Promising immunotherapy against fungal diseases

Fungal Vaccine Development: State of the Art and Perspectives Using Immunoinformatics

Fungal infections represent a serious global health problem, causing damage to health and the economy on the scale of millions. Although vaccines are the most effective therapeutic approach used to combat infectious agents, at the moment, no fungal vaccine has been approved for use in humans. However, the scientific community has been working hard to overcome this challenge. In this sense, we aim to describe here an update on the development of fungal vaccines and the progress of methodological and experimental immunotherapies against fungal infections. In addition, advances in immunoinformatic tools are described as an important aid by which to overcome the difficulty of achieving success in fungal vaccine development. In silico approaches are great options for the most important and difficult questions regarding the attainment of an efficient fungal vaccine. Here, we suggest how bioinformatic tools could contribute, considering the main challenges, to an effective fungal vaccine.

Immunotherapies against human bacterial and fungal infectious diseases: A review

Nations' ongoing struggles with a number of novel and reemerging infectious diseases, including the ongoing global health issue, the SARS-Co-V2 (severe acute respiratory syndrome coronavirus 2) outbreak, serve as proof that infectious diseases constitute a serious threat to the global public health. Moreover, the fatality rate in humans is rising as a result of the development of severe infectious diseases brought about by multiple drug-tolerant pathogenic microorganisms. The widespread use of traditional antimicrobial drugs, immunosuppressive medications, and other related factors led to the establishment of such drug resistant pathogenic microbial species. To overcome the difficulties commonly encountered by current infectious disease management and control processes, like inadequate effectiveness, toxicities, and the evolution of drug tolerance, new treatment solutions are required. Fortunately, immunotherapies already hold great potential for reducing these restrictions while simultaneously expanding the boundaries of healthcare and medicine, as shown by the latest discoveries and the success of drugs including monoclonal antibodies (MAbs), vaccinations, etc. Immunotherapies comprise methods for treating diseases that specifically target or affect the body's immune system and such immunological procedures/therapies strengthen the host's defenses to fight those infections. The immunotherapy-based treatments control the host's innate and adaptive immune responses, which are effective in treating different pathogenic microbial infections. As a result, diverse immunotherapeutic strategies are being researched more and more as alternative treatments for infectious diseases, leading to substantial improvements in our comprehension of the associations between pathogens and host immune system. In this review we will explore different immunotherapies and their usage for the assistance of a broad spectrum of infectious ailments caused by various human bacterial and fungal pathogenic microbes. We will discuss about the recent developments in the therapeutics against the growing human pathogenic microbial diseases and focus on the present and future of using immunotherapies to overcome these diseases. Graphical AbstractThe graphical abstract shows the therapeutic potential of different types of immunotherapies like vaccines, monoclonal antibodies-based therapies, etc., against different kinds of human Bacterial and Fungal microbial infections.

Role of carbohydrate antigens in antifungal glycoconjugate vaccines and immunotherapy

The emergence of fungal infection is a growing public health concern that in the latest years is becoming a serious threat to humans, particularly for immunocompromised individuals. Invasive fungal infections (IFIs), which are associated with significant morbidity and mortality, are on the rise due to the availability of only a few old antifungal agents. In addition to this, the growing use of antibiotics makes the population increasingly susceptible to these infections. Since carbohydrates are the main component of the fungal cell wall, the study of fungal glycans as potential targets for the fight against IFIs has aroused much interest in recent decades. In most fungal species the saccharides of the core are made up of chitin and β-glucans, while the outer layer carbohydrates vary according to the fungal species, such as mannans for Candida albicans, galactomannans for Aspergillus fumigatus hyphae, α-glucans for Aspergillus fumigatus and Cryptococcus neoformans, glucuronoxylomannans (GXM) and galactoxylomannans (GalXM) for Criptococcus neoformans. Being surface antigens, fungal carbohydrates are a logical target for the development of antifungal glycoconjugate vaccines and for immunotherapy with monoclonal antibodies. This review summarizes recent findings on active and passive immunization strategies based on fungal carbohydrates explored preclinically for three of the major fungal pathogens: Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus.

