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Differential stimulation of microglial pro-inflammatory cytokines by Acanthamoeba culbertsoni versus Acanthamoeba
Francine Marciano-Cabral1, Christina Ludwick, Robyn A Puffenbarger
1Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, VA 23298-0678, USA. fmcabral@hsc.vcu.edu
Abstract:
Acanthamoeba spp. are opportunistic pathogens that cause granulomatous amebic encephalitis. We compared the highly pathogenic species A. culbertsoni to the relatively less pathogenic species A. castellanii for its capacity to elicit from neonatal rat microglia the gene expression of pro-inflammatory cytokines. Acanthamoeba culbertsoni elicited a robust cytokine gene response by neonatal rat microglia in vitro as compared to A. castellanii. The preponderant cytokine elicited at the mRNA and protein levels was interleukin-1beta. In addition, transmission electron microscopy revealed that microglial cells were capable of phagocytozing A. castellanii. In contrast, A. culbertsoni destroyed microglia. Collectively, these results suggest that a combined action of pro-inflammatory cytokines and destruction of host cells by amebae contribute to the pathology caused by the more pathogenic species.
Insights
Acanthamoeba culbertsoni causes more severe inflammation and microglia destruction than Acanthamoeba castellanii, contributing to granulomatous amebic encephalitis. Interleukin-1beta is a key pro-inflammatory cytokine.
Area of Science:
- Immunology
- Microbiology
- Neuroscience
Background:
- Acanthamoeba spp. are opportunistic pathogens.
- Granulomatous amebic encephalitis is a severe infection caused by Acanthamoeba.
- Understanding the pathogenic mechanisms is crucial for treatment.
Purpose of the Study:
- To compare the pro-inflammatory cytokine gene expression elicited by Acanthamoeba culbertsoni and Acanthamoeba castellanii in neonatal rat microglia.
- To investigate the interaction between Acanthamoeba species and microglia.
Main Methods:
- Primary neonatal rat microglia cultures were exposed to A. culbertsoni and A. castellanii.
- Cytokine gene expression was analyzed using quantitative PCR.
- Protein levels of cytokines were measured.
- Microglial cell morphology and interaction with Acanthamoeba were examined using transmission electron microscopy.
Main Results:
- Acanthamoeba culbertsoni induced a significantly higher pro-inflammatory cytokine gene response in microglia compared to A. castellanii.
- Interleukin-1beta was the predominant cytokine upregulated at both mRNA and protein levels.
- Microglia phagocytosed A. castellanii, but A. culbertsoni caused microglial cell destruction.
- A. culbertsoni demonstrated greater virulence towards microglia.
Conclusions:
- The higher pathogenicity of A. culbertsoni is associated with a robust pro-inflammatory cytokine response, particularly interleukin-1beta.
- Destruction of microglia by A. culbertsoni, alongside cytokine release, likely contributes to granulomatous amebic encephalitis pathogenesis.
- Differential interactions with microglia distinguish pathogenic from less pathogenic Acanthamoeba species.
