Editors’ Picks

        Fungus among us

        Candida albicans is a common pathogen at barrier sites under immunosuppressed conditions. In order to more clearly elucidate the cell types and cytokine networks involved in resistance to such infection in the skin, Kashem and colleagues employed an epicutaneous C. albicans infection murine model that does not require immunosuppression for infection. These studies revealed that resistance requires interleukin (IL)-17A produced by γδ T cells. In addition, IL-23 derived from CD301+ dermal dendritic cells was required for this IL-17A production. Most interestingly, these investigators demonstrated that sensory neurons directly respond to C. albicans, resulting in efficient clearance of the pathogen via a mechanism mediated by the neuropeptide calcitonin gene-related peptide (CGRP). These results highlight complex events that link sensory neurons, dendritic cells, and γδ T cells in the efficient response to a fungal pathogen at the epidermal barrier. (Immunity 43:515-526, 2015) Selected by N. Ward

        Atopic epidemic

        Although great strides have been made in unearthing genetic mutations and disease processes in atopic dermatitis (AD), the basis for the sudden and dramatic increase in atopic disease in general over the last 50 years remains a mystery. Mechanisms, including the hygiene hypothesis, natural TH2 skewing during pregnancy and early life confounded by environmental exposure to chemical allergens, and the underlying primary abnormality in barrier function, have garnered support. Thyssen and colleagues recently penned a perspective analysis in support of a role of reduced environmental UV exposure as the driver of this current atopic epidemic. Citing studies documenting the potential benefits of blue-light therapy in premature neonates as well as UVB irradiation-induced improvement of skin barrier function, reduction of S. aureus colonization, reduced pruritus, and increased sun-induced vitamin D production, these investigators suggest that decreased solar radiation exposure may explain the increased prevalence of AD in urban children. Ultimately, this intriguing hypothesis offers a unique, but not exclusive, partial explanation of factors that influence AD prevalence. (J Allergy Clin Immunol 136:1163–1169, 2015) Selected by H. Williams

        New insight from the chemical barrier

        Despite continuous exposure to microorganisms, the skin is rarely infected thanks to the presence of the stratum corneum as well as the presence of a chemical barrier of antimicrobial peptides and proteins. Pseudomonas aeruginosa causes severe infections especially in cystic fibrosis patients and burn victims, and the emerging antibiotic resistance of these organisms demands development of novel effective drugs. Hansmann and colleagues demonstrated that the water-insoluble filaggrin-2 (FLG2) is present in stratum corneum, especially in palmar and plantar skin, a location proximal to soil- and water-borne microorganisms. Upon cultivation on stratum corneum with P. aeruginosa, C-terminal FLG2 fragments are generated upon breakdown of the stratum corneum components by the bacteria, resulting in membrane blebbing of the bacteria. These fragments exhibit antimicrobial activity toward P. aeruginosa via interference with the bacterial replication machinery, leading to bacterial death. These exciting findings highlight the potential of FLG2 C-terminal fragments as novel antimicrobials for the eradication of P. aeruginosa infection, which especially threatens cystic fibrosis patients. (PLoS Pathog 11:e1005159, 2015) Selected by T. Schwarz

        Fighting fungal infections

        Fungal infections are particularly problematic for immunocompromised populations; yet, despite constant exposure and colonization of body surfaces with fungi, healthy individuals remain remarkably unscathed. While antimicrobial peptides are the main candidate effector molecules, our understanding of these fungal defense strategies is relatively limited. Hein and colleagues recently identified disulphide-reduced psoriasin (redS100A7) as a primary antifungal agent on human body surfaces. Additional analyses revealed that redS100A7 is a broad-spectrum antifungal that induces apoptosis-like cell death in fungi in a zinc-dependent manner. In addition, redS100A7 along with another cell-penetrating, zinc-chelating fungal agent, TPEN (N,N,N’,N’-tetrakis[2-pyridylmethyl]-ethylenediamine), prevented infection following dermatophyte infection in a guinea pig tinea pedes model and prevented death from invasive fungal infection following infection of immunocompromised mice with a lethal dose of Aspergillus. This discovery suggests that fungus-penetrating, zinc-chelating antifungal agents may be important novel therapeutics for opportunistic or invasive fungal infections. (PNAS 112:13039-13044, 2015) Selected by T. Schwarz

        Into the sunlight

        Erythropoietic protoporphyria is a devastating photodermatosis characterized by acute phototoxicity, severe pain, and a decreased quality of life as a result of accumulated protoporphyrin in erythroid cells and tissues in the absence of effective treatments. In a phase 3, multicenter, randomized, double-blind, placebo-controlled trial involving 167 patients in both the European Union and the United States, Langendonk and colleagues demonstrated that afamelanotide (Scenesse, Clinuvel Pharmaceuticals), a potent α-melanocyte-stimulating hormone analog, was safe and effective for treating photosensitivity in patients with erythropoietic protoporphyria. Significant improvements in duration of pain-free sun exposure time, severity of phototoxic reactions, and recovery time were observed in patients treated with afamelanotide. Furthermore, a favorable effect on patient quality of life was detected following treatment. Thus, afamelanotide-induced eumelanin synthesis may offer antioxidant defense in melanocytes, neutralizing the effects of sunlight and allowing more direct exposure to sunlight without pain in these patients. (N Engl J Med 373:48-59, 2015) Selected by T. Schwarz