Human Brain Organoids as an In Vitro Model System of Viral Infectious Diseases

Brain organoids, or brainoids, have shown great promise in the study of central nervous system (CNS) infection. Modeling Zika virus (ZIKV) infection in brain organoids may help elucidate the relationship between ZIKV infection and microcephaly. Brain organoids have been used to study the pathogenesis of SARS-CoV-2, human immunodeficiency virus (HIV), HSV-1, and other viral infections of the CNS. In this review, we summarize the advances in the development of viral infection models in brain organoids and their potential application for exploring mechanisms of viral infections of the CNS and in new drug development. The existing limitations are further discussed and the prospects for the development and application of brain organs are prospected.

A multi-omics investigation of the composition and function of extracellular vesicles along the temporal trajectory of COVID-19.

Exosomes represent a subtype of extracellular vesicle that is released through retrograde transport and fusion of multivesicular bodies with the plasma membrane1. Although no perfect methodologies currently exist for the high-throughput, unbiased isolation of pure plasma exosomes2,3, investigation of exosome-enriched plasma fractions of extracellular vesicles can confer a glimpse into the endocytic pathway on a systems level. Here we conduct high-coverage lipidomics with an emphasis on sterols and oxysterols, and proteomic analyses of exosome-enriched extracellular vesicles (EVs hereafter) from patients at different temporal stages of COVID-19, including the presymptomatic, hyperinflammatory, resolution and convalescent phases. Our study highlights dysregulated raft lipid metabolism that underlies changes in EV lipid membrane anisotropy that alter the exosomal localization of presenilin-1 (PS-1) in the hyperinflammatory phase. We also show in vitro that EVs from different temporal phases trigger distinct metabolic and transcriptional responses in recipient cells, including in alveolar epithelial cells, which denote the primary site of infection, and liver hepatocytes, which represent a distal secondary site. In comparison to the hyperinflammatory phase, EVs from the resolution phase induce opposing effects on eukaryotic translation and Notch signalling. Our results provide insights into cellular lipid metabolism and inter-tissue crosstalk at different stages of COVID-19 and are a resource to increase our understanding of metabolic dysregulation in COVID-19.

Lung organoids, useful tools for investigating epithelial repair after lung injury.

Organoids are derived from stem cells or organ-specific progenitors. They display structures and functions consistent with organs in vivo. Multiple types of organoids, including lung organoids, can be generated. Organoids are applied widely in development, disease modelling, regenerative medicine, and other multiple aspects. Various human pulmonary diseases caused by several factors can be induced and lead to different degrees of lung epithelial injury. Epithelial repair involves the participation of multiple cells and signalling pathways. Lung organoids provide an excellent platform to model injury to and repair of lungs. Here, we review the recent methods of cultivating lung organoids, applications of lung organoids in epithelial repair after injury, and understanding the mechanisms of epithelial repair investigated using lung organoids. By using lung organoids, we can discover the regulatory mechanisms related to the repair of lung epithelia. This strategy could provide new insights for more effective management of lung diseases and the development of new drugs.

Early Detection of Severe Acute Respiratory Syndrome Coronavirus 2 Antibodies as a Serologic Marker of Infection in Patients With Coronavirus Disease 2019.

BACKGROUND: Thousands of medical staff have been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with hundreds of deaths reported. Such loss could be prevented if there were a serologic assay for SARS-CoV-2-specific antibodies for serological surveillance of its infection at the early stage of disease. METHODS: Using Chinese hamster ovarian (CHO) cell-expressed full-length SARS-CoV-2 S1 protein as capturing antigen, a coronavirus disease 2019 (COVID-19)/SARS-CoV-2 S1 serology enzyme-linked immunosorbent assay (ELISA) kit was developed and validated with negative samples collected prior to the outbreak or during the outbreak and positive samples from patients confirmed with COVID-19. RESULTS: The specificity of the ELISA kit was 97.5%, as examined against total 412 normal human samples. The sensitivity was 97.1% by testing against 69 samples from hospitalized and/or recovered COVID-19 patients. The overall accuracy rate reached 97.3%. The assay was able to detect SARS-CoV-2 antibody on day 1 after the onset of COVID-19 disease. The average antibody levels increased during hospitalization and 14 days after discharge. SARS-CoV-2 antibodies were detected in 28 of 276 asymptomatic medical staff and 1 of 5 nucleic acid test-negative "close contacts" of COVID-19 patients. CONCLUSIONS: With the assays developed here, we can screen medical staff, incoming patients, passengers, and people who are in close contact with the confirmed patients to identify the "innocent viral spreaders," protect the medical staff, and stop further spread of the virus.

