SARS-CoV-2 infects human neural progenitor cells and brain organoids

Dear Editor,Coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 1 has resulted in over 13 million confirmed cases and more than 580,045 deaths across 218 countries and geographical regions as of July 16, 2020.This novel coronavirus primarily causes respiratory illness with clinical manifestations largely resembling those of SARS.However, neurological symptoms including headache, anosmia, ageusia, confusion, seizure, and encephalopathy have also been frequently reported in COVID-19 patients. 2,3In a study of 214 hospitalized COVID-19 patients in Wuhan, China, neurologic findings were reported in 36.4% of patients, and were more commonly observed in patients with severe infections (45.5%). 2 Similarly, a study from France reported neurologic findings in 84.5% (49/58) of COVID-19 patients admitted to hospital. 3Importantly, a recent study in Germany demonstrated that SARS-CoV-2 RNA could be detected in brain biopsies in 36.4% (8/22) of fatal COVID-19 cases, 4 which highlights the potential for viral infections in the human brain.To date, there has been no direct experimental evidence of SARS-CoV-2 infection in the human central nervous system (CNS).We recently demonstrated that SARS-CoV-2 could infect and replicate in cells of neuronal origin. 5In line with this finding, we showed that SARS-CoV-2 could infect and damage the olfactory sensory neurons of hamsters. 6In addition, angiotensin-converting enzyme 2 (ACE2), the entry receptor of SARS-CoV-2, is widely detected in the brain and is highly concentrated in a number of locations including substantia nigra, middle temporal gyrus, and posterior cingulate cortex. 7ogether, these findings suggest that the human brain might be an extra-pulmonary target of SARS-CoV-2 infection.To explore the direct involvement of SARS-CoV-2 in the CNS in physiologically relevant models, we assessed SARS-CoV-2 infection in induced pluripotent stem cells (iPSCs)-derived human neural progenitor cells (hNPCs), neurospheres, and brain organoids. 8We first evaluated the expression of ACE2 and key coronavirus entry-associated proteases in hNPCs.Our data suggested that ACE2, TMPRSS2, cathepsin L, and furin were readily detected in the hNPCs (Supplementary information, Fig. S1).Next, we challenged iPSC-derived hNPCs with SARS-CoV-2 at 10 multiplicity of infection (MOI) and with SARS-CoV as a control.Supernatant was harvested at 0, 24, and 48 h post infection (hpi) for virus replication assessment.Interestingly, our data suggested that SARS-CoV-2, but not SARS-CoV, could replicate in hNPCs (Fig. 1a; Supplementary information, Fig. S2).In addition, we quantified the cell viability of SARS-CoV-2infected hNPCs.Importantly, SARS-CoV-2 infection significantly reduced the viability of hNPCs to 4.7% (P < 0.0001) and 2.5% (P < 0.0001) of that of the mock-infected hNPCs at 72 and 120 hpi, respectively (Fig. 1a).In contrast to the substantial cytotoxicity induced by SARS-CoV-2 in the infected hNPCs, SARS-CoV-2 infection did not significantly upregulate interferon (Supplementary information, Fig. S3) and pro-inflammatory (Supplementary information, Fig. S4) response in the infected