Dendritic cells and fungi

Dysbiosis of skin mycobiome in atopic dermatitis

Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease with an increasing prevalence worldwide. The aetiology and pathogenesis of AD have not been fully elucidated. Previous studies have suggested the role of fungi as a triggering factor in the development AD. Here we conducted a systematic review to investigate the skin mycobiome profiles in AD and to address whether there is an association between fungal dysbiosis and AD. We searched Medline/PubMed, Embase and Web of Science for research studies published in English between January 1st, 2010 and April 21st, 2021. A total of 11 human studies and 3 animal studies were included in this analysis. Fungal dysbiosis was observed in AD lesions with a depleted amount of Malassezia and a higher abundance of filamentous fungi. A positive correlation between Candida and Staphylococcus was also demonstrated in AD. We supposed that specific species of Malassezia spp. and Candida spp. may play a role in the pathogenesis of AD by interacting with the pathogenic bacteria. Topical application of emollients could improve the skin barrier function and restore the skin fungal flora by increasing the amount of Malassezia. Further studies focusing on the complex interplay between specific skin fungi and the host can provide better insight into the role of microorganisms in the pathogenesis of AD.

Role of Antimicrobial Peptides in Skin Barrier Repair in Individuals with Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that exhibits a complex interplay of skin barrier disruption and immune dysregulation. Patients with AD are susceptible to cutaneous infections that may progress to complications, including staphylococcal septicemia. Although most studies have focused on filaggrin mutations, the physical barrier and antimicrobial barrier also play critical roles in the pathogenesis of AD. Within the physical barrier, the stratum corneum and tight junctions play the most important roles. The tight junction barrier is involved in the pathogenesis of AD, as structural and functional defects in tight junctions not only disrupt the physical barrier but also contribute to immunological impairments. Furthermore, antimicrobial peptides, such as LL-37, human b-defensins, and S100A7, improve tight junction barrier function. Recent studies elucidating the pathogenesis of AD have led to the development of barrier repair therapy for skin barrier defects in patients with this disease. This review analyzes the association between skin barrier disruption in patients with AD and antimicrobial peptides to determine the effect of these peptides on skin barrier repair and to consider employing antimicrobial peptides in barrier repair strategies as an additional approach for AD management.

The clinical significance of fungi in atopic dermatitis

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin diseases and is caused by multiple factors including genetic factors, skin barrier defects, host immune responses, allergen sensitivity, environmental effects, and infections. Commonly, bacterial and viral infections are present in the eczematous lesions of AD patients and clearly aggravate the symptoms. However, studies of fungal infections in AD are limited in spite of the fact that there are reports showing that Malassezia, Candida, and some dermatophytes can affect the symptoms of AD. Moreover, certain fungal infections are sometimes overlooked and need to be considered particularly in AD patients with treatment failure as clinical features of those fungal infections could mimic eczematous lesions in AD. Here, we review the epidemiology, pathogenesis, clinical manifestations, and overlooked features of fungal infections associated with the symptoms of AD including the diagnosis and effectiveness of fungal treatments in AD patients.

The Role of Fungi in Atopic Dermatitis

There is little doubt that Malassezia spp plays a role in atopic dermatitis because it may interact with the local skin immune responses and barrier function, and sensitization against this skin-colonizing yeast can correlate with disease activity. Also, antifungal therapy shows beneficial effects in some patients. However, the pathogenetic mechanism and mutual interaction between Malassezia spp and atopic dermatitis still remain partly unclear and need further investigation.

The Role of Malassezia spp. in Atopic Dermatitis

Malassezia spp. is a genus of lipophilic yeasts and comprises the most common fungi on healthy human skin. Despite its role as a commensal on healthy human skin, Malassezia spp. is attributed a pathogenic role in atopic dermatitis. The mechanisms by which Malassezia spp. may contribute to the pathogenesis of atopic dermatitis are not fully understood. Here, we review the latest findings on the pathogenetic role of Malassezia spp. in atopic dermatitis (AD). For example, Malassezia spp. produces a variety of immunogenic proteins that elicit the production of specific IgE antibodies and may induce the release of pro-inflammatory cytokines. In addition, Malassezia spp. induces auto-reactive T cells that cross-react between fungal proteins and their human counterparts. These mechanisms contribute to skin inflammation in atopic dermatitis and therefore influence the course of this disorder. Finally, we discuss the possible benefit of an anti-Malassezia spp. treatment in patients with atopic dermatitis.

