Modulation of the immune response by Fonsecaea pedrosoi morphotypes in the course of experimental chromoblastomycosis and their role on inflammatory response chronicity

PLoS Negl Trop Dis. 2017 Mar 29;11(3):e0005461. doi: 10.1371/journal.pntd.0005461. eCollection 2017 Mar.

Abstract

A common theme across multiple fungal pathogens is their ability to impair the establishment of a protective immune response. Although early inflammation is beneficial in containing the infection, an uncontrolled inflammatory response is detrimental and may eventually oppose disease eradication. Chromoblastomycosis (CBM), a cutaneous and subcutaneous mycosis, caused by dematiaceous fungi, is capable of inducing a chronic inflammatory response. Muriform cells, the parasitic form of Fonsecaea pedrosoi, are highly prevalent in infected tissues, especially in long-standing lesions. In this study we show that hyphae and muriform cells are able to establish a murine CBM with skin lesions and histopathological aspects similar to that found in humans, with muriform cells being the most persistent fungal form, whereas mice infected with conidia do not reach the chronic phase of the disease. Moreover, in injured tissue the presence of hyphae and especially muriform cells, but not conidia, is correlated with intense production of pro-inflammatory cytokines in vivo. High-throughput RNA sequencing analysis (RNA-Seq) performed at early time points showed a strong up-regulation of genes related to fungal recognition, cell migration, inflammation, apoptosis and phagocytosis in macrophages exposed in vitro to muriform cells, but not conidia. We also demonstrate that only muriform cells required FcγR and Dectin-1 recognition to be internalized in vitro, and this is the main fungal form responsible for the intense inflammatory pattern observed in CBM, clarifying the chronic inflammatory reaction observed in most patients. Furthermore, our findings reveal two different fungal-host interaction strategies according to fungal morphotype, highlighting fungal dimorphism as an important key in understanding the bipolar nature of inflammatory response in fungal infections.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Ascomycota / physiology*
  • Chromoblastomycosis / immunology*
  • Chromoblastomycosis / microbiology
  • Chromoblastomycosis / pathology
  • Cytokines / immunology
  • Disease Models, Animal
  • High-Throughput Nucleotide Sequencing
  • Host-Pathogen Interactions*
  • Humans
  • Hyphae / physiology
  • Lectins, C-Type / metabolism*
  • Macrophages / immunology
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Phagocytosis / immunology
  • Sequence Analysis, RNA
  • Spores, Fungal / physiology
  • Up-Regulation

Substances

  • CLEC7A protein, human
  • Cytokines
  • Lectins, C-Type

Grants and funding

Funding for these studies was provided by Fundação de Apoio à Pesquisa do Distrito Federal (FAPDF), Conselho Nacional de Pesquisa (CNPq) for financial support and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) CAPES for graduate students grants. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.