RESUMEN
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.
Asunto(s)
Antifúngicos/farmacología , Aspergilosis/inmunología , Aspergilosis/microbiología , Aspergillus fumigatus/inmunología , Pruebas Inmunológicas de Citotoxicidad , Interferón gamma/metabolismo , Células Asesinas Naturales/inmunología , Células Asesinas Naturales/microbiología , Antifúngicos/química , Antifúngicos/metabolismo , Aspergilosis/prevención & control , Aspergillus fumigatus/crecimiento & desarrollo , Degranulación de la Célula/inmunología , Células Cultivadas , Técnicas de Cocultivo , Humanos , Interferón gamma/toxicidad , Células K562 , Células Asesinas Naturales/metabolismo , Esporas Fúngicas/crecimiento & desarrollo , Esporas Fúngicas/inmunologíaRESUMEN
Aspergillus fumigatus is currently the major air-borne fungal pathogen. It is able to cause several forms of disease in humans of which invasive aspergillosis is the most severe. The high mortality rate of this disease prompts increased efforts to disclose the basic principles of A. fumigatus pathogenicity. According to our current knowledge, A. fumigatus lacks sophisticated virulence traits; it is nevertheless able to establish infection due to its robustness and ability to adapt to a wide range of environmental conditions. This review focuses on two crucial aspects of invasive aspergillosis: (i) properties of A. fumigatus that are relevant during infection and may distinguish it from non-pathogenic Aspergillus species and (ii) interactions of the pathogen with the innate and adaptive immune systems.
Asunto(s)
Aspergilosis/microbiología , Aspergillus fumigatus/patogenicidad , Aspergilosis Pulmonar Invasiva/microbiología , Infecciones Oportunistas/microbiología , Adaptación Fisiológica , Inmunidad Adaptativa , Aspergilosis/inmunología , Aspergilosis/mortalidad , Aspergillus fumigatus/inmunología , Aspergillus fumigatus/fisiología , Humanos , Inmunidad Innata , Huésped Inmunocomprometido , Aspergilosis Pulmonar Invasiva/inmunología , Aspergilosis Pulmonar Invasiva/mortalidad , Infecciones Oportunistas/inmunología , Infecciones Oportunistas/mortalidad , Factores de Virulencia/metabolismoRESUMEN
Two-component signaling systems are widespread in bacteria, but also found in fungi. In this study, we have characterized TcsC, the only Group III two-component sensor kinase of Aspergillus fumigatus. TcsC is required for growth under hyperosmotic stress, but dispensable for normal growth, sporulation and conidial viability. A characteristic feature of the ΔtcsC mutant is its resistance to certain fungicides, like fludioxonil. Both hyperosmotic stress and treatment with fludioxonil result in a TcsC-dependent phosphorylation of SakA, the final MAP kinase in the high osmolarity glycerol (HOG) pathway, confirming a role for TcsC in this signaling pathway. In wild type cells fludioxonil induces a TcsC-dependent swelling and a complete, but reversible block of growth and cytokinesis. Several types of stress, such as hypoxia, exposure to farnesol or elevated concentrations of certain divalent cations, trigger a differentiation in A. fumigatus toward a "fluffy" growth phenotype resulting in white, dome-shaped colonies. The ΔtcsC mutant is clearly more susceptible to these morphogenetic changes suggesting that TcsC normally antagonizes this process. Although TcsC plays a role in the adaptation of A. fumigatus to hypoxia, it seems to be dispensable for virulence.
Asunto(s)
Aspergillus fumigatus/enzimología , Proteínas Fúngicas/metabolismo , Proteínas Quinasas/metabolismo , Transducción de Señal , Estrés Fisiológico , Animales , Aspergilosis/microbiología , Aspergilosis/patología , Aspergillus fumigatus/genética , Aspergillus fumigatus/crecimiento & desarrollo , Aspergillus fumigatus/patogenicidad , AMP Cíclico/farmacología , Dioxoles/farmacología , Farmacorresistencia Fúngica/efectos de los fármacos , Farmacorresistencia Fúngica/efectos de la radiación , Fungicidas Industriales/farmacología , Histidina Quinasa , Humanos , Huésped Inmunocomprometido , Luz , Ratones , Pruebas de Sensibilidad Microbiana , Modelos Biológicos , Mutación/genética , Fenotipo , Fosforilación/efectos de los fármacos , Fosforilación/efectos de la radiación , Pirroles/farmacología , Transducción de Señal/efectos de los fármacos , Transducción de Señal/efectos de la radiación , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/efectos de la radiación , Virulencia/efectos de los fármacos , Virulencia/efectos de la radiaciónRESUMEN
Neutrophil extracellular traps (NETs) represent a distinct mechanism to control and eliminate microbial infections. Our results show that conidia and germ tubes of the human pathogenic mold Aspergillus fumigatus are able to trigger the formation of NETs. Viable fungal cells are not essentially required for this host-pathogen interaction. Neutrophils engulf conidia and thereby inhibit their germination, a process that is independent of NETosis. In the experimental set-up used in this study neutrophils do not kill germ tubes, but reduce their polar growth and this inhibition depends on NETs as it can be overcome by the addition of DNase-1. The Zn(2+) chelator calprotectin is associated with the Aspergillus-induced NETs and addition of Zn(2+) abrogates the NET-mediated growth inhibition. In summary, our data provide evidence that NETs are not sufficient to kill A. fumigatus, but might be a valuable tool to confine infection.