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Published on: December 10, 2013
Dual-transcriptome analyses of high- and low-virulence strains of Cryptococcus gattii cocultured with RAW264.7
Chen Yang1,2, Yangyu Zhou3, Yu Zhong4
1National Engineering Research Center of Immunological Products, Department of Microbiology and Biochemical Pharmacy, College of Pharmacy, Army Medical University, Chongqing, China.
Abstract:
Cryptococcus gattii (C. gattii) is an aggressive fungus that can infect both immunocompetent and immunosuppressed hosts. As a first line of immunity in humans, macrophages can phagocytose and kill C. gattii; yet macrophages can also provide a favorable ecological niche for its proliferation and immune escape. Using dual-transcriptome analysis, which allows for the exploration of transcriptional expression levels in pathogen-host interactions, we aimed to quantitatively measure host (RAW264.7 macrophage) immune responses to strains of C. gattii with different virulence, including transcriptional changes in both host and fungus. We evaluated 31 strains of C. gattii and divided them into high virulence (HV) and low virulence (LV) based on phenotype. Compared to the LV strains, the HV strains inhibited development of M1 macrophages, killing of the HV strains by macrophages was weaker, and transcription levels of virulence and growth genes were increased. We also found that macrophages after contact with HV C. gattii strains had high expression of genes related to cell adhesion but lower expression of those related to antigen presentation, immune response, and oxidative stress. Inhibition of macrophage immune response to HV C. gattii was confirmed in vitro and in vivo. Our data add to what is known about the mechanisms of immune escape by C. gattii.
Insights
Highly virulent Cryptococcus gattii (C. gattii) strains evade macrophage immune responses by inhibiting M1 macrophage development and downregulating key immune genes. This fungal immune evasion enhances C. gattii virulence and proliferation.
Area of Science:
- Mycology
- Immunology
- Pathogen-Host Interactions
Background:
- Cryptococcus gattii (C. gattii) is an opportunistic fungal pathogen.
- Macrophages are crucial for innate immunity against C. gattii but can also support fungal growth.
- Understanding host-pathogen transcriptional dynamics is key to C. gattii immune escape mechanisms.
Purpose of the Study:
- To quantitatively assess host (RAW264.7 macrophage) immune responses to C. gattii strains of varying virulence.
- To explore transcriptional changes in both host and fungus during infection.
- To elucidate mechanisms of C. gattii immune evasion.
Main Methods:
- Dual-transcriptome analysis of RAW264.7 macrophages infected with 31 C. gattii strains.
- Phenotypic classification of C. gattii strains into high virulence (HV) and low virulence (LV) groups.
- In vitro and in vivo confirmation of macrophage immune response inhibition.
Main Results:
- HV C. gattii strains inhibited M1 macrophage differentiation and were killed less effectively by macrophages compared to LV strains.
- HV C. gattii strains exhibited increased transcription of virulence and growth genes.
- Macrophages interacting with HV C. gattii showed upregulated cell adhesion genes but downregulated antigen presentation, immune response, and oxidative stress genes.
Conclusions:
- High virulence C. gattii strains actively suppress macrophage immune functions, including M1 polarization and effector responses.
- Upregulation of virulence genes and modulation of host gene expression contribute to C. gattii immune escape.
- These findings provide insights into the molecular mechanisms underlying C. gattii pathogenesis and host immune evasion.
