Systemic therapeutic options for severe atopic dermatitis

Systemic therapy of severe atopic dermatitis (AD) is difficult in some cases, because the use of immunosuppressive agents such as cyclosporine A, mofetil mycophenolate, tacrolimus, and azathioprine is limited by adverse reactions or contraindications. Recent reports suggest a helpful role for biologics, methotrexate, anti-IgE antibodies, and immunotherapy. We review the modes of action, as well as advantages and disadvantages of current and new systemic therapeutic options for severe AD.

Genome-wide scan on total serum IgE levels identifies FCER1A as novel susceptibility locus

High levels of serum IgE are considered markers of parasite and helminth exposure. In addition, they are associated with allergic disorders, play a key role in anti-tumoral defence, and are crucial mediators of autoimmune diseases. Total IgE is a strongly heritable trait. In a genome-wide association study (GWAS), we tested 353,569 SNPs for association with serum IgE levels in 1,530 individuals from the population-based KORA S3/F3 study. Replication was performed in four independent population-based study samples (total n = 9,769 individuals). Functional variants in the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) on chromosome 1q23 (rs2251746 and rs2427837) were strongly associated with total IgE levels in all cohorts with P values of 1.85 x 10(-20) and 7.08 x 10(-19) in a combined analysis, and in a post-hoc analysis showed additional associations with allergic sensitization (P = 7.78 x 10(-4) and P = 1.95 x 10(-3)). The "top" SNP significantly influenced the cell surface expression of FCER1A on basophils, and genome-wide expression profiles indicated an interesting novel regulatory mechanism of FCER1A expression via GATA-2. Polymorphisms within the RAD50 gene on chromosome 5q31 were consistently associated with IgE levels (P values 6.28 x 10(-7)-4.46 x 10(-8)) and increased the risk for atopic eczema and asthma. Furthermore, STAT6 was confirmed as susceptibility locus modulating IgE levels. In this first GWAS on total IgE FCER1A was identified and replicated as new susceptibility locus at which common genetic variation influences serum IgE levels. In addition, variants within the RAD50 gene might represent additional factors within cytokine gene cluster on chromosome 5q31, emphasizing the need for further investigations in this intriguing region. Our data furthermore confirm association of STAT6 variation with serum IgE levels.

Proactive treatment of atopic dermatitis in adults with 0.1% tacrolimus ointment

BACKGROUND

Long-term treatment for atopic dermatitis (AD) using low dose, intermittent, topical anti-inflammatory agents may control acute disease and prevent relapses. This 12-month, European, multicentre, randomized study investigated whether the proactive use of 0.1% tacrolimus ointment applied twice weekly can keep AD in remission and reduce the incidence of disease exacerbations (DE).

METHODS

During the initial open-label period, 257 adults with AD applied 0.1% tacrolimus ointment twice daily (b.i.d.) for up to 6 weeks to affected areas. When an Investigator Global Assessment (IGA) score of <or=2 was achieved, the patient entered the disease control period (DCP) and was randomized to either proactive tacrolimus (n = 116) or vehicle ointment (n = 108) twice weekly for 12 months. Exacerbations were treated with 0.1% tacrolimus ointment b.i.d. until an IGA <or=2 was regained, then randomized treatment was restarted. The primary endpoint was the number of DEs during the DCP that required a substantial therapeutic intervention.

RESULTS

Proactive tacrolimus 0.1% ointment application significantly reduced the number of DEs requiring substantial therapeutic intervention (median difference 2; P < 0.001; Wilcoxon rank sum test), the percentage of DE treatment days (median difference: 15.2%; P < 0.001; Wilcoxon rank sum test) and increased the time to first DE (median 142 vs 15 days; P < 0.001; stratified log-rank test). The adverse event profile was similar for the two treatment approaches.

