N-chlorotaurine is highly active against respiratory viruses including SARS-CoV-2 (COVID-19) in vitro

N-chlorotaurine (NCT) a long-lived oxidant generated by leukocytes, can be synthesized chemically and applied topically as an anti-infective to different body sites, including the lung via inhalation. Here, we demonstrate the activity of NCT against viruses causing acute respiratory tract infections, namely severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza viruses, and respiratory syncytial virus (RSV). Virucidal activity of NCT was tested in plaque assays, confirmed by RT-qPCR assays. Attack on virus proteins was investigated by mass spectrometry. NCT revealed broad virucidal activity against all viruses tested at 37 degrees C and pH 7. A significant reduction in infectious particles of SARS-CoV-2 isolates from early 2020 by 1 log(10) was detected after 15 min of incubation in 1% NCT. Proteinaceous material simulating body fluids enhanced this activity by transchlorination mechanisms (1 -2 log(10) reduction within 1-10 min). Tested SARS-CoV-2 variants B.1.1.7 (Alpha) und B.1.351 (Beta) showed a similar susceptibility. Influenza virus infectious particles were reduced by 3 log(10) (H3N2) to 5 log(10) (H1N1pdm), RSV by 4 log(10) within a few min. Mass spectrometry of NCT-treated SARS-CoV-2 spike protein and 3C-like protease, influenza virus haemagglutinin and neuraminidase, and RSV fusion glycoprotein disclosed multiple sites of chlorination and oxidation as the molecular mechanism of action. Application of 1.0% NCT as a prophylactic and therapeutic strategy against acute viral respiratory tract infections deserves comprehensive clinical investigation.

Automated summary

This study demonstrates the broad antiviral activity of N-chlorotaurine (NCT) against various viruses causing acute respiratory tract infections, including SARS-CoV-2, influenza viruses, and RSV. NCT exerts virucidal effects by chlorinating and oxidizing viral proteins, with enhanced activity in the presