Mycovirus infection disrupts Aspergillus fumigatus iron acquisition through down regulation of HapX

Author:

Amer Ali Abd El-Hafeez1, Gabriele Sass2, David A. Stevens2,3, Vladimír Havlíček4,5, Ioly Kotta-Loizou6,7, Joe Hsu1

Author address:

1. Division of Pulmonary, Allergy, and Critical Care Medicine, Stanford University, Stanford, CA 94305, USA
2. California Institute for Medical Research, San Jose, CA 95128, USA
3. Division of Infectious Diseases & Geographic Medicine, Stanford University, Stanford, CA 94305, USA
4. Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
5. Palacký University, Olomouc, Czech Republic
6. Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
7. Department of Clinical, Pharmaceutical and Biological Science, School of Life and Medical Sciences, University of Hertfordshire, College Lane Campus, Hatfield AL10 9AB, UK

Abstract:

Background:
Aspergillus fumigatus (Af) infections have a significant impact on global health. Despite potent antifungal drugs, mortality rates remain high, and the emergence of multidrug-resistant strains underscores the need for novel treatment strategies. Fungi are susceptible to infections by viruses known as mycoviruses. Our knowledge of the mechanisms behind their influence on fungal metabolism and virulence is incomplete. It has been shown that mycoviral infection impairs the ability of Af to compete with Pseudomonas aeruginosa (PA) through a decreased capacity to acquire iron. The current study seeks to better understand the mechanisms underlying the role of Aspergillus fumigatus polymycovirus-1 (AfuPmV-1) infection on fungal iron acquisition and the association between mycoviral infection and Af virulence.
Methods:
Three Af strains were used: (i) Af293, naturally infected with AfuPmV-1 (wild-type (WT)); (ii) Af293 treated with cycloheximide to eliminate AfuPmV-1 (mycovirus-free); and (iii) Af293 reinfected with AfuPmV-1 following cycloheximide treatment (mycovirus-reinfected). The mycovirus-reinfected strain was used to control for any impact cycloheximide treatment might have on fungal phenotype. These Af strains were cultured under three conditions: low iron (RPMI alone), high iron (RPMI supplemented with iron sulfate (0.65 mM)), and a further iron-depleted medium (RPMI and PA culture filtrate (PA-CF)). PA-CF contains bacterial siderophores that further reduce the iron content of the media. Fungal mycelia were collected at 0, 3, 12, and 36 hours post-inoculation (hpi) and total RNA was extracted using the RNeasy mini kit (Qiagen, CA, USA). Expression of fungal iron metabolism genes were studied using real-time PCR (RT-PCR) comparing the three Af strains over time. Radial growth was assessed in both iron replete (Aspergillus minimal medium + iron sulfate (3 mM)) and iron depleted growth conditions (Aspergillus minimal medium). To investigate the impact of mycovirus infection in vivo, we compared the survival of mice infected with either mycovirus-reinfected or mycovirus-free Af in a model of corticosteroid-induced invasive pulmonary aspergillosis.
Results:
The expression of hapX, a gene that encodes a fungal transcription factor related to the regulation of iron homeostasis, was significantly upregulated in mycovirus-free Af compared to both WT and mycovirus-reinfected Af strains in low iron (6.6-fold and 8.23-fold, respectively) and in iron-depleted conditions (2.85-fold and 3.28-fold, respectively) from 12 hpi onwards (P<0.0001). In low iron and iron-depleted media, AfuPmV-1 infection was associated with a marked decrease in the expression of genes related to iron acquisition, including those responsible for siderophore production (sidA, sidI, sidH, and sidG) and siderophore transport (mirB). The mycovirus-free Af strain exhibited significantly increased radial growth as compared to the WT and mycovirus-reinfected Af strains in both iron depleted and replete conditions. In corticosteroid treated mice, animals infected with mycovirus-reinfected Af had significantly higher survival compared to those infected with mycovirus-free Af (P=0.01). Conclusion: Taken together these results suggest that AfuPmV-1 induced alterations in fungal iron acquisition, mediated through dysregulation of hapX expression, which contributed to reduced fungal growth and virulence. Further studies on the relationship between mycovirus infection and hapX expression could hold promise for the development of novel therapeutic strategies against Aspergillus infections.

Abstract Number: 73

Conference Year: 2024

Conference abstracts, posters & presentations

Showing 10 posts of 17325 posts found.

  • Title

    Author

    Year

    Number

    Poster