Local expression of IFN-gamma mRNA in skin lesions of patients with dermatophytosis

Comparative evaluation of host immune response and cytokine signature pertaining to Th1 and Th2 immune arms in serum and tissue among patients of acute localised vs. chronic disseminated dermatophytosis

BACKGROUND

India is witnessing an epidemic of dermatophytosis. The role of host immune response against fungi in chronicity and dissemination is topic of ongoing research. We conducted cross-sectional comparative study to determine the difference in Th1 (IFN-γ) and Th2 (IL4) response in serum and tissue between acute and localised vs. chronic and disseminated cases.

METHODS

Patients (18-60 years) were divided in two groups-group A (n = 114, BSA <5%, single anatomic site, duration <6 months, n = 118) and group B (n = 107 BSA >10%, > one anatomic site, duration >12 months, n = 118). Clinical parameters along with serum levels of IgE, IL-4 and IFN-γ and expression of IL4 and IFN-γ in dermal infiltrate were compared between group.

RESULTS

Trichophyton mentagrophytes complex was commonest causative fungi. Serum levels of IgE were significantly higher (median A-539.2, B-2901.0, p < .001) whereas levels IL-4(median A-21.3, B-20.4, p < .001) and IFN-γ(median A-9.6, B-5.1, p < .001) were significantly lower in chronic cases. Expression of IL-4 was observed in most biopsy specimens in both groups without any difference in intensity of staining. Expression of IFN-γ was not detected in all but one specimen across both the groups. Severe itching (OR:0.050, CI:0.018, 0.139, p < .001), sign of topical steroid abuse (OR:0.203,CI:0.077, 0.537; p = .001), ↓IFN-γ (OR:4.683, CI:1.634, 13.418; p = .004) correlated significantly and independently with chronic dermatophytosis.

CONCLUSION

Our study shows chronic and disseminated cases of dermatophytosis differ immunologically in terms of higher IgE, and lower IL4 and IFN-γ. Expression of IL4 is present in tissue of both acute, localised and chronic disseminated cases. Expression of IFN-γ cannot be established in our study.

Pathophysiology of psoriasis: A review

Psoriasis is a complex chronic inflammatory skin disease caused by the dynamic interplay between multiple genetic risk foci, environmental risk factors, and excessive immunological abnormalities. Psoriasis affects approximately 2% of the population worldwide, and dramatic advances have been achieved in the understanding and treatment options for psoriasis. Recent progress in biological therapies has revealed the fundamental roles of tumor necrosis factor-α, interleukin (IL)-23p19, and the IL-17A axis together with skin-resident immune cells and major signal transduction pathways in the pathogenesis of psoriasis. In addition to IL-17-producing T helper17 cells, innate lymphoid cell (ILC)3 induces psoriasis rashes directly without T-cell/antigen interaction in response to the released antimicrobial peptides from activated keratinocytes and inflammatory cytokines. ILC3 typically expresses retinoic acid receptor-related orphan receptor gamma t in the nucleus, matures in the presence of IL-7 and IL-23, and produces IL-17 and IL-22. The number of ILC3s is increased in the blood, psoriasis rash, and even in nonrash areas of psoriatic skin. Psoriasis is significantly associated with cardiovascular disease, metabolic syndrome, and inflammatory disorders, particularly the severe type. The similarity of enterobacteria in the psoriasis gut to that in diabetic patients may be related to its pathogenesis. In the current review, we focus on the pathophysiology of psoriasis in the accelerated immunological inflammatory loop, danger signal from keratinocytes, and cytokines, particularly IL-17 and IL-23p19. In addition, pathophysiological speculation with regard to morphology has been supplemented. Finally, the differences and similarities between psoriasis and atopic dermatitis are discussed.

