Aspergillus fumigatus Stimulates the NLRP3 Inflammasome through a Pathway Requiring ROS Production and the Syk Tyrosine Kinase

Invasive aspergillosis (IA) is a life-threatening disease that occurs in immunodepressed patients when infected with Aspergillus fumigatus. This fungus is the second most-common causative agent of fungal disease after Candida albicans. Nevertheless, much remains to be learned about the mechanisms by which A. fulmigatus activates the innate immune system. We investigated the inflammatory response to conidia and hyphae of A. fumigatus and specifically, their capacity to trigger activation of an inflammasome. Our results show that in contrast to conidia, hyphal fragments induce NLRP3 inflammasome assembly, caspase-1 activation and IL-1β release from a human monocyte cell line. The ability of Aspergillus hyphae to activate the NLRP3 inflammasome in the monocytes requires K+ efflux and ROS production. In addition, our data show that NLRP3 inflammasome activation as well as pro-IL-1β expression relies on the Syk tyrosine kinase, which is downstream from the pathogen recognition receptor Dectin-1, reinforcing the importance of Dectin-1 in the innate immune response against fungal infection. Furthermore, we show that treatment of monocytes with corticosteroids inhibits transcription of the gene encoding IL-1β. Thus, our data demonstrate that the innate immune response against A. fumigatus infection involves a two step activation process, with a first signal promoting expression and synthesis of pro-IL-1β; and a second signal, involving Syk-induced activation of the NLRP3 inflammasome and caspase-1, allowing processing and secretion of the mature cytokine

Caspofungin at catheter lock concentrations eradicates mature biofilms of Candida lusitaniae and Candida guilliermondii

The antibiofilm activities of caspofungin, anidulafungin, micafungin, and liposomal amphotericin B were studied against Candida lusitaniae, Candida guilliermondii, and a Candida albicans control strain. While anidulafungin and micafungin (0.007 to 2,048 mg/liter) showed reduced activity against biofilms of both test species, caspofungin displayed concentration-dependent antibiofilm activity, reaching complete and persistent eradication at concentrations achievable during lock therapy (512 to 2,048 mg/liter, P<0.05). Although liposomal amphotericin B strongly inhibited mature biofilms, it possessed lower antibiofilm activity than caspofungin (P<0.05). Copyright © 2014, American Society for Microbiology. All Rights Reserved

Expression of Immunomodulatory Genes in Human Monocytes Induced by Voriconazole in the Presence of Aspergillus fumigatus

We assessed the effect of voriconazole (VRC) on the expression and release of selected cytokines and chemokines in the THP-1 human monocytic cell line in response to Aspergillus fumigatus hyphal fragments (HF) by cDNA microarray analysis, reverse transcriptase (RT) PCR, and enzyme-linked immunosorbent assay. Stimulation of THP-1 cells by HF alone caused a significant up-regulation of CCL4 (MIP1B) and CCL16, while CCL2 (MCP1) was down-regulated. By comparison, in the presence of VRC, a large number of genes such as CCL3 (MIP1A), CCL4 (MIP1B), CCL5 (RANTES), CCL7 (MCP3), CCL11 (EOTAXIN), CCL15 (MIP1Δ), CXCL6, and CXCL13 were strongly up-regulated in THP-1 cells challenged by HF, whereas CCL20 (MIP3A) and CCL21 (MIP2) were down-regulated. Among five genes differentially expressed in THP-1 cells, IL12A, IL12B, and IL-16 were down-regulated whereas IL-11 and TGFB1 were significantly up-regulated in the presence of VRC. The inflammation-related genes IFNγ, IL1R1, and TNFA were also up-regulated in THP-1 cells exposed to HF only in the presence of VRC. RT-PCR of four selected genes validated the results of microarrays. The release of interleukin 1β (IL-1β) and IL-12 was significantly increased from monocytes stimulated either by HF alone (P < 0.05) or in the presence of VRC (P < 0.01 and P < 0.05, respectively). In contrast, tumor necrosis factor alpha release from monocytes was enhanced only in the presence of VRC (P < 0.01). The chemokines monocyte chemoattractant protein 1 and macrophage inflammatory protein 1β were decreased under both conditions (P < 0.01). These results demonstrate that in the presence of VRC, HF induces a more pronounced profile of gene expression in THP-1 cells than HF alone, potentially leading to more-efficient host resistance to A. fumigatus