Modulatory role of vitamin A on the Candida albicans-induced immune response in human monocytes

A comprehensive guide to assess gut mycobiome and its role in pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is an immune mediated chronic inflammatory disorder of gastrointestinal tract, which has underlying multifactorial pathogenic determinants such as environmental factors, susceptibility genes, gut microbial dysbiosis and a dysregulated immune response. Human gut is a frequent inhabitant of complex microbial ecosystem encompassing bacteria, viruses, parasites, fungi and other microorganisms that have an undisputable role in maintaining balanced homeostasis. All of these microbes interact with immune system and affect human gut physiology either directly or indirectly with interaction of each other. Intestinal fungi represent a smaller but crucial component of the human gut microbiome. Besides interaction with bacteriome and virome, it helps in balancing homoeostasis between pathophysiological and physiological processes, which is often dysregulated in patients with IBD. Understanding of gut mycobiome and its clinical implications are still in in its infancy as opposed to bacterial component of gut microbiome, which is more often focused. Modulation of gut mycobiome represents a novel and promising strategy in the management of patients with IBD. Emerging mycobiome-based therapies such as diet interventions, fecal microbiota transplantation (FMT), probiotics (both fungal and bacterial strains) and antifungals exhibit substantial effects in calibrating the gut mycobiome and restoring dysbalanced immune homeostasis by restoring the core gut mycobiome. In this review, we summarized compositional and functional diversity of the gut mycobiome in healthy individuals and patients with IBD, gut mycobiome dysbiosis in patients with IBD, host immune-fungal interactions and therapeutic role of modulation of intestinal fungi in patients with IBD.

Modulatory role of vitamins A, B3, C, D, and E on skin health, immunity, microbiome, and diseases

Disruption of the skin barrier and immunity has been associated with several skin diseases, namely atopic dermatitis (AD), psoriasis, and acne. Resident and non-resident immune cells and the barrier system of the skin are integral to innate immunity. Recent advances in understanding skin microbiota have opened the scope of further understanding the various communications between these microbiota and skin immune cells. Vitamins, being one of the important micronutrients, have been reported to exert antioxidant, anti-inflammatory, and anti-microbial effects. The immunomodulatory action of vitamins can halt the progression of skin diseases, and thus, understanding the immuno-pharmacology of these vitamins, especially for skin diseases can pave the way for their therapeutic potential. At the same time, molecular and cellular markers modulated with these vitamins and their derivatives need to be explored. The present review is focused on significant vitamins (vitamins A, B3, C, D, and E) consumed as nutritional supplements to discuss the outcomes and scope of studies related to skin immunity, health, and diseases.

Mycobiome and Inflammatory Bowel Disease: Role in Disease Pathogenesis, Current Approaches and Novel Nutritional-based Therapies

Inflammatory bowel disease (IBD), a disorder characterized by chronic inflammation of the gastrointestinal (GI) tract and a range of adverse health effects including diarrhea, abdominal pain, vomiting, and bloody stools, affects nearly 3.1 million genetically susceptible adults in the United States today. Although the etiology of IBD remains unclear, genetics, stress, diet, and gut microbiota dysbiosis- especially in immunocompromised individuals- have been identified as possible causes of disease. Although previous research has largely focused on the role of bacteria in IBD pathogenesis, recently observed alterations of fungal load and biodiversity in the GI tract of afflicted individuals suggest interkingdom interactions amongst different gut microbial communities, particularly between bacteria and fungi. These discoveries point to the potential utilization of treatment approaches such as antibiotics, antifungals, probiotics, and postbiotics that target both bacteria and fungi in managing IBD. In this review, we discuss the impact of specific fungi on disease pathogenesis, with a focus on the highly virulent genus Candida and how the presence of certain co-enzymes impacts its virulence. In addition, we evaluate current gut microbiome-based therapeutic approaches with the intention of better understanding the mechanisms behind novel therapies.

