A novel coronavirus-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-emerged in humans in Wuhan, China, in December 2019 and has since disseminated globally 1,2 . As of April 16, 2020, the confirmed case count of coronavirus disease 2019 (COVID-19) had surpassed 2 million. Based on full-genome sequence analysis, SARS-CoV-2 shows high homology to SARS-related coronaviruses identified in horseshoe bats 1,2 . Here we show the establishment and characterization of expandable intestinal organoids derived from horseshoe bats of the Rhinolophus sinicus species that can recapitulate bat intestinal epithelium. These bat enteroids are fully susceptible to SARS-CoV-2 infection and sustain robust viral replication. Development of gastrointestinal symptoms in some patients with COVID-19 and detection of viral RNA in fecal specimens suggest that SARS-CoV-2 might cause enteric, in addition to respiratory, infection 3,4 . Here we demonstrate active replication of SARS-CoV-2 in human intestinal organoids and isolation of infectious virus from the stool specimen of a patient with diarrheal COVID-19. Collectively, we established the first expandable organoid culture system of bat intestinal epithelium and present evidence that SARS-CoV-2 can infect bat intestinal cells. The robust SARS-CoV-2 replication in human intestinal organoids suggests that the human intestinal tract might be a transmission route of SARS-CoV-2.

Hong Kong has been severely affected by severe acute respiratory syndrome (SARS). Contact in households and health-care settings is thought to be important for transmission, putting children at particular risk. Most data so far, however, have been for adults. We prospectively followed up the first ten children with SARS managed during the early phase of the epidemic in Hong Kong. All the children had been in close contact with infected adults. Persistent fever, cough, progressive radiographic changes of chest and lymphopenia were noted in all patients. The children were treated with high-dose ribavirin, oral prednisolone, or intravenous methylprednisolone, with no short-term adverse effects. Four teenagers required oxygen therapy and two needed assisted ventilation. None of the younger children required oxygen supplementation. Compared with adults and teenagers, SARS seems to have a less aggressive clinical course in younger children.

Human intestinal tract as an alternative route to acquire MERS-CoV infection.

Viruses are obligate intracellular microbes that exploit the host metabolic machineries to meet their biosynthetic demands, making these host pathways potential therapeutic targets. Here, by exploring a lipid library, we show that AM580, a retinoid derivative and RAR-α agonist, is highly potent in interrupting the life cycle of diverse viruses including Middle East respiratory syndrome coronavirus and influenza A virus. Using click chemistry, the overexpressed sterol regulatory element binding protein (SREBP) is shown to interact with AM580, which accounts for its broad-spectrum antiviral activity. Mechanistic studies pinpoint multiple SREBP proteolytic processes and SREBP-regulated lipid biosynthesis pathways, including the downstream viral protein palmitoylation and double-membrane vesicles formation, that are indispensable for virus replication. Collectively, our study identifies a basic lipogenic transactivation event with broad relevance to human viral infections and represents SREBP as a potential target for the development of broad-spectrum antiviral strategies.

SignificanceInfluenza virus infection represents a major threat to public health worldwide. There is no biologically relevant, reproducible, and readily available in vitro model for predicting the infectivity of influenza viruses in humans. Based on the long-term expanding 3D human airway organoids, we developed proximal differentiation and further established a 2D monolayer culture of airway organoids. The resultant 3D and 2D proximal differentiated airway organoids can morphologically and functionally simulate human airway epithelium and as a proof of concept can discriminate human-infective influenza viruses from poorly human-infective viruses. Thus, the proximal differentiated airway organoids can be utilized to predict the infectivity of influenza viruses and, more broadly, provide a universal platform for studying the biology and pathology of the human airway.