Coagulation Dysfunction.

CONTEXT.­: The coronavirus disease 2019 (COVID-19) is a highly contagious respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Coagulation dysfunction is a hallmark in patients with COVID-19. Fulminant thrombotic complications emerge as critical issues in patients with severe COVID-19. OBJECTIVE.­: To present a review of the literature and discuss the mechanisms of COVID-19 underlying coagulation activation and the implications for anticoagulant and thrombolytic treatment in the management of COVID-19. DATA SOURCES.­: We performed a systemic review of scientific papers on the topic of COVID-19, available online via the PubMed NCBI, medRxiv, and Preprints as of May 15, 2020. We also shared our experience on the management of thrombotic events in patients with COVID-19. CONCLUSIONS.­: COVID-19-associated coagulopathy ranges from mild laboratory alterations to disseminated intravascular coagulation (DIC) with a predominant phenotype of thrombotic/multiple organ failure. Characteristically, high D-dimer levels on admission and/or continuously increasing concentrations of D-dimer are associated with disease progression and poor overall survival. SARS-CoV-2 infection triggers the immune-hemostatic response. Drastic inflammatory responses including, but not limited to, cytokine storm, vasculopathy, and NETosis may contribute to an overwhelming activation of coagulation. Hypercoagulability and systemic thrombotic complications necessitate anticoagulant and thrombolytic interventions, which provide opportunities to prevent or reduce "excessive" thrombin generation while preserving "adaptive" hemostasis and bring additional benefit via their anti-inflammatory effect in the setting of COVID-19.

Immunological and inflammatory profiles in mild and severe cases of COVID-19.

COVID-19 is associated with 5.1% mortality. Although the virological, epidemiological, clinical, and management outcome features of COVID-19 patients have been defined rapidly, the inflammatory and immune profiles require definition as they influence pathogenesis and clinical expression of COVID-19. Here we show lymphopenia, selective loss of CD4+ T cells, CD8+ T cells and NK cells, excessive T-cell activation and high expression of T-cell inhibitory molecules are more prominent in severe cases than in those with mild disease. CD8+ T cells in patients with severe disease express high levels of cytotoxic molecules. Histochemical studies of lung tissue from one fatality show sub-anatomical distributions of SARS-CoV-2 RNA and massive infiltration of T cells and macrophages. Thus, aberrant activation and dysregulation of CD8+ T cells occur in patients with severe COVID-19 disease, an effect that might be for pathogenesis of SARS-CoV-2 infection and indicate that immune-based targets for therapeutic interventions constitute a promising treatment for severe COVID-19 patients.

Omics-Driven Systems Interrogation of Metabolic Dysregulation in COVID-19 Pathogenesis.

The coronavirus disease 2019 (COVID-19) pandemic presents an unprecedented threat to global public health. Herein, we utilized a combination of targeted and untargeted tandem mass spectrometry to analyze the plasma lipidome and metabolome in mild, moderate, and severe COVID-19 patients and healthy controls. A panel of 10 plasma metabolites effectively distinguished COVID-19 patients from healthy controls (AUC = 0.975). Plasma lipidome of COVID-19 resembled that of monosialodihexosyl ganglioside (GM3)-enriched exosomes, with enhanced levels of sphingomyelins (SMs) and GM3s, and reduced diacylglycerols (DAGs). Systems evaluation of metabolic dysregulation in COVID-19 was performed using multiscale embedded differential correlation network analyses. Using exosomes isolated from the same cohort, we demonstrated that exosomes of COVID-19 patients with elevating disease severity were increasingly enriched in GM3s. Our work suggests that GM3-enriched exosomes may partake in pathological processes related to COVID-19 pathogenesis and presents the largest repository on the plasma lipidome and metabolome distinct to COVID-19.