Renal allograft recipients fail to increase interferon-γ during invasive fungal diseases

Antifungal chemotherapies and immunotherapies for the future

Human fungal pathogens cause a broad plethora of infections, spanning cutaneous dermatophytoses to invasive infections in immunocompromised hosts. As eukaryotic pathogens are capable of morphotype switching, they present unique challenges both for drug development and the immunological response. Whilst current antifungal therapies are limited to the orally available triazoles, intravenous echonocandins and polyenes, and flucytosine and terbinafine, there has been recent significant progress in the antifungal armamentorium with ibrexafungerp, a novel orally available terpanoid that inhibits 1,3-beta-D-glucan-approved by Food and Drug Administration in 2021, and fosmanogepix, an orally available pro-drug of manogepix, which targets glycosylphosphatidylinositol-anchored protein maturation entering Phase 3 studies for candidaemia. A number of further candidates are in development. There has been significant use of existing immunotherapies such as recombinant interferon-γ and G-CSF for fungal disease in immunocompromised patients, and there are emerging opportunities for monoclonal antibodies targeting TH2 inflammation. Omalizumab, an anti-IgE monoclonal antibody in asthma, is now used routinely for the treatment of allergic bronchopulmonary aspergillosis, and further agents targeting IL-4 and IL-5 are being evaluated. In addition, T-cell CAR therapy is showing early promise for fungal disease. Thus, we are likely to see rapid advances to our approach to the management of fungal disease in the near future.

Serum Cytokine Profile in Patients with Candidemia versus Bacteremia

Bloodstream Candida infections constitute a major threat for hospitalized patients in intensive care units and immunocompromised hosts. Certain serum cytokines play a decisive role in anti-microbial host defense. Cytokines may act as discriminatory biomarkers that can significantly increase in candidemia compared to bacteremia patients. The concentration of secreted cytokine/chemokines was determined using a multiplexed cytometric bead array run on a cell analyzer. The cytokines tested during the study were interleukin (IL)-1β, IL-6, IL-17A, IL-10, IFN-γ, IL-4, IL-2, IL-8, IL-12p70 and the tumor necrosis factor (TNF)-α. The cytokines of 51 candidemia patients were characterized and compared to the cytokine levels of 20 bacteremia patients. Levels were significantly elevated in patients with bloodstream infections compared to healthy controls. Cytokines comprising IL-2, IL-17A, IL-6 and IL-10 were significantly elevated in the patients with bloodstream Candida infection as compared to the patients having bloodstream bacterial infections. The levels were found to be promising as a potential diagnostic marker for bloodstream Candida infections.

Diagnostic efficacy of serum cytokines and chemokines in patients with candidemia and bacteremia

BACKGROUND

The role of serum cytokines/chemokines in differential diagnosis between fungal infections and bacterial infections have not been fully understood. This study aims to measure the serum levels of cytokines/chemokines in cases of candidemia and to compare them with those observed in cases of bacteremia.

MATERIAL AND METHODS

Patients with febrile episodes and were identified as bloodstream infections through blood culture were enrolled, while healthy people were included as control group. Fourteen serum cytokine and chemokine levels were detected with multiplex platform. ROC analysis was performed and an area under the curve (AUC), sensitivity and specificity values were calculated to determine the efficacy of various cytokines and chemokines for candidemia and bacteremia. Binary logistic regression was performed to further explore the combination mode of cytokines and chemokines, which could increase the diagnostic efficiency.

RESULTS

We included 40 patients with an episode of microbiologically proven fungal infection, 175 patients with bacteremia (85 with Gram-positive bacteremia and 90 with Gram-negative bacteremia) and another 30 healthy controls. Routine laboratory parameters including CRP and PCT were not statistically significant between candidemia group and bacteremia group (both gram-positive and gram-negative). There were significantly higher levels of IFN-γ, TNF-α, IL-10 and lower levels of IL-3, IL-4 in candidemia group, compared with gram-positive and gram-negative bacteremia groups. G-CSF was significantly lower and MIP-1β was higher in candidemia group, when compared with gram-negative bacteremia group. While IL-6, IL-8 and IL-17 were all significantly higher in candidemia group, when compared with gram-positive bacteremia group. Combination of IFN-γ and IL-17 could improve the diagnostic efficiency between candidemia and gram-positive bacteremia, with the AUROC of 0.873 (95% CI: 0.767-0.929). While combination of G-CSF and MIP-1β improved the diagnostic efficiency between candidemia and gram-negative bacteremia, with the AUROC of 0.896 (95% CI: 0.792-0.939).

