Inhibiting SARS-CoV-2 infection in vitro by suppressing its receptor, angiotensin-converting enzyme 2, via aryl-hydrocarbon receptor signal.

Since understanding molecular mechanisms of SARS-CoV-2 infection is extremely important for developing effective therapies against COVID-19, we focused on the internalization mechanism of SARS-CoV-2 via ACE2. Although cigarette smoke is generally believed to be harmful to the pathogenesis of COVID-19, cigarette smoke extract (CSE) treatments were surprisingly found to suppress the expression of ACE2 in HepG2 cells. We thus tried to clarify the mechanism of CSE effects on expression of ACE2 in mammalian cells. Because RNA-seq analysis suggested that suppressive effects on ACE2 might be inversely correlated with induction of the genes regulated by aryl hydrocarbon receptor (AHR), the AHR agonists 6-formylindolo(3,2-b)carbazole (FICZ) and omeprazole (OMP) were tested to assess whether those treatments affected ACE2 expression. Both FICZ and OMP clearly suppressed ACE2 expression in a dose-dependent manner along with inducing CYP1A1. Knock-down experiments indicated a reduction of ACE2 by FICZ treatment in an AHR-dependent manner. Finally, treatments of AHR agonists inhibited SARS-CoV-2 infection into Vero E6 cells as determined with immunoblotting analyses detecting SARS-CoV-2 specific nucleocapsid protein. We here demonstrate that treatment with AHR agonists, including FICZ, and OMP, decreases expression of ACE2 via AHR activation, resulting in suppression of SARS-CoV-2 infection in mammalian cells.

Duration of Infectious Virus Shedding in Patients With Severe Coronavirus Disease 2019 Who Required Mechanical Ventilation (preprint)

Approximately 5% of patients with coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 develop severe COVID-19. Severe COVID-19 requires respiratory management with mechanical ventilation and an extended period of treatment. Prolonged infectious virus shedding is a concern in severe COVID-19 cases, but few reports have examined the duration of infectious virus shedding. Therefore, we investigated the duration of infectious virus shedding in patients transferred to Hiroshima University Hospital with severe COVID-19 requiring mechanical ventilation. Nasopharyngeal swab specimens were collected and analyzed using both viral culture and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) tests between December 2020 and February 2021. Of the 23 patients tested, the proportions of those with positive test results at first specimen collection on RT-qPCR and viral culture tests were 95·7% and 30·4%, respectively. All six patients with positive viral culture test results who were followed-up tested negative 24 days after symptom onset but remained positive on RT-qPCR. The longest negative conversion time was observed in a dialysis patient on immunosuppressive drugs. This study indicated that patients with severe COVID-19 remain culture positive for ≥ 10 days after symptom onset. Additionally, immunosuppressed patients with severe COVID-19 could consider isolation for ≥ 20 days.

Ethanol susceptibility of SARS-CoV-2 and other enveloped viruses (preprint)

Ethanol is an effective disinfectant against the novel coronavirus SARS-CoV-2. However, its effective concentration has not been shown, and we therefore analyzed the effects of different concentrations of ethanol on SARS-CoV-2. When SARS-CoV-2 was treated with varying ethanol concentrations and examined for changes in infectivity, the ethanol concentration at which 99% of the infectious titers were reduced was 24.1%(w/w) [29.3%(v/v)]. For reference, ethanol susceptibility was also examined with other envelope viruses, including influenza virus, vesicular stomatitis virus in the family Rhabdoviridae, and Newcastle disease virus in the family Paramyxoviridae, and the 99% inhibitory concentrations were found to be 28.8%(w/w) [34.8%(v/v)], 24.0%(w/w) [29.2%(v/v)], and 13.3%(w/w) [16.4%(v/v)], respectively. Some differences from SARS-CoV-2 were observed, but the differences were not significant. It was concluded that ethanol at a concentration of 30%(w/w) [36.2%(v/v)] almost completely inactivates SARS-CoV-2.

Duration of Infectious Virus Shedding in Patients with Severe Coronavirus Disease 2019 Who Required Mechanical Ventilation (preprint)

Background: Around 5% of patients with coronavirus disease ( COVID-19) caused by severe acute respiratory syndrome coronavirus 2 develop severe COVID-19. Severe COVID-19 requires respiratory management with mechanical ventilation and an extended period of treatment. Prolonged infectious virus shedding is a concern in severe COVID-19 cases, but few reports have examined the duration of infectious virus shedding. We investigated the duration of infectious virus shedding in patients transferred to Hiroshima University Hospital with severe COVID-19 requiring mechanical ventilation. Methods: Nasopharyngeal swab specimens were collected and analyzed using both viral culture and reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) tests between December 2020 and February 2021.Findings: Of the 23 patients tested, the percentage of those with positive test results at first specimen collection (the median number of days to first specimen collection after symptom onset was ten) on RT-qPCR and viral culture was 95 ·7% (n = 22) and 30·4% (n = 7), respectively. All six patients with positive viral culture test results who were followed-up tested negative by day 24 after symptom onset but remained positive on RT-qPCR. Specimen viral loads based on PCR testing did not decrease over time, but viral loads determined via culture tests loads decreased over time. The longest negative conversion time was observed in a dialysis patient on immunosuppressive drugs.Interpretation: This study indicated that patients with severe COVID-19 remain culture positive ≥ ten days after symptom onset. The work also suggests that immunosuppressed patients with severe COVID-19 could consider isolation for ≥ 20 days.Funding: NoneDeclaration of Interests: We declare no competing interests.Ethics Approval Statement: This research was approved by the Ethical Committee for Epidemiology of Hiroshima University (approval number: E-2157).