Analysis of a mathematical model of immune response to fungal infection

Fungi are cells found as commensal residents, on the skin, and on mucosal surfaces of the human body, including the digestive track and urogenital track, but some species are pathogenic. Fungal infection may spread into deep-seated organs causing life-threatening infection, especially in immune-compromised individuals. Effective defense against fungal infection requires a coordinated response by the innate and adaptive immune systems. In the present paper we introduce a simple mathematical model of immune response to fungal infection consisting of three partial differential equations, for the populations of fungi (F), neutrophils (N) and cytotoxic T cells (T), taking N and T to represent, respectively, the innate and adaptive immune cells. We denote by [Formula: see text] the aggressive proliferation rate of the fungi, by [Formula: see text] and [Formula: see text] the killing rates of fungi by neutrophils and T cells, and by [Formula: see text] and [Formula: see text] the immune strengths, respectively, of N and T of an infected individual. We take the expression [Formula: see text] to represent the coordinated defense of the immune system against fungal infection. We use mathematical analysis to prove the following: If [Formula: see text], then the infection is eventually stopped, and [Formula: see text] as [Formula: see text]; and (ii) if [Formula: see text] then the infection cannot be stopped and F converges to some positive constant as [Formula: see text]. Treatments of fungal infection include anti-fungal agents and immunotherapy drugs, and both cause the parameter I to increase.

A Novel Diagnostic Method for Invasive Fungal Disease Using the Factor G Alpha Subunit From Limulus polyphemus

Deaths due to invasive fungal disease (IFD) have been increasing every year. Early and rapid detection is important to reduce the mortality rate associated with IFD. In this study, we explored a novel diagnostic method for detecting IFD, which involves the G Factor α subunit (GFαSub) from Limulus polyphemus. The GFαSub double-sandwich method was developed to detect (1,3)-β-D-glucans in human serum using purified GFαSub and horseradish peroxidase-labeled GFαSub. The GFαSub double-sandwich method and the G test were performed and compared. Using GFαSub sequence analysis, the expression plasmid pET30a-GFαSub252-668 was synthesized, and GFαSub252-668 was expressed and purified via isopropyl-β-d-thiogalactoside induction and nickel-nitrilotriacetic acid affinity. The optimization method was established via the orthogonal method. Using this method, the sera of 36 patients with IFD and 92 volunteers without IFD underwent detection, and the receiver operating characteristic curve of the GFαSub252-668 double-sandwich method was described. The sensitivity and specificity of the GFαSub252-668 double-sandwich method were 91.67 and 82.61%, respectively, and there was good correlation with the G test for the serum specimens of 36 patients with pulmonary IFD (R 2 = 0.7592). In conclusion, our study suggests that the GFαSub252-668 double-sandwich method was satisfactory at detecting IFD cases. This method can be promoted and further developed as a novel method for diagnosing IFD.

Mechanism of Antifungal Activity by 5-Aminoimidazole-4-Carbohydrazonamide Derivatives against Candida albicans and Candida krusei

Systemic mycoses are one major cause of morbidity/mortality among immunocompromised/debilitated individuals. Studying the mechanism of action is a strategy to develop safer/potent antifungals, warning resistance emergence. The major goal of this study was to elucidate the mechanism of action of three (Z)-5-amino-N’-aryl-1-methyl-1H-imidazole-4-carbohydrazonamides (2h, 2k, 2l) that had previously demonstrated strong antifungal activity against Candida krusei and C. albicans ATCC strains. Activity was confirmed against clinical isolates, susceptible or resistant to fluconazole by broth microdilution assay. Ergosterol content (HPLC-DAD), mitochondrial dehydrogenase activity (MTT), reactive oxygen species (ROS) generation (flow cytometry), germ tube inhibition and drug interaction were evaluated. None of the compounds inhibited ergosterol synthesis. Ascorbic acid reduced the antifungal effect of compounds and significantly decreased ROS production. The metabolic viability of C. krusei was significantly reduced for values of 2MIC. Compounds 2h and 2k caused a significant increase in ROS production for MIC values while for 2l a significant increase was only observed for concentrations above MIC. ROS production seems to be involved in antifungal activity and the higher activity against C. krusei versus C. albicans may be related to their unequal sensitivity to different ROS. No synergism with fluconazole or amphotericin was observed, but the association of 2h with fluconazole might be valuable due to the significant inhibition of the dimorphic transition, a C. albicans virulence mechanism.