CONCLUSION

Our study demonstrates that serum cytokines and chemokines including IFN-γ, MIP-1β, IL-17 and G-CSF could be considered as diagnostic markers to distinguish between candidemia and bacteremia. Combination of these biomarkers might improve the diagnostic efficiency of candidemia when compared with bacteremia.

Aspergillus fumigatus Infection in Humans With STAT3-Deficiency Is Associated With Defective Interferon-Gamma and Th17 Responses

In humans, loss-of-function mutation in the Signal Transducer and Activator of Transcription 3 (STAT3) gene is frequently associated with susceptibility to bacterial as well as fungal infections including aspergillosis, although its pathogenesis remains largely unknown. In the present study, we investigated the immune responses obtained after stimulation with Aspergillus fumigatus in STAT3-deficient patients. A. fumigatus conidial killing efficiencies of both monocytes and neutrophils isolated from whole blood samples of STAT3-deficient patients were not different compared to those of healthy controls. After stimulation with A. fumigatus conidia, lower concentrations of adaptive cytokines (IFN-γ, IL-17 and IL-22) were secreted by peripheral blood mononuclear cells from STAT3-deficient patients compared to those from healthy controls. Moreover, the frequency of IFN-γ and IL-17 producing CD4+ T cells was lower in STAT3-deficient patients vs. healthy controls. Among the STAT3-deficient patients, those with aspergillosis showed further lower secretion of IFN-γ upon stimulation of their PBMCs with A. fumigatus conidia compared to the patients without aspergillosis. Together, our study indicated that STAT3-deficiency leads to a defective adaptive immune response against A. fumigatus infection, particularly with a lower IFN-γ and IL-17 responses in those with aspergillosis, suggesting potential therapeutic benefit of recombinant IFN-γ in STAT3-deficient patients with aspergillosis.

Diagnostic efficacy of serum cytokines and chemokines in fungal bloodstream infection in febrile patients

BACKGROUND

The role of serum cytokines/chemokines in early diagnosis of fungal infections has not been clearly clarified yet. This study aims to measure the serum levels of cytokines/chemokines in cases of fungemia and to compare them with culture-negative controls.

METHODS

In total, fourteen types of serum cytokines and chemokines from 41 patients with fungemia were compared with 57 patients with negative blood culture results. The cytokine and chemokine levels were detected with multiplex platform. We then performed statistical analysis as a two-tailed P < .05. ROC analysis was performed, and an area under the curve (AUC), and sensitivity and specificity values were calculated to determine the efficacy of various cytokines and chemokines for fungemia. Binary logistic regression was performed to further explore the combination mode of cytokines and chemokines, which could increase the diagnostic efficiency.

RESULTS

C-reactive protein and procalcitonin were significantly higher compared with those in negative control group, while white blood cell, percentage of neutrophil, percentage of lymphocyte, and ratio of neutrophil and lymphocyte did not differentiate between two groups. Serum levels of IFN-γ, TNF-α, MIP-1β, IL-6, IL-8, IL-10, IL-12p70, and IL-17 were significantly higher in patients with fungemia compared with the control group. Combination of MIP-1β and IL-17 could improve the AUC, sensitivity, and specificity for the diagnosis of fungemia.

CONCLUSION

Our study demonstrates that serum cytokines and chemokines including IFN-γ, TNF-α, MIP-1β, IL-6, IL-8, IL-10, IL-12p70, and IL-17 could be considered as diagnostic markers for fungemia. Combination of these biomarkers might improve the diagnostic efficiency of fungemia.