Dendritic cell interactions with Histoplasma and Paracoccidioides

Fungi are among the most common microbes encountered by humans. More than 100, 000 fungal species have been described in the environment to date, however only a few species cause disease in humans. Fungal infections are of particular importance to immunocompromised hosts in whom disease is often more severe, especially in those with impaired cell-mediated immunity such as individuals with HIV infection, hematologic malignancies, or those receiving TNF-α inhibitors. Nevertheless, environmental disturbances through natural processes or as a consequence of deforestation or construction can expose immunologically competent people to a large number of fungal spores resulting in asymptomatic acquisition to life-threatening disease. In recent decades, the significance of the innate immune system and more importantly the role of dendritic cells (DC) have been found to play a fundamental role in the resolution of fungal infections, such as in dimorphic fungi like Histoplasma and Paracoccidioides. In this review article the general role of DCs will be illustrated as the bridge between the innate and adaptive immune systems, as well as their specific interactions with these 2 dimorphic fungi.

Human monocyte-derived dendritic cells exposed to microorganisms involved in hypersensitivity pneumonitis induce a Th1-polarized immune response

Hypersensitivity pneumonitis (HP) is an immunoallergic disease characterized by a prominent interstitial infiltrate composed predominantly of lymphocytes secreting inflammatory cytokines. Dendritic cells (DCs) are known to play a pivotal role in the lymphocytic response. However, their cross talk with microorganisms that cause HP has yet to be elucidated. This study aimed to investigate the initial interactions between human monocyte-derived DCs (MoDCs) and four microorganisms that are different in nature (Saccharopolyspora rectivirgula [actinomycetes], Mycobacterium immunogenum [mycobacteria], and Wallemia sebi and Eurotium amstelodami [filamentous fungi]) and are involved in HP. Our objectives were to determine the cross talk between MoDCs and HP-causative agents and to determine whether the resulting immune response varied according to the microbial extract tested. The phenotypic activation of MoDCs was measured by the increased expression of costimulatory molecules and levels of cytokines in supernatants. The functional activation of MoDCs was measured by the ability of MoDCs to induce lymphocytic proliferation and differentiation in a mixed lymphocytic reaction (MLR). E. amstelodami-exposed (EA) MoDCs expressed higher percentages of costimulatory molecules than did W. sebi-exposed (WS), S. rectivirgula-exposed (SR), or M. immunogenum-exposed (MI) MoDCs (P < 0.05, Wilcoxon signed-rank test). EA-MoDCs, WS-MoDCs, SR-MoDCs, and MI-MoDCs induced CD4(+) T cell proliferation and a Th1-polarized immune response. The present study provides evidence that, although differences were initially observed between MoDCs exposed to filamentous fungi and MoDCs exposed to bacteria, a Th1 response was ultimately promoted by DCs regardless of the microbial extract tested.

Dendritic cell are able to differentially recognize Sporothrix schenckii antigens and promote Th1/Th17 response in vitro

Sporotrichosis is a disease caused by the dimorphic fungus Sporothrix schenckii. The main clinical manifestations occur in the skin, however the number of systemic and visceral cases has increased, especially in immunocompromised patients. Dendritic cells (DCs) are highly capable to recognize the fungus associated data and translate it into differential T cells responses both in vivo and in vitro. Although, the mechanisms involved in the interaction between DCs and S. schenckii are not fully elucidated. The present study investigated the phenotypic and functional changes in bone marrow dendritic cells (BMDCs) stimulated in vitro with the yeast form of S. schenckii or exoantigen (ExoAg) and its ability to trigger a cellular immune response in vitro. Our results demonstrated that the live yeast of S. schenckii and its exoantigen, at a higher dose, were able to activate BMDCs and made them capable of triggering T cell responses in vitro. Whereas the yeast group promoted more pronounced IFN-γ production rather than IL-17, the Exo100 group generated similar production of both cytokines. The exoantigen stimulus suggests a capability to deviate the immune response from an effector Th1 to an inflammatory Th17 response. Interestingly, only the Exo100 group promoted the production of IL-6 and a significant increase of TGF-β, in addition to IL-23 production. Interestingly, only Exo100 group was capable to promote the production of IL-6 and a significant increase on TGF-β, in addition with IL-23 detection. Our results demonstrated the plasticity of DCs in translating the data associated with the fungus S. schenckii and ExoAg into differential T cell responses in vitro. The possibility of using ex vivo-generated DCs as vaccinal and therapeutic tools for sporotrichosis is a challenge for the future.

