Immunotherapy against invasive fungal diseases in stem cell transplant recipients

Immunomodulation for the Treatment of Fungal Infections: Opportunities and Challenges

Opportunistic fungal infections are major causes of morbidity and mortality in patients with single or multiple defects in their immunity. Antifungal agents targeting the pathogen remain the treatment of choice for fungal infections. However, antifungal agents are toxic to the host mainly due to the close evolutionary similarity of fungi and humans. Moreover, antifungal therapy is ineffective in patients with immunosuppression. For this reason, there is an increased demand to develop novel strategies to enhance immune function and augment the existing antifungal drugs. In recent times, targeting the immune system to improve impaired host immune responses becomes a reasonable approach to improve the effectiveness of antifungal drugs. In this regard, immunomodulating therapeutic agents that turn up the immune response in the fight against fungal infections hold promise for enhancing the efficacy and safety of conventional antifungal therapy. In general, immunomodulating therapies are safe with decreased risk of resistance and broad spectrum of activity. In this review, therefore, clinical evidences supporting the opportunities and challenges of immunomodulation therapies in the treatment of invasive fungal infections are included.

Immunotherapy for viral and fungal infections

Allogenic stem cell transplantation (allo-SCT) represents the only curative option for several hematological malignancies. Due to a delayed and dysfunctional immunological recovery infectious complications and residual tumor cells following allo-SCT are still major causes of failure of this procedure. Here we discuss the most common infectious complications of allo-SCT and describe current and future strategies to prophylaxe or treat these complications using novel immunotherapeutic strategies.

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

IL4 and IFNalpha generation of dendritic cells reveals great migratory potential and NFkB and cJun expression in IL4DCs

Dendritic cells (DCs) recently revealed as a potent tumor vaccine component, are commonly differentiated from monocytes by cultivation with IL-4 and GM-CSF. Despite the different opinions, the use of IFNalpha can promote DCs differentiation and activation. The aim of this study was to compare the functionality and phenotypic characterization of monocyte-derived DC generated by IL-4 (IL4DC) and IFNalpha (IFNalphaDC) modified protocols. To this aim, we investigated the expression of maturation markers, co-stimulatory molecules, relevant miRNA, cytokine and migratory profiles and the functional ability of these cells to stimulate autologous T cells in vitro. We herein investigated the molecular mechanism underlying the parameters previously described, as the relative expression of NF-kB p65, c-fos and c-jun, transcription factors. Our results demonstrated that IL4DC presented a stable phenotype, an increase in migratory capacity and NF-KB activation, in addition to lower levels of miR-146 a and miR-221. We believe that the IL4DC migratory potential and increase in NFkBp65 expression may be involved in higher IL12 expression and migration, suggesting a preferential activation of TH1 immune responses by IL4DC.

LAB/NTAL facilitates fungal/PAMP-induced IL-12 and IFN-γ production by repressing β-catenin activation in dendritic cells

Fungal pathogens elicit cytokine responses downstream of immunoreceptor tyrosine-based activation motif (ITAM)-coupled or hemiITAM-containing receptors and TLRs. The Linker for Activation of B cells/Non-T cell Activating Linker (LAB/NTAL) encoded by Lat2, is a known regulator of ITAM-coupled receptors and TLR-associated cytokine responses. Here we demonstrate that LAB is involved in anti-fungal immunity. We show that Lat2-/- mice are more susceptible to C. albicans infection than wild type (WT) mice. Dendritic cells (DCs) express LAB and we show that it is basally phosphorylated by the growth factor M-CSF or following engagement of Dectin-2, but not Dectin-1. Our data revealed a unique mechanism whereby LAB controls basal and fungal/pathogen-associated molecular patterns (PAMP)-induced nuclear β-catenin levels. This in turn is important for controlling fungal/PAMP-induced cytokine production in DCs. C. albicans- and LPS-induced IL-12 and IL-23 production was blunted in Lat2-/- DCs. Accordingly, Lat2-/- DCs directed reduced Th1 polarization in vitro and Lat2-/- mice displayed reduced Natural Killer (NK) and T cell-mediated IFN-γ production in vivo/ex vivo. Thus our data define a novel link between LAB and β-catenin nuclear accumulation in DCs that facilitates IFN-γ responses during anti-fungal immunity. In addition, these findings are likely to be relevant to other infectious diseases that require IL-12 family cytokines and an IFN-γ response for pathogen clearance.