TLR2-/- Mice Display Increased Clearance of Dermatophyte Trichophyton mentagrophytes in the Setting of Hyperglycemia

Dermatophytosis is one of the most common human infections affecting both immunocompetent individuals and immunocompromised patients, in whom the disease is more aggressive and can reach deep tissues. Over the last decades, cases of deep dermatophytosis have increased and the dermatophyte-host interplay remains poorly investigated. Pattern recognition molecules, such as Toll-like receptors (TLR), play a crucial role against infectious diseases. However, there has been very little research reported on dermatophytosis. In the present study, we investigated the role of TLR2 during the development of experimental deep dermatophytosis in normal mice and mice with alloxan-induced diabetes mellitus, an experimental model of diabetes that exhibits a delay in the clearance of the dermatophyte, Trichophyton mentagrophytes (Tm). Our results demonstrated that inoculation of Tm into the footpads of normal mice increases the expression of TLR2 in CD115⁺Ly6C^high blood monocytes and, in hypoinsulinemic-hyperglycemic (HH) mice infected with Tm, the increased expression of TLR2 was exacerbated. To understand the role of TLR2 during the development of murine experimental deep dermatophytosis, we employed TLR2 knockout mice. Tm-infected TLR2^-/- and TLR2^+/+ wild-type mice exhibited similar control of deep dermatophytic infection and macrophage activity; however, TLR2^-/- mice showed a noteworthy increase in production of IFN-γ, IL-10, and IL-17, and an increased percentage of splenic CD25⁺Foxp3⁺ Treg cells. Interestingly, TLR2^-/- HH-Tm mice exhibited a lower fungal load and superior organization of tissue inflammatory responses, with high levels of production of hydrogen peroxide by macrophages, alongside low TNF-α and IL-10; high production of IL-10 by spleen cells; and increased expansion of Tregs. In conclusion, we demonstrate that TLR2 diminishes the development of adaptive immune responses during experimental deep dermatophytosis and, in a diabetic scenario, acts to intensify a non-protective inflammatory response.

Are Th17 Cells Playing a Role in Immunity to Dermatophytosis?

Despite their superficial localization in the skin, pathogenic dermatophytes can induce a complex but still misunderstood immune response in their hosts. The cell-mediated immunity (CMI) is correlated with both clinical recovery and protection against reinfection, and CD4+ T lymphocytes have been recognized as a crucial component of the immune defense against dermatophytes. Before the discovery of the Th17 pathway, CMI was considered to be only dependent of Th1 cells, and thus most studies on the immunology of dermatophytosis have focused on the Th1 pathway. Nevertheless, the fine comparative analysis of available scientific data on immunology of dermatophytosis in one hand and on the Th17 pathway mechanisms involved in opportunistic mucosal fungal infections in the other hand reveals that some key elements of the Th17 pathway can be activated by dermatophytes. Stimulation of the Th17 pathway could occur through the activation of some C-type lectin-like receptors and inflammasome in antigen-presenting cells. The Th17 cells could go back to the affected skin and by the production of signature cytokines could induce the effector mechanisms like the recruitment of polymorphonuclear neutrophils and the synthesis of antimicrobial peptides. In conclusion, besides the Th1 pathway, which is important to the immune response against dermatophytes, there are also growing evidences for the involvement of the Th17 pathway.

Chronic widespread dermatophytosis due to Trichophyton rubrum: a syndrome associated with a Trichophyton-specific functional defect of phagocytes

Dermatophytes are agents of typically benign superficial infections. However, an increasing number of severe infections in immunocompromised hosts has been reported. We aimed to understand the factors underlying the existence of a cohort of patients presenting with chronic widespread dermatophytosis (CWD) due to Trichophyton rubrum, but with no signs of immunodeficiency. Their disease is usually recurrent and difficult to manage. Fourteen patients meeting the following criteria for CWD were studied: T. rubrum culture-proven skin lesions of ≥10 cm in at least one dimension; the involvement of at least three non-contiguous localizations of >1 year's duration; and no predisposing conditions. For comparison, we also studied 13 acute Tinea pedis patients. Macrophages and neutrophils were isolated and tested for T. rubrum conidia phagocytic and killing activity. H2O2, NO, and pro- and anti-inflammatory cytokine release were measured. All experiments were run with age- and sex-matched healthy donors' cells in parallel. CWD patients' macrophages and neutrophils presented with reduced T. rubrum-phagocytic and killing abilities, and reduced H2O2 and NO release when compared with those of healthy donors. CWD patients' macrophages secreted lower levels of the proinflammatory cytokines interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α, but enhanced levels of the anti-inflammatory cytokine IL-10. Neutrophil secretion closely followed this unbalanced pattern. In contrast, responses to the positive controls zymosan, lipopolysaccharide, and phorbol myristate acetate were comparable with those of healthy donors. The same experiments were performed with macrophages and neutrophils from the acute Tinea pedis patients and showed no differences when compared with the matched healthy donors. Patients with CWD have a T. rubrum-related functional deficiency of phagocytes and may represent a distinct clinical entity in the complex spectrum of the Trichophyton-host interaction.