Murine dendritic cells transcriptional modulation upon Paracoccidioides brasiliensis infection

Limited information is available regarding the modulation of genes involved in the innate host response to Paracoccidioides brasiliensis, the etiologic agent of paracoccidioidomycosis. Therefore, we sought to characterize, for the first time, the transcriptional profile of murine bone marrow-derived dendritic cells (DCs) at an early stage following their initial interaction with P. brasiliensis. DCs connect innate and adaptive immunity by recognizing invading pathogens and determining the type of effector T-cell that mediates an immune response. Gene expression profiles were analyzed using microarray and validated using real-time RT-PCR and protein secretion studies. A total of 299 genes were differentially expressed, many of which are involved in immunity, signal transduction, transcription and apoptosis. Genes encoding the cytokines IL-12 and TNF-α, along with the chemokines CCL22, CCL27 and CXCL10, were up-regulated, suggesting that P. brasiliensis induces a potent proinflammatory response in DCs. In contrast, pattern recognition receptor (PRR)-encoding genes, particularly those related to Toll-like receptors, were down-regulated or unchanged. This result prompted us to evaluate the expression profiles of dectin-1 and mannose receptor, two other important fungal PRRs that were not included in the microarray target cDNA sequences. Unlike the mannose receptor, the dectin-1 receptor gene was significantly induced, suggesting that this β-glucan receptor participates in the recognition of P. brasiliensis. We also used a receptor inhibition assay to evaluate the roles of these receptors in coordinating the expression of several immune-related genes in DCs upon fungal exposure. Altogether, our results provide an initial characterization of early host responses to P. brasiliensis and a basis for better understanding the infectious process of this important neglected pathogen.

Paracoccidioidomycosis is a systemic disease that has an important mortality and morbidity impact in Latin America, mainly affecting rural workers of Argentina, Colombia, Venezuela and Brazil. Upon host infection, one of the most important aspects contributing to disease outcome is the initial encounter of the Paracoccidioides brasiliensis fungus with dendritic cells. This phagocytic cell is specialized in decoding microbial information and triggering specific immune responses. Thus, using a molecular biology technique to examine the response of thousand of genes, we aimed to identify the ways in which murine dendritic cells interact with P. brasiliensis during an early time point following infection. This approach allowed us to recognize diverse modulated genes, in particular those associated with a proinflamatory response and fungal recognition. Our work provides an initial molecular characterization of early infection process and should promote further investigations into the innate host response to this important fungal pathogen.

Experimental models of cryptococcosis

Cryptococcosis is a life-threatening fungal disease that infects around one million people each year. Establishment and progression of disease involves a complex interplay between the fungus and a diverse range of host cell types. Over recent years, numerous cellular, tissue, and animal models have been exploited to probe this host-pathogen interaction. Here we review the range of experimental models that are available for cryptococcosis research and compare the relative advantages and limitations of the different systems.

Short native antimicrobial peptides and engineered ultrashort lipopeptides: similarities and differences in cell specificities and modes of action

Due to the rapid emergence of resistant microbes to the currently available antibiotics, cationic antimicrobial peptides have attracted considerable interest as a possible new generation of anti-infective compounds. However, low cost development for therapeutic or industrial purposes requires, among other properties, that the peptides will be small and with simple structure. Therefore, considerable research has been devoted to optimizing peptide length combined with a simple design. This review focuses on the similarities and differences in the mode of action and target cell specificity of two families of small peptides: the naturally occurring temporins from the skin of amphibia and the engineered ultrashort lipopeptides. We will also discuss the finding that acylation of cationic peptides results in molecules with a more potent spectrum of activity and a higher resistance to proteolytic degradation. Conjugation of fatty acids to linear native peptide sequences is a powerful strategy to engineer novel successful anti-infective drugs.

Limited role of secreted aspartyl proteinases Sap1 to Sap6 in Candida albicans virulence and host immune response in murine hematogenously disseminated candidiasis

Candida albicans secreted aspartyl proteinases (Saps) are considered virulence-associated factors. Several members of the Sap family were claimed to play a significant role in the progression of candidiasis established by the hematogenous route. This assumption was based on the observed attenuated virulence of sap-null mutant strains. However, the exclusive contribution of SAP genes to their attenuated phenotype was not unequivocally confirmed, as the Ura status of these mutant strains could also have contributed to the attenuation. In this study, we have reassessed the importance of SAP1 to SAP6 in a murine model of hematogenously disseminated candidiasis using sap-null mutant strains not affected in their URA3 gene expression and compared their virulence phenotypes with those of Ura-blaster sap mutants. The median survival time of BALB/c mice intravenously infected with a mutant strain lacking SAP1 to SAP3 was equivalent to that of mice infected with wild-type strain SC5314, while those infected with mutant strains lacking SAP5 showed slightly extended survival times. Nevertheless, no differences could be observed between the wild type and a Δsap456 mutant in their abilities to invade mouse kidneys. Likewise, a deficiency in SAP4 to SAP6 had no noticeable impact on the immune response elicited in the spleens and kidneys of C. albicans-infected mice. These results contrast with the behavior of equivalent Ura-blaster mutants, which presented a significant reduction in virulence. Our results suggest that Sap1 to Sap6 do not play a significant role in C. albicans virulence in a murine model of hematogenously disseminated candidiasis and that, in this model, Sap1 to Sap3 are not necessary for successful C. albicans infection.

