Replication kinetic, cell tropism and associated immune responses in SARS-CoV-2 and H5N1 virus infected human iPSC derived neural models

Abstract

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is associated with a wide variety of neurological complications. Even though SARS-CoV-2 is rarely detected in the central nervous system (CNS) or cerebrospinal fluid, evidence is accumulating that SARS-CoV-2 might enter the CNS via the olfactory nerve. However, what happens after SARS-CoV-2 enters the CNS is poorly understood. Therefore, we investigated the replication kinetics, cell tropism, and associated immune responses of SARS-CoV-2 infection in different types of neural cultures derived from human induced pluripotent stem cells (hiPSCs). SARS-CoV-2 was compared to the neurotropic and highly pathogenic H5N1 influenza A virus. SARS-CoV-2 infected a minority of individual mature neurons, without subsequent virus replication and spread, despite ACE2, TMPRSS2 and NPR1 expression in all cultures. However, this sparse infection did result in the production of type-III-interferons and IL-8. In contrast, H5N1 virus replicated and spread very efficiently in all cell types in all cultures. Taken together, our findings support the hypothesis that neurological complications might result from local immune responses triggered by virus invasion, rather than abundant SARS-CoV-2 replication in the CNS.

3D Bioprinted Neural‐Like Tissue as a Platform to Study Neurotropism of Mouse‐Adapted SARS‐CoV‐2

“…[71] Both cofactors, TMPRSS2 and neuropilin-1, were expressed by astrocytes and neurons (Figure S7B, Supporting Information), as also observed in previous works. [72,73] Neuronal infection by MA-SARS-CoV-2 led to cell-cell fusion and the formation of neuronal syncytium (Figure 4A), corroborating the specificity of the mouse-adapted virus to this cell type, once this behavior was not observed for cells infected by hSARS-CoV-2 (Figure S6B-ii, Supporting Information). Spike protein present at the plasma membrane of cells is able to trigger syncytia formation, in which the cell-cell fusion is mediated by TMPRSS2.…”

“…reported low presence of the virus in neurons/astrocytes coculture. [ 72 ] Here, the presence of neurons in the 3D structure seemed not to affect the capacity of the virus to infect the tissue, when comparing to results obtained for bioprinted astrocytes.…”

“…Here, mature neurons were able to replicate the virus, evidence also observed by Song et al., which suggested that SARS‐CoV‐2 may use neuron cell machinery for replication. [ 14 ] On the other hand, different works have reported a poor or no capacity of neurons to actively replicate the virus, even though they expressed ACE2 [ 72 ] and were susceptible to SARS‐CoV‐2 entry. [ 11 ] However, it is relevant to point out the use of different cell sources and protocols of infection among these studies, which directly affect viral response.…”

“…[ 71 ] Both cofactors, TMPRSS2 and neuropilin‐1, were expressed by astrocytes and neurons (Figure S7B , Supporting Information), as also observed in previous works. [ 72 , 73 ]…”

SARS-CoV-2 infection of human neurons requires endosomal cell entry and can be blocked by inhibitors of host phosphoinositol-5 kinase

“…Postmortem analysis of deceased COVID-19 patients has indicated sporadic presence of viral components in neurons, glial, and endothelial cells in different regions of the brain including the olfactory bulb (OB), which connects the olfactory sensory neurons of the nasal epithelium to the central nervous system (CNS) via a dense network of nerves (3)(4)(5)(6)(7)(8). In in vitro cell culture models, SARS-CoV-2 can infect neurons derived from human embryonic stem cells (ESCs) and iPSCs in both two-dimensional (monolayers) and three-dimensional models (e.g., organoids) (7,(9)(10)(11)(12)(13)(14)(15). Some studies also reported infection in iPSC/hESC-derived astrocytes (8,13,15).…”