The landscape of human brain immune response in patients with severe COVID-19 (preprint)

In coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the relationship between brain tropism, neuroinflammation and host immune response has not been well characterized. We analyzed 68,557 single-nucleus transcriptomes from three brain regions (dorsolateral prefrontal cortex, medulla oblongata and choroid plexus) and identified an increased proportion of stromal cells and monocytes in the choroid plexus of COVID-19 patients. Differential gene expression, pseudo-temporal trajectory and gene regulatory network analyses revealed microglial transcriptome perturbations, mediating a range of biological processes, including cellular activation, mobility and phagocytosis. Quantification of viral spike S1 protein and SARS-CoV-2 transcripts did not support the notion of brain tropism. Overall, our findings suggest extensive neuroinflammation in patients with acute COVID-19.

Immunological and cardio-vascular pathologies associated with SARS-CoV-2 infection in golden syrian hamster (preprint)

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection in golden Syrian hamster (GSH) causes lungs pathology and resembles to human corona virus disease (Covid-19). Extra-pulmonary pathologies and immunological parameters of SARS-CoV-2 infection remained undefined in GSH. Using in silico modelling, we identified the similarities between human and hamster angiotensin-converting enzyme-2 (ACE-2), neuropilin-1 (NRP-1) that bind to receptor-binding domain (RBD) and S1 fragment of spike protein of SARS-CoV-2. SARS-CoV-2 infection led to lung pathologies, and cardiovascular complications (CVC) marked by interstitial coronary fibrosis and acute inflammatory response. Serum lipidomic and metabolomic profile of SARS-CoV-2-infected GSH revealed changes in serum triglycerides (TG) and low-density lipoprotein (LDL), and alterations in metabolites that correlated with Covid19. Together, we propose GSH as an animal model to study SARS-CoV-2 infection and its therapy associated with pulmonary and extra-pulmonary pathologies.

Hypoxia reduces cell attachment of SARS-CoV-2 spike protein by modulating the expression of ACE2 and heparan sulfate (preprint)

A main clinical parameter of Covid-19 pathophysiology is hypoxia. Here we show that hypoxia decreases the attachment of the receptor binding domain (RBD) and the S1 subunit (S1) of the spike protein to epithelial cells. In Vero E6 cells, hypoxia reduces the protein levels of ACE2, which might in part explain the observed reduction of the infection rate. However, hypoxia also inhibits the binding of the spike to human lung epithelial cells lacking ACE2 expression, indicating that hypoxia modulates the expression of additional binding partners of SARS-CoV-2. We show that hypoxia also decreases the total cell surface levels of heparan sulfate, a known attachment receptor of SARS-CoV-2, by reducing the expression of syndecan-1 and syndecan3, the main proteoglycans containing heparan sulfate. Our study indicates that hypoxia acts to prevent SARS-CoV-2 infection, suggesting that the hypoxia signaling pathway might offer therapeutic opportunities for the treatment of Covid-19.

Common genetic variation in humans impacts in vitro susceptibility to SARS-CoV-2 infection (preprint)

The host response to SARS-CoV-2, the etiologic agent of the COVID-19 pandemic, demonstrates significant inter-individual variability. In addition to showing more disease in males, the elderly, and individuals with underlying co-morbidities, SARS-CoV-2 can seemingly render healthy individuals with profound clinical complications. We hypothesize that, in addition to viral load and host antibody repertoire, host genetic variants also impact vulnerability to infection. Here we apply human induced pluripotent stem cell (hiPSC)-based models and CRISPR-engineering to explore the host genetics of SARS-CoV-2. We demonstrate that a single nucleotide polymorphism (rs4702), common in the population at large, and located in the 3UTR of the protease FURIN, impacts alveolar and neuron infection by SARS-CoV-2 in vitro. Thus, we provide a proof-of-principle finding that common genetic variation can impact viral infection, and thus contribute to clinical heterogeneity in SARS-CoV-2. Ongoing genetic studies will help to better identify high-risk individuals, predict clinical complications, and facilitate the discovery of drugs that might treat disease.