Direct Visualization of Fungal Burden in Filamentous Fungus-Infected Silkworms.

Yidong Yu,Ann-Katrin Wolf,Sina Thusek,Ulrich Terpitz,Andreas Beilhack,Sven Krappmann,Axel A Brakhage,Kerstin Voigt,Michael Bromley,Thorsten Heinekamp

doi:10.3390/jof7020136

Abstract

Invasive fungal infections (IFIs) are difficult to diagnose and to treat and, despite several available antifungal drugs, cause high mortality rates. In the past decades, the incidence of IFIs has continuously increased. More recently, SARS-CoV-2-associated lethal IFIs have been reported worldwide in critically ill patients. Combating IFIs requires a more profound understanding of fungal pathogenicity to facilitate the development of novel antifungal strategies. Animal models are indispensable for studying fungal infections and to develop new antifungals. However, using mammalian animal models faces various hurdles including ethical issues and high costs, which makes large-scale infection experiments extremely challenging. To overcome these limitations, we optimized an invertebrate model and introduced a simple calcofluor white (CW) staining protocol to macroscopically and microscopically monitor disease progression in silkworms (Bombyx mori) infected with the human pathogenic filamentous fungi Aspergillus fumigatus and Lichtheimia corymbifera. This advanced silkworm A. fumigatus infection model could validate knockout mutants with either attenuated, strongly attenuated or unchanged virulence. Finally, CW staining allowed us to efficiently visualize antifungal treatment outcomes in infected silkworms. Conclusively, we here present a powerful animal model combined with a straightforward staining protocol to expedite large-scale in vivo research of fungal pathogenicity and to investigate novel antifungal candidates.

Highlights

In the past decades, invasive fungal infections (IFIs) have been continuously rising, among immunocompromised individuals [1,2,3]
The initial silkworm A. fumigatus infection model established by Nakamura et al [21]
We first asked whether it is possible to increase the incubation temperature post infection, which could accelerate the growth of A. fumigatus in vivo and increase virulence to shorten the incubation time

Summary

Introduction

Invasive fungal infections (IFIs) have been continuously rising, among immunocompromised individuals [1,2,3]. Fighting against IFIs requires a deeper and more comprehensive understanding of fungal virulence determinants, which helps to develop novel antifungal strategies. Animal models are still indispensable for studying fungal pathogenicity as well as for the development of new antifungals. The use of mammals, e.g., mice and rats, faces various challenges such as increasing regulatory hurdles, ethical concerns, and high costs that almost preclude large-scale experiments. To overcome these challenges, several invertebrate infection models were proposed as a cost- and time-effective replacement for mammalian hosts with respect to large-scale, preliminary in vivo studies

Objectives

Methods

Results

Conclusion