Mouse Organotypic Brain Slice Cultures: A Novel Model for Studying Neuroimmune Responses to Cryptococcal Brain Infections.

Cryptococcal meningitis affects millions of people worldwide and is especially prevalent in regions with a high burden of HIV/AIDS. The study of the pathophysiology of this often fatal disease has been significantly hindered by the lack of reliable experimental models, especially at the level of the brain, which is the main organ of injury. Here we outline our novel protocol for the use of hippocampal organotypic brain slice cultures (HOCs) to study the host-fungal interactions during cryptococcal infections of the brain. HOCs are a powerful platform for investigating neuroimmune interactions as they allow for the preservation of all innate neuroglial cells including microglia, astrocytes, and neurons, all of which maintain their three-dimensional architecture and functional connectivity. We made HOCs from neonatal mice and infected these with a fluorescent strain of Cryptococcus neoformans for 24 h. Using immunofluorescent staining, we confirmed the presence and morphology of microglia, astrocytes, and neurons in HOCs prior to infection. Using fluorescent and light microscopy, we also confirmed that Cryptococcus neoformans encapsulates and buds in vitro, as it would in a host. Finally, we demonstrate that infection of HOCs with Cryptococcus neoformans results in close association of the fungal cells with host microglial cells. Our results demonstrate the utility of HOCs as a model to study the pathophysiology and host neuroimmune responses in neurocryptococcosis, which may assist in improving our collective understanding of the pathogenesis of this disease.