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Updated: Jun 9, 2026
Visualizing Non-lytic Exocytosis of Cryptococcus neoformans from Macrophages Using Digital Light Microscopy
Published on: October 21, 2014
An integrative ultrastructural and transcriptomic analysis of host-pathogen interactions with human brain
Priya Krishnan1, Gautham Arunachal Udupi2, Rashmi Santhoshkumar3
1Dept of Neuromicrobiology, National Institute of Mental Health and Neuro Sciences, Institute of National Importance, Bengaluru, India.
Background:
In humans, Cryptococcus neoformans and Cryptococcus gattii species complexes are the leading cause of fungal meningitis globally. To establish CNS infection, Cryptococcus must breach the BBB, primarily comprised of specialized brain microvascular endothelial cells (BMECs), which is the prerequisite for cryptococci to invade the brain. Despite its clinical impact, the mechanisms underlying host-pathogen interaction at the BBB particularly involving environmental isolates remain under-characterized.
Objective:
This study aimed to investigate the cyto-morphological and transcriptomic responses of HBMECs to infection by clinical and environmental Cryptococcus isolates using a dual approach-ultrastructural electron microscopy and high-throughput dual RNA-Seq.
Methods:
HBMECs were infected in vitro with molecularly typed clinical and environmental isolates of C. neoformans and C. gattii at two infection time points (4 hpi and 18 hpi). Transmission electron microscopy was used to visualize host cell ultrastructural alterations, while dual RNA-Seq was performed to assess differential gene expression in both host and pathogen.
Results:
TEM revealed extensive ultrastructural changes in infected HBMECs, including membrane ruffling, increased microvilli, mitochondrial alterations, ER dilation, Golgi fragmentation, nuclear deformation, and autophagosome formation. Transcriptomic profiling demonstrated functional enrichment of several critical cryptococcal virulence-associated genes linked to immune evasion and stress adaptation including various immune signaling pathways elicited by the HBMECs as a counter measure to the cryptococcal invasion.
Conclusion:
Clinical and environmental Cryptococcus isolates exhibit comparable invasive potential and elicit similar host endothelial responses with consistent effects observed across all isolates and time points. This integrative study combining ultrastructural and transcriptomic analyses highlights conserved host-pathogen interactions at the BBB, identifies potential molecular targets for antifungal therapy and underscores the pathogenic relevance of environmental reservoirs in cryptococcal meningitis. cryptococcal meningitis, blood-brain barrier, invasion, transmission electron microscopy, Dual RNASeq, differential gene expression, host-pathogen interaction, HBMECs, ultrastructural alterations.
Insights
Cryptococcus causes fungal meningitis by breaching the blood-brain barrier (BBB). This study reveals similar invasion mechanisms and host responses for both clinical and environmental isolates, aiding in developing new antifungal therapies.
Area of Science:
- Neuroscience
- Infectious Diseases
- Microbiology
Background:
- Cryptococcus neoformans and Cryptococcus gattii are leading causes of fungal meningitis globally.
- Cryptococcus invasion of the central nervous system (CNS) requires breaching the blood-brain barrier (BBB), primarily composed of brain microvascular endothelial cells (BMECs).
- Mechanisms of host-pathogen interaction at the BBB, especially with environmental isolates, are not well understood.
Purpose of the Study:
- To investigate the cyto-morphological and transcriptomic responses of human brain microvascular endothelial cells (HBMECs) to infection by clinical and environmental Cryptococcus isolates.
- To utilize a dual approach combining ultrastructural electron microscopy and high-throughput dual RNA-Seq for comprehensive analysis.
Main Methods:
- Human brain microvascular endothelial cells (HBMECs) were infected in vitro with molecularly typed clinical and environmental isolates of C. neoformans and C. gattii at 4 and 18 hours post-infection (hpi).
- Transmission electron microscopy (TEM) was employed to visualize ultrastructural alterations in HBMECs.
- Dual RNA-Seq was performed to analyze differential gene expression in both host cells and the pathogen.
Main Results:
- TEM revealed significant ultrastructural changes in infected HBMECs, including membrane ruffling, increased microvilli, mitochondrial damage, ER dilation, Golgi fragmentation, nuclear deformation, and autophagosome formation.
- Transcriptomic profiling identified enrichment of cryptococcal virulence genes related to immune evasion and stress adaptation.
- HBMECs exhibited immune signaling pathways as a defense mechanism against Cryptococcus invasion.
Conclusions:
- Clinical and environmental Cryptococcus isolates demonstrate comparable invasive potential and elicit similar host endothelial responses.
- This integrated study highlights conserved host-pathogen interactions at the BBB.
- Findings identify potential molecular targets for antifungal therapy and emphasize the role of environmental reservoirs in cryptococcal meningitis pathogenesis.
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