Mycostatic effect of recombinant dermcidin against Trichophyton rubrum and reduced dermcidin expression in the sweat of tinea pedis patients

Trichophytosis, a common dermatophytosis, affects nearly 20-25% of the world's population. However, little is known about mechanisms for preventing colonization of Trichophyton on the skin. Dermcidin, an antimicrobial peptide that provides innate immunity to the skin and is constitutively secreted even in the absence of inflammatory stimulation, was studied to elucidate its antimycotic activity against Trichophyton. Recombinant dermcidin was determined to have antimycotic activity against Trichophyton rubrum, as evaluated by colony-forming unit (CFU) assays. The killing rate of dermcidin was 40.5% and 93.4% at 50 μg/mL (the average dermcidin concentration in healthy subjects) and 270 μg/mL, respectively. An effect of dermcidin treatment was found to be a reduction of the metabolic activity of Trichophyton as determined by nicotinamide adenine dinucleotide assay. Further, dermcidin concentrations in sweat of tinea pedis patients were found to be lower than those of healthy subjects. These findings suggest a mycostatic role for dermcidin, at normal sweat concentrations. Accordingly, we suspect that dermcidin, at normal sweat concentrations, inhibits growth of Trichophyton, where Trichophyton is subsequently eliminated in conjunction with epidermis turnover. Dermcidin, therefore, appears to play a role in the skin protection mechanism that prevents colonization of tinea pedis.

IFN-γ impairs Trichophyton rubrum proliferation in a murine model of dermatophytosis through the production of IL-1β and reactive oxygen species

Trichophyton rubrum is the main etiological agent of dermatophytosis, an infection of the skin that affects millions of people worldwide. In this study, we developed a murine model of the dermatophytosis caused by T. rubrum in which C57BL/6 wild-type, interleukin (IL)-12(-/-), and interferon-gamma (IFN-γ(-/-)) mice were inoculated with 1 × 10(6) conidia/animal. The fungal burden, myeloperoxidase and N-acetylglucosaminidase activities, cytokine and chemokine profiles, and histopathology of the skin were evaluated on the seventh and fourteenth days post infection. Phagocytic indices, intracellular proliferation rates, and oxidative bursts generated by macrophages from WT and IFN-γ(-/-) mice were determined. On day 7 post infection, higher fungal burdens were observed comparison with burdens on day 14 post infection. The IL-12(-/-) and IFN-γ(-/-) mice showed higher fungal burdens on the skin and lower levels of IL-1β. Conversely, the WT mice showed lower fungal burdens with higher production of TNF-α, IL-1β, and chemokine ligand 1/keratinocyte chemoattractant (CXCL1/KC). The macrophages from WT mice proved to be more efficient at engulfing and killing T. rubrum conidia through the production of reactive oxygen species. The results show that our model is a useful tool for understanding the pathogenesis of dermatophytosis caused by T. rubrum and that IL-12 and IFN-γ are pivotal in controlling the infection through the recruitment and activation of neutrophils and macrophages.

Barrier Function, Epidermal Differentiation, and Human β-Defensin 2 Expression in Tinea Corporis

Tinea corporis is a superficial mycotic infection resulting in substantial epidermal changes. We determined skin barrier function, epidermal differentiation, and human-beta-defensin 2 (hBD-2) protein expression in 10 patients with tinea corporis caused by Trichophyton rubrum (T. rubrum). We found disturbed skin barrier function as shown by a significant increase in transepidermal water loss (TEWL) and specific ultrastructural changes including disturbed formation of extracellular lipid bilayers, lamellar body extrusion, and deposit of clotted material at the stratum granulosum/stratum corneum interface. Epidermal proliferation in tinea increased several fold and accordingly, proliferation and inflammation-associated keratins K6, K16, and K17 were expressed. Expression of basal keratins K5 and K14 increased, whereas differentiation-associated K10 was reduced. Reduction of the cornified envelope proteins involucrin, loricrin, and the S100 protein filaggrin was also seen. Reduced filaggrin expression correlated with reduced skin hydration; protein breakdown products of filaggrin have been shown to be important for water binding. Surprisingly, we found pronounced epidermal protein expression of hBD-2, which may be related to disturbed epidermal differentiation and inflammation. hBD-2 showed a weak, although significant, antifungal activity against T. rubrum in the turbidimetric assay and the immunohistological staining was somewhat less pronounced in areas directly underneath fungal hyphae in the stratum corneum. Together, we describe profound changes in skin barrier structure and function, epidermal proliferation, and differentiation including pronounced protein expression of hBD-2 in tinea corporis.

