The Role of IL-17-Producing Cells in Cutaneous Fungal Infections

High prevalence of dermatophytosis of the feet in acral melanoma of the foot

The clinical characteristics and pathogenesis of acral melanoma of the foot (AMF) have not been sufficiently elucidated. Clinical or subclinical persistent inflammation of the feet is caused by dermatophytosis of the feet (DPF). Persistent inflammation is potentially associated with oncogenesis. Moreover, diabetes has been reported to be associated with the development of dermatophytosis and cancer. The present study aimed to elucidate the clinical association between DPF and AMF, with consideration of diabetes. The medical records of 114 Japanese patients were retrospectively examined and divided into an AMF group (n = 30) and a control group consisting of patients with foot diseases other than melanoma (n = 84). Microscopic DPF screening was performed on all patients who reported symptoms in the foot, with or without AMF. Patients underwent a microscopic test to detect the presence of dermatophytes, and the diagnosis of DPF was made based on a positive result. In the AMF group, 18 (60.0%) and eight (26.7%) patients had DPF and diabetes, respectively. Four patients (13.3%) had both DPF and diabetes. In the control group, 25 (29.8%) and 11 (13.1%) patients had DPF and diabetes, respectively. Five patients (6.0%) had both DPF and diabetes. Univariate analyses showed a significantly higher prevalence of DPF in the AMF group than in the control group (odds ratio, 3.540; p = 0.003, Pearson χ2 test). Furthermore, multivariate analyses of sex, body mass index, DPF, and diabetes revealed DPF as a significant factor associated with AMF (odds ratio, 4.285; p = 0.002, logistic regression analysis). The hyperkeratotic type of DPF was more frequently observed in patients with AMF than in control patients (odds ratio, 11.083; p < 0.001, Pearson χ2 test). In conclusion, the present study found a significantly higher prevalence of DPF, especially its hyperkeratotic type, in patients with AMF. DPF may be associated with AMF pathogenesis.

Skin innate immune response against fungal infections and the potential role of trained immunity

Fungal skin infections are distributed worldwide and can be associated with economic and social traits. The immune response related to skin cells is complex and its understanding is essential to the comprehension of each cell's role and the discovery of treatment alternatives. The first studies of trained immunity (TI) described the ability of monocytes, macrophages and natural killer (NK) cells to develop a memory-like response. However, the duration of TI does not reflect the shorter lifespan of these cells. These conclusions supported later studies showing that TI can be observed in stem and haematopoietic cells and, more recently, also in non-immune skin cells such as fibroblasts, highlighting the importance of resident cells in response to skin disorders. Besides, the participation of less studied proinflammatory cytokines in the skin immune response, such as IL-36γ, shed light into a new possibility of inflammatory pathway blockade by drugs. In this review, we will discuss the skin immune response associated with fungal infections, the role of TI in skin and clinical evidence supporting opportunities and challenges of TI and other inflammatory responses in the pathogenesis of fungal skin infections.

New Immunological Markers in Chromoblastomycosis-The Importance of PD-1 and PD-L1 Molecules in Human Infection

The pathogenesis of chromoblastomycosis (CBM) is associated with Th2 and/or T regulatory immune responses, while resistance is associated with a Th1 response. However, even in the presence of IFN-γ, fungi persist in the lesions, and the reason for this persistence is unknown. To clarify the factors associated with pathogenesis, this study aimed to determine the polarization of the cellular immune response and the densities of cells that express markers of exhaustion in the skin of CBM patients. In the skin of patients with CBM, a moderate inflammatory infiltrate was observed, characterized primarily by the occurrence of histiocytes. Analysis of fungal density allowed us to divide patients into groups that exhibited low and high fungal densities; however, the intensity of the inflammatory response was not related to mycotic loads. Furthermore, patients with CBM exhibited a significant increase in the number of CD4+ and CD8+ cells associated with a high density of IL-10-, IL-17-, and IFN-γ-producing cells, indicating the presence of a chronic and mixed cellular immune response, which was also independent of fungal load. A significant increase in the number of PD-1+ and PD-L1+ cells was observed, which may be associated with the maintenance of the fungus in the skin and the progression of the disease.