CONCLUSION

A 12-month, twice weekly proactive tacrolimus ointment application was an effective treatment in most study patients which prevented, delayed and reduced the occurrence of AD exacerbations

Important research questions in allergy and related diseases: nonallergic rhinitis: a GA2LEN paper

Nonallergic rhinitis (NAR) can be defined as a chronic nasal inflammation which is not caused by systemic IgE-dependent mechanisms. It is common and probably affects far more than 200 million people worldwide. Both children and adults are affected. However, its exact prevalence is unknown and its phenotypes need to be evaluated using appropriate methods to better understand its pathophysiology, diagnosis and management. It is important to differentiate between infectious rhinitis, allergic/NAR and chronic rhinosinusitis, as management differs for each of these cases. Characterization of the phenotype, mechanisms and management of NAR represents one of the major unmet needs in allergic and nonallergic diseases. Studies on children and adults are required in order to appreciate the prevalence, phenotype, severity and co-morbidities of NAR. These studies should compare allergic and NAR and consider different age group populations including elderly subjects. Mechanistic studies should be carried out to better understand the disease(s) and risk factors and to guide towards an improved diagnosis and therapy. These studies need to take the heterogeneity of NAR into account. It is likely that neuronal mechanisms, T cells, innate immunity and possibly auto-immune responses all play a role in NAR and may also contribute to the symptoms of allergic rhinitis.

Proactive treatment of atopic dermatitis in adults with 0.1% tacrolimus ointment

BACKGROUND

Long-term treatment for atopic dermatitis (AD) using low dose, intermittent, topical anti-inflammatory agents may control acute disease and prevent relapses. This 12-month, European, multicentre, randomized study investigated whether the proactive use of 0.1% tacrolimus ointment applied twice weekly can keep AD in remission and reduce the incidence of disease exacerbations (DE).

METHODS

During the initial open-label period, 257 adults with AD applied 0.1% tacrolimus ointment twice daily (b.i.d.) for up to 6 weeks to affected areas. When an Investigator Global Assessment (IGA) score of < or =2 was achieved, the patient entered the disease control period (DCP) and was randomized to either proactive tacrolimus (n = 116) or vehicle ointment (n = 108) twice weekly for 12 months. Exacerbations were treated with 0.1% tacrolimus ointment b.i.d. until an IGA < or =2 was regained, then randomized treatment was restarted. The primary endpoint was the number of DEs during the DCP that required a substantial therapeutic intervention.

RESULTS

Proactive tacrolimus 0.1% ointment application significantly reduced the number of DEs requiring substantial therapeutic intervention (median difference 2; P < 0.001; Wilcoxon rank sum test), the percentage of DE treatment days (median difference: 15.2%; P < 0.001; Wilcoxon rank sum test) and increased the time to first DE (median 142 vs 15 days; P < 0.001; stratified log-rank test). The adverse event profile was similar for the two treatment approaches.

CONCLUSION

A 12-month, twice weekly proactive tacrolimus ointment application was an effective treatment in most study patients which prevented, delayed and reduced the occurrence of AD exacerbations.

Distribution of Langerhans cells and mast cells within the human oral mucosa: new application sites of allergens in sublingual immunotherapy?

BACKGROUND

Sublingual immunotherapy (SLIT) represents an alternative to subcutaneous immunotherapy. While antigen-presenting cells such as Langerhans cells (LCs) are thought to contribute to the effectiveness of SLIT, mast cells (MCs) most likely account for adverse reactions such as sublingual edema. As little is known about LCs and MCs within the oral cavity, we investigated their distribution in search for mucosal sites with highest LCs and lowest MCs density.

METHODS

Biopsies were taken simultaneously from human vestibulum, bucca, palatum, lingua, sublingua, gingiva, and skin. Immunohistochemistry and flow cytometry were used to detect MCs, LCs and high affinity receptor for IgE (FcepsilonRI) expression of LCs. Mixed lymphocyte reactions were performed to assess their stimulatory capacity.

