Bifunctional Small Molecules Enhance Neutrophil Activities Against Aspergillus fumigatus in vivo and in vitro

Abstract

Aspergillosis is difficult to treat and carries a high mortality rate in immunocompromised patients. Neutrophils play a critical role in control of infection but may be diminished in number and function during immunosuppressive therapies. Here, we measure the effect of three bifunctional small molecules that target Aspergillus fumigatus and prime neutrophils to generate a more effective response against the pathogen. The molecules combine two moieties joined by a chemical linker: a targeting moiety (TM) that binds to the surface of the microbial target, and an effector moiety (EM) that interacts with chemoattractant receptors on human neutrophils. We report that the bifunctional compounds enhance the interactions between primary human neutrophils and A. fumigatus in vitro , using three microfluidic assay platforms. The bifunctional compounds significantly enhance the recruitment of neutrophils, increase hyphae killing by neutrophils in a uniform concentration of drug, and decrease hyphal tip growth velocity in the presence of neutrophils compared to the antifungal targeting moiety alone. We validated that the bifunctional compounds are also effective in vivo , using a zebrafish infection model with neutrophils expressing the appropriate EM receptor. We measured significantly increased phagocytosis of A. fumigatus conidia by neutrophils expressing the EM receptor in the presence of the compounds compared to receptor-negative cells. Finally, we demonstrate that treatment with our lead compound significantly improved the antifungal activity of neutrophils from immunosuppressed patients ex vivo . This type of bifunctional compounds strategy may be utilized to redirect the immune system to destroy fungal, bacterial, and viral pathogens.

Sordarin— An anti‐fungal antibiotic with a unique modus operandi

“…In addition to challenging the cell wall and membrane metabolism, which are unique metabolic fungal elements targeted by numerous antibiotics, there are also several metabolic targets that are considered as promising targets for anti-fungal therapies. They include the glycosylphosphatidylinositol synthesis pathway (Liston et al, 2020) and the application of bifunctional small molecules: the so-called cloud break molecules (Jones et al, 2019). Furthermore, amino acid transporters can be considered as promising targets for anti-fungals, including siderophore iron transporters (McCarthy & Walsh, 2018).…”

Microphysiological Systems for Studying Cellular Crosstalk During the Neutrophil Response to Infection

“…One such study describes bifunctional compounds that bind to both the microbial target ( A. fumigatus ) and the neutrophil chemoattractant receptors. These compounds were able to assist neutrophils in slowing hyphal growth and were also able to enhance phagocytosis of conidia ( 185 ).…”

Human Neutrophils Respond to Complement Activation and Inhibition in Microfluidic Devices

“…Examples of studies enabled by the new tools include the probing of neutrophil chemotaxis signatures in response to various chemoattractants ( 25 – 27 ), neutrophil neutralization of various pathogens ( 28 ), and the cooperation between neutrophils during swarming against clusters of microbes ( 29 , 30 ). The benefits of microfluidic tools for probing the activity of neutrophils from patients have been demonstrated in sepsis ( 31 , 32 ), diabetes ( 33 ), trauma and burn injuries ( 34 , 35 ), chronic granulomatous disease ( 29 ), organ transplant ( 27 , 36 ) and Alzheimer’s disease ( 37 ). Bridging the clinical and basic research spaces, microfluidic assays for quantifying neutrophil activities represent attractive diagnostic, monitoring, and drug screening tools.…”