The Lymphocytic Scavenger Receptor CD5 Shows Therapeutic Potential in Mouse Models of Fungal Infection

Invasive fungal diseases represent an unmet clinical need that could benefit from novel immunotherapeutic approaches. Host pattern recognition receptors (e.g., Toll-like receptors, C-type lectins, or scavenger receptors) that sense conserved fungal cell wall constituents may provide suitable immunotherapeutic antifungal agents. Thus, we explored the therapeutic potential of the lymphocyte class I scavenger receptor CD5, a nonredundant component of the antifungal host immune response that binds to fungal β-glucans. Antifungal properties of the soluble ectodomain of human CD5 (shCD5) were assessed in vivo in experimental models of systemic fungal infection induced by pathogenic species (Candida albicans and Cryptococcus neoformans). In vitro mechanistic studies were performed by means of fungus-spleen cell cocultures. shCD5-induced survival of lethally infected mice was dose and time dependent and concomitant with reduced fungal load and increased leukocyte infiltration in the primary target organ. Additive effects were observed in vivo after shCD5 was combined with suboptimal doses of fluconazole. Ex vivo addition of shCD5 to fungus-spleen cell cocultures increased the release of proinflammatory cytokines involved in antifungal defense (tumor necrosis factor alpha and gamma interferon) and reduced the number of viable C. albicans organisms. The results prompt further exploration of the adjunctive therapeutic potential of shCD5 in severe invasive fungal diseases.

Priming with FLO8-deficient Candida albicans induces Th1-biased protective immunity against lethal polymicrobial sepsis

The morphological switch between yeast and hyphae of Candida albicans is essential for its interaction with the host defense system. However, the lack of understanding of host–pathogen interactions during C. albicans infection greatly hampers the development of effective immunotherapies. Here, we found that priming with the C. albicans FLO8-deficient (flo8) mutant, locked in yeast form, protected mice from subsequent lethal C. albicans infection. Deficiency of Dectin-2, a fungus-derived α-mannan recognition receptor, completely blocked flo8 mutant-induced protection. Mechanistically, the flo8 mutant-induced Dectin-2/CARD9-mediated IL-10 production in DCs and macrophages to block thymus atrophy by inhibiting the C. albicans-induced apoptosis of thymic T cells, which facilitated the continuous output of naive T cells from the thymus to the spleen. Continuous recruitment of naive T cells to the spleen enhanced Th1-biased antifungal immune responses. Consequently, depletion of CD4+ T cells or blockade of IL-10 receptor function using specific antibodies in mice completely blocked the protective effects of flo8 mutant priming against C. albicans infection. Moreover, mannans exposed on the surface of the flo8 mutant were responsible for eliciting protective immunity by inhibiting the C. albicans-induced apoptosis of thymic T cells to sustain the number of naive T cells in the spleen. Importantly, priming with the flo8 mutant extensively protected mice from polymicrobial infection caused by cecal ligation and puncture (CLP) by enhancing Th1-biased immune responses. Together, our findings imply that targeting FLO8 in C. albicans elicits protective immune responses against polymicrobial infections and that mannans extracted from the flo8 mutant are potential immunotherapeutic candidate(s) for controlling infectious diseases.

Medication association and immunomodulation: An approach in fungal diseases and in particular in the treatment of paracoccidioidomycosis

Fungal infections have been increasing in recent decades, mainly affecting immunocompromised individuals, although certain mycoses, such as paracoccidioidomycosis (PCM), infect immunologically competent individuals. The major problems observed regarding fungal diseases are inadequate diagnosis, prolonged treatment time, the reduced number of drugs available for treatment, in addition to the fact that there are no vaccines for clinical use. Drug combination in order to immunomodulate the immune response is a new strategy used for the treatment of mycoses, since it is difficult to develop new antifungal drugs. The aim of this study is to present and analyze strategies recently suggested for the treatment of fungi of medical interest, in particular for PCM, such as the utilization of combinations of protein fractions or dead microorganisms, as vaccinal antigens, and cellular immunotherapy. We will also propose new therapeutic alternatives, such as lipids, vitamins, synthetic or natural products as well as the use of low intensity LASER therapy (LLLT) to modulate the immune response of the host, enhancing the efficiency of the existing treatments of mycoses of medical interest and in particular of PCM.

Immunotherapy as an Antifungal Strategy in Immune Compromised Hosts

Purpose of Review

IFIs cause high morbidity and mortality in the immunocompromised host worldwide. Although highly effective, conventional antifungal chemotherapy faces new challenges due to late diagnosis and increasing numbers of drug-resistant fungal strains. Thus, antifungal immunotherapy represents a viable treatment option, and recent advances in the field are summarized in this review.

Recent Findings

Antifungal immunotherapies include application of immune cells as well as the administration of cytokines, growth factors, and antibodies. Novel strategies to treat IFIs in the immunocompromised host target intracellular signaling pathways using SMTs such as checkpoint inhibitors.

