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Human microglia mediate anti-Cryptococcus neoformans activity in the presence of specific antibody
S C Lee1, Y Kress, D W Dickson
1Department of Pathology (Neuropathology), Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Abstract:
The interaction of the opportunistic fungus Cryptococcus neoformans with human microglia was studied in vitro in the presence and absence of capsule binding antibody. In the absence of capsule binding antibody there was little or no phagocytosis. Addition of the murine monoclonal antibody (mAb) 2H1 (IgG1, kappa) to the capsular glucuronoxylomannan (GXM) produced a dose-dependent enhancement of C. neoformans phagocytosis by microglia. Phagocytosis resulted in marked inhibition of fungal proliferation. Microglial antifungal activity was studied by colony forming unit assay, L-[3H]leucine incorporation assay, and phase contrast microscopy. At microglia: C. neoformans ratios of 10:1 to 80:1 fungal growth was reduced by 61-95%. Inhibitors of nitric oxide synthase and reactive oxygen intermediates did not prevent antifungal activity mediated by human microglia. Transmission electron microscopic studies revealed that although some internalized yeast cells were killed, the majority were intact consistent with fungistasis. Human microglia cells are potent effector cells against C. neoformans in vitro in the presence of specific antibody. Enhancement of microglial activity in vivo by opsonins may be a useful therapeutic strategy.
Insights
Human microglia effectively combat Cryptococcus neoformans fungal infections when aided by specific antibodies. Antibody enhancement of microglial phagocytosis significantly inhibits fungal growth, suggesting a potential therapeutic strategy.
Area of Science:
- Immunology
- Mycology
- Neuroscience
Background:
- Cryptococcus neoformans is an opportunistic fungal pathogen.
- Human microglia are key immune cells in the central nervous system.
- The interaction between microglia and C. neoformans is crucial in cryptococcosis.
Purpose of the Study:
- To investigate the in vitro interaction between human microglia and Cryptococcus neoformans.
- To determine the role of capsule-binding antibodies in microglial phagocytosis and antifungal activity.
Main Methods:
- In vitro co-culture of human microglia and C. neoformans.
- Monoclonal antibody (mAb) 2H1 opsonization of fungal capsular glucuronoxylomannan (GXM).
- Phagocytosis assays, colony forming unit (CFU) assays, leucine incorporation, phase contrast, and transmission electron microscopy.
Main Results:
- Little to no phagocytosis of C. neoformans by microglia without antibody.
- Dose-dependent enhancement of phagocytosis and fungal growth inhibition (61-95%) with mAb 2H1.
- Microglial antifungal activity was independent of nitric oxide synthase and reactive oxygen intermediates.
Conclusions:
- Human microglia are potent effector cells against C. neoformans in vitro when opsonized by specific antibodies.
- Antibody-mediated enhancement of microglial phagocytosis leads to fungistasis.
- Therapeutic strategies enhancing microglial opsonization may be beneficial for treating cryptococcosis.