RESULTS

Highest density of MCs was detected within the gingiva, while the lowest density of MCs was found within the palatum and lingua. However, sublingual MCs were located within glands, which might explain swelling of sublingual caruncle in some SLIT patients. Highest density of LCs was detected within the vestibular region with lowest density in sublingual region. Highest expression of FcepsilonRI was detected on LCs within the vestibulum. Furthermore LCs from different regions displayed similar stimulatory capacity towards allogeneic T cells.

CONCLUSIONS

In view of our data, different mucosal regions such as the vestibulum might represent alternative SLIT application sites with potent allergen uptake. Our data might serve as a basis for new application strategies for SLIT to enhance efficiency and reduce local adverse reactions.

Effects of histamine and diamine oxidase activities on pregnancy: a critical review

BACKGROUND

Histamine has been assumed to contribute to embryo-uterine interactions due to its vasoactive, differentiation and growth-promoting properties. However, its exact functions in pregnancy are unclear. The histamine-degrading enzyme diamine oxidase (DAO) is produced in high amounts by the placenta and has been supposed to act as a metabolic barrier to prevent excessive entry of bioactive histamine from the placenta into the maternal or fetal circulation.

METHODS

The literature available on PubMed published in English between 1910 and 2008 has been searched using the isolated and combined key words histamine, diamine oxidase, pregnancy, placenta, endometrium, miscarriage, implantation, pre-eclampsia, intrauterine growth retardation, diabetes and embryonic histamine-releasing factor (EHRF).

RESULTS

High expression of the histamine-producing enzyme histidine decarboxylase in the placenta, histamine receptors at the feto-maternal interface and the existence of an EHRF suggest a physiological role of histamine during gestation. The balance between histamine and DAO seems to be crucial for an uncomplicated course of pregnancy. Reduced DAO activities have been found in multiple heterogeneous complications of pregnancy such as diabetes, threatened and missed abortion and trophoblastic disorders. Whether women with histamine intolerance suffer from more complicated pregnancies and higher abortion rates due to impaired DAO activities and if low DAO levels or genetic modifications in the DAO gene might therefore represent a prognostic factor for a higher risk of abortion, has not been investigated yet.

CONCLUSIONS

Low activities of the histamine-degrading enzyme DAO might indicate high-risk pregnancies, although high intra- and interindividual variations limit its value as a screening tool.

The immune privilege of the oral mucosa

Despite high bacterial colonization and frequent allergen contact, acute inflammatory and allergic reactions are rarely seen in the oral mucosa. Therefore we assert that immune tolerance predominates at this site and antigen presenting cells, such as dendritic cells and different T cell subtypes, serve as key players in oral mucosal tolerance induction. In this article we describe the mechanisms that lead to tolerance induced in the oral mucosa and how they differ from tolerance induced in the lower gastrointestinal tract. Furthermore we discuss ways in which novel nonparenteral approaches for immune intervention, such as allergen-specific immunotherapy applied by way of the sublingual route, might be improved to target the tolerogenic properties of the sophisticated oral mucosal immune network.

Toll-like receptor 7 agonists and skin

Toll-like receptor (TLR) 7 is an intracellular TLR that is expressed on membranes of endosomes and recognizes nucleosides and nucleotides from intracellular pathogens. Synthetic agonists of TLR7 comprise guanine nucleoside analogues, stabilized immune modulatory RNA, as well as imidoazoquinoline-based compounds. Activation of pattern recognition receptors such as TLR with appropriate agonists induces a sophisticated defense machinery of the innate immune system. Targeting TLR pathways represents a cleverly devised and promising therapeutic strategy. At present, imiquimod is the most frequently used TLR7 ligand in clinical practice and has been approved for the treatment of external genital warts and (pre-) cancerous skin lesions such as actinic keratoses and superficial basal cell carcinoma. Upon topical application, this TLR7 agonist induces increased production of interferon-alpha, interleukin-12, tumor necrosis factor-alpha and a Th1 prone immune response. Imiquimod enforces the recruitment of myeloid and plasmacytoid dendritic cell subtypes and cytotoxic T cells, and increases the capacity of antigen-presenting cells to induce reactive T cells. Based on its multifaceted functions including proapoptotic, antifibrotic, antiangiogenic and antiaging effects, several reports about the efficacy of imiquimod as a treatment of various other skin diseases exist. This review summarizes the current knowledge about the immunological mechanisms induced by the TLR7 agonist imiquimod as well as established clinical therapies and putative applications of TLR7 agonists in the near future.