In vitro release of interferon-gamma by trichophytin-stimulated whole blood cell cultures from ringworm-vaccinated and control calves experimentally inoculated with Trichophyton verrucosum

Of a group of seven calves, four were vaccinated against bovine ringworm with the vaccine Ringvac bovis LTF-130 (Alpharma, Oslo, Norway), while three calves were left unvaccinated. All calves were inoculated epicutaneously with a virulent strain of Trichophyton verrucosum. Clinical signs were recorded. In response to stimulation with trichophytin, in vitro interferon-gamma (IFN-gamma) production in whole blood cell cultures was assessed in samples obtained pre- and post-vaccination and pre- and post-inoculation. A commercial enzyme immunoas say kit was used to measure IFN-gamma levels (Bovigam, CSL, Victoria, Australia). Control calves developed typical ringworm lesions, whereas vaccinated calves did not. Following vaccination, release of IFN-gamma in whole blood cell cultures indicated the presence of circulating trichophytin-specific lymphocytes. After inoculation with T. verrucosum, IFN-gamma production was demonstrated in samples from both vaccinated and control calves. This study showed that vaccination with Ringvac bovis LTF-130 elicits a protective immune response suggesting involvement of the cellular branch of the immune system. Experimental infection of naïve nonvaccinated calves with T. verrucosum, also indicated stimulation of a cell-mediated immune response essential for resolution of lesions.

Interferon-gamma production in peripheral lymphocytes of patients with tinea pedis: comparison of patients with and without tinea unguium

The precise mechanism of the host defense that protects the nail from dermatophyte invasion is not known. Recent immunological findings in dermatophytosis suggest the hypothesis that the T helper 1 (Th1) response may play a role in protecting the nail from dermatophyte invasion. Our present study focused on interferon-gamma (IFN-gamma) release in patients with tinea pedis with or without tinea unguium, and pathogenesis of tinea unguium is discussed in relation to the association with a possible deficiency of Th1 response in the host defense mechanism. The production of IFN-gamma by peripheral blood mononuclear cells from the patients with tinea unguium in response to stimulation with trichophytin was not impaired in contrast to that from the patients without tinea unguium. Comparable lymphocyte proliferation to trichophytin was observed in both groups. Normal healthy persons with no clinical evidence of tinea could be divided into two groups based on lymphocyte proliferation and IFN-gamma production in response to trichophytin: high responder and low responder, with high responders being correlated with a clinical history of previous tinea pedis. In this study, a lack of a Th1 response to dermatophyte antigen was not shown in patients with tinea unguium by measuring the release of IFN-gamma, which plays a role in the effector phase of the delayed-type hypersensitivity reaction. A deficiency in the Th1 response to dermatophyte antigen, therefore, does not appear to play an important role in the establishment of tinea unguium.

Local cytokine expression in steroid-modified tinea faciei

In tinea faciei, a dermatophyte infection of the face, early stage lesions show erythema with crust and/or vesicles, a condition often misdiagnosed as dermatitis. Steroid application retards the healing in some cases and may induce penetration of the dermatophyte hyphae into hair and hair follicles. In the present study, we examined local immunity mediated by cytokines derived from lesional T lymphocytes in late stage of this disease. Interferon-gamma (IFN-gamma) and macrophage migration inhibitory factor (MIF) were highly expressed, but neither interleukin-4 (IL-4) nor interleukin-5 (IL-5) could be detected by RT-PCR using cryosections. These data suggested that IFN-gamma and MIF may be important in the delayed-type hypersensitivity (DTH) response against the fungus in the hair follicle in late stages.