Despite the strong interest in the NK cell-mediated immunity toward malignant cells and viruses, there is a relative lack of data on the interplay between NK cells and filamentous fungi, especially Aspergillus fumigatus, which is the major cause of invasive aspergillosis. By studying the in vitro interaction between human NK cells and A. fumigatus, we found only germinated morphologies to be highly immunogenic, able to induce a Th1-like response, and capable of upregulating cytokines such as IFN-γ and TNF-α. Moreover, priming NK cells with human rIL-2 and stimulating NK cells by direct NK cell–pathogen contact were essential to induce damage against A. fumigatus. However, the most interesting finding was that NK cells did not mediate anti-Aspergillus cytotoxicity through degranulation of their cytotoxic proteins (perforin, granzymes, granulysine), but via an alternative mechanism involving soluble factor(s). To our knowledge, our study is the first to demonstrate that IFN-γ, released by NK cells, directly damages A. fumigatus, attributing new properties to both human NK cells and IFN-γ and suggesting them as possible therapeutic tools against IA.
Chemokines represent central players of the innate and adaptive immunity and are involved in the regulation of inflammatory events occurring during infectious complications or during graft vs. host disease (GvHD). Patients after allogeneic stem cell transplantation (alloSCT) are at a high risk for the development of acute GvHD or to suffer from fungal infections. Susceptibility to fungal infections and the course of GvHD can be genetically influenced by single nucleotide polymorphisms (SNPs), which regulate expression or biological activity of chemokines, and therefore have an impact on the outcome of invasive aspergillosis and GvHD. High lightened studies of abetting factors for GvHD revealed SNPs in TNFA, IL-6, IL-10, INF-γ, CCL2, CCL5 (RANTES), IL-1Ra, IL-23R, IL-7Ralpha, IL-10RB, and CCR9 genes as prevalent considerable. Furthermore, additional SNPs were described to be significantly associated with fungal infections (Aspergillus fumigatus, Candida albicans), including markers in CCL3, CCL4, CCL20, CXCL2, CXCL8, CXCL10, CCR1, and CCR2. This review summarizes the current knowledge about the growing number of genetic markers in chemokine genes and their relevance for patients after alloSCT.
Invasive aspergillosis is a significant cause of morbidity and mortality in patients after stem cell transplantation, in solid organ transplant recipients, and in patients with hematological malignancies. The interactions between human immature dendritic cells (iDCs) and Aspergillus fumigatus antigens are widely uncharacterized. We analyzed the immune response of iDCs to different recombinant A. fumigatus antigens (Aspf1 and Crf1). One of these antigens, the 18-kDa RNase Aspf1, triggered the increased level of expression of genes encoding proinflammatory cytokines and chemokines, and augmented the activation of NFB and the apoptosis of iDCs. Furthermore, by fluorescence microscopy, we could demonstrate that in the first 3 h a major portion of Aspf1 accumulates on the cell surface. Finally, we could show an increased segregation of cytokines and chemokines after the stimulation of iDCs by an Aspf1 deletion mutant strain of A. fumigatus.
1640 Poster Board I-666 Introduction Natural killer (NK) cells are CD3- CD56+ lymphocytes demonstrating confirmed cytotoxicity against neoplastic and virus infected host cells. Increasing data provide evidence of a direct NK cell effect against extracellular pathogens, such as bacteria, parasites and yeasts, but there is a relative lack of data on their interaction with filamentous fungus and especially with Aspergillus fumigatus. Aspergillus is an omnipresent mold, living in close vicinity with humans, being constantly inhaled in the lungs and thereafter cleared by the innate immune system. Otherwise harmless for healthy people, it is at the origin of invasive Aspergillosis (IA), an extremely devastating disease for immunocompromised subjects. Host's innate immune system controls Aspergillus growth through a complex system of potent effector cells, mediating their antifungal activity mainly by phagocytosis. Our study aims to shed light for the first time on the direct interaction between human NK cells, mediators of extracellular cytotoxicity, and Aspergillus. Methods NK cells were isolated after magnetic depletion of the peripheral blood of healthy volunteers and they were used after 24h priming with 500 U/ml recombinant interleukin – 2 rhIL-2. To determine gene expression and cytokine release of interferon gamma (IFNg) and Tumor Necrosis Factor- a (TNF-a), NK cells were stimulated for 0, 3, 6 and 12h with different morphologies of Aspergillus: conidia and germlings. To evaluate the lethal impact of NK cells on Aspergillus, plate killing assays were performed at 0, 3 and 6h time points. To illustrate the role of antibody dependent cellular cytotoxicity, ADCC a monoclonal IgG antibody, against germlings, was tested. Transwell permeable membranes, with pores of 0,4 μm, prohibiting the direct contact of cells placed on their opposite sides, but allowing the free circulation of molecules, were used to estimate the effect of cell-fungal contact. To investigate the cytotoxic mechanism involved, NK cells were depleted from perforin and granzymes by treatment with strontium chloride and they had their death ligands, TNF- related apoptosis- inducing ligand (TRAIL) and FasL, neutralised by means of blocking antibodies. The release of cytotoxic granules was estimated by the NK cell surface expression of the marker of degranulation CD107a/b. Results Observing the in vitro interaction of NK cells with Aspergillus, fungal germinated morphologies (germlings) showed to be highly immunogenic towards NK cells, compared to conidia, inducing the gene expression and cytokine release of Th1 immune mediators such as IFN-g (p <0,05) and TNF-a.(p <0,1). NK cells demonstrated also a strong lethal impact against germlings (p <0,05). Moreover, the presence of antifungal antibody further potentiated both immunoregulatory and cytotoxic activities. Investigating the means engaged by NK cells to perceive and kill Aspergillus, direct effector–pathogen cell to cell contact was revealed as prerequisite; when this condition was not present there was neither cytokine induction, nor fungal damage (p <0,05). This finding was confirmed by the lack of surface expression of CD107a/b, after NK cell- Aspergillus co-incubation. Investigating the killing pathway we compared the effectiveness of perforin – granzymes depleted NK cells to this of intact cells against germlings and it was found equivalent (p =NS). In a similar way, neutralisation of TRAIL and FasL ligands did not alter the cytotoxic ability of NK cells towards Aspergillus. Conclusion Our data show that human NK cells are stimulated in vitro by Aspergillus germlings, which triggers an immunoregulatory Th1 orientated response and causes important fungal killing. NK cells are not aware of conidia, they are not stimulated by them and par consequence they do not kill them. Finally, we showed that NK cells do not mediate their cytotoxic effect via perforin – granzymes pathway, neither through the engagement of TRAIL, FasL death receptors, suggesting that another pathway is involved in NK cell – Aspergillus fumigatus interplay. We suggest that further investigation of these striking findings might offer a potent immunotherapeutic tool against IA. Disclosures No relevant conflicts of interest to declare.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.