Risk of candidiasis associated with interleukin-17 inhibitors: Implications and management

The application of interleukin-17 (IL-17) inhibitors, including secukinumab, ixekizumab, brodalumab, and bimekizumab, are associated with elevated risk of candidiasis. These medications interfere with the IL-17 pathway, which is essential for maintaining mucosal barriers and coordinating the immune response against Candida species. The observational data and clinical trials demonstrate the increased incidence of candidiasis in individuals treated with IL-17 inhibitors. Brodalumab and bimekizumab pose a greater risk than secukinumab in eliciting candidiasis, whereas the data regarding ixekizumab are equivocal. Higher doses and prolonged treatment duration of IL-17 inhibitors increase the risk of candidiasis by compromising the immune response against Candida species. Prior to prescribing IL-17 inhibitors, healthcare professionals should comprehensively evaluate patients' medical histories and assess their risk factors. Patients should be educated on the signs and symptoms of candidiasis to facilitate early detection and intervention. Future research should focus on identifying the risk factors associated with candidiasis in patients receiving IL-17 inhibitors. Prospective studies and long-term surveillance are required to explore the impact of specific inhibitors on the incidence and severity of candidiasis and to evaluate the effectiveness of combination therapies, such as concurrent use of IL-17 inhibitors and prophylactic antifungal agents.

Percentage of Th1 and Th17 cells and serum level of IL-17 and IFN-γ cytokines in COVID-19-associated mucormycosis

The considerable number of the 2019 coronavirus disease (COVID-19) patients who developed mucormycosis infections in West and Central Asia urged a need to investigate the underlying causes of this fatal complication. It was hypothesized that an immunocompromised state secondary to the excessive administration of anti-inflammatory drugs was responsible for the outburst of mucormycosis in COVID-19 patients. Therefore, we aimed to study the implication of two major subsets of adaptive immunity T helper (Th)-1 and Th17 cells in disease development. Thirty patients with COVID-19-associated mucormycosis, 38 with COVID-19 without any sign or symptom of mucormycosis, and 26 healthy individuals were included. The percentage of Th1 and Th17 cells in peripheral blood, as well as the serum levels of interleukin (IL)-17 and interferon-gamma (IFN-γ), were evaluated using flow cytometry and ELISA techniques, respectively. Th17 cell percentage in patients with COVID-19-associated mucormycosis was significantly lower than in COVID-19 patients (P-value: <0.001) and healthy subjects (P-value: 0.01). In addition, the serum level of IL-17 in COVID-19 patients was significantly higher than that of healthy individuals (P-value: 0.01). However, neither the frequency of Th1 cells nor the serum level of IFN-γ was different between the study groups. Given the critical role of Th17 cells in the defense against mucosal fungal infections, these findings suggest that low numbers of Th17 and insufficient levels of IL-17 might be a predisposing factor for the development of mucormycosis during or after COVID-19 infection.

Candida Infection Associated with Anti-IL-17 Medication: A Systematic Analysis and Review of the Literature

Anti-interleukin (IL)-17 agents have shown excellent therapeutic efficacy in patients with psoriasis and are expected to be expanded to other chronic inflammatory diseases. However, patients receiving anti-IL-17 agents are at an increased risk of developing Candida infection, with some agents reported to increase the incidence in a dose-dependent manner. Interleukin-17 is secreted by the Th17 subset of CD4+ lymphocytes, CD8+ T cells, and innate cells, including natural killer T cells, lymphoid tissue inducer cells, innate lymphoid cells, and γδ-T cells, and plays an important role in antifungal defense. Genetic defects in the IL-17-signaling pathway in both humans and animal models render susceptibility to candidiasis caused by Candida albicans. The purpose of this narrative review is to evaluate the literature on the role of IL-17 in protection against candidiasis, the prevalence of candidiasis in anti-IL-17 agent use, and to offer clinical recommendations on the diagnosis and management of anti-IL-17 medication-associated candidiasis.

