Functional characterization of clinical isolates of the opportunistic fungal pathogenAspergillus nidulans

Abstract

<jats:title>Abstract</jats:title><jats:p><jats:italic>Aspergillus nidulans</jats:italic> is an opportunistic fungal pathogen in patients with immunodeficiency and virulence of <jats:italic>A. nidulans</jats:italic> isolates has mainly been studied in the context of the chronic granulomatous disease (CGD), with characterization of clinical isolates obtained from non-CGD patients remaining elusive. This study therefore carried out a detailed biological characterization of two <jats:italic>A. nidulans</jats:italic> clinical isolates (CIs), obtained from a patient with breast carcinoma and pneumonia and from a patient with cystic fibrosis that underwent lung transplantation, and compared them to the reference, non-clinical A4 strain. Both CIs presented increased growth in comparison to the reference strain in the presence of physiologically-relevant carbon sources. Metabolomic analyses showed that the three strains are metabolically very different from each other in these carbon sources. Furthermore, the CIs were highly susceptible to cell wall perturbing agents but not to other physiologically-relevant stresses. Genome analyses identified several frame-shift variants in genes encoding cell wall integrity (CWI) signalling components. Significant differences in CWI signalling were confirmed by western blotting among the three strains. <jats:italic>In vivo</jats:italic> virulence studies using several different models revealed that strain MO80069 had significantly higher virulence in hosts with impaired neutrophil function when compared to the other strains. In summary, this study presents detailed biological characterization of two <jats:italic>A. nidulans sensu stricto</jats:italic> clinical isolates. Just like in <jats:italic>A. fumigatus,</jats:italic> strain heterogeneity exists in <jats:italic>A. nidulans</jats:italic> clinical strains that can define virulence traits. Further studies are required to fully characterize <jats:italic>A. nidulans</jats:italic> strain-specific virulence traits and pathogenicity.</jats:p><jats:sec><jats:title>Importance</jats:title><jats:p>Immunocompromised patients are susceptible to infections with opportunistic filamentous fungi from the genus <jats:italic>Aspergillus.</jats:italic> Although <jats:italic>A. fumigatus</jats:italic> is the main etiological agent of <jats:italic>Aspergillus</jats:italic> spp.-related infections, other species, such as <jats:italic>A. nidulans</jats:italic> are prevalent in a condition-specific manner. <jats:italic>A. nidulans</jats:italic> is a predominant infective agent in patients suffering from chronic granulomatous disease (CGD). <jats:italic>A. nidulans</jats:italic> isolates have mainly been studied in the context of CGD, although infection with <jats:italic>A. nidulans</jats:italic> also occurs in non-CGD patients. This study carried out a detailed biological characterization of two non-CGD <jats:italic>A. nidulans</jats:italic> clinical isolates and compared it to a reference strain. Phenotypic, metabolomic and genomic analyses highlight fundamental differences in carbon source utilization, stress responses and maintenance of cell wall integrity among the strains. One clinical strain had increased virulence in models with impaired neutrophil function. Just as in <jats:italic>A. fumigatus,</jats:italic> strain heterogeneity exists in <jats:italic>A. nidulans</jats:italic> clinical strains that can define virulence traits.</jats:p></jats:sec>

Pathogenic Allodiploid Hybrids of Aspergillus Fungi

“…To gain insights into A. nidulans pathogenicity, we sequenced 9 clinical isolates that were originally identified as A. nidulans from patients with various pulmonary diseases, including 2 isolates from CGD patients. Two of these isolates belong to A. nidulans and have been described in detail elsewhere [27]. However, our phenotypic and genomic analyses showed that 6 of the remaining 7 isolates are not A. nidulans but rather allodiploid hybrids of Aspergillus latus, a species that arose from allodiploid hybridization between Aspergillus spinulosporus and an unknown second parental species closely related to Aspergillus quadrilineatus (both from section Nidulantes).…”

Aspergillus fumigatusand aspergillosis: From basics to clinics

“…nidulans (4.1 × 10 -11 ), which can be used, for instance, to more precisely date the divergence between two strains or the origin of clinical outbreaks. Other sequencing studies have shown that relationships between genome and phenotypic plasticity can be mapped by comparing genomes and phenotypes from different isolates ( Bastos et al. 2020 , Drott et al.…”

An evolutionary genomic approach reveals both conserved and species-specific genetic elements related to human disease in closely relatedAspergillusfungi

“…As more genomes from strains and species in section Fumigati become available, our power to detect quantitative differences will increase, and allow us to more robustly test the conserved pathogenicity model and expand our species-specific pathogenicity model to include "strainspecific" elements. This will be especially important considering the continued and growing appreciation for strain-specific traits and differences in Aspergillus genomes and pathogenicity (Keller 2017;Bastos et al 2020;Dos Santos et al 2020;Steenwyk, Lind, Ries, et al 2020;Kowalski et al 2021). Future studies will also place A. oerlinghausenensis, another species closely related to A. fumigatus (Houbraken et al 2016), within this evolutionary framework of pathogenicity, but due to our previous genome-wide phylogenomic analyses of A. oerlinghausenensis, A. fischeri, and A. fumigatus ), we do not anticipate that inclusion of A. oerlinghausenensis will drastically change our findings.…”