Identification of App1 as a regulator of phagocytosis and virulence of Cryptococcus neoformans
Chiara Luberto, … , Edward Balish, Maurizio Del Poeta
Chiara Luberto, … , Edward Balish, Maurizio Del Poeta
Published October 1, 2003
Citation Information: J Clin Invest. 2003;112(7):1080-1094. https://doi.org/10.1172/JCI18309.
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Article Infectious disease

Identification of App1 as a regulator of phagocytosis and virulence of Cryptococcus neoformans

Abstract

Cryptococcus neoformans is a fungal pathogen that, after inhalation, can disseminate to the brain. Host alveolar macrophages (AMs) represent the first defense against the fungus. Once phagocytosed by AMs, fungal cells are killed by a concerted mechanism, involving the host-cellular response. If the cellular response is impaired, phagocytosis of the fungus may be detrimental for the host, since C. neoformans can grow within macrophages. Here, we identified a novel cryptococcal gene encoding antiphagocytic protein 1 (App1). App1 is a cryptococcal cytoplasmic protein that is secreted extracellularly and found in the serum of infected patients. App1 does not affect melanin production, capsule formation, or growth of C. neoformans. Treatment with recombinant App1 inhibited phagocytosis of fungal cells through a complement-mediated mechanism, and Δapp1 mutant is readily phagocytosed by AMs. Interestingly, the Δapp1 mutant strain showed a decreased virulence in mice deficient for complement C5 (A/Jcr), but it was hypervirulent in mice deficient for T and NK cells (Tgε26). This study identifies App1 as a novel regulator of virulence for C. neoformans, and it highlights that internalization of fungal cells by AMs increases the dissemination of C. neoformans when the host cellular response is impaired.

Authors

Chiara Luberto, Beatriz Martinez-Mariño, Daniel Taraskiewicz, Benjamin Bolaños, Pasquale Chitano, Dena L. Toffaletti, Gary M. Cox, John R. Perfect, Yusuf A. Hannun, Edward Balish, Maurizio Del Poeta

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Figure 3

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Disruption of APP1 gene. (a) Schematic representation for disruption and...
Disruption of APP1 gene. (a) Schematic representation for disruption and reconstitution of APP1 gene. (b) Southern analysis. Genomic DNA from C. neoformans WT H99, Δapp1, and Δapp1Rec strains were extracted, digested with PstI, electrophoresed in a 0.7% agarose gel, transferred to a Nytran membrane, and blotted against 5′-UTR and ADE2 probes. The Δapp1 strain showed a deletion of the APP1 gene with insertion of the ADE2 gene. Reintroduction of the APP1 gene in the APP1 locus is shown in the Δapp1Rec strain. (c) Western analysis of cell lysate from WT, Δapp1, and Δapp1Rec cell cultures using rabbit anti-App1 polyclonal antibodies. App1 protein is absent in the Δapp1 mutant and reconstituted in the Δapp1Rec strain. (d) Western analysis of crude cytoplasmic extract, serum of two AIDSpatients, serum from two normal subjects, and growth culture medium. App1 is secreted extracellularly in vitro and during cryptococcal meningoencephalitis. HYG, hygromycin B gene.