Immunotherapeutic approaches to treatment of fungal diseases

Fungal infections cause morbidity worldwide and are associated with an unacceptably high mortality despite the availability of antifungal drugs. The incidence of mycoses is rising because of the HIV pandemic and because immunomodulatory drugs are increasingly used to treat autoimmune diseases and cancer. New classes of antifungal drugs have only been partly successful in improving the prognosis for patients with fungal infection. Adjunctive host-directed therapy is therefore believed to be the only option to further improve patient outcomes. Recent advances in the understanding of complex interactions between fungi and host have led to the design and exploration of novel therapeutic strategies in cytokine therapy, vaccines, and cellular immunotherapy, each of which might become viable adjuncts to existing antifungal regimens. In this report, we discuss immunotherapeutic approaches-the rationale behind their design, the challenges in their use, and the progress that is so urgently needed to overcome the devastating effect of fungal diseases.

Calcineurin Orchestrates Lateral Transfer of Aspergillus fumigatus during Macrophage Cell Death

RATIONALE

Pulmonary aspergillosis is a lethal mold infection in the immunocompromised host. Understanding initial control of infection and how this is altered in the immunocompromised host are key goals for comprehension of the pathogenesis of pulmonary aspergillosis.

OBJECTIVES

To characterize the outcome of human macrophage infection with Aspergillus fumigatus and how this is altered in transplant recipients on calcineurin inhibitor immunosuppressants.

METHODS

We defined the outcome of human macrophage infection with A. fumigatus, as well as the impact of calcineurin inhibitors, through a combination of single-cell fluorescence imaging, transcriptomics, proteomics, and in vivo studies.

MEASUREMENTS AND MAIN RESULTS

Macrophage phagocytosis of A. fumigatus enabled control of 90% of fungal germination. However, fungal germination in the late phagosome led to macrophage necrosis. During programmed necroptosis, we observed frequent cell-cell transfer of A. fumigatus between macrophages, which assists subsequent control of germination in recipient macrophages. Lateral transfer occurred through actin-dependent exocytosis of the late endosome in a vasodilator-stimulated phosphoprotein envelope. Its relevance to the control of fungal germination was also shown by direct visualization in our zebrafish aspergillosis model in vivo. The calcineurin inhibitor FK506 (tacrolimus) reduced cell death and lateral transfer in vitro by 50%. This resulted in uncontrolled fungal germination in macrophages and also resulted in hyphal escape.

CONCLUSIONS

These observations identify programmed, necrosis-dependent lateral transfer of A. fumigatus between macrophages as an important host strategy for controlling fungal germination. This process is critically dependent on calcineurin. Our studies provide fundamental insights into the pathogenesis of pulmonary aspergillosis in the immunocompromised host.

Phagocytosis-dependent activation of a TLR9-BTK-calcineurin-NFAT pathway co-ordinates innate immunity to Aspergillus fumigatus

Transplant recipients on calcineurin inhibitors are at high risk of invasive fungal infection. Understanding how calcineurin inhibitors impair fungal immunity is a key priority for defining risk of infection. Here, we show that the calcineurin inhibitor tacrolimus impairs clearance of the major mould pathogen Aspergillus fumigatus from the airway, by inhibiting macrophage inflammatory responses. This leads to defective early neutrophil recruitment and fungal clearance. We confirm these findings in zebrafish, showing an evolutionarily conserved role for calcineurin signalling in neutrophil recruitment during inflammation. We find that calcineurin–NFAT activation is phagocytosis dependent and collaborates with NF-κB for TNF-α production. For yeast zymosan particles, activation of macrophage calcineurin–NFAT occurs via the phagocytic Dectin-1–spleen tyrosine kinase pathway, but for A. fumigatus, activation occurs via a phagosomal TLR9-dependent and Bruton's tyrosine kinase-dependent signalling pathway that is independent of MyD88. We confirm the collaboration between NFAT and NF-κB for TNF-α production in primary alveolar macrophages. These observations identify inhibition of a newly discovered macrophage TLR9–BTK–calcineurin–NFAT signalling pathway as a key immune defect that leads to organ transplant-related invasive aspergillosis.

