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Updated: Mar 10, 2026
Macrophage Cholesterol Depletion and Its Effect on the Phagocytosis of Cryptococcus neoformans
Published on: December 19, 2014
MHC-I Upregulation and Increased Glucose Dependence Define Innate Antifungal Immune Responses to Cryptococcus
Ayesha S Nair1, Karen L Wozniak1
1Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma.
Background:
Cryptococcus neoformans, the etiologic agent of cryptococcosis, can survive and replicate within host immune cells, contributing to development of cryptococcal meningitis. Within the lung, C neoformans interacts with innate immune subsets, including macrophages and dendritic cells (DCs). Our previous work demonstrated that Ly6c- monocyte-like macrophages restrict fungal proliferation, whereas CD11b+ DCs promote fungal growth. Transcriptomic profiling revealed differential expression of MHC-I gene H2-K1, calreticulin, and metabolic genes. Therefore, we hypothesized that H2-K1 and metabolic pathways modulate intracellular fungal fate within pulmonary macrophages and DCs.
Methods:
H2-K1 expression was knocked down by siRNA in J774 macrophages and bone marrow-derived DCs induced by granulocyte-macrophage colony-stimulating factor. Antifungal activity was determined by colony-forming unit enumeration. Phagocytic uptake, cathepsin B activity, Nos2 expression, and reactive oxygen species production were quantified by flow cytometry. Metabolic dependencies were evaluated through SCENITH assay (single-cell energetic metabolism by profiling translational inhibition).
Results:
H2-K1 knockdown in J774 cells significantly reduced antifungal activity as compared with controls. H2-K1 knockdown also decreased calreticulin gene expression, suggesting that H2-k1 has downstream effects in the pathway. H2-K1 silencing did not significantly alter phagocytic uptake, cathepsin B activity, or Nos2 expression. However, reactive oxygen species production was significantly reduced in H2-K1 knockdown J774 cells, indicating impaired responses. SCENITH analysis revealed that antifungal macrophages shift their metabolism toward glucose oxidation for ATP generation, which is important for antifungal activity.
Conclusions:
These findings indicate that metabolic reprogramming is critical for effective antifungal responses. Our data provide a foundation for future studies aimed at targeting host immune and metabolic pathways to enhance antifungal immunity.
Insights
Host immune cells like macrophages and dendritic cells play a role in fighting Cryptococcus neoformans. Targeting metabolic pathways and H2-K1 expression can enhance antifungal immunity.
Area of Science:
- Immunology
- Cell Biology
- Infectious Disease
Background:
- Cryptococcus neoformans causes cryptococcosis, including meningitis, by surviving within host immune cells.
- Pulmonary macrophages and dendritic cells (DCs) interact with C. neoformans, with differing effects on fungal growth.
- Differential gene expression, including H2-K1, Calreticulin (Calr), and metabolic genes, was observed between these immune subsets.
Purpose of the Study:
- To investigate the role of H2-K1 and metabolic pathways in modulating the intracellular fate of C. neoformans within pulmonary macrophages and DCs.
- To understand how H2-K1 expression influences the antifungal activity of macrophages.
Main Methods:
- H2-K1 expression was reduced using siRNA in J774 macrophages and bone marrow-derived DCs (BMDCs).
- Antifungal activity was assessed via colony-forming unit (CFU) enumeration.
- Phagocytosis, cathepsin B activity, Nos2 expression, reactive oxygen species (ROS) production, and metabolic profiles (SCENITH assay) were quantified.
Main Results:
- H2-K1 knockdown in J774 cells significantly impaired antifungal activity and reduced ROS production.
- H2-K1 silencing decreased Calr gene expression, suggesting downstream effects.
- Metabolic analysis revealed that antifungal macrophages utilize glucose oxidation for ATP generation, crucial for their function.
Conclusions:
- Metabolic reprogramming is essential for effective host defense against fungal infections.
- Targeting host immune and metabolic pathways holds potential for enhancing antifungal immunity.
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