Human dendritic cell maturation and activation by a heat-killed recombinant yeast (Saccharomyces cerevisiae) vector encoding carcinoembryonic antigen

Tumor-associated antigens are weakly immunogenic. Human carcinoembryonic antigen (CEA) is overexpressed on a wide range of human carcinomas and represents an attractive target for cancer immunotherapy. This study analyzes the ability of a Saccharomyces cerevisiae vector containing the transgene encoding CEA (yeast-CEA) to activate human dendritic cells (DCs) and stimulate CEA-specific T-cell responses. We demonstrate for the first time that treatment with yeast-CEA can activate human DCs, resulting in increases in surface expression of CD80, CD83, CD54, CD58, and MHC class II, and increased production by DCs of IL-12p70, TNF-alpha, IFN-gamma, IL-8, IL-2, IL-13, IL-10, and IL-1beta. We also show that human DCs treated with yeast-CEA can activate CEA-specific T-cell lines and can act as antigen-presenting cells (APCs) to generate CEA-specific T-cell lines capable of lysing CEA(+) human tumor cells. Gene expression profiles of human DCs treated with yeast-CEA show increased expression of numerous genes involved in the production of chemokines and cytokines and their receptors, and genes related to antigen uptake, antigen presentation, and signal transduction.

Using pathway signatures as means of identifying similarities among microarray experiments

Widespread use of microarrays has generated large amounts of data, the interrogation of the public microarray repositories, identifying similarities between microarray experiments is now one of the major challenges. Approaches using defined group of genes, such as pathways and cellular networks (pathway analysis), have been proposed to improve the interpretation of microarray experiments. We propose a novel method to compare microarray experiments at the pathway level, this method consists of two steps: first, generate pathway signatures, a set of descriptors recapitulating the biologically meaningful pathways related to some clinical/biological variable of interest, second, use these signatures to interrogate microarray databases. We demonstrate that our approach provides more reliable results than with gene-based approaches. While gene-based approaches tend to suffer from bias generated by the analytical procedures employed, our pathway based method successfully groups together similar samples, independently of the experimental design. The results presented are potentially of great interest to improve the ability to query and compare experiments in public repositories of microarray data. As a matter of fact, this method can be used to retrieve data from public microarray databases and perform comparisons at the pathway level.

Vaccination with a recombinant Saccharomyces cerevisiae expressing a tumor antigen breaks immune tolerance and elicits therapeutic antitumor responses

PURPOSE

Saccharomyces cerevisiae, a nonpathogenic yeast, has been used previously as a vehicle to elicit immune responses to foreign antigens, and tumor-associated antigens, and has been shown to reduce tumor burden in mice. Studies were designed to determine if vaccination of human carcinoembryonic antigen (CEA)-transgenic (CEA-Tg) mice (where CEA is a self-antigen) with a recombinant S. cerevisiae construct expressing human CEA (yeast-CEA) elicits CEA-specific T-cell responses and antitumor activity.

EXPERIMENTAL DESIGN

CEA-Tg mice were vaccinated with yeast-CEA, and CD4(+) and CD8(+) T-cell responses were assessed after one and multiple administrations or vaccinations at multiple sites per administration. Antitumor activity was determined by tumor growth and overall survival in both pulmonary metastasis and s.c. pancreatic tumor models.

RESULTS

These studies demonstrate that recombinant yeast can break tolerance and that (a) yeast-CEA constructs elicit both CEA-specific CD4(+) and CD8(+) T-cell responses; (b) repeated yeast-CEA administration causes increased antigen-specific T-cell responses after each vaccination; (c) vaccination with yeast-CEA at multiple sites induces a greater T-cell response than the same dose given at a single site; and (d) tumor-bearing mice vaccinated with yeast-CEA show a reduction in tumor burden and increased overall survival compared to mock-treated or control yeast-vaccinated mice in both pulmonary metastasis and s.c. pancreatic tumor models.

