AUTHOR=Escobar Natalia , Ordonez Soledad R. , Wösten Han A. B. , Haas Pieter-Jan A. , de Cock Hans , Haagsman Henk P. 

TITLE=Hide, Keep Quiet, and Keep Low: Properties That Make Aspergillus fumigatus a Successful Lung Pathogen

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00438

DOI=10.3389/fmicb.2016.00438

ISSN=1664-302X

ABSTRACT=<p>Representatives of the genus <italic>Aspergillus</italic> are opportunistic fungal pathogens. Their conidia can reach the alveoli by inhalation and can give rise to infections in immunocompromised individuals. <italic>Aspergillus fumigatus</italic> is the causal agent of invasive aspergillosis in nearly 90% of the cases. It is not yet well-established what makes this fungus more pathogenic than other aspergilli such as <italic>A. niger</italic>. Here, we show that <italic>A. fumigatus</italic> and <italic>A. niger</italic> conidia adhere with similar efficiency to lung epithelial A549 cells but <italic>A. fumigatus</italic> conidia internalized 17% more efficiently. Conidia of both aspergilli were taken up in phagolysosomes 8 h after the challenge. These organelles only acidified in the case of <italic>A. niger</italic>, which is probably due to the type of melanin coating of the conidia. Viability of both types of conidia was not affected after uptake in the phagolysosomes. Germination of <italic>A. fumigatus</italic> and <italic>A. niger</italic> conidia in the presence of epithelial cells was delayed when compared to conidia in the medium. However, germination of <italic>A. niger</italic> conidia was still higher than that of <italic>A. fumigatus</italic> 10 h after exposure to A549 cells. Remarkably, <italic>A. fumigatus</italic> hyphae grew mainly parallel to the epithelium, while growth direction of <italic>A. niger</italic> hyphae was predominantly perpendicular to the plane of the cells. Neutrophils reduced germination and hyphal growth of <italic>A. niger</italic>, but not of <italic>A fumigatus</italic>, in presence of epithelial cells. Taken together, efficient internalization, delayed germination, and hyphal growth parallel to the epithelium gives a new insight into what could be the causes for the success of <italic>A. fumigatus</italic> compared to <italic>A. niger</italic> as an opportunistic pathogen in the lung.</p>