Human brain organoids: a new model to study Cryptococcus neoformans neurotropism

With the rise in immunocompromised individuals and patients with immune-related comorbidities such as COVID-19, the rate of fungal infections is growing. This increase, along with the current plateau in anti-fungal drug development, has made understanding the pathogenesis and dissemination of these organisms more pertinent than ever. The mouse model of fungal infection, while informative on a basic science level, has severe limitations in terms of translation to the human disease. Here we present data supporting the implementation of the human cerebral organoid model, which is generated from human embryonic stem cells and accurately recapitulates relevant brain cell types and structures, to study fungal infection and dissemination to the central nervous system (CNS). This approach provides direct insight into the relevant pathogenesis of specific fungal organisms in human tissues where in vivo models are impossible. With this model system we assessed the specific brain tropisms and cellular effects of fungal pathogens that are known to cross the blood brain barrier such as Cryptococcus neoformans. We determined the effects this fungal pathogen has on the overall gross morphology, cellular architecture, and cytokine release of these model organoids. Furthermore, we demonstrated that C. neoformans can penetrate and invade the organoid tissue and remain present throughout the course of infection. These results demonstrate the utility of this new model to the field and highlight the potential for this system to elucidate fungal pathogenesis to new therapeutic strategies to prevent and treat the terminal stages of fungal diseases such as cryptococcal meningitis.