The increasing prevalence of antifungal-resistant human pathogenic fungi, particularly azole-resistant Aspergillus fumigatus, is a life-threatening challenge to the immunocompromised population.... Show moreThe increasing prevalence of antifungal-resistant human pathogenic fungi, particularly azole-resistant Aspergillus fumigatus, is a life-threatening challenge to the immunocompromised population. Autophagy-related processes such as LC3-associated phagocytosis have been shown to be activated in the host response against fungal infection, but their overall effect on host resistance remains uncertain. To analyze the relevance of these processes in vivo, we used a zebrafish animal model of invasive Aspergillosis. To confirm the validity of this model to test potential treatments for this disease, we confirmed that immunosuppressive treatments or neutropenia rendered zebrafish embryos more susceptible to A. fumigatus. We used GFP-Lc3 transgenic zebrafish to visualize the autophagy-related processes in innate immune phagocytes shortly after phagocytosis of A. fumigatus conidia, and found that both wild-type and melanin-deficient conidia elicited Lc3 recruitment. In macrophages, we observed GFP-Lc3 accumulation in puncta after phagocytosis, as well as short, rapid events of GFP-Lc3 decoration of single and multiple conidia-containing vesicles, while neutrophils covered single conidia-containing vesicles with bright and long-lasting GFP-Lc3 signal. Next, using genetic and pharmacological stimulation of three independent autophagy-inducing pathways, we showed that the antifungal autophagy response improves the host survival against A. fumigatus infection, but only in the presence of phagocytes. Therefore, we provide proof-of-concept that stimulating the (auto)phagolysosomal pathways is a promising approach to develop host-directed therapies against invasive Aspergillosis, and should be explored further either as adjunctive or stand-alone therapy for drug-resistant Aspergillus infections. Show less
Grijmans, B.J.M.; Kooij, S.B. van der; Varela Alvarez, M.; Meijer, A.H. 2022
Cells of the innate immune system continuously patrol the extracellular environment for potential microbial threats that are to be neutralized by phagocytosis and delivery to lysosomes. In addition... Show moreCells of the innate immune system continuously patrol the extracellular environment for potential microbial threats that are to be neutralized by phagocytosis and delivery to lysosomes. In addition, phagocytes employ autophagy as an innate immune mechanism against pathogens that succeed to escape the phagolysosomal pathway and invade the cytosol. In recent years, LC3-associated phagocytosis (LAP) has emerged as an intermediate between phagocytosis and autophagy. During LAP, phagocytes target extracellular microbes while using parts of the autophagic machinery to label the cargo-containing phagosomes for lysosomal degradation. LAP contributes greatly to host immunity against a multitude of bacterial pathogens. In the pursuit of survival, bacteria have developed elaborate strategies to disarm or circumvent the LAP process. In this review, we will outline the nature of the LAP mechanism and discuss recent insights into its interplay with bacterial pathogens. Show less
The aim of this thesis is to investigate the role of chronic inflammation as well as acute inflammatory response on muscle aging. We conclude that high chronic inflammation is associated with low... Show moreThe aim of this thesis is to investigate the role of chronic inflammation as well as acute inflammatory response on muscle aging. We conclude that high chronic inflammation is associated with low muscle strength, while high acute pro-inflammatory response is associated with high muscle strength. Show less
In a world where bacterial infections are becoming harder and harder to fight due to rising antibiotic resistance, disease models that allow high throughput screening are needed more than ever. An... Show moreIn a world where bacterial infections are becoming harder and harder to fight due to rising antibiotic resistance, disease models that allow high throughput screening are needed more than ever. An ideal model organism for high throughput screening is the zebrafish embryo. However, models for high throughput screening of infection are still wanted. In this thesis the fish pathogen Edwardsiella tarda was tested for use in high throughput studies of infectious disease in zebrafish. First the genome of Edwardsiella tarda was sequenced to determine the virulence factors of this bacterium. Next different types of exposure of zebrafish to Edwardsiella tarda were tested. This showed an absence of detectable infection after static immersion, but a reproducible infection on the level of single embryos after caudal vein injection. Finally, using the caudal vein injection method, the zebrafish knock-out mutant in the gene Myd88 was characterized. This is the first zebrafish knock-out mutant in a gene central in the innate immune system. Show less
The scope of the current thesis is to obtain insight in immunological aspects of transplantation and diabetes. This thesis underscores the current concept of collaboration between the innate and... Show moreThe scope of the current thesis is to obtain insight in immunological aspects of transplantation and diabetes. This thesis underscores the current concept of collaboration between the innate and adaptive immune system by showing close interactions between both immune systems. Mannose binding lectin as a major recognition molecule of the lectin pathway and as a key protein of the immune system was studied in relation to its functional characteristics. Appreciating the Jekyll-and-Hyde character of MBL and the fact that MBL serum levels and functionality are under strict genetic control, MBL was studied under distinct pathological conditions. Chapter 2 describes molecular and biological aspects of mannose binding lectin and the interaction of MBL with the adaptive immune system. Chapter 3 focuses on the involvement of MBL in autoimmunity, by studying juvenile type 1 diabetic patients at disease onset. Chapter 4 addresses the role of the liver in production of serum MBL and evaluates the effect of MBL variant alleles on the susceptibility to infection after liver transplantation. Chapter 5 focuses on the effect of the adaptive immune system on islet transplantation, a novel treatment of type 1 diabetes. Show less