A gut-oral microbiome-driven axis controls oropharyngeal candidiasis through retinoic acid

A side effect of antibiotics is outgrowth of the opportunistic fungus Candida albicans in the oropharynx (oropharyngeal candidiasis, OPC). IL-17 signaling is vital for immunity to OPC, but how the microbiome impacts antifungal immunity is not well understood. Mice in standard specific pathogen-free (SPF) conditions are resistant to OPC, whereas we show that germ-free (GF) or antibiotic-treated mice are susceptible. Oral type 17 cells and IL-17-dependent responses were impaired in antibiotic-treated and GF mice. Susceptibility could be rescued in GF mice by mono-colonization with segmented filamentous bacterium (SFB), an intestine-specific constituent of the microbiota. SFB protection was accompanied by restoration of oral IL-17+CD4+ T cells and gene signatures characteristic of IL-17 signaling. Additionally, RNA-Seq revealed induction of genes in the retinoic acid (RA) and RA receptor-α (RARα) pathway. Administration of RA rescued immunity to OPC in microbiome-depleted or GF mice, while RAR inhibition caused susceptibility in immunocompetent animals. Surprisingly, immunity to OPC was independent of serum amyloids. Moreover, RAR inhibition did not alter oral type 17 cytokine levels. Thus, mono-colonization with a component of the intestinal microflora confers protection against OPC by type 17 and RA/RARα, which act in parallel to promote antifungal immunity. In principle, manipulation of the microbiome could be harnessed to maintain antifungal immunity.

Voriconazole is superior to combined itraconazole/isotretinoin therapy and itraconazole monotherapy in recalcitrant dermatophytosis

BACKGROUND

There has been an emergence of recalcitrant, recurrent, and difficult-to-treat tinea. Monotherapy with oral antifungals leads to partial clearance or high recurrence of lesions. Isotretinoin is a good adjuvant to systemic antifungals in chronic dermatophytosis. Voriconazole could be a future alternative due to its efficacy against dermatophytes and little resistance.

OBJECTIVE

To evaluate the efficacy and safety of oral itraconazole, combined itraconazole/isotretinoin therapy, and voriconazole for recalcitrant tinea.

PATIENTS AND METHODS

This study included 90 patients with chronic, recurrent, and/or recalcitrant tinea. They were equally divided into 3 groups: itraconazole monotherapy, combined itraconazole/isotretinoin therapy, and voriconazole monotherapy. All patients received treatments for 6 weeks. The clinical response was classified as either a complete or incomplete clinical cure. Potassium hydroxide microscopy and culture were performed to identify mycological cure. Patients with complete cure were followed up for another 6 months to detect any recurrence.

RESULTS

Complete clinical cure was observed in 53.3% of the itraconazole group, 70% of the itraconazole/isotretinoin group, and 83.3% of the voriconazole group. Mycological cure was detected in 56.7% of the itraconazole group, 83.3% of the itraconazole/isotretinoin group, and 86.7% of the voriconazole group. There was a statistically significant difference between the three groups in favor of voriconazole, then the combined group. No significant adverse effects were observed. The recurrence rate was significantly lower in the voriconazole group compared to the other two groups.

CONCLUSIONS

Voriconazole could be a future alternative for the treatment of recalcitrant dermatophytosis.

Acitretin: Could it be a new therapeutic player in the field of onychomycosis?

BACKGROUND

Onychomycosis represents a therapeutic challenge. The complete cure rate with itraconazole pulse therapy remains unsatisfactory implying the need for an effective therapeutic regimen. Given the successful treatment of recurrent dermatophytosis with isotretinoin and itraconazole, we investigated the therapeutic use of acitretin in onychomycosis.

AIM

To evaluate and compare the efficacy of combined itraconazole and acitretin versus monotherapy with each in onychomycosis.

