and their associated skin microbiome dysbiosis and we review the existing scientific data and clinical trials undertaken to combat these skin conditions. The skin microbiome represents a novel platform for therapy. Transplantation of a complete microbiome or application of single strains has demonstrated beneficial therapeutic application.

The infectious complications of atopic dermatitis

OBJECTIVE

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is complicated by an increased risk for skin and systemic infections. Preventive therapy for AD is based on skin barrier improvement and anti-inflammatory treatments, whereas overt skin and systemic infections require antibiotics or antiviral treatments. This review updates the pathophysiology, diagnosis, management, controversy of antibiotic use, and potential treatments of infectious complications of AD.

DATA SOURCES

Published literature obtained through PubMed database searches and clinical pictures.

STUDY SELECTIONS

Studies relevant to the mechanisms, diagnosis, management, and potential therapy of infectious complications of AD.

RESULTS

Skin barrier defects, type 2 inflammation, Staphylococcusaureus colonization, and cutaneous dysbiosis are the major predisposing factors for the increased infections in AD. Although overt infections require antibiotics, the use of antibiotics in AD exacerbation remains controversial.

CONCLUSION

Infectious complications are a comorbidity of AD. Although not common, systemic bacterial infections and eczema herpeticum can be life-threatening. Preventive therapy of infections in AD emphasizes skin barrier improvement and anti-inflammatory therapy. The use of antibiotics in AD exacerbation requires further studies.

Therapeutic New Era for Atopic Dermatitis: Part 1. Biologics

Atopic dermatitis (AD) is a chronic, inflammatory cutaneous disease driven by immune dysregulation and skin barrier dysfunction. We are currently experiencing a new era of understanding of the pathogenesis of AD and, as a consequence, a new era of innovation in therapeutics, including small molecules and biologic therapy. Recently, advances in translational research have challenged the traditional AD pathogenesis paradigm of AD being solely a Th2-dominant disease. Other immune pathways seem to play a role in the complex AD pathophysiology, although the clinical relevance of these additional immune pathway abnormalities is unclear. Type 1, type 22, and type 17 pathway activation (with related cytokines/chemokines) have been demonstrated in the skin and blood of AD patients. Type 2 (interleukin [IL]-4, IL-13), IL-31, and type 22 (IL-22) pathway cytokines are increased in AD acute lesions. IL-22 induces both an epidermal hyperplasia at the onset of acute AD and a marked increase in the terminal differentiation S100 genes. This understanding of pathogenesis corresponds to a historic increase in therapeutic development in AD. The extreme clinical heterogeneity and the chronic progression of AD establish the need for newer, safer, and more effective treatments, control the disease, and improve the quality of life of affected patients.

On the surface: Skin microbial exposure contributes to allergic disease

OBJECTIVE

To discuss the skin microbiome modulates immunity by interactions between skin immunology with keratinocytes to combat pathogens. Allergic disorders are classified by immunoglobulin E sensitivity and aberrant TH2 cell responses, and an increasing number of studies have described the associations with skin microbiome fluctuations. In this review, we discuss commensal-epidermal homeostasis and its influence on allergic disease.

DATA SOURCES

All included references were obtained from the PubMed database.

STUDY SELECTIONS

Studies addressing relevant aspects of commensal-epidermal homeostasis, skin microbiome dysbiosis, microbiome-targeted therapeutics, and prevention in allergy were included.

RESULTS

Homeostasis between the commensal microbiome and the epidermis is important in protecting against allergic disease. Commensals promote antiallergic TH1 and TH17 immunophenotypes within the skin and induce keratinocytes to secrete antimicrobial peptides and alarmins that enhance barrier function and antagonize proallergic organisms. Perturbations in this homeostasis, however, is associated with allergic disease development. Atopic dermatitis is associated with decreases in skin commensals and increases in the pathogen, Staphylococcus aureus. Fluctuations in the skin microbiome contributes to decreased barrier dysfunction, allergic sensitization, and TH2 cytokine secretion. Little is known about how the skin microbiome affects food allergy, allergic rhinitis, and asthma, and it is poorly understood how cutaneous inflammation influences systemic allergic responses. Therapies are targeted toward maintenance of the skin barrier, replacement of healthy commensals, and anti-TH2 biologic therapy.

CONCLUSION

Although the effects of commensal-epidermal homeostasis on allergy within the skin are becoming increasingly clear, future studies are necessary to assess its effects on extracutaneous allergic disorders and explore potential therapeutics targeting the skin microbiome.

Physiopathologie de la dermatite atopique et des autres maladies atopiques : une approche globale est-elle possible ?