CXCR3 <-> ligand-mediated skin inflammation in cutaneous lichenoid graft-versus-host disease

BACKGROUND

Lichenoid graft-versus-host disease (liGVHD) histologically shares several common features with other lichenoid dermatoses, such as cutaneous lupus erythematosus and lichen planus (LP), which collectively show a junctional infiltrate of cytotoxic lymphocytes with liquefaction of the basal layer ("interface dermatitis"). Because recent studies have shown a role for type I interferon (IFN)-associated inflammation, including lymphocyte recruitment via CXCR3 <-> ligand interaction in cutaneous lupus erythematosus and LP, we hypothesized that similar mechanisms might also be involved in liGVHD.

METHODS

Ten representative lesional skin biopsies taken from patients with different subsets of chronic cutaneous graft versus host disease (GvDH) were recovered from the authors' archives. Eight LP specimens and 5 punch biopsies taken from healthy skin were analyzed for control purposes. Immunohistochemistry was performed to characterize the lesional infiltrate (CD3, CD4, CD8, CD20, CD56, or CD68), to analyze type I IFN signaling (MxA), and to investigate expression of the IFN-inducible chemokines CXCL9 and CXCL10 and their ligand CXCR3. In situ hybridization was performed to visualize IFNalpha expression on the mRNA level.

RESULTS

Our analyses revealed striking similarities between the inflammatory pattern seen in LP and liGVHD. Both disorders presented with a predominantly T-cellular inflammation with CD8(+) lymphocytes affecting the basal epidermal layer. The majority of lesional lymphocytes expressed the chemokine receptor CXCR3. The corresponding chemokines CXCL9 and CXCL10 were found in the epidermis and within the inflammatory infiltrate. Analyses of MxA and IFNalpha mRNA expression supported a role for type I IFNs in these conditions.

LIMITATIONS

This study was limited by the number of well characterized cases in our archives. In situ hybridization was realizable only in single cases.

CONCLUSION

Our results support the hypothesis that CXCR3 <-> ligand-mediated lymphocyte recruitment is involved in cutaneous liGVHD. The fact that CXCL10 was seen in precisely those areas with extensive liquefaction of the basal epidermis supports a role of this chemokine for the development of the typical histologic "interface" pattern.

Molecular basis of atopic dermatitis

PURPOSE OF REVIEW

Atopic dermatitis is a common chronic inflammatory skin disease and there are numerous publications on this topic. This review will focus on developments in understanding the molecular basis of atopic dermatitis while considering the genetic background, skin barrier impairment, immune system deviation and microbial superinfections.

RECENT FINDINGS

Atopic dermatitis is a complex genetic disease in which gene-gene and gene-environment interactions play a key role. Surprisingly some genetic regions of interest were found to be overlapping with loci identified to play a role in another very common inflammatory skin disease, psoriasis, while no overlap has so far been observed with asthma. Impairment of the skin barrier followed by antigens trespassing seems to play an important role, favouring sensitization via transepidermal penetration which is the focus of current investigations. Superinfections by pathogens such as Staphylococcus aureus due to a weak innate defence seem to be significant in atopic dermatitis as they elicit a strong inflammatory response.

SUMMARY

Atopic dermatitis is a chronic inflammatory skin disease with a high incidence in school children and adults. Disease pathogenesis is complex and the background is multifactorial, making the underlying predispositions elusive. Understanding new pathogenic pathways may lead to the development of new drugs with enhanced benefit for the patient.