CONCLUSIONS

Vaccination with a heat-killed recombinant yeast expressing the tumor-associated antigen CEA induces CEA-specific immune responses, reduces tumor burden, and extends overall survival in CEA-Tg mice. These studies thus form the rationale for the incorporation of recombinant yeast-CEA and other recombinant yeast constructs in cancer immunotherapy protocols.

White button mushroom enhances maturation of bone marrow-derived dendritic cells and their antigen presenting function in mice

Mushrooms have been shown to enhance immune response, which contributes to their antitumor property. White button mushrooms (Agaricus bisporus) (WBM) constitute 90% of the total mushrooms consumed in the United States; however, the health benefit of this strain in general is not well studied. Furthermore, little is known about WBM's immunologic effects. Dendritic cells (DC) are the most potent antigen presenting cells and play a pivotal role in immune response by linking innate and adaptive immune responses. In this study, we investigated the effect of in vitro supplementation with WBM on maturation of bone marrow-derived DC (BMDC) of C57BL mice. BMDC were differentiated in the presence of whole mushroom concentrate at 50, 100, or 200 mg/L. Results showed that mushroom supplementation dose dependently increased the expression of maturation markers CD40, CD80, CD86, and major histocompatibility complex-II. Consistent with the changes in the phenotypic markers, functional assay for DC maturation showed that mushroom supplementation decreased DC endocytosis and increased intracellular interleukin (IL)-12 levels. Furthermore, using a syngeneic T cell activation model, we found that WBM-supplemented DC from BALB/c mice presented ovalbumin antigen to T cells from DO11.10 mice more efficiently as demonstrated by increased T cell proliferation and IL-2 production. In conclusion, WBM promote DC maturation and enhance their antigen-presenting function. This effect may have potential in enhancing both innate and T cell-mediated immunity leading to a more efficient surveillance and defense mechanism against microbial invasion and tumor development.

The Malassezia sympodialis allergen Mala s 11 induces human dendritic cell maturation, in contrast to its human homologue manganese superoxide dismutase

BACKGROUND

Recently, we identified a major Malassezia sympodialis allergen, Mala s 11, which displays a high degree of DNA sequence homology to human manganese superoxide dismutase (hMnSOD). In atopic eczema patients sensitized to M. sympodialis, hMnSOD can elicit eczematous reactions and positive skin prick tests, suggesting cross- reactivity to Mala s 11 based on molecular mimicry. The objective of the current study was to compare the influence of Mala s 11 and hMnSOD on human dendritic antigen-presenting cells.

METHODS

Monocyte-derived dendritic cells (MDDCs) from healthy blood donors were co-cultured with recombinant Mala s 11 (rMala s 11), recombinant hMnSOD (rhMnSOD), lipopolysaccharide or cultured in medium alone. Phenotypic changes were analysed using flow cytometry and allogeneic lymphocyte proliferation assays. Cytokine release into culture supernatants was investigated using cytometric bead array.

RESULTS

Whereas rhMnSOD did not affect the MDDC phenotype, rMala s 11 up-regulated the maturation marker CD83, the co-stimulatory molecules CD40, CD80, CD86 and HLA-DR to a similar extent as lipopolysaccharide. Furthermore, rMala s 11, but not rhMnSOD, induced significantly higher levels of TNF-alpha, IL-6, IL-8, IL-10 and IL-12p70 in the culture supernatants at 24 h in comparison with MDDCs cultured in medium alone. Finally, MDDCs pre-incubated with rMala s 11 induced a significantly higher proliferation of allogeneic CD14-depleted peripheral blood monocytes than MDDCs pre-incubated with rhMnSOD.

CONCLUSION

Our results suggest that Mala s 11, but not hMnSOD, affects the immune response of healthy individuals through dendritic cell maturation and cytokine release. This indicates that dendritic cells possess the ability to distinguish between Mala s 11 and its human homologue MnSOD.

Atopic dermatitis

Atopic dermatitis is an especially common and frustrating condition, and the prevalence is increasing. The disease can adversely affect the quality of life of patients and caregivers. Significant advances in our understanding of the pathogenesis have led to improvements in therapy. Patient and caregiver education, avoidance of potential triggering factors, optimal skin care, and pharmacotherapy offer the potential for good control for most patients.

