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Can BioSAXS detect ultrastructural changes of antifungal compounds in Candida albicans?-an exploratory study
Kai Hilpert1, Christoph Rumancev2, Jurnorain Gani1
1Institute of Infection and Immunology, St. George's, University of London (SGUL), London, United Kingdom.
Abstract:
The opportunistic yeast Candida albicans is the most common cause of candidiasis. With only four classes of antifungal drugs on the market, resistance is becoming a problem in the treatment of fungal infections, especially in immunocompromised patients. The development of novel antifungal drugs with different modes of action is urgent. In 2016, we developed a groundbreaking new medium-throughput method to distinguish the effects of antibacterial agents. Using small-angle X-ray scattering for biological samples (BioSAXS), it is now possible to screen hundreds of new antibacterial compounds and select those with the highest probability for a novel mode of action. However, yeast (eukaryotic) cells are highly structured compared to bacteria. The fundamental question to answer was if the ultrastructural changes induced by the action of an antifungal drug can be detected even when most structures in the cell stay unchanged. In this exploratory work, BioSAXS was used to measure the ultrastructural changes of C. albicans that were directly or indirectly induced by antifungal compounds. For this, the well-characterized antifungal drug Flucytosine was used. BioSAXS measurements were performed on the synchrotron P12 BioSAXS beamline, EMBL (DESY, Hamburg) on treated and untreated yeast C. albicans. BioSAXS curves were analysed using principal component analysis (PCA). The PCA showed that Flucytosine-treated and untreated yeast were separated. Based on that success further measurements were performed on five antifungal peptides {1. Cecropin A-melittin hybrid [CA (1-7) M (2-9)], KWKLFKKIGAVLKVL; 2. Lasioglossin LL-III, VNWKKILGKIIKVVK; 3. Mastoparan M, INLKAIAALAKKLL; 4. Bmkn2, FIGAIARLLSKIFGKR; and 5. optP7, KRRVRWIIW}. The ultrastructural changes of C. albicans indicate that the peptides may have different modes of action compared to Flucytosine as well as to each other, except for the Cecropin A-melittin hybrid [CA (1-7) M (2-9)] and optP7, showing very similar effects on C. albicans. This very first study demonstrates that BioSAXS shows promise to be used for antifungal drug development. However, this first study has limitations and further experiments are necessary to establish this application.
Insights
Small-angle X-ray scattering for biological samples (BioSAXS) can detect antifungal drug effects on Candida albicans ultrastructure. This method shows promise for developing new antifungal drugs to combat rising resistance.
Area of Science:
- Biophysics
- Microbiology
- Drug Discovery
Background:
- Antifungal drug resistance in *Candida albicans* is a growing concern, necessitating novel treatments.
- Existing antifungal drug classes are limited, and new modes of action are urgently required, especially for immunocompromised patients.
- Small-angle X-ray scattering for biological samples (BioSAXS) was previously established for antibacterial screening.
Purpose of the Study:
- To explore the utility of BioSAXS for detecting ultrastructural changes in *Candida albicans* induced by antifungal compounds.
- To assess if BioSAXS can identify distinct modes of action for different antifungal agents.
- To evaluate the potential of BioSAXS as a tool for antifungal drug development.
Main Methods:
- BioSAXS measurements were performed on *Candida albicans* yeast cells treated with the antifungal drug Flucytosine and five antifungal peptides.
- Synchrotron radiation at the P12 BioSAXS beamline was utilized for high-resolution data acquisition.
- Principal Component Analysis (PCA) was employed to analyze the BioSAXS data and differentiate between treated and untreated yeast samples.
Main Results:
- PCA successfully distinguished between Flucytosine-treated and untreated *Candida albicans* cells, demonstrating BioSAXS's sensitivity to drug-induced changes.
- Analysis of five antifungal peptides revealed distinct ultrastructural alterations in *C. albicans*, suggesting varied modes of action.
- The Cecropin A-melittin hybrid and optP7 peptides exhibited similar effects on *C. albicans*, differentiating them from other tested peptides and Flucytosine.
Conclusions:
- This study demonstrates the potential of BioSAXS as a valuable tool for antifungal drug discovery and development.
- BioSAXS can detect subtle ultrastructural changes in yeast cells, aiding in the identification of novel antifungal compounds and their mechanisms of action.
- Further research is warranted to fully establish BioSAXS for routine antifungal drug screening and characterization.
