Antifungal peptide 2

Background: With the emergence of drug-resistant fungi and the increased population prone to fungal infections, more effective antifungal drugs are needed. Aurein 1.2 is a potent antimicrobial peptide. Here, we designed a novel derivative of Aurein 1.2, called Aurein N3, which is a modified form of Aurein N2 (another Aurein 1.2 derivative), in which Lys 8 residue was replaced with Leu 13, and was also modified by creating two other mutations. Methods: Aurein N3 was designed using several algorithms and docking studies. All peptides were synthesized and some of their bio-activity indices such as antifungal properties on 11 fungi, cytotoxicity, hemolysis, and time of the killing were investigated. Electron microscopy, lived/dead staining, and ergosterol binding assay were performed to study their mechanism of action. Results: In comparison to Aurein 1.2 and N2, the docking studies showed that Aurein N3 has reduced binding energy toward ergosterol. The antifungal assessments showed that both Aurein N2 and N3 had strong activity against many fungi. Aurein N3 had lower cytotoxicity and higher binding capability to ergosterol. The hemolytic activity of Aurein N2 and N3 was less than parental Aurein 1.2. All peptides were able to attack the cell wall/membrane and enter the fungi cells. Conclusion: Here we introduced a novel derivative of Aurein 1.2 which has lower cytotoxicity, higher ergosterol-binding capability, and comparable antifungal activity compared to the original peptides. It can bind to ergosterol and can also attack the cell wall/membrane of fungi, although more studies are required to find its accurate mechanism of action.

In pursuit of ultrashort peptide-based antifungals, a new structural class, His(2-aryl)-Trp-Arg is reported. Structural changes were investigated on His-Trp-Arg scaffold to demonstrate the impact of charge and lipophilic character on the biological activity. The presence and size of the aryl moiety on imidazole of histidine modulated overall amphiphilic character, and biological activity. Peptides exhibited IC50 of 0.37-9.66 μg/mL against C. neoformans. Peptide 14f [His(2-p-(n-butyl)phenyl)-Trp-Arg-OMe] exhibited two-fold potency (IC50 = 0.37 μg/mL, MIC = 0.63 μg/mL) related to amphotericin B, without any cytotoxic effects up to 10 μg/mL. Peptide 14f act by nuclear fragmentation, membranes permeabilization, disruption and pore formations in the microbial cells as determined by the mechanistic studies employing Trp-quenching, CLSM, SEM, and HR-TEM. The amalgamation of short sequence, presence of appropriate aryl group on l-histidine, potent anticryptococcal activity, no cytotoxicity, and detailed mechanistic studies directed to the identification of 14f as a new antifungal structural lead.

Invasive fungal infections have increased over the last decades and the therapeutic choices to treat them are limited. The antifungal agents currently available are useful and have optimal in vitro activity; however, their activity can be lowered due to the development of fungal resistance. The increase in primary or secondary resistance to some antifungal drugs has led to the search of alternatives such as the combination of drugs or the development of new antifungals. In this paper, the activity of the main families of antifungal drugs, polyenes, azoles, echinocandins, 5-fluorocytosine and other new antifungal drugs, are reviewed. The main resistance mechanisms developed by fungi are also described.