Modelling Amoebic Brain Infection Caused byBalamuthia mandrillarisUsing a Human Cerebral Organoid

The lack of disease models adequately resembling human tissue has hindered our understanding of amoebic brain infection. Three-dimensional structured organoids provide a microenvironment similar to human tissue. This study demonstrates the use of cerebral organoids to model a rare brain infection caused by the highly lethal amoeba Balamuthia mandrillaris . Cerebral organoids were generated from human pluripotent stem cells and infected with clinically isolated B. mandrillaris trophozoites. Histological examination showed amoebic invasion and neuron damage following coculture with the trophozoites. The transcript profile suggested an alteration in neuron growth and a proinflammatory response. The release of intracellular proteins specific to neuronal bodies and astrocytes was detected at higher levels postinfection. The amoebicidal effect of the repurposed drug nitroxoline was examined using the human cerebral organoids. Overall, the use of human cerebral organoids helped unravel the host response, identify biomarkers for brain injury, and in the testing of a potential amoebicidal drug in a context similar to the human brain. Author summary Brain inflammation caused by a free-living amoeba Balamuthia mandrillaris is really rare but life-threatening infectious disease. Given its rarity and difficulty to obtain a clinical isolate for further study, this disease has been neglected despite high mortality rate. Many gaps in our understanding of the disease remain opened. Emergence of the organoid platform allows modelling human diseases in an in vitro setting, leading to identification of potential molecular pathway as drug targets. Thus, this work attempts to deploy a human brain organoid to reveal such pathways, which are altered by the amoeba. A strain of B. mandrillaris was isolated from human biopsied brain. In the co-culture between brain organoid and amoeba, data suggested an alteration in neuron growth and increase of proinflammatory response. Brain organoid release brain trauma biomarkers. Importantly, we show therapeutic effect of the antibiotic nitroxoline using the human cerebral organoids. Thereby, the use of the human cerebral organoids unravels the host response, identify potential biomarkers, and provide an alternative way for testing a potential drug targeting the amoeba.