PATIENTS AND METHODS

The study included 135 adult patients with finger- and/or toe-nail onychomycosis. They were equally subdivided into 3 groups: Itraconazole pulse therapy, acitretin, and combined itraconazole/acitretin therapy. The drugs were administered for 3 months. Evaluation of severity was done by onychomycosis severity index score. Potassium hydroxide microscopy and culture were performed at baseline and at the end of the study.

RESULTS

Mycological and complete cure of onychomycosis was observed in 51.1% and 20% of the itraconazole group, 28.9% and 28.9% of the acitretin group, and 80% and 53.3% of the combined group. There was a statistically-significant difference between groups in favor of the combined itraconazole/acitretin therapy (P ≤ 0.05).

LIMITATIONS

Small sample and short therapy duration.

CONCLUSIONS

Acitretin could be a powerful therapeutic player in the field of onychomycosis, with greater efficacy when combined with itraconazole.

Antibody ligation of CEACAM1, CEACAM3, and CEACAM6, differentially enhance the cytokine release of human neutrophils in responses to Candida albicans

Invasive candidiasis is a healthcare-associated fungal infection with a high mortality rate. Neutrophils, the first line of defense during fungal infections, express the immunoregulatory Candida albicans receptors CEACAM1, CEACAM3, and CEACAM6. We analyzed the effects of specific antibodies on C. albicans-induced neutrophil responses. CEACAM6 ligation by 1H7-4B and to some extent CEACAM1 ligation by B3-17, but not CEACAM3 ligation by 308/3-3, resulted in the immediate release of stored CXCL8 and altered transcriptional responses of the C. albicans-stimulated neutrophils. Integrated network analyses and dynamic simulations of signaling cascades predicted alterations in apoptosis and cytokine secretion. We verified that CEACAM6 ligation enhanced Candida-induced neutrophil apoptosis and increased long-term IL-1β/IL-6 release in responses to C. albicans. CEACAM3 ligation, but not CEACAM1 ligation, increased the long-term release of pro-inflammatory IL-1β/IL-6. Taken together, we demonstrated for the first time that ligation of CEACAM receptors differentially affects the regulation of C. albicans-induced immune functions in human neutrophils.

Trifarotene: A Current Review and Perspectives in Dermatology

Retinoids have numerous applications in inflammatory, dyskeratotic, and oncohematology diseases. Retinoids have now reached the fourth generation, progressively reducing toxicity whilst increasing their efficacy. Trifarotene is a new fourth-generation retinoid with a selective action on RAR-γ. In this review, we reported the trials—both concluded and in progress—including the use of trifarotene in dermatological diseases. Studies were identified by searching electronic databases (MEDLINE, EMBASE, PubMed, Cochrane, Trials.gov) from 2012 to today and reference lists of respective articles. Only articles published in English language were included. Randomized trials evaluating trifarotene tolerability, safety, and efficacy in congenital ichthyosis and acne have demonstrated great results and mild side effects, leading to the approval by the FDA of trifarotene for the treatment of lamellar ichthyosis in 2014, and of acne vulgaris in October 2019. No high-quality randomized clinical trials have evaluated the treatment of primary cutaneous lymphomas with trifarotene. Finally, we are hypothesizing future perspectives in the treatment of non-melanoma skin cancers, fungal infections, photoaging, and hand-foot skin reactions with trifarotene.

Antifungal Effect of All-trans Retinoic Acid against Aspergillus fumigatus In Vitro and in a Pulmonary Aspergillosis In Vivo Model

Aspergillus fumigatus is the most common opportunistic fungal pathogen and causes invasive pulmonary aspergillosis (IPA), with high mortality among immunosuppressed patients. The fungistatic activity of all-trans retinoic acid (ATRA) has been recently described in vitro.

Aspergillus fumigatus is the most common opportunistic fungal pathogen and causes invasive pulmonary aspergillosis (IPA), with high mortality among immunosuppressed patients. The fungistatic activity of all-trans retinoic acid (ATRA) has been recently described in vitro. We evaluated the efficacy of ATRA in vivo and its potential synergistic interaction with other antifungal drugs. A rat model of IPA and in vitro experiments were performed to assess the efficacy of ATRA against Aspergillus in association with classical antifungal drugs and in silico studies used to clarify its mechanism of action. ATRA (0.5 and 1 mM) displayed a strong fungistatic activity in Aspergillus cultures, while at lower concentrations, synergistically potentiated fungistatic efficacy of subinhibitory concentration of amphotericin B (AmB) and posaconazole (POS). ATRA also enhanced macrophagic phagocytosis of conidia. In a rat model of IPA, ATRA reduced mortality similarly to posaconazole. Fungistatic efficacy of ATRA alone and synergistically with other antifungal drugs was documented in vitro, likely by inhibiting fungal heat shock protein 90 (Hsp90) expression and Hsp90-related genes. ATRA treatment reduced mortality in a model of IPA in vivo. Those findings suggest ATRA as a suitable fungistatic agent that can also reduce dosage and adverse reactions of classical antifungal drugs and add to the development of new therapeutic strategies against IPA and systemic fungal infections.

Predictive role of vitamin A serum concentration in psoriatic patients treated with IL-17 inhibitors to prevent skin and systemic fungal infections

The use of biological drugs in psoriasis is replacing traditional therapies due to their specific mechanism and limited side effects. However, the use of Interleukin 17 inhibitors and the modification of its cytokine pathway could favor the risk of fungal infections. All-trans retinoic acid is an active metabolite of vitamin A with anti-inflammatory and immunoregulatory properties through its capacity to stimulate both innate and adaptive immunity and to its effects on proliferation, differentiation and apoptosis in a variety of immune cells. Furthermore, it has been recently discovered that All-trans retinoic acid has a direct fungistatic effect against Candida and Aspergillus Fumigatus. On the basis of these new insights, in the current review, we suggest that the evaluation of serum level of All-trans retinoic acid or vitamin A should be considered as a predictive marker for the development of fungal infections among psoriatic patients treated with Interleukin 17 inhibitors. In clinical practice, vitamin A test could be added in the routine hospital diagnostic management for a better selection of psoriatic patients eligible to Interleukin 17 inhibitors.

Intestinal Macrophages Balance Inflammatory Expression Profiles via Vitamin A and Dectin-1-Mediated Signaling

Tissue resident intestinal macrophages are known to exhibit an anti-inflammatory phenotype and produce little pro-inflammatory cytokines upon TLR ligation, allowing symbiotic co-existence with the intestinal microbiota. However, upon acute events such as epithelial damage and concomitant influx of microbes, these macrophages must be able to quickly mount a pro-inflammatory response while more inflammatory macrophages are recruited from the blood stream simultaneously. Here, we show that dietary intake of vitamin A is required for the maintenance of the anti-inflammatory state of tissue resident intestinal macrophages. Interestingly, these anti-inflammatory macrophages were characterized by high levels of Dectin-1 expression. We show that Dectin-1 expression is enhanced by the vitamin A metabolite retinoic acid and our data suggests that Dectin-1 triggering might provide a switch to induce a rapid production of pro-inflammatory cytokines. In addition, Dectin-1 stimulation resulted in an altered metabolic profile which is linked to a pro-inflammatory response. Together, our data suggests that presence of vitamin A in the small intestine enhances an anti-inflammatory phenotype as well as Dectin-1 expression by macrophages and that this anti-inflammatory phenotype can rapidly convert toward a pro-inflammatory state upon Dectin-1 signaling.

Unaltered Fungal Burden and Lethality in Human CEACAM1-Transgenic Mice During Candida albicans Dissemination and Systemic Infection

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CD66a) is a receptor for Candida albicans. It is crucial for the immune response of intestinal epithelial cells to this opportunistic pathogen. Moreover, CEACAM1 is of importance for the mucosal colonization by different bacterial pathogens. We therefore studied the influence of the human CEACAM1 receptor in human CEACAM1-transgenic mice on the C. albicans colonization and infection utilizing a colonization/dissemination and a systemic infection mouse model. Our results showed no alterations in the host response between the transgenic mice and the wild-type littermates to the C. albicans infections. Both mouse strains showed comparable C. albicans colonization and mycobiota, similar fungal burdens in various organs, and a similar survival in the systemic infection model. Interestingly, some of the mice treated with anti-bacterial antibiotics (to prepare them for C. albicans colonization via oral infection) also showed a strong reduction in endogenous fungi instead of the normally observed increase in fungal numbers. This was independent of the expression of human CEACAM1. In the systemic infection model, the human CEACAM1 expression was differentially regulated in the kidneys and livers of Candida-infected transgenic mice. Notably, in the kidneys, a total loss of the largest human CEACAM1 isoform was observed. However, the overwhelming immune response induced in the systemic infection model likely covered any CEACAM1-specific effects in the transgenic animals. In vitro studies using bone marrow-derived neutrophils from both mouse strains also revealed no differences in their reaction to C. albicans. In conclusion, in contrast to bacterial pathogens interacting with CEACAM1 on different mucosal surfaces, the human CEACAM1-transgenic mice did not reveal a role of human CEACAM1 in the in vivo candidiasis models used here. Further studies and different approaches will be needed to reveal a putative role of CEACAM1 in the host response to C. albicans.

Retinoids as an Immunity-modulator in Dermatology Disorders

The skin is the largest epithelial surface protecting the body from invading microbes. Vitamin A plays vital roles in the host defence of the skin, including promoting epithelial cell integrity, proliferation, and differentiation and even mediating immune responses. Furthermore, vitamin A derivatives, retinoid drugs, are widely used to treat skin diseases, such as acne and psoriasis. However, the immunoregulatory mechanisms of retinoids in dermatology have not been systematically described. In this paper, we discuss the immunological functions of retinoids during disease treatment, especially in skin disorders caused by exogenous infections.

Immunomodulation as Therapy for Fungal Infection: Are We Closer?

Invasive fungal disease (IFD) causes significant morbidity in immunocompromised patients due to their weakened immune system. Immunomodulatory therapy, in synergy with existing antifungal therapy, is an attractive option to enhance their immune system and aid clearance of these opportunistic pathogens. From a scientific and clinical perspective, we explore the immunotherapeutic options to augment standard antifungal drugs for patients with an IFD. We discuss the range of immunomodulatory therapies being considered in IFD - from cytokines, including G-CSF, GM-CSF, M-CSF, IFN-γ, and cytokine agonists, to cellular therapies, consisting of granulocyte transfusion, adoptive T-cell, CAR T-cell, natural killer cell therapies, and monoclonal antibodies. Adjunct pharmaceutical agents which augment the immunity are also being considered. Lastly, we explore the likelihood of the use of probiotics and manipulation of the microbiome/mycobiome to enhance IFD treatment outcomes.

Combination of Classifiers Identifies Fungal-Specific Activation of Lysosome Genes in Human Monocytes

Blood stream infections can be caused by several pathogens such as viruses, fungi and bacteria and can cause severe clinical complications including sepsis. Delivery of appropriate and quick treatment is mandatory. However, it requires a rapid identification of the invading pathogen. The current gold standard for pathogen identification relies on blood cultures and these methods require a long time to gain the needed diagnosis. The use of in situ experiments attempts to identify pathogen specific immune responses but these often lead to heterogeneous biomarkers due to the high variability in methods and materials used. Using gene expression profiles for machine learning is a developing approach to discriminate between types of infection, but also shows a high degree of inconsistency. To produce consistent gene signatures, capable of discriminating fungal from bacterial infection, we have employed Support Vector Machines (SVMs) based on Mixed Integer Linear Programming (MILP). Combining classifiers by joint optimization constraining them to the same set of discriminating features increased the consistency of our biomarker list independently of leukocyte-type or experimental setup. Our gene signature showed an enrichment of genes of the lysosome pathway which was not uncovered by the use of independent classifiers. Moreover, our results suggest that the lysosome genes are specifically induced in monocytes. Real time qPCR of the identified lysosome-related genes confirmed the distinct gene expression increase in monocytes during fungal infections. Concluding, our combined classifier approach presented increased consistency and was able to "unmask" signaling pathways of less-present immune cells in the used datasets.

Fungal biomarker discovery by integration of classifiers

Background

The human immune system is responsible for protecting the host from infection. However, in immunocompromised individuals the risk of infection increases substantially with possible drastic consequences. In extreme, systemic infection can lead to sepsis which is responsible for innumerous deaths worldwide. Amongst its causes are infections by bacteria and fungi. To increase survival, it is mandatory to identify the type of infection rapidly. Discriminating between fungal and bacterial pathogens is key to determine if antifungals or antibiotics should be administered, respectively. For this, in situ experiments have been performed to determine regulation mechanisms of the human immune system to identify biomarkers. However, these studies led to heterogeneous results either due different laboratory settings, pathogen strains, cell types and tissues, as well as the time of sample extraction, to name a few.

Methods

To generate a gene signature capable of discriminating between fungal and bacterial infected samples, we employed Mixed Integer Linear Programming (MILP) based classifiers on several datasets comprised of the above mentioned pathogens.

Results

When combining the classifiers by a joint optimization we could increase the consistency of the biomarker gene list independently of the experimental setup. An increase in pairwise overlap (the number of genes that overlap in each cross-validation) of 43% was obtained by this approach when compared to that of single classifiers. The refined gene list was composed of 19 genes and ranked according to consistency in expression (up- or down-regulated) and most of them were linked either directly or indirectly to the ERK-MAPK signalling pathway, which has been shown to play a key role in the immune response to infection. Testing of the identified 12 genes on an unseen dataset yielded an average accuracy of 83%.

Conclusions

In conclusion, our method allowed the combination of independent classifiers and increased consistency and reliability of the generated gene signatures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-4006-x) contains supplementary material, which is available to authorized users.

Global analysis of glycoproteins identifies markers of endotoxin tolerant monocytes and GPR84 as a modulator of TNFα expression

Exposure of human monocytes to lipopolysaccharide (LPS) induces a temporary insensitivity to subsequent LPS challenges, a cellular state called endotoxin tolerance. In this study, we investigated the LPS-induced global glycoprotein expression changes of tolerant human monocytes and THP-1 cells to identify markers and glycoprotein targets capable to modulate the immunosuppressive state. Using hydrazide chemistry and LC-MS/MS analysis, we analyzed glycoprotein expression changes during a 48 h LPS time course. The cellular snapshots at different time points identified 1491 glycoproteins expressed by monocytes and THP-1 cells. Label-free quantitative analysis revealed transient or long-lasting LPS-induced expression changes of secreted or membrane-anchored glycoproteins derived from intracellular membrane coated organelles or from the plasma membrane. Monocytes and THP-1 cells demonstrated marked differences in glycoproteins differentially expressed in the tolerant state. Among the shared differentially expressed glycoproteins G protein-coupled receptor 84 (GPR84) was identified as being capable of modulating pro-inflammatory TNFα mRNA expression in the tolerant cell state when activated with its ligand Decanoic acid.