Atopy is defined by the propensity to develop an exaggerated type-2 inflammatory response to environmental molecules. Clinically, atopy is diagnosed when atopic disease occurs: atopic dermatitis, food allergy, atopic asthma and allergic rhinitis and conjunctivitis. Whereas the classical "atopic march" is increasingly challenged through epidemiological studies, type-2 cellular inflammation is a characteristic shared by the atopic diseases. This inflammation can be innate (non-specific: eosinophils, mast cells, dendritic cells, innate lymphoid cells [ILC]), or adaptive (antigen-specific, involving T cells). Interleukins (IL-)4, 5 and 13 are major actors of type-2 inflammation and are mainly produced by ILC and T cells. The efficacy of treatments targeting these type-2 cytokines highlight the importance of type-2 inflammation in atopic diseases. However, several patients do not respond to type-2 targeting treatments, highlighting the presence of other actors in pathophysiology of atopic diseases: alteration of epithelial barrier, IgE-mediated allergic responses, type-17 inflammation. Thus, the term "endotype" can illustrate this diversity in pathophysiology. Finally, a global approach of atopic diseases, as type-2 inflammatory diseases, is fundamental, but not sufficient. An approach by endotype is advisable, in a personalized medicine perspective. © 2020 Elsevier Masson SAS. All rights reserved.

Translational perspectives to treat Epidermolysis bullosa-Where do we stand?

Epidermolysis bullosa (EB) is the prototypical example of genetic skin fragility disorders. Genotypic heterogeneity, modifier genes, epigenetic, biochemical and environmental factors alter and determine pathogenic traits and, ultimately, the wide and striking phenotypic variability in EB. Besides the primary structural-functional defect, chronic tissue damage with induction and dysregulation of inflammatory pathways is a common pathogenic mechanism in EB. In localized variants, the inflammatory aberrations may mainly affect the micromilieu of lesional skin, while a systemic inflammatory response was shown to contribute to the systemic morbidity in severe EB subtypes with extensive cutaneous involvement. Our continued understanding of the pathophysiology of EB, as well as advances in molecular technologies, has paved the way for translational therapeutic approaches. The spectrum comprises of corrective and symptom-relieving therapies that include innovative therapeutic options garnered from the bench, repurposed drugs approved for other diseases, as well as strategies for gene-, protein- and cell-based therapies. Immunological traits further define new targets of therapy, aimed at improving skin barrier restoration, microbial surveillance and infection control, wound healing and anti-neoplastic effects. Clinical availability and feasibility of these approaches for all EB patients and subtypes are currently limited, reflecting issues of efficacy, specificity, tolerability and safety. A multistep targeting approach and highly individualized, risk-stratified combinatory treatment plans will thus be essential for sustained efficacy and improved overall quality of life in EB.

Which Way Do We Go? Complex Interactions in Atopic Dermatitis Pathogenesis

Atopic dermatitis (AD) is a common, chronic, inflammatory skin condition characterized by recurrent and pruritic skin eruptions. Multiple factors contribute to the pathogenesis of AD, including skin barrier dysfunction, microbial dysbiosis, and immune dysregulation. Interactions among these factors form a complex, multidirectional network that can reinforce atopic skin disease but can also be ameliorated by targeted therapies. This review summarizes the complex interactions among contributing factors in AD and the implications on disease development and therapeutic interventions.

Biologics for Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that has become a global health problem. The pathophysiology of AD includes both skin barrier and immune abnormalities, with type 2 immune deviation central to several clinical phenotypes and underlying endotypes. Recognition of the persistent nature and systemic aspects of AD provides a rationale for treatment with a biologic. Dupilumab has been approved for patients 6 years of age and older with moderate to severe AD. Monoclonal antibodies are in phase 3 trials and may become part of a precision medicine approach to AD.

Dupilumab use in atopic dermatitis and beyond in skin diseases

Atopic dermatitis (AD) is a chronic inflammatory condition that affects 5-10% of adults and 9-18% of children and its pathology is rooted in the Th-2-mediated immune response. Dupilumab is a fully human IgG4 monoclonal antibody that targets the IL-4 receptor alpha subunit that is endogenously bound by the Th-2 cytokines IL-4 and IL-13. Successful clinical trials of dupilumab showing marked improvements in clinical signs of AD, patient reported symptoms and quality of life measures led to its approval for clinical use for moderate-to-severe AD in 2017. This review details the current body of evidence on the drug's mechanism of action, pharmacology, clinical efficacy and safety as well as post market and real world use.

Targeting T2 Inflammation by Dupilumab Impacts on the Microbiomic "Ménage à Trois" of Atopic Dermatitis

Dupilumab leads to an improvement of the dysbiosis in lesional and non-lesional skin in atopic dermatitis (AD). Although the causal relationship between inflammation and dysbiosis remains unclear, strategies to normalize microbiome composition remain a relevant approach in AD. How and when to best individually impact on the microbiome to improve AD in the long-term and potentially modify disease is worthy of additional exploration.

Allergic skin inflammation and S. aureus skin colonization are mutually reinforcing

Atopic dermatitis (AD) lesional skin is often colonized with S. aureus, and the load of S. aureus correlates with disease severity. However, a causative and mechanistic link between S. aureus skin colonization and severity of AD is not well established. We made use of well-established mouse model of AD elicited by epicutaneous sensitization of tape stripped skin with ovalbumin to investigate the relationship between allergic skin inflammation and cutaneous S. aureus colonization. Topical application of S aureus exacerbated allergic skin inflammation induced by epicutaneous sensitization with ovalbumin, whereas allergic skin inflammation generated a permissive environment for S. aureus persistence. Our results establish a mutually reinforcing role of allergic skin inflammation and S. aureus skin colonization.