Phenotypic and functional characterization of vaginal dendritic cells in a rat model of Candida albicans vaginitis

This study analyzes the phenotype of vaginal dendritic cells (VDCs), their antigenic presentation and activation of T-cell cytokine secretion, and their protective role in a rat model of Candida vaginitis. Histological observation demonstrated a significant accumulation of OX62(+) VDCs in the mucosal epithelium of Candida albicans-infected rats at the third round of infection. We identified two subsets of OX62(+) VDCs differing in the expression of CD4 molecule in both noninfected and Candida-infected rats. The OX62(+) CD4(+) subset of VDCs displayed a lymphoid cell-like morphology and expressed the T-cell antigen CD5, whereas the OX62(+) CD4(-) VDC subset exhibited a myeloid morphology and was CD5 negative. Candida infection resulted in VDC maturation with enhanced expression of CD80 and CD134L on both CD4(+) and CD4(-) VDC subsets at 2 and 6 weeks after Candida infection. CD5(-) CD4(-) CD86(-) CD80(-) CD134L(+) VDCs from infected, but not noninfected, rats spontaneously released large amounts of interleukin-12 (IL-12) and tumor necrosis factor alpha, whereas all VDC subsets released comparable levels of IL-10 and IL-2 cytokines. Furthermore, OX62(+) VDCs from infected rats primed naïve CD4(+) T-cell proliferation and release of cytokines, including gamma interferon, IL-2, IL-6, and IL-10, in response to staphylococcal enterotoxin B stimulation in vitro. Adoptive transfer of highly purified OX62(+) VDCs from infected rats induced a significant acceleration of fungal clearance compared with that in rats receiving naive VDCs, suggesting a protective role of VDCs in the anti-Candida mucosal immunity. Finally, VDC-mediated protection was associated with their ability to rapidly migrate to the vaginal mucosa and lymph nodes, as assessed by adoptive transfer of OX62(+) VDCs labeled with 5 (and 6-)-carboxyfluorescein diacetate succinimidyl ester.

The role of microorganisms in atopic dermatitis

Atopic dermatitis (AD) is a common, fluctuating skin disease that is often associated with atopic conditions such as asthma and IgE-mediated food allergy and whose skin lesions are characterized by a Th-2 cell-mediated response to environmental antigens. The increasing prevalence and severity of atopic diseases including AD over the last three decades has been attributed to decreased exposure to microorganisms during early life, which may result in an altered Th-1/Th-2-balance and/or reduced T cell regulation of the immune response. Patients with AD exhibit defects in innate and acquired immune responses resulting in a heightened susceptibility to bacterial, fungal and viral infections, most notably colonization by S. aureus. Toxins produced by S. aureus exacerbate disease activity by both the induction of toxin-specific IgE and the activation of various cell types including Th-2 cells, eosinophils and keratinocytes. Allergens expressed by the yeast Malazessia furfur, a component of normal skin flora, have also been implicated in disease pathogenesis in a subset of AD patients. Microorganisms play an influential role in AD pathogenesis, interacting with disease susceptibility genes to cause initiation and/or exacerbation of disease activity.

Malassezia sympodialis differently affects the expression of LL-37 in dendritic cells from atopic eczema patients and healthy individuals

BACKGROUND

Atopic eczema (AE) is a multifactorial disease, which has increased in prevalence. The skin-colonizing yeast Malasezzia sympodialis can induce IgE- and T-cell reactivity in patients with AE. LL-37 is an endogenous peptide antibiotic belonging to the cathelicidin family. The aim of this study was to examine whether exposure to M. sympodialis would affect the expression of LL-37 in dendritic cells.

METHODS

The presence of LL-37 was analyzed in monocyte-derived dendritic cells (MDDCs) generated from healthy individuals and patients with AE by Western blotting and the corresponding cDNA by real-time quantitative RT-PCR. Antibacterial activity was measured with an inhibition zone assay in fractions after reverse phase chromatography.

RESULTS

For the first time we here present data, showing that LL-37 is produced by MDDCs. Notably, the secretion of LL-37 was substantially enhanced in M. sympodialis-exposed MDDCs generated from patients with a high degree of eczema, as measured by SCORAD, compared to healthy controls and patients with a low SCORAD. The relative expression of LL-37 transcript in MDDCs generated from patients was up-regulated after 1 h of exposure to M. sympodialis and declined gradually at the time points analyzed, whereas the transcription was unaffected in the MDDCs of healthy controls.

CONCLUSIONS

Our results suggest that M. sympodialis can trigger the innate immune response differently in patients with AE and healthy individuals. The enhanced LL-37 secretion from the MDDCs in the patients with AE may reflect the severity of their inflammatory response to M. sympodialis.