Serum Inflammatory Cytokine Markers of Invasive Fungal Infection in Previously Immunocompetent Battle Casualties

BACKGROUND

Invasive fungal infection (IFI) is described increasingly in individuals experiencing high-energy military trauma. Hallmarks of successful treatment involve aggressive surgical debridement and early initiation of systemic antimicrobial therapy. Currently, intravenous anti-fungal therapy commences based on appearance of wounds and patient's clinical course. Whereas some clinical protocols exist to predict which critically injured patients should receive anti-fungal therapies, there are no established serum markers associated with IFI. Our hypothesis is that serum inflammatory cytokines exist that can assist in identifying individuals at risk for IFI.

METHODS

This is a retrospective case control study at a single institution. Nine patients with IFI (Saksenaea vasiformis, Fusarium sp., Graphium sp., Scedosporium sp., Aspergillus sp., Mucor sp., and Alternaria sp.) after battlefield trauma were matched to nine individuals with similar injury patterns whose laboratory results were negative for IFI. The combination of serum inflammatory cytokines from the first and second debridements was examined with multiplex platform proteomic analysis. We defined statistical significance as a two-tailed α<0.05 after adjusting for multiple comparisons using the false discovery rate method. This model was refined further with correlation-based filter selection and the area under the curve of the receiver operating characteristics (AUROC) was tested.

RESULTS

Both groups had similar Injury Severity Scores (ISS) (mean±standard deviation [SD]) (26.8±15.5 vs. 29.2±16.8, p=0.766). Elevated RANTES (regulated on activation, normal T cell expressed and secreted) alone (10,492.8±4,450.1 vs. 5,333.3±4,162.2, p=0.006) correlated with IFI. Also, the combination of persistent elevations in RANTES, interleukin (IL)-2R, and IL-15 was a robust model for predicting IFI with the AUROC being 0.9.

CONCLUSIONS

Elevation in serum cytokines, particularly RANTES, correlated with IFI in this small group of patients. This demonstrates the potential of future rapid serum testing for early initiation and guidance of anti-fungal therapies.

Fungal infections in renal transplant patients

Organ transplantation has always been considered to be the standard therapeutic interventions in patients with end-stage organ failure. In 2008, more than 29,000 organ transplants were performed in US. Survival rates among transplant recipients have greatly improved due to better understanding of transplant biology and more effective immunosuppressive agents. After transplant, the extent of the immune response is influenced by the amount of interleukin 2 (IL-2) being produced by the T-helper cells. Transplant immunosuppressive therapy primarily targets T cell-mediated graft rejection. Calcineurin inhibitor, which includes cyclosporine, pimecrolimus and tacrolimus, impairs calcineurin-induced up-regulation of IL-2 expression, resulting in increased susceptibility to invasive fungal diseases. This immunosuppressive state allows infectious complication, leading to a high mortality rate. Currently, overall mortality due to invasive fungal infections (IFIs) in solid organ transplant recipients ranges between 25% and 80%. The risk of IFI following renal transplant is associated with the dosage of immunosuppressive agents given, environmental factors and post-transplant duration. Most fungal infections occur in the first 6 months after transplant because of the use of numerous immunosuppressors. Candida spp. and Cryptococcus spp. are the yeasts most frequently isolated, while most frequent filamentous fungi (molds) isolated are Aspergillus spp. The symptoms of systemic fungal infections are non-specific and early detection of fungal infections and proper therapy are important in improving survival and reducing mortality. This article will provide an insight on the risk factors and clinical presentation, compare variation in treatment of IFIs in renal transplant patients, and evaluate the role of prophylactic therapy in this group of patients. We also report the course and management of two renal transplant recipients admitted to Staten Island University Hospital, both of whom developed pulmonary complications secondary to Aspergillus infection.

