Bridging the Gap to Non-toxic Fungal Control: Lupinus-Derived Blad-Containing Oligomer as a Novel Candidate to Combat Human Pathogenic Fungi

Abstract

The lack of antifungal drugs with novel modes of action reaching the clinic is a serious concern. Recently a novel antifungal protein referred to as Blad-containing oligomer (BCO) has received regulatory approval as an agricultural antifungal agent. Interestingly its spectrum of antifungal activity includes human pathogens such as Candida albicans, however, its mode of action has yet to be elucidated. Here we demonstrate that BCO exerts its antifungal activity through inhibition of metal ion homeostasis which results in apoptotic cell death in C. albicans. HIP HOP profiling in Saccharomyces cerevisiae using a panel of signature strains that are characteristic for common modes of action identified hypersensitivity in yeast lacking the iron-dependent transcription factor Aft1 suggesting restricted iron uptake as a mode of action. Furthermore, global transcriptome profiling in C. albicans also identified disruption of metal ion homeostasis as a potential mode of action. Experiments were carried out to assess the effect of divalent metal ions on the antifungal activity of BCO revealing that BCO activity is antagonized by metal ions such as Mn2+, Zn2+, and Fe2+. The transcriptome profile also implicated sterol synthesis as a possible secondary mode of action which was subsequently confirmed in sterol synthesis assays in C. albicans. Animal models for toxicity showed that BCO is generally well tolerated and presents a promising safety profile as a topical applied agent. Given its potent broad spectrum antifungal activity and novel multitarget mode of action, we propose BCO as a promising new antifungal agent for the topical treatment of fungal infections.

Maximizing Blad-containing oligomer fungicidal activity in sweet cultivars of Lupinus albus seeds

“…BCO finds application under real, open air agriculture, withstanding the effect of UV sunlight and producing results which equal or exceed those of the commercially available chemical pesticides. Its mechanism of action is multitarget (Pinheiro et al, 2017) PCT/IB2006/052403, PCT/EP2011/067824, PCT/EP2011/067821 and PCT/EP2011/067828 (Ferreira et al, 2006;Carreira et al, 2011aCarreira et al, , 2011bCarreira et al, , 2011c.…”

Fusion proteins towards fungi and bacteria in plant protection

“…In the study recently published by Pinheiro et al . [ 15 ], BCO showed no evidence of topical toxicity, genotoxicity and carcinogenicity towards mammalian cells after acute or short-term exposure. In addition, BCO safety as a plant protection product has been corroborated by the national regulatory entities of all countries where the product has already been approved.…”

“…Lupinus albus L. seeds were purchased from Inveja SAS (France) and were germinated as described by Pinheiro and colleagues [ 15 ].…”

“…The characteristics that makes the BCO a unique, versatile and multi-functional protein [ 13 ], as well as its powerful and broad-spectrum antifungal activity towards both plant and human pathogens, have been fully discussed [ 13, 14 ]. Its mode of action was also recently described as a multi-site fungicide that disturbs microbial cell homeostasis leading, ultimately, to cell death [ 15 ].…”