How Environmental Fungi Cause a Range of Clinical Outcomes in Susceptible Hosts

• Published in: Journal of molecular biology 2019-07, Vol.431 (16), p.2982-3009
• Main Authors: Denham, Steven T., Wambaugh, Morgan A., Brown, Jessica C.S.
• Format: Article
• Language: English
• Subjects: fungal pathogenesis; Fungi - classification; Fungi - pathogenicity; Host Microbial Interactions; Humans; Immune Evasion; latent disease; Mycoses - immunology; Mycoses - microbiology; Opportunistic Infections - immunology; Opportunistic Infections - microbiology; opportunistic pathogens; systemic disease
• ISSN: 0022-2836; 1089-8638; 1089-8638
• DOI: 10.1016/j.jmb.2019.05.003

Environmental fungi are globally ubiquitous and human exposure is near universal. However, relatively few fungal species are capable of infecting humans, and among fungi, few exposure events lead to severe systemic infections. Systemic infections have mortality rates of up to 90%, cost the US healthcare system $7.2 billion annually, and are typically associated with immunocompromised patients. Despite this reputation, exposure to environmental fungi results in a range of outcomes, from asymptomatic latent infections to severe systemic infection. Here we discuss different exposure outcomes for five major fungal pathogens: Aspergillus, Blastomyces, Coccidioides, Cryptococcus, and Histoplasma species. These fungi include a mold, a budding yeast, and thermal dimorphic fungi. All of these species must adapt to dramatically changing environments over the course of disease. These dynamic environments include the human lung, which is the first exposure site for these organisms. Fungi must defend themselves against host immune cells while germinating and growing, which risks further exposing microbe-associated molecular patterns to the host. We discuss immune evasion strategies during early infection, from disruption of host immune cells to major changes in fungal cell morphology. [Display omitted] •Exposure to environmental fungi is frequent and universal.•Environmental fungi cause a range of outcomes, from asymptomatic infections to severe systemic disease.•Fungi must adapt to different conditions in the environment and the host and the selective pressures conferred by the former facilitate the latter.