Recent advances in atopic dermatitis

The prevalence and disease burden of atopic dermatitis (AD) is substantial. AD causes significant impairment in quality of life. It is also associated with mental disorders as well as cardiovascular diseases. Many factors including race, environment, skin barrier dysfunction, immune regulatory abnormalities, and microbiome have been reported to affect the pathophysiology of AD. A variety of cell types including Th2, Th17, Th22, and type 2 innate lymphoid cells contribute to AD. Cytokines from these immune cells cause abnormal epidermal differentiation and skin barrier dysfunction. Moreover, microbial dysbiosis and deficiency of antimicrobial peptides result in Staphylococcus aureus infection. Recently, new drugs have been successfully launched to target polarized immune pathways that lead to moderate-to-severe AD.

A Calm, Dispassionate Look at Skin Microbiota in Atopic Dermatitis: An Integrative Literature Review

Atopic dermatitis (AD) is a chronic common inflammatory skin disorder with clinical characteristics of pruritic, dry, and recurrent flares that involve the whole body. Recent studies have demonstrated that the skin microbiota, characterized by an overgrowth of Staphylococcus aureus (S. aureus), plays a critical role in the manifestation of AD. There is striking evidence that skin microbiota can modulate the development and progression of AD. Therefore, more and more therapeutic approaches are adopted for modifying skin microbiota. Here we discuss the role of skin microbiota in the etiology and maintenance of AD; furthermore, we summarize the effects of therapeutic treatments on skin microbiota in AD based on published literature. With the help of the theoretical guidance suggested by microbial metagenome analysis, the reconstitution of microbiota should be a promising way to harness the pathogens of AD and could be used as a brand-new therapeutic strategy in clinical trials. We believe that the targeted therapy of dysbiosis in AD may possibly become a unique approach to an integrated treatment program in the near future.

Critical Points on the Use of Biologicals in Allergic Diseases and Asthma

Improved understanding of the contribution of immune-inflammatory mechanisms in allergic diseases and asthma has encouraged development of biologicals and small molecules specifically targeting the innate and adaptive immune response. There are several critical points impacting the efficacy of this stratified approach, from the complexity of disease endotypes to the effectiveness in real-world settings. We discuss here how these barriers can be overcome to facilitate the development of implementation science for allergic diseases and asthma.

The role of bacterial skin infections in atopic dermatitis: expert statement and review from the International Eczema Council Skin Infection Group

Patients with atopic dermatitis (AD) have an increased risk of bacterial skin infections, which cause significant morbidity and, if untreated, may become systemic. Staphylococcus aureus colonizes the skin of most patients with AD and is the most common organism to cause infections. Overt bacterial infection is easily recognized by the appearance of weeping lesions, honey‐coloured crusts and pustules. However, the wide variability in clinical presentation of bacterial infection in AD and the inherent features of AD – cutaneous erythema and warmth, oozing associated with oedema, and regional lymphadenopathy – overlap with those of infection, making clinical diagnosis challenging. Furthermore, some features may be masked because of anatomical site‐ and skin‐type‐specific features, and the high frequency of S. aureus colonization in AD makes positive skin swab culture of suspected infection unreliable as a diagnostic tool. The host mechanisms and microbial virulence factors that underlie S. aureus colonization and infection in AD are incompletely understood. The aim of this article is to present the latest evidence from animal and human studies, including recent microbiome research, to define the clinical features of bacterial infections in AD, and to summarize our current understanding of the host and bacterial factors that influence microbial colonization and virulence.

The influence of treatment in alpine and moderate maritime climate on the composition of the skin microbiome in patients with difficult to treat atopic dermatitis

BACKGROUND

The skin microbiome, characterized by an overgrowth of Staphylococcus aureus, plays an important role in the pathogenesis of atopic dermatitis (AD). Multidisciplinary treatment in alpine climate is known for its positive effect on disease severity in children with AD and can result in a different immune response compared with moderate maritime climate. However, the effect on the composition of the skin microbiome in AD is unknown.

OBJECTIVE

To determine the effect of treatment in alpine climate and moderate maritime climate on the microbiome for lesional and non-lesional skin in children with difficult to treat AD.

RESULTS

Alpine climate treatment led to a significant change in the microbiota on lesional skin, whereas no significant change was found after moderate maritime climate. On both lesional and non-lesional skin, we observed a significant increase in Shannon diversity and a significant decrease in both Staphylococcus abundance and S aureus load after alpine climate treatment. The decrease in S aureus was significantly larger on lesional skin following alpine climate treatment compared with moderate maritime climate treatment. Staphylococcus epidermidis load was stable over time.

CONCLUSIONS AND CLINICAL RELEVANCE

Alpine climate treatment leads to significant changes in the composition of the skin microbiome in children with AD, mainly caused by a reduction in the Staphylococcus genus. This study shows new perspectives in the potential mode of action for therapies in AD.