Review of secukinumab-induced adverse events of special interest and its potential pathogenesis

Although secukinumab has demonstrated high efficacy and favorable safety in moderate-to-severe psoriasis and psoriatic arthritis, patients developing adverse events of special interest (AESI) were reported increasingly in real-world practice. A systematic literature search of the PubMed database was conducted to identify clinical studies or case reports on secukinumab-induced AESI. More than 1077 patients (aged 18-74 years) from 55 studies were reported to have 24 AESI 3 days to 96 weeks after secukinumab treatment. The four most common AESI was inflammatory bowel disease (n > 1000), eczematous drug eruption (n > 30), drug-associated vasculitis (n = 8), and drug-induced lupus erythematosus (n = 4). Most of these AESI were only mild to moderately severe and resolved after secukinumab discontinuation without or with symptomatic treatment. Secukinumab has the potential to develop a number of AESI by probably dysregulating the different expression of polar T-cell axes (Th1, Th2, Th17, Th22, and/or Treg) and driving various cytokines in some patients. Physicians should be aware of these AESI for timely diagnosis and proper treatment. This article is protected by copyright. All rights reserved.

Reviewing the Etiologic Agents, Microbe-Host Relationship, Immune Response, Diagnosis, and Treatment in Chromoblastomycosis

Chromoblastomycosis (CBM) is a neglected human disease, caused by different species of pigmented dematiaceous fungi that cause subcutaneous infections. This disease has been considered an occupational disease, occurring among people working in the field of agriculture, particularly in low-income countries. In 1914, the first case of CBM was described in Brazil, and although efforts have been made, few scientific and technological advances have been made in this area. In the field of fungi and host cell relationship, a very reduced number of antigens were characterized, but available data suggest that ectoantigens bind to the cell membrane of host cells and modulate the phagocytic, immunological, and microbicidal responses of immune cells. Furthermore, antigens cleave extracellular proteins in tissues, allowing fungi to spread. On the contrary, if phagocytic cells are able to present antigens in MHC molecules to T lymphocytes in the presence of costimulation and IL-12, a Th1 immune response will develop and a relative control of the disease will be observed. Despite knowledge of the resistance and susceptibility in CBM, up to now, no effective vaccines have been developed. In the field of chemotherapy, most patients are treated with conventional antifungal drugs, such as itraconazole and terbinafine, but these drugs exhibit limitations, considering that not all patients heal cutaneous lesions. Few advances in treatment have been made so far, but one of the most promising ones is based on the use of immunomodulators, such as imiquimod. Data about a standard treatment are missing in the medical literature; part of it is caused by the existence of a diversity of etiologic agents and clinical forms. The present review summarizes the advances made in the field of CBM related to the diversity of pathogenic species, fungi and host cell relationship, antigens, innate and acquired immunity, clinical forms of CBM, chemotherapy, and diagnosis.

Genetic Susceptibility to Fungal Infections and Links to Human Ancestry

Over the ages, fungi have associated with different parts of the human body and established symbiotic associations with their host. They are mostly commensal unless there are certain not so well-defined factors that trigger the conversion to a pathogenic state. Some of the factors that induce such transition can be dependent on the fungal species, environment, immunological status of the individual, and most importantly host genetics. In this review, we discuss the different aspects of how host genetics play a role in fungal infection since mutations in several genes make hosts susceptible to such infections. We evaluate how mutations modulate the key recognition between the pathogen associated molecular patterns (PAMP) and the host pattern recognition receptor (PRR) molecules. We discuss the polymorphisms in the genes of the immune system, the way it contributes toward some common fungal infections, and highlight how the immunological status of the host determines fungal recognition and cross-reactivity of some fungal antigens against human proteins that mimic them. We highlight the importance of single nucleotide polymorphisms (SNPs) that are associated with several of the receptor coding genes and discuss how it affects the signaling cascade post-infection, immune evasion, and autoimmune disorders. As part of personalized medicine, we need the application of next-generation techniques as a feasible option to incorporate an individual’s susceptibility toward invasive fungal infections based on predisposing factors. Finally, we discuss the importance of studying genomic ancestry and reveal how genetic differences between the human race are linked to variation in fungal disease susceptibility.