Massive Effect on LncRNAs in Human Monocytes During Fungal and Bacterial Infections and in Response to Vitamins A and D

Mycoses induced by C.albicans or A.fumigatus can cause important host damage either by deficient or exaggerated immune response. Regulation of chemokine and cytokine signaling plays a crucial role for an adequate inflammation, which can be modulated by vitamins A and D. Non-coding RNAs (ncRNAs) as transcription factors or cis-acting antisense RNAs are known to be involved in gene regulation. However, the processes during fungal infections and treatment with vitamins in terms of therapeutic impact are unknown. We show that in monocytes both vitamins regulate ncRNAs involved in amino acid metabolism and immune system processes using comprehensive RNA-Seq analyses. Compared to protein-coding genes, fungi and bacteria induced an expression change in relatively few ncRNAs, but with massive fold changes of up to 4000. We defined the landscape of long-ncRNAs (lncRNAs) in response to pathogens and observed variation in the isoforms composition for several lncRNA following infection and vitamin treatment. Most of the involved antisense RNAs are regulated and positively correlated with their sense protein-coding genes. We investigated lncRNAs with stimulus specific immunomodulatory activity as potential marker genes: LINC00595, SBF2-AS1 (A.fumigatus) and RP11-588G21.2, RP11-394l13.1 (C.albicans) might be detectable in the early phase of infection and serve as therapeutic targets in the future.

Differential Effects of Vitamins A and D on the Transcriptional Landscape of Human Monocytes during Infection

Vitamin A and vitamin D are essential nutrients with a wide range of pleiotropic effects in humans. Beyond their well-documented roles in cellular differentiation, embryogenesis, tissue maintenance and bone/calcium homeostasis, both vitamins have attracted considerable attention due to their association with-immunological traits. Nevertheless, our knowledge of their immunomodulatory potential during infection is restricted to single gene-centric studies, which do not reflect the complexity of immune processes. In the present study, we performed a comprehensive RNA-seq-based approach to define the whole immunomodulatory role of vitamins A and D during infection. Using human monocytes as host cells, we characterized the differential role of both vitamins upon infection with three different pathogens: Aspergillus fumigatus, Candida albicans and Escherichia coli. Both vitamins showed an unexpected ability to counteract the pathogen-induced transcriptional responses. Upon infection, we identified 346 and 176 immune-relevant genes that were regulated by atRA and vitD, respectively. This immunomodulatory activity was dependent on the inflammatory stimulus, allowing us to distinguish regulatory patterns which were specific for each stimulatory setting. Moreover, we explored possible direct and indirect mechanisms of vitamin-mediated regulation of the immune response. Our findings highlight the importance of vitamin-monitoring in critically ill patients. Moreover, our results underpin the potential of atRA and vitD as therapeutic options for anti-inflammatory treatment.

Fungistatic activity of all-trans retinoic acid against Aspergillus fumigatus and Candida albicans

PURPOSE

Fungal infections are a major complication in hematologic and neoplastic patients causing severe morbidity and mortality. Aspergillus fumigatus and Candida albicans are among the most invasive opportunistic pathogens in immunocompromised patients, and classic antifungal drugs are frequently unsuccessful in these patients. Recent reports hypothesize that the antifungal efficacy of all-trans retinoic acid (ATRA) is mainly related to its strong capacity to stimulate monocyte-mediated immunity, but no consideration was given to its potential direct fungistatic activity. Moreover, ATRA offers the opportunity for systemic therapy.

METHODS AND RESULTS

We investigated the efficacy of ATRA at different concentrations for its antifungal activity against opportunistic A. fumigatus and C. albicans obtained from clinical samples according to standard protocols. A fungistatic activity of ATRA on A. fumigatus and C. albicans at 0.5-1 mM concentration was documented up to 7 days.

CONCLUSION

This is the first evidence of a direct and strong fungistatic activity of ATRA against A. fumigatus and C. albicans. The potential adjuvant therapeutic application of ATRA might be useful in the treatment and/or prevention of systemic mycoses in immunocompromised patients. The discovery of a direct fungistatic activity, in association with its reported immunomodulatory properties, makes ATRA an excellent candidate for new combined antifungal strategies for systemic mycoses in immunocompromised and cancer patients.