Activity and Safety Optimization of Mesoricin: A Dual-Domain Antifungal Peptide from Mesorhizobium sp

Area of Science:

• Microbiology
• Biochemistry
• Drug Discovery

Background:

• Cryptococcus neoformans infections represent a significant global health challenge.
• Antimicrobial peptides (AMPs) are a potential therapeutic class, but challenges like cytotoxicity and efficacy remain.
• Novel AMP scaffolds are needed for effective treatment of invasive fungal infections.

Purpose of the Study:

• To introduce and characterize mesoricin, a novel dual-domain AMP scaffold.
• To optimize mesoricin for enhanced antifungal activity and reduced cytotoxicity.
• To evaluate the efficacy of optimized mesoricin against Cryptococcus and Candida species.

Main Methods:

• In silico identification of mesoricin scaffold from Mesorhizobium sp. using an antifungal activity index (AFI).
• Rational design involving α-helix domain removal and AFI-guided mutations for optimization.
• In vitro assessment of antifungal activity (MIC, sub-MIC effects, biofilm control) and cytotoxicity (IC50) against human cell lines.

Main Results:

• The mesoricin scaffold possesses distinct α-helix and β-sheet domains with different mechanisms of action.
• Rational design yielded an optimized mesoricin variant with significantly reduced hemolytic activity and enhanced antifungal potency.
• Optimized mesoricin demonstrated broad-spectrum activity against Cryptococcus and Candida species (MIC 8-16 μg/mL) with high biosafety (IC50 > 128 μg/mL).
• The variant showed enhanced fungicidal effects at sub-MIC levels and superior biofilm inhibition compared to the prototype.

Conclusions:

• Mesoricin represents a promising novel AMP scaffold for developing therapeutics against Cryptococcus infections.
• Rational design and optimization can significantly improve the therapeutic index of AMPs.
• The optimized mesoricin exhibits potent and safe antifungal properties, warranting further investigation for clinical applications.