Cell response analysis in SARS-CoV-2 infected bronchial organoids.

The development of an in vitro cell model that can be used to study severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) research is expected. Here we conducted infection experiments in bronchial organoids (BO) and an BO-derived air-liquid interface model (BO-ALI) using 8 SARS-CoV-2 variants. The infection efficiency in BO-ALI was more than 1,000 times higher than that in BO. Among the bronchial epithelial cells, we found that ciliated cells were infected with the virus, but basal cells were not. Ciliated cells died 7 days after the viral infection, but basal cells survived after the viral infection and differentiated into ciliated cells. Fibroblast growth factor 10 signaling was essential for this differentiation. These results indicate that BO and BO-ALI may be used not only to evaluate the cell response to SARS-CoV-2 and coronavirus disease 2019 (COVID-19) therapeutic agents, but also for airway regeneration studies.

Epigallocatechin gallate (EGCG) attenuates severe acute respiratory coronavirus disease 2 (SARS-CoV-2) infection by blocking the interaction of SARS-CoV-2 spike protein receptor-binding domain to human angiotensin-converting enzyme 2.

The outbreak of the coronavirus disease 2019 caused by the severe acute respiratory syndrome coronavirus 2 triggered a global pandemic where control is needed through therapeutic and preventive interventions. This study aims to identify natural compounds that could affect the fusion between the viral membrane (receptor-binding domain of the severe acute respiratory syndrome coronavirus 2 spike protein) and the human cell receptor angiotensin-converting enzyme 2. Accordingly, we performed the enzyme-linked immunosorbent assay-based screening of 10 phytochemicals that already showed numerous positive effects on human health in several epidemiological studies and clinical trials. Among these phytochemicals, epigallocatechin gallate, a polyphenol and a major component of green tea, could effectively inhibit the interaction between the receptor-binding domain of the severe acute respiratory syndrome coronavirus 2 spike protein and the human cell receptor angiotensin-converting enzyme 2. Alternately, in silico molecular docking studies of epigallocatechin gallate and angiotensin-converting enzyme 2 indicated a binding score of -7.8 kcal/mol and identified a hydrogen bond between R393 and angiotensin-converting enzyme 2, which is considered as a key interacting residue involved in binding with the severe acute respiratory syndrome coronavirus 2 spike protein receptor-binding domain, suggesting the possible blocking of interaction between receptor-binding domain and angiotensin-converting enzyme 2. Furthermore, epigallocatechin gallate could attenuate severe acute respiratory syndrome coronavirus 2 infection and replication in Caco-2 cells. These results shed insight into identification and validation of severe acute respiratory syndrome coronavirus 2 entry inhibitors.

Isolation of SARS-CoV-2 from COVID-19 Patients and an Asymptomatic Individual.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China, in December 2019. Despite the recent introduction of vaccines against SARS-CoV-2, more effective vaccines and antiviral drugs must be developed. Here, we isolated five SARS-CoV-2 strains from four patients with coronavirus disease (COVID-19) and an asymptomatic individual using pharyngeal swabs, nasopharyngeal swabs, and sputum samples. Cytopathic effects in inoculated Vero cells were observed between days 3 and 7. SARS-CoV-2 infection was confirmed by quantitative reverse-transcription polymerase chain reaction (RT-qPCR) and next-generation sequencing. Phylogenetic analyses of the whole genome sequences showed that the virus isolates from the clinical samples belonged to the Wuhan and European lineages. These findings and the isolated viruses may contribute to the development of diagnostic tools, vaccines, and antiviral drugs for COVID-19.

[Clinical Study of 45 Cases of COVID-19 and a Consideration of Severity Classification by the Kanagawa Model]

The outbreak of the novel coronavirus infection in Wuhan City, Hubei Province, China, in December 2019, has spread rapidly around the world, and the number of cases with no apparent route of transmission (cases of community transmission) is increasing in Japan. We have encountered 45 cases of COVID-19 infection, including 33 male and 12 female patients. The average age of the patients was 50.6 years. The symptoms were fever in 39 (86.7%) cases, cough in 33 (73.3%) cases, malaise in 24 (53.3%) cases, and diarrhea in 5 (11.1%) cases. In addition, according to the Kanagawa-model severity classification constructed by Kanagawa Prefecture to avoid collapse of the medical infrastructure caused by a sudden increase in patients, 30 cases were classified as having mild disease, 14 as having moderately severe disease, and 1 as having severe disease. Of the 30 patients with mild disease, 1 (3.3%) showed deterioration to moderately severe disease during the clinical course, and of the 14 patients with moderately severe disease, 6 (42.9%) showed deterioration to severe disease. The findings in respect of the subsequent clinical course of the patients suggest that the Kanagawa-model severity classification is a reasonable classification for satisfactory triage of patients.