Nebulised amphotericin B-polymethacrylic acid nanoparticle prophylaxis prevents invasive aspergillosis

Aspergillus species are the major life threatening fungal pathogens in transplant patients. Germination of inhaled fungal spores initiates infection, causes severe pneumonia, and has a mortality of > 50%. This is leading to the consideration of pre-exposure prophylaxis to prevent infection. We made a very low MWt amphotericin B-polymethacrylic acid nanoparticle. It was not toxic to lung epithelial cells or monocyte-derived-macrophages in-vitro, or in an in-vivo transplant immuno-suppression mouse model of life threatening invasive aspergillosis. Three days of nebuliser based prophylaxis delivered the nanoparticle effectively to lung and prevented both fungal growth and lung inflammation. Protection from disease was associated with > 99% killing of the Aspergillus and a 90% reduction in lung TNF-α; the primary driver of tissue destructive immuno-pathology. This study provides in-vivo proof-of-principle that very small and cost-effective nanoparticles can be made simply, and delivered safely and effectively to lung by the aerosol route to prevent fungal infections.

From the Clinical Editor

Aspergillus is an opportunistic pathogen, which affects immunocompromised patients. One novel way to help fight against this infection is pre-exposure prophylaxis. The authors here made PMA based anionic hydrogels carrying amphotericin B, with mucoadhesive behavior. They showed that aerosol route of the drug was very effective in protecting against the disease in an in-vivo model and should provide a stepping-stone towards clinical trials in the future.

Clinical implications of interferon-γ genetic and epigenetic variants

Interferon-γ (IFN-γ) is an integral and critical molecule of the immune system, with multiple functions, mostly related to the T helper type 1 (Th1) response to infection. It is critical for defence against mycobacterial infection and is of increasing interest in defence against fungi. In this article, we review the genetic and epigenetic variants affecting IFN-γ expression and investigate its role in disease, with an emphasis on fungal diseases such as invasive and chronic pulmonary aspergillosis. Over 347 IFN-γ gene variants have been described, in multiple ethnic populations. Many appear to confer a susceptibility to disease, especially tuberculosis (TB) and hepatitis, but also some non-infectious conditions such as aplastic anaemia, cervical cancer and psoriasis. Several epigenetic modifications are also described, increasing IFN-γ expression in Th1 lymphocytes and reducing IFN-γ expression in Th2 lymphocytes. Recombinant IFN-γ administration is licensed for the prophylaxis of infection (bacterial and fungal) in patients with the phagocyte functional deficiency syndrome chronic granulomatous disease, although the benefits appear limited. Interferon-γ therapy is given to patients with profound defects in IFN-γ and interleukin-12 production and appears to be beneficial for patients with invasive aspergillosis and cryptococcal meningitis, but the studies are not definitive. A high proportion of patients with chronic pulmonary aspergillosis are poor producers of IFN-γ in response to multiple stimuli and could also benefit from IFN-γ administration. The investigation and management of patients with possible or demonstrated IFN-γ deficiency in adulthood is poorly studied and could be greatly enhanced with the integration of genetic data.

Interferon-gamma as adjunctive immunotherapy for invasive fungal infections: a case series

Background

Invasive fungal infections are very severe infections associated with high mortality rates, despite the availability of new classes of antifungal agents. Based on pathophysiological mechanisms and limited pre-clinical and clinical data, adjunctive immune-stimulatory therapy with interferon-gamma (IFN-γ) may represent a promising candidate to improve outcome of invasive fungal infections by enhancing host defence mechanisms.

Methods

In this open-label, prospective case series, we describe eight patients with invasive Candida and/or Aspergillus infections who were treated with recombinant IFN-γ (rIFN-γ, 100 μg s.c., thrice a week) for 2 weeks in addition to standard antifungal therapy.

Results

Recombinant IFN-γ treatment in patients with invasive Candida and/or Aspergillus infections partially restored immune function, as characterized by an increased HLA-DR expression in those patients with a baseline expression below 50%, and an enhanced capacity of leukocytes from treated patients to produce proinflammatory cytokines involved in antifungal defence.

Conclusions

The present study provides evidence that adjunctive immunotherapy with IFN-γ can restore immune function in fungal sepsis patients, warranting future clinical studies to assess its potential clinical benefit.

Trial registration

ClinicalTrials.gov - NCT01270490