Virulence Factors Detection in Aspergillus Isolates from Clinical and Environmental Samples

Aspergillus hubkae, a Novel Species Isolated from a Patient with Probable Invasive Pulmonary Aspergillosis

A 50-year-old man, previously diagnosed with pulmonary tuberculosis and lung cavities, presented with symptoms including fever, shortness of breath, and cough. A pulmonary CT scan revealed multiple cavities, consolidation and tree-in-bud in the upper lungs. Further investigation through direct examination of bronchoalveolar lavage fluid showed septate hyphae with dichotomous acute branching. Subsequent isolation and morphological analysis identified the fungus as belonging to Aspergillus section Nigri. The patient was diagnosed with probable invasive pulmonary aspergillosis and successfully treated with a three-month oral voriconazole therapy. Phylogenetic analysis based on partial β-tubulin, calmodulin and RNA polymerase second largest subunit sequences revealed that the isolate represents a putative new species related to Aspergillus brasiliensis, and is named Aspergillus hubkae here. Antifungal susceptibility testing demonstrated that the isolate is resistant to itraconazole but susceptible to voriconazole. This phenotypic and genetic characterization of A. hubkae, along with the associated case report, will serve as a valuable resource for future diagnoses of infections caused by this species. It will also contribute to more precise and effective patient management strategies in similar clinical scenarios.

Prolonged Subculturing of Aspergillus fumigatus on Galleria Extract Agar Results in Altered Virulence and Sensitivity to Antifungal Agents

Aspergillus fumigatus is an environmental saprophyte and opportunistic fungal pathogen of humans. The aim of the work presented here was to examine the effect of serially subculturing A. fumigatus on agar generated from Galleria mellonella larvae in order to characterize the alterations in the phenotypes that might occur. The passaged strains showed alterations in virulence, antifungal susceptibility, and in protein abundances that may indicate adaptation after 25 passages over 231 days on Galleria extract agar. Passaged strains demonstrated reduced virulence in G. mellonella larvae and increased tolerance to hemocyte-mediated killing, hydrogen peroxide, itraconazole, and amphotericin B. A label-free proteomic analysis of control and passaged A. fumigatus strains revealed a total of 3329 proteins, of which 1902 remained following filtration, and 32 proteins were statistically significant as well as differentially abundant. Proteins involved in the response to oxidative stress were altered in abundance in the passaged strain and included (S)-S-oxide reductase (+2.63-fold), developmental regulator FlbA (+2.27-fold), and histone H2A.Z (-1.82-fold). These results indicate that the prolonged subculturing of A. fumigatus on Galleria extract agar results in alterations in the susceptibility to antifungal agents and in the abundance of proteins associated with the oxidative stress response. The phenomenon may be a result of selection for survival in adverse conditions and highlight how A. fumigatus may adapt to tolerate the pulmonary immune response in cases of human infection.

Moonlighting proteins in medically relevant fungi

Moonlighting proteins represent an intriguing area of cell biology, due to their ability to perform two or more unrelated functions in one or many cellular compartments. These proteins have been described in all kingdoms of life and are usually constitutively expressed and conserved proteins with housekeeping functions. Although widely studied in pathogenic bacteria, the information about these proteins in pathogenic fungi is scarce, but there are some reports of their functions in the etiological agents of the main human mycoses, such as Candida spp., Paracoccidioides brasiliensis, Histoplasma capsulatum, Aspergillus fumigatus, Cryptococcus neoformans, and Sporothrix schenckii. In these fungi, most of the described moonlighting proteins are metabolic enzymes, such as enolase and glyceraldehyde-3-phosphate dehydrogenase; chaperones, transcription factors, and redox response proteins, such as peroxiredoxin and catalase, which moonlight at the cell surface and perform virulence-related processes, contributing to immune evasion, adhesions, invasion, and dissemination to host cells and tissues. All moonlighting proteins and their functions described in this review highlight the limited information about this biological aspect in pathogenic fungi, representing this a relevant opportunity area that will contribute to expanding our current knowledge of these organisms' pathogenesis.

Gene Expression Analysis of Non-Clinical Strain of Aspergillus fumigatus (LMB-35Aa): Does Biofilm Affect Virulence?

Aspergillus fumigatus LMB-35Aa, a saprophytic fungus, was used for cellulase production through biofilms cultures. Since biofilms usually favor virulence in clinical strains, the expression of the related genes of the LMB 35-Aa strain was analyzed by qPCR from the biomass of planktonic cultures and biofilms developed on polyester cloth and polystyrene microplates. For this, virulence-related genes reported for the clinical strain Af293 were searched in A. fumigatus LMB 35-Aa genome, and 15 genes were identified including those for the synthesis of cell wall components, hydrophobins, invasins, efflux transporters, mycotoxins and regulators. When compared with planktonic cultures at 37 °C, invasin gene calA was upregulated in both types of biofilm and efflux transporter genes mdr4 and atrF were predominantly upregulated in biofilms on polystyrene, while aspHs and ftmA were upregulated only in biofilms formed on polyester. Regarding the transcription regulators, laeA was downregulated in biofilms, and medA did not show a significant change. The effect of temperature was also evaluated by comparing the biofilms grown on polyester at 37 vs. 28 °C. Non-significant changes at the expression level were found for most genes evaluated, except for atrF, gliZ and medA, which were significantly downregulated at 37 °C. According to these results, virulence appears to depend on the interaction of several factors in addition to biofilms and growth temperature.