Summary

Studies using cytokines or chemokines exerted a potential adjuvant role to conventional antifungal therapy, but issues on toxicity for some agents have to be resolved. Cell-based immunotherapies are very labor-intense and costly, but NK cell transfer and CAR T cell therapy provide exciting strategies to combat IFIs. Antibody-mediated protection and checkpoint inhibition are additional novel immunotherapeutic approaches.

Role of FDG PET/CT in monitoring treatment response in patients with invasive fungal infections

Introduction

Invasive fungal infections (IFIs) occur mostly in immunosuppressed patients and can be life-threatening. Inadequate treatment is associated with high morbidity and mortality. We examined the role of 2-fluorodeoxyglucose positron emission tomography integrated with CT (FDG-PET/CT) in monitoring IFIs and therapy decision-making, and evaluated the role of baseline metabolic parameters in predicting the metabolic response.

Methods

All patients between October 2009 and March 2018, diagnosed with IFIs, treated with antifungal drugs, and who underwent FDG-PET/CT at baseline and at one or more timepoints during treatment were retrospectively included. The electronic patient files were reviewed for pathology, microbiology, and laboratory findings. All FDG-PET/CT scans were performed according to standardized European Association of Nuclear Medicine/EANM Research Limited (EANM/EARL) protocols. For each scan, the global total lesion glycolysis (TLG) and metabolic volume (MV), highest maximum standardized uptake value (SUVmax), and peak standardized uptake value (SUVpeak) were determined. The role of FDG-PET/CT on monitoring antifungal therapy was assessed by looking at the clinical decision made as result of the scan. Furthermore, the added value of the baseline metabolic parameters in predicting metabolic response to the antifungal treatment was evaluated.

Results

Twenty-eight patients with in total 98 FDG-PET/CT scans were included with a mean age of 43 ± 22 years. FDG-PET/CT altered management in 14 out of the 28 patients (50%). At the final FDG-PET/CT scan, 19 (68%) had a complete metabolic response (CMR), seven a partial response and two patients were defined as having progressive disease. Using receiver operative analysis, the cut-off value, sensitivity, specificity, and significance for the baseline TLG and MV to discriminate patients with CMR were 160, 94%, 100%, p < 0.001 and 60, 84%, 75%, p = 0.001 respectively.

Conclusion

FDG-PET/CT is useful in the monitoring of IFIs resulting in management therapy change in half of the patients. Baseline TLG and MV were found to be able to predict the metabolic response to antifungal treatment.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4192-z) contains supplementary material, which is available to authorized users.

Effect of ArtinM on Human Blood Cells During Infection With Paracoccidioides brasiliensis

Infections caused by fungi are prominent in our environment and can be potentially fatal. paracoccidioidomycosis (PCM), caused by fungi of the Paracoccidioides genus, is the most frequent systemic mycosis in Brazil and the main cause of death among immunocompetent individuals. The antifungal therapy for PCM is usually effective but side effects and relapses are often reported. The latter could be avoided with alternative or complementary therapies aimed at boosting the immune response to combat this pathogen. Recent reports have pointed at the importance of an effective cellular immune response, with the participation of Th1 cells, in the resistance to and control of Paracoccidioides infection. The ArtinM lectin, extracted from jackfruit (Artocarpus heterophyllus) seeds, exhibits immunomodulatory activity against several intracellular pathogens, including Paracoccidioides brasiliensis, by promoting the development of a Th1 immune response. The aim of this work was to characterize the effect of ArtinM on peripheral blood cells of patients with PCM and on those of control individuals infected with fungal yeasts cells in vitro. Our results demonstrate that ArtinM activates human neutrophils in vitro, leading to an increase in cytokine production and CD54 expression. ArtinM activated P. brasiliensis-infected neutrophils from both healthy individuals and patients with PCM. This activation was not dependent on the dectin-1 receptor, because pre-incubation with laminarin, a dectin-1 receptor blocker, did not reverse the activated state of the cells. ArtinM also stimulated human peripheral blood mononuclear cells to secrete pro-inflammatory Th1-related cytokines, which are protective against Paracoccidioides infection. These data support the immunostimulatory action of ArtinM and encourage new studies using the lectin for the immunotherapy of PCM.

