HXP124, a Plant Defensin, Represents a Novel Antifungal Therapeutic

N. L. van der Weerden1, B. Hayes2, M. Baker1, K. Harris2, M. Bleackley2, M. Anderson2

Author address: 

1Hexima Limited, Melbourne, Australia, 2La Trobe Univ., Melbourne, Australia

Abstract: 

Background: Plant defensins with potent antifungal activity have the potential to be developed as effective and robust treatments for fungal infections in humans. The cysteine-stabilised structure of plant defensin’s makes them extremely stable and able to withstand extremes of pH and temperature. Here we investigate the antifungal properties of a novel plant defensin, HXP124, against a range of clinically important fungal pathogens.Methods: HXP124 was recombinantly expressed using the Pichia pastoris yeast expression system and purified using a scalable two-step purification method. The activity of HXP124 against a range of fungal and bacterial pathogens was tested using the microbroth dilution method and the ability of HXP124 to kill human U937 cells was examined by monitoring the uptake of propidium iodide using FACS.Results: HXP124 has potent antifungal activity against a range of human fungal pathogens including Candida spp, Cryptococcus spp, dermatophytes and non-dermatophytic moulds. HXP124 is highly selective for fungal cells having no effect on mammalian cells, including red blood cells, at concentrations more than 50 times the MIC for fungus. HXP124 is also fungicidal, killing fungal cells within 1 h of exposure after the induction of reactive oxygen species and disruption of fungal membranes. Plant defensins contain four disulphide bonds which stabilise the three-dimensional structure. As such, they are stable at extremes of pH (95°C). HXP124 can be produced recombinantly in yeast with very high yields. Its small size and positive charge makes it easy to purify and highly pure protein can be achieved with a simple two-step purification process.Conclusions: HXP124 is a potent antifungal molecule and an excellent candidate for the development of a novel antifungal therapeutic useful in a number of clinical settings.
2016

abstract No: 

SUNDAY-391

Full conference title: 

ASM Microbe 2016
    • ASM microbe 1st (2016)