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ABSTRACT. Objective. To study the epidemiologic, clinical, laboratory, and radiologic features, prognostic indicators, and short-term to medium-term outcomes for children with severe acute respiratory syndrome (SARS) and to validate the performance characteristics of a clinical case definition, calculated with respect to SARSassociated coronavirus (SARS-CoV) seroconversion.Methods. Children <18 years of age, from a singlesite outbreak, who satisfied a clinical case definition for SARS, with subsequent serologic confirmation, were treated according to a standard protocol and prospectively monitored.Results. Forty-four children were included. The median age was 12 years. Forty-two children (95.5%) demonstrated an epidemiologic link. Fever, cough, malaise, coryza, sputum production, headache, myalgia, lymphopenia, and elevated lactate dehydrogenase levels were common presenting features. Radiographic findings were nonspecific, but high-resolution computed tomography of the thorax was an early diagnostic aid. A specific reverse transcription-polymerase chain reaction assay for SARS-CoV yielded positive results for <50% of children. Of 9 children who developed hypoxemia, 8 were treated with methylprednisolone. Of 5 children who received intensive care, 3 required assisted ventilation. All children recovered, and serious adverse events in response to treatment were not observed. The outcomes at 3 to 6 months after disease onset, including exercise tolerance, pulmonary functions, and psychologic status, were favorable. An age of >12 years was associated with methylprednisolone therapy for severe illness. After exclusion of the only infant, an age of >12 years was associated with oxygen requirements. Sore throat, high neutrophil count at presentation, and peak neutrophilia were independent factors predicting severe illness. The clinical case definition demonstrated good sensitivity, specificity, and positive and negative predictive values (97.8%, 92.7%, 88%, and 98.7%, respectively) for diagnostic accuracy.Conclusions. 1 Although the majority were adults, 121 children (6.9%) Ͻ18 years of age were registered, yielding an age-specific attack rate of 8.9 cases per 100 000 persons Ͻ18 years of age and a case fatality rate of 0%. A total of 89 hospitalized children in Hong Kong demonstrated serologic evidence of infection by the SARS-associated coronavirus (SARS-CoV) (e-SARS database, Hospital Authority, Hong Kong Special Administrative Region, data on file).Published articles on pediatric SARS have focused on reporting the demographic, clinical, laboratory, and radiologic characteristics. Definitive virologic data, prognostic indicators, and short-term to medium-term follow-up information were lacking in those preliminary reports. [2][3][4] We prospectively monitored a cohort of 44 children with laboratory confirmation of SARS who were treated at a referral center for pediatric infectious diseases that admitted the largest number of pediatric patients with SARS in Hong Kong. Their epidemiologic links; clinical, laboratory,...

The airways and alveoli of the human respiratory tract are lined by two distinct types of epithelium, which are the primary targets of respiratory viruses. We previously established long-term expanding human lung epithelial organoids from lung tissues and developed a ‘proximal’ differentiation protocol to generate mucociliary airway organoids. However, a respiratory organoid system with bipotential of the airway and alveolar differentiation remains elusive. Here we defined a ‘distal’ differentiation approach to generate alveolar organoids from the same source for the derivation of airway organoids. The alveolar organoids consisting of type I and type II alveolar epithelial cells (AT1 and AT2, respectively) functionally simulate the alveolar epithelium. AT2 cells maintained in lung organoids serve as progenitor cells from which alveolar organoids derive. Moreover, alveolar organoids sustain a productive SARS-CoV-2 infection, albeit a lower replicative fitness was observed compared to that in airway organoids. We further optimized 2-dimensional (2D) airway organoids. Upon differentiation under a slightly acidic pH, the 2D airway organoids exhibit enhanced viral replication, representing an optimal in vitro correlate of respiratory epithelium for modeling the high infectivity of SARS-CoV-2. Notably, the higher infectivity and replicative fitness of the Omicron variant than an ancestral strain were accurately recapitulated in these optimized airway organoids. In conclusion, we have established a bipotential organoid culture system able to reproducibly expand the entire human respiratory epithelium in vitro for modeling respiratory diseases, including COVID-19.