Quantitative Simulations Predict Treatment Strategies Against Fungal Infections in Virtual Neutropenic Patients

The condition of neutropenia, i.e., a reduced absolute neutrophil count in blood, constitutes a major risk factor for severe infections in the affected patients. Candida albicans and Candida glabrata are opportunistic pathogens and the most prevalent fungal species in the human microbiota. In immunocompromised patients, they can become pathogenic and cause infections with high mortality rates. In this study, we use a previously established approach that combines experiments and computational models to investigate the innate immune response during blood stream infections with the two fungal pathogens C. albicans and C. glabrata. First, we determine immune-reaction rates and migration parameters under healthy conditions. Based on these findings, we simulate virtual patients and investigate the impact of neutropenic conditions on the infection outcome with the respective pathogen. Furthermore, we perform in silico treatments of these virtual patients by simulating a medical treatment that enhances neutrophil activity in terms of phagocytosis and migration. We quantify the infection outcome by comparing the response to the two fungal pathogens relative to non-neutropenic individuals. The analysis reveals that these fungal infections in neutropenic patients can be successfully cleared by cytokine treatment of the remaining neutrophils; and that this treatment is more effective for C. glabrata than for C. albicans.

Timing Determination of Invasive Fungal Infection Prophylaxis According to Immune Function in HSCT Patients

Patients who receive a hematopoietic stem cell transplantation (HSCT) exhibit an immune defect after recovering from neutropenia. The current guidelines do not recommend fungal prophylaxis in these patients, except for grades III to IV GVHD in HSCT. Thus, the timing for the initiation and cessation of IFI prophylaxis in immune-compromised patients remains a challenging endeavor. We retrospectively analyzed patients who received auto or allo-HSCT and monitored their immune function after recovering from neutropenia by measuring the levels of IgG, IgA, IgM, as well as the number of T, B, NK cells. We found that the level of IgG and NK cell count exhibited a significant difference with the incidence of IFI by logistic regression (p = 0.000 vs. 0.000, respectively) and conditional logistic regression (p = 0.009 vs. p = 0.002). The initiation of IFI prophylaxis was determined to be IgG < 7 mg/mL and NK cell count < 6.5 × 104/mL by an receiver operating characteristic curve separately. Tests in parallel increased the test sensitivity and specificity. Thus, the optimal timing for initiating prophylaxis in patients after HSCT could be IgG < 7 mg/mL or NK cell count < 6.5 × 104/mL. Future large-scale prospective clinical trials are required to verify these findings. Patients who are immuno-compromised after auto or allo-HSCT may benefit from a lower fungi infection incidence with immune surveillance and proper fungal prophylaxis.

Targeting the Immune System with Plant Lectins to Combat Microbial Infections

The arsenal of drugs available to treat infections caused by eukaryotic and prokaryotic microbes has been declining exponentially due to antimicrobial resistance phenomenon, leading to an urgent need to develop new therapeutic strategies. Host-directed immunotherapy has been reported as an attractive option to treat microbial infections. It consists in the improvement of host defenses by increasing the expression of inflammatory mediators and/or controlling of inflammation-induced tissue injury. Although the in vitro antimicrobial and immunomodulatory activities of lectins have been extensively demonstrated, few studies have evaluated their in vivo effects on experimental models of infections. This review aims to highlight the experimental use of immunomodulatory plant lectins to improve the host immune response against microbial infections. Lectins have been used in vivo both prophylactically and therapeutically resulting in the increased survival of mice under microbial challenge. Other studies successfully demonstrated that lectins could be used in combination with parasite antigens in order to induce a more efficient immunization. Therefore, these plant lectins represent new candidates for management of microbial infections. Furthermore, immunotherapeutic studies have improved our knowledge about the mechanisms involved in host–pathogen interactions, and may also help in the discovery of new drug targets.

Invasive candidiasis: future directions in non-culture based diagnosis

INTRODUCTION

Delayed initial antifungal therapy is associated with high mortality rates caused by invasive candida infections, since accurate detection of the opportunistic pathogenic yeast and its identification display a diagnostic challenge. diagnosis of candida infections relies on time-consuming methods such as blood cultures, serologic and histopathologic examination. to allow for fast detection and characterization of invasive candidiasis, there is a need to improve diagnostic tools. trends in diagnostics switch to non-culture-based methods, which allow specified diagnosis within significantly shorter periods of time in order to provide early and appropriate antifungal treatment. Areas covered: within this review comprise novel pathogen- and host-related testing methods, e.g. multiplex-PCR analyses, T2 magnetic resonance, fungus-specific DNA microarrays, microRNA characterization or analyses of IL-17 as biomarker for early detection of invasive candidiasis. Expert commentary: Early recognition and diagnosis of fungal infections is a key issue for improved patient management. As shown in this review, a broad range of novel molecular based tests for the detection and identification of Candida species is available. However, several assays are in-house assays and lack standardization, clinical validation as well as data on sensitivity and specificity. This underscores the need for the development of faster and more accurate diagnostic tests.