Dendritic cells in allogeneic hematopoietic stem cell transplantation

In allogeneic hematopoietic stem cell transplantation (SCT), dendritic cells (DCs) as the most potent antigen-presenting cells play a central role in the development of acute and chronic graft-vs-host disease (GVHD), in graft-vs-leukemia or -malignancy reactions and in fighting infectious complications. Functional maturity and distribution of DC sub-types (DC1 and DC2) differ between the different stem cell sources used (bone marrow, granulocyte colony-stimulating factor-mobilised peripheral blood and cord blood) resulting in various rates of graft-vs-host disease and graft-vs-leukemia activity. Although DC recovery following stem cell transplantation is prompt, graft-vs-host disease and the use of immunosuppressive drugs result in qualitative and quantitative disturbances in DC homeostasis and have been observed for up to 1 year after transplantation. Complete donor DC chimerism seems to be a pre-requisite for the development of chronic GVHD and for graft-vs-leukemia activity, at least following reduced-intensity transplants, although in the early phase of acute graft-vs-host disease the presence of host antigen-presenting cells is essential. Preliminary data show promising results with DC-based immunotherapy for treatment of viral and fungal infections and of leukemic relapse following allogeneic stem cell transplantation. More information on the mechanisms and interactions between dendritic cells and regulatory T cells is needed for DC vaccination concepts for modulation of graft-vs-host disease.

Ganoderma lucidumMycelium and Spore Extracts as Natural Adjuvants for Immunotherapy

OBJECTIVES

Ganoderma lucidum (GL) is one of the most commonly used Chinese herbs in the oriental community, with more than 30% of pediatric cancer patients taking GL. The immunomodulating and anticancer effects exerted by GL extracts have been demonstrated by in vitro and in vivo studies. There was, however, no comparison between the immunomodulating effects of GL mycelium extract (GL-M) and spore extracts on human immune cells. Dendritic cells (DCs) are professional antigen-presenting cells and their role in DC-based tumor vaccine has been well defined. The possibility of GL as natural adjuvant for human DCs remains unknown.

DESIGN

This study explored the differential effect of GL-M and GL spore extract (GL-S) on proliferation and Th1/Th2 cytokine mRNA expression of human peripheral blood mononuclear cells (PBMCs) and monocytes. Their effects on the phenotypic and functional maturation of human monocyte-derived DCs were also investigated.

RESULTS

GL-M induced the proliferation of PBMCs and monocytes, whereas GL-S showed a mild suppressive effect. Both extracts could stimulate Th1 and Th2 cytokine mRNA expression, but GL-M was a relatively stronger Th1 stimulator. Different from GL-S, GL-M enhanced maturation of DCs in terms of upregulation of CD40, CD80, and CD86, and also reduced fluorescein isothiocyanate-dextran endocytosis. Interestingly, GLM- treated DCs only modestly enhanced lymphocyte proliferation in allogenic mixed lymphocyte culture with mild enhancement in Th development.

CONCLUSION

These findings provide evidences that GL-M has immunomodulating effects on human immune cells and therefore can be used as a natural adjuvant for cancer immunotherapy with DCs.

Yeasts encoding tumour antigens in cancer immunotherapy

Immunotherapy for cancer represents an attractive therapeutic target because of its specificity and lack of toxicity, but products investigated so far have been limited by neutralisation, complexity of manufacturing and requirement for patient-specific products. Recombinant yeast cells are capable of stimulating the immune system to produce highly specific and potent cellular responses against target protein antigens with little toxicity. Data from animal models suggest that Tarmogens (yeast-based immunotherapeutics) can elicit protective immunity against xenografted and chemically induced tumours. This concept is now being tested in a Phase I trial in patients with colorectal, pancreatic and non-small cell lung cancers.

Antithetical effects of hemicellulase-treated Agaricus blazei on the maturation of murine bone-marrow-derived dendritic cells

We report the effects of hemicellulase-treated Agaricus blazei (ABH) on the maturation of bone-marrow-derived dendritic cells (BMDCs). ABH activated immature BMDCs, inducing up-regulation of surface molecules, such as CD40, CD80 and major histocompatibility complex class I antigens, as well as inducing allogeneic T-cell proliferation and T helper type 1 cell development. However, unlike lipopolysaccharide (LPS), ABH did not stimulate the BMDCs to produce proinflammatory cytokines, such as interleukin-12 (IL-12) p40, tumour necrosis factor-alpha, or IL-1beta. In addition, ABH suppressed LPS-induced DC responses. Pretreatment of DCs with ABH markedly reduced the levels of LPS-induced cytokine secretion, while only slightly decreasing up-regulation of the surface molecules involved in maturation. ABH also had a significant impact on peptidoglycan-induced or CpG oligodeoxynucleotide-induced IL-12p40 production in DCs. The inhibition of LPS-induced responses was not associated with a cytotoxic effect of ABH nor with an anti-inflammatory effect of IL-10. However, ABH decreased NF-kappaB-induced reporter gene expression in LPS-stimulated J774.1 cells. Interestingly, DCs preincubated with ABH and then stimulated with LPS augmented T helper type 1 responses in culture with allogeneic T cells as compared to LPS-stimulated but non-ABH-pretreated DCs. These observations suggest that ABH regulates DC-mediated responses.

