Although COVID-19 is considered to be primarily a respiratory disease, SARS-CoV-2 affects multiple organ systems including the central nervous system (CNS). Yet, there is no consensus on the consequences of CNS infections. Here, we used three independent approaches to probe the capacity of SARS-CoV-2 to infect the brain. First, using human brain organoids, we observed clear evidence of infection with accompanying metabolic changes in infected and neighboring neurons. However, no evidence for type I interferon responses was detected. We demonstrate that neuronal infection can be prevented by blocking ACE2 with antibodies or by administering cerebrospinal fluid from a COVID-19 patient. Second, using mice overexpressing human ACE2, we demonstrate SARS-CoV-2 neuroinvasion in vivo. Finally, in autopsies from patients who died of COVID-19, we detect SARS-CoV-2 in cortical neurons and note pathological features associated with infection with minimal immune cell infiltrates. These results provide evidence for the neuroinvasive capacity of SARS-CoV-2 and an unexpected consequence of direct infection of neurons by SARS-CoV-2.

Although COVID-19 is considered to be primarily a respiratory disease, SARS-CoV-2 affects multiple organ systems including the central nervous system (CNS). Reports indicate that 30-60% of patients with COVID-19 suffer from CNS symptoms. Yet, there is no consensus whether the virus can infect the brain, or what the consequences of infection are. Following SARS-CoV-2 infection of human brain organoids, clear evidence of infection was observed, with accompanying metabolic changes in the infected and neighboring neurons. Further, no evidence for the type I interferon responses was detected. We demonstrate that neuronal infection can be prevented either by blocking ACE2 with antibodies or by administering cerebrospinal fluid from a COVID-19 patient. Finally, using mice overexpressing human ACE2, we demonstrate in vivo that SARS-CoV-2 neuroinvasion, but not respiratory infection, is associated with mortality. These results provide evidence for the neuroinvasive capacity of SARS-CoV2, and an unexpected consequence of direct infection of neurons by SARS-CoV2.

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Transforming growth factor beta (TGFβ) is a cytokine that regulates cellular adhesion, proliferation and apoptosis. Its canonical downstream effectors include receptor-regulated Smad2/3 proteins, which are phosphorylated and then translocated to the nucleus to alter transcription. Additionally, other atypical pathways are simultaneously initiated by TGFβ, including that of p38 (a mitogen activated protein kinase). TGFβ acts as a tumour suppressor in its normal epithelial environment, but in tumor cells, it promotes epithelial-mesenchymal transition and cell migration. The manner in which tumor cells overcome the growth suppressive effects of TGFβ is not well-understood, especially since downstream TGFβ signaling is still apparent in these cells. This may point to selective pathway activation as a reason for its dual roles. Thus, it is important to consider membrane trafficking—a central process that directs signaling between various cascades. Previous studies from our lab demonstrate that perturbation of aPKC signaling alters TGFβ receptor trafficking and Smad signal transduction. Furthermore, we have also observed increased access to the p38 MAPK pathway in cells that have been silenced for aPKC expression. We are currently assessing the trafficking of the TGFβ receptor complex in order to investigate the mechanism(s) responsible differential access to specific signaling pathways. This will be addressed using techniques such as co-immunoprecipitation, immunofluorescence microscopy, subcellular fractionation and western blotting. Determining these mechanisms will further our understanding on cancerous TGFβ pathway regulation, and may lead to the discovery of promising therapeutic targets. Citation Format: Evelyn Ng, John Di Guglielmo. Analysis of transforming growth factor β receptor trafficking on different signaling transduction pathways. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4593.