Host pathways mediating changes in immune states elicited by intestinal microbial colonization are incompletely characterized. Here we describe alterations of the host immune state induced by ...colonization of germ-free zebrafish larvae with an intestinal microbial community or single bacterial species. We show that microbiota-induced changes in intestinal leukocyte subsets and whole-body host gene expression are dependent on the innate immune adaptor gene myd88. Similar patterns of gene expression are elicited by colonization with conventional microbiome, as well as mono-colonization with two different zebrafish commensal bacterial strains. By studying loss-of-function myd88 mutants, we find that colonization suppresses Myd88 at the mRNA level. Tlr2 is essential for microbiota-induced effects on myd88 transcription and intestinal immune cell composition.
Summary
The number of root nodules developing on legume roots after rhizobial infection is controlled by the plant shoot through autoregulation and mutational inactivation of this mechanism leads to ...hypernodulation. We have characterised the Pisum sativum (pea) Sym28 locus involved in autoregulation and shown that it encodes a protein similar to the Arabidopsis CLAVATA2 (CLV2) protein. Inactivation of the PsClv2 gene in four independent sym28 mutant alleles, carrying premature stop codons, results in hypernodulation of the root and changes to the shoot architecture. In the reproductive phase sym28 shoots develops additional flowers, the stem fasciates, and the normal phyllotaxis is perturbed. Mutational substitution of an amino acid in one leucine rich repeat of the corresponding Lotus japonicus LjCLV2 protein results in increased nodulation. Similarly, down‐regulation of the Lotus Clv2 gene by RNAi mediated reduction of the transcript level also resulted in increased nodulation. Gene expression analysis of LjClv2 and Lotus hypernodulation aberrant root formation Har1 (previously shown to regulate nodule numbers) indicated they have overlapping organ expression patterns. However, we were unable to demonstrate a direct protein–protein interaction between LjCLV2 and LjHAR1 proteins in contrast to the situation between equivalent proteins in Arabidopsis. LjHAR1 was localised to the plasma membrane using a YFP fusion whereas LjCLV2‐YFP localised to the endoplasmic reticulum when transiently expressed in Nicotiana benthamiana leaves. This finding is the most likely explanation for the lack of interaction between these two proteins.
Among opportunistically pathogenic filamentous fungi of the Aspergillus genus, Aspergillus fumigatus stands out as a drastically more prevalent cause of infection than others. Utilizing the zebrafish ...embryo model, we applied a combination of non-invasive real-time imaging and genetic approaches to compare the infectious development of A. fumigatus with that of the less pathogenic A. niger. We found that both species evoke similar immune cell migratory responses, but A. fumigatus is more efficiently phagocytized than A. niger. Though efficiently phagocytized, A. fumigatus conidia retains the ability to germinate and form hyphae from inside macrophages leading to serious infection even at relatively low infectious burdens. By contrast, A. niger appears to rely on extracellular germination, and rapid hyphal growth to establish infection. Despite these differences in the mechanism of infection between the species, galactofuranose mutant strains of both A. fumigatus and A. niger display attenuated pathogenesis. However, deficiency in this cell wall component has a stronger impact on A. niger, which is dependent on rapid extracellular hyphal growth. In conclusion, we uncover differences in the interaction of the two fungal species with innate immune cells, noticeable from very early stages of infection, which drive a divergence in their route to establishing infections.
Major molecular mechanisms that underpin the toxicity of nanoparticles (NPs) are the formation of reactive oxygen species and the induction of inflammation. The latter is frequently observed in vitro ...and in mammalian organisms, yet in aquatic organisms, such NP-induced inflammatory responses remain largely unexplored. Zebrafish offer a wide range of molecular tools to investigate immune responses in an aquatic organism, and were therefore used here to describe how copper (Cu) NPs (25 nm; 1 mg L −1 ) and soluble Cu as well as polystyrene (PS) NPs (25 nm; 10 mg L 1− ) induce innate immune responses, focussing on the skin cells and the intestine as likely organs of interaction. mRNA expression of the immune responsive genes interleukin 1 beta ( il1β ) and immunoresponsive gene 1-like ( irg1l ) of CuNP exposed embryos was observed to be weaker in the intestinal tissue compared to the rest of the body, indicating a strong outer epithelium response. Specifically, NPs were observed to accumulate in the cavities of lateral neuromasts in the skin, which coincided with an increased local expression of il1β . Exposure to CuNPs triggered the strongest transcriptional changes in pro-inflammatory-related genes and was also observed to increase migration of neutrophils in the tail, indicating a NP-specific inflammatory response. This is the first in vivo evidence for waterborne NP exposure triggering alterations of immune system regulating genes in the skin and intestine of zebrafish embryos. The observed molecular responses have the potential to be linked to adverse effects at higher levels of biological organization and hence might be used for screening purposes in nanotoxicology or as building blocks for adverse outcome pathways.
The rapid and persistent increase of drug-resistant
(
) infections poses increasing global problems in combatting tuberculosis (TB), prompting for the development of alternative strategies including ...host-directed therapy (HDT). Since
is an intracellular pathogen with a remarkable ability to manipulate host intracellular signaling pathways to escape from host defense, pharmacological reprogramming of the immune system represents a novel, potentially powerful therapeutic strategy that should be effective also against drug-resistant
. Here, we found that host-pathogen interactions in
-infected primary human macrophages affected host epigenetic features by modifying histone deacetylase (HDAC) transcriptomic levels. In addition, broad spectrum inhibition of HDACs enhanced the antimicrobial response of both pro-inflammatory macrophages (Mϕ1) and anti-inflammatory macrophages (Mϕ2), while selective inhibition of class IIa HDACs mainly decreased bacterial outgrowth in Mϕ2. Moreover, chemical inhibition of HDAC activity during differentiation polarized macrophages into a more bactericidal phenotype with a concomitant decrease in the secretion levels of inflammatory cytokines. Importantly,
chemical inhibition of HDAC activity in
-infected zebrafish embryos, a well-characterized animal model for tuberculosis, significantly reduced mycobacterial burden, validating our
findings in primary human macrophages. Collectively, these data identify HDACs as druggable host targets for HDT against intracellular
.
is the most common nontuberculous mycobacterium (NTM) species causing infectious disease. Here, we characterized a
infection model in zebrafish larvae, and compared it to
infection, a model of ...tuberculosis.
bacteria are efficiently phagocytosed and frequently induce granuloma-like structures in zebrafish larvae. Although macrophages can respond to both mycobacterial infections, their migration speed is faster in infections caused by
. Tlr2 is conservatively involved in most aspects of the defense against both mycobacterial infections. However, Tlr2 has a function in the migration speed of macrophages and neutrophils to infection sites with
that is not observed with
. Using RNAseq analysis, we found a distinct transcriptome response in cytokine-cytokine receptor interaction for
and
infection. In addition, we found differences in gene expression in metabolic pathways, phagosome formation, matrix remodeling, and apoptosis in response to these mycobacterial infections. In conclusion, we characterized a new
infection model in zebrafish that can be further used in studying pathological mechanisms for NTM-caused diseases.
The original version of this Article contained an error in the spelling of the author Shuxin Yang, which was incorrectly given as Shuxing Yang. This has now been corrected in both the PDF and HTML ...versions of the Article.
Chitin is a vital polysaccharide component of protective structures in many eukaryotic organisms but seems absent in vertebrates. Chitin or chitin oligomers are therefore prime candidates for ...non-self-molecules, which are recognized and degraded by the vertebrate immune system. Despite the absence of polymeric chitin in vertebrates, chitinases and chitinase-like proteins (CLPs) are well conserved in vertebrate species. In many studies, these proteins have been found to be involved in immune regulation and in mediating the degradation of chitinous external protective structures of invading pathogens. Several important aspects of chitin immunostimulation have recently been uncovered, advancing our understanding of the complex regulatory mechanisms that chitin mediates. Likewise, the last few years have seen large advances in our understanding of the mechanisms and molecular interactions of chitinases and CLPs in relation to immune response regulation. It is becoming increasingly clear that their function in this context is not exclusive to chitin producing pathogens, but includes bacterial infections and cancer signaling as well. Here we provide an overview of the immune signaling properties of chitin and other closely related biomolecules. We also review the latest literature on chitinases and CLPs of the GH18 family. Finally, we examine the existing literature on zebrafish chitinases, and propose the use of zebrafish as a versatile model to complement the existing murine models. This could especially be of benefit to the exploration of the function of chitinases in infectious diseases using high-throughput approaches and pharmaceutical interventions.
Many host-microbiota interactions depend on the recognition of microbial constituents by toll-like receptors of the host. The impacts of these interactions on host health can shape the hosts response ...to environmental pollutants such as nanomaterials. Here, we assess the role of toll-like receptor 2 (TLR2) signaling in the protective effects of colonizing microbiota against silver nanoparticle (nAg) toxicity to zebrafish larvae. Zebrafish larvae were exposed to nAg for two days, from 3 to 5 days post-fertilization. Using an il1ß-reporter line, we first characterized the accumulation and particle-specific inflammatory effects of nAg in the total body and intestinal tissues of the larvae. This showed that silver gradually accumulated in both the total body and intestinal tissues, yet specifically caused particle-specific inflammation on the skin of larvae. Subsequently, we assessed the effects of microbiota-dependent TLR2 signaling on nAg toxicity. This was done by comparing the sensitivity of loss-of-function zebrafish mutants for TLR2, and each of the TLR2-adaptor proteins MyD88 and TIRAP (Mal), under germ-free and microbially-colonized conditions. Irrespective of their genotype, microbially-colonized larvae were less sensitive to nAg than their germ-free siblings, supporting the previously identified protective effect of microbiota against nAg toxicity. Under germ-free conditions, tlr2, myd88 and tirap mutants were equally sensitive to nAg as their wildtype siblings. However, when colonized by microbiota, tlr2 and tirap mutants were more sensitive to nAg than their wildtype siblings. The sensitivity of microbially-colonized myd88 mutants did not differ significantly from that of wildtype siblings. These results indicate that the protective effect of colonizing microbiota against nAg-toxicity to zebrafish larvae involves TIRAP-dependent TLR2 signaling. Overall, this supports the conclusion that host-microbiota interactions affect nanomaterial toxicity to zebrafish larvae.
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•Interactions of microbiota with Toll-Like Receptors (TLRs) affect nanoparticle toxicity.•Exposure of zebrafish larvae to silver nanoparticles causes dermal inflammation.•Silver nanoparticles are more lethal to zebrafish larvae without functional TLR2.•The sensitivity of germ-free larvae to silver nanoparticles does not depend on TLR2.
Metal-based nanoparticles exhibiting antimicrobial activity are of emerging concern to human and environmental health. In addition to their direct adverse effects to plants and animals, indirect ...effects resulting from disruption of beneficial host-microbiota interactions may contribute to the toxicity of these particles. To explore this hypothesis, we compared the acute toxicity of silver and zinc oxide nanoparticles (nAg and nZnO) to zebrafish larvae that were either germ-free or colonized by microbiota. Over two days of exposure, germ-free zebrafish larvae were more sensitive to nAg than microbially colonized larvae, whereas silver ion toxicity did not differ between germ-free and colonized larvae. Using response addition modeling, we confirmed that the protective effect of colonizing microbiota against nAg toxicity was particle-specific. Nearly all mortality among germ-free larvae occurred within the first day of exposure. In contrast, mortality among colonized larvae increased gradually over both exposure days. Concurrent with this gradual increase in mortality was a marked reduction in the numbers of live host-associated microbes, suggesting that bactericidal effects of nAg on protective microbes resulted in increased mortality among colonized larvae over time. No difference in sensitivity between germ-free and colonized larvae was observed for nZnO, which dissolved rapidly in the exposure medium. At sublethal concentrations, these particles moreover did not exert detectable bactericidal effects on larvae-associated microbes. Altogether, our study shows the importance of taking host-microbe interactions into account in assessing toxic effects of nanoparticles to microbially colonized hosts, and provides a method to screen for microbiota interference with nanomaterial toxicity.
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