Symbiotic NCR Peptide Fragments Affect the Viability, Morphology and Biofilm Formation of Candida Species.

Bettina Szerencsés,Éva Kondorosi,Hilda Tiricz,Ilona Pfeiffer,János Szolomajer,Ildikó Domonkos,Gabriella Endre,Csaba Vágvölgyi,Gábor K Tóth,Attila Gácser,Dian H O Howan

doi:10.3390/ijms22073666

Abstract

The increasing rate of fungal infections causes global problems not only in human healthcare but agriculture as well. To combat fungal pathogens limited numbers of antifungal agents are available therefore alternative drugs are needed. Antimicrobial peptides are potent candidates because of their broad activity spectrum and their diverse mode of actions. The model legume Medicago truncatula produces >700 nodule specific cysteine-rich (NCR) peptides in symbiosis and many of them have in vitro antimicrobial activities without considerable toxicity on human cells. In this work we demonstrate the anticandidal activity of the NCR335 and NCR169 peptide derivatives against five Candida species by using the micro-dilution method, measuring inhibition of biofilm formation with the XTT (2,3-Bis-(2-Methoxy-4-Nitro-5-Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide) assay, and assessing the morphological change of dimorphic Candida species by microscopy. We show that both the N- and C-terminal regions of NCR335 possess anticandidal activity as well as the C-terminal sequence of NCR169. The active peptides inhibit biofilm formation and the yeast-hypha transformation. Combined treatment of C. auris with peptides and fluconazole revealed synergistic interactions and reduced 2-8-fold the minimal inhibitory concentrations. Our results demonstrate that shortening NCR peptides can even enhance and broaden their anticandidal activity and therapeutic potential.

Highlights

Fungal infections are increasing and represent serious health threat in the increasing population of immunosuppressed patients
We investigated how the most effective peptides act on the biofilm formation and on the yeast to hypha morphological switch of C. albicans and C. tropicalis as hyphal growth represents an important virulence factor in these dimorphic species [16,17]
NCR335 is one of the most cationic nodule specific cysteine-rich (NCR) peptides but it is exceptional due to its 64 amino acid (RLNTTFRPLNFKMLRFWGQNRNIMKHRGQKVHFSLILSDCKTNKDCPKLRRANVRCRKSYCVPI) long sequence compared to the average length of 33 amino acids of NCRs

Summary

Introduction

Fungal infections are increasing and represent serious health threat in the increasing population of immunosuppressed patients. Invasive fungal infections are generally associated with high mortality [1] and the use of effective antifungal drugs is crucial for the outcome of the patient’s disease. The repertoire of antifungal agents is rather limited and for systemic therapy only three classes of drugs are available: polyenes, triazoles and echinocandins. In addition to the limited spectrum of antifungals, to bacterial resistance against the antibiotics, development of drug resistance against these agents has been reported in Candida and Cryptococcus species and in some moulds [2]. There is a great and urgent need for novel types of antifungal agents, and alternative antifungal strategies both in healthcare therapies and in the agriculture [3]

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