infection-zebrafish-larvae-with-aspergillus-spores-for-analysis-host

Infection of Zebrafish Larvae with <em>Aspergillus</em> Spores for Analysis of Host-Pathogen Interactions

Invasive aspergillosis (IA) is one of&#160;the most common fungal infections among immunocompromised individuals. Despite the availability of antifungal ...

Clemson University

Antifungal therapy can fail in a remarkable number of patients with invasive fungal disease, resulting in significant morbidity worldwide. A major contributor to this failure is that while these drugs have high potency , we do not fully understand how they work inside infected hosts. Here, we used a transparent larval zebrafish model of  infection amenable to real-time imaging of invasive disease as an  intermediate vertebrate model to investigate the efficacy and mechanism of the antifungal drug voriconazole. We found that the ability of voriconazole to protect against  infection depends on host innate immune cells and, specifically, on the presence of macrophages. While voriconazole inhibits fungal spore germination and growth , it does not do so in larval zebrafish. Instead, live imaging of whole, intact larvae over a multiday course of infection revealed that macrophages slow down initial fungal growth, allowing voriconazole time to target and kill  hyphae postgermination. These findings shed light on how antifungal drugs such as voriconazole may synergize with the immune response in living hosts.

Efficacy of Voriconazole against Aspergillus fumigatus Infection Depends on Host Immune Function.

The specific roles of the two major innate immune cell types - neutrophils and macrophages - in response to infection and sterile inflammation are areas of great interest. The larval zebrafish model of innate immunity, and the imaging capabilities it provides, is a source of new research and discoveries in this field. Multiple methods have been developed in larval zebrafish to specifically deplete functional macrophages or neutrophils. Each of these has pros and cons, as well as caveats, that often make it difficult to directly compare results from different studies. The purpose of this Review is to (1) explore the pros, cons and caveats of each of these immune cell-depleted models; (2) highlight and place into a broader context recent key findings on the specific functions of innate immune cells using these models; and (3) explore future directions in which immune cell depletion methods are being expanded.

Determining macrophage versus neutrophil contributions to innate immunity using larval zebrafish.

Macrophages are a key cell type in innate immunity. Years of  cell culture studies have unraveled myriad macrophage pathways that combat pathogens and how pathogen effectors subvert these mechanisms. However,  cell culture studies may not accurately reflect how macrophages fit into the context of an innate immune response in whole animals with multiple cell types and tissues. Larval zebrafish have emerged as an intermediate model of innate immunity and host-pathogen interactions to bridge the gap between cell culture studies and mammalian models. These organisms possess an innate immune system largely conserved with humans and allow for state-of-the-art genetic and imaging techniques, all in the context of an intact organism. Using larval zebrafish, researchers are elucidating the function of macrophages in response to many different infections, including both bacterial and fungal pathogens. The goal of this review is to highlight studies in zebrafish that utilizing live imaging techniques to analyze macrophage activities in response to pathogens. Recent studies have explored the role of specific pathways and mechanisms in macrophage killing ability, explored how pathogens subvert these responses, identified subsets of macrophages with differential microbicidal activity, and implicated macrophages as an intracellular niche for pathogen survival and trafficking. Research in this model continues to advance our understanding of how macrophages, and specific pathways inside of these cells, fit into complex multicellular innate immune responses , providing important information on how pathogens evade these pathways and how we can exploit them for treatment development against microbial infections.

Article	Year
Efficacy of Voriconazole against Aspergillus fumigatus Infection Depends on Host Immune Function. Antimicrobial agents and chemotherapy\| PubMed ID: 31740552	2020
Determining macrophage versus neutrophil contributions to innate immunity using larval zebrafish. Disease models & mechanisms\| PubMed ID: 31932292	2020
Illuminating macrophage contributions to host-pathogen interactions : the power of zebrafish. Infection and immunity\| PubMed ID: 32179583	2020

Emily E. Rosowski

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