Prospects for dendritic cell vaccination against fungal infections in hematopoietic transplantation

Dendritic cells (DCs) are uniquely able to initiate and control the immune response to fungi. DCs function at three levels in the manipulation of the immune response to these pathogens. First, they mount an immediate or innate response to them, for example, by producing inflammatory mediators upon capture and phagocytosis; second, through these preceding innate functions, they decode the fungus-associated information and translate it in qualitatively different Th responses, and third, they are key in containing and dampening inflammatory responses by tolerization through the induction of regulatory T cells (Treg). DCs sense fungi in a morphotype-specific manner, through the engagement of distinct recognition receptors ultimately affecting cytokine production and costimulation. Both myeloid and plasmacytoid murine and human DCs phagocytose fungi and undergo functional maturation in response to them. However, their activation program for cytokine production was different, being IL-12 mainly produced by myeloid DCs and IL-12, IL-10 and IFN-alpha mainly produced by plasmacytoid DCs. This resulted in a distinct ability for T cell priming, being Th1, Th2, and Treg differently activated by the different DC subsets. The ability of fungus-pulsed DCs to prime for Th1 and Th2 cell activation upon adoptive transfer in vivo correlated with the occurrence of resistance and susceptibility to the infections, respectively. Antifungal protective immunity was also induced upon adoptive transfer of DCs transfected with fungal RNA. The efficacy was restricted to DCs transfected with RNA from yeasts or conidia but not with RNA from fungal hyphae. The effect was fungus-specific, as no cross-protection was observed upon adoptive transfer of DCs pulsed with either fungal species. The infusion of fungus-pulsed or RNA-transfected DCs accelerated the recovery of functional antifungal Th1 responses in mice with allogeneic hematopoietic stem cell transplantation (HSCT) and affected the outcome of the infections. As the ability of phagocytose fungi was defective in peripheral DCs from patients with HSCT, soon after the transplant, our findings suggest that the adoptive transfer of DCs may restore immunocompetence in HSCT by contributing to the educational program of T cells. Thus, the remarkable functional plasticity of DCs in response to fungi can be exploited for the deliberate targeting of cells and pathways of cell-mediated immunity in response to fungal vaccines.

Elevated Levels of IgG and IgG4 to Malassezia Allergens in Atopic Eczema Patients with IgE Reactivity to Malassezia

BACKGROUND

The opportunistic yeast Malassezia is considered to be one of the factors that can contribute to atopic eczema (AE). Elevated serum IgE levels, T-cell proliferation and positive skin prick test (SPT) and atopy patch test (APT) reactions to Malassezia are found among AE patients.

METHODS

Sera from 127 AE patients, 14 patients with seborrheic dermatitis (SD) and 33 healthy controls were investigated for IgE and IgG4 to M. sympodialis extract and four recombinant Malassezia allergens; rMala s 1, rMala s 5, rMala s 6, and rMala s 9. In addition, IgG to the recombinant allergens was analyzed. The IgG and IgG4 levels were compared to IgE levels and in vivo reactions (SPT and APT) to Malassezia.

RESULTS

AE patients with serum IgE levels >0.35 kU/l to M. sympodialis extract had significantly higher IgG4 levels to M. sympodialis extract than AE patients without detectable serum IgE to M. sympodialis extract, SD patients and healthy controls. Among the AE patients with and without detectable serum IgE to M. sympodialis extract, respectively, there were no differences in IgG4 levels between patients with positive or negative in vivo reactions to M. sympodialis extract. IgG4 to the rMala s allergens was almost exclusively found among patients with IgE to the same allergen. Within the four tested rMala s allergens, most IgG4 reactions were found to rMala s 6, an allergen with homology to cyclophilin.

CONCLUSIONS

Elevated serum IgG4 to M. sympodialis extract accompanies elevated serum IgE to the extract. This is further confirmed by the association between IgG/IgG4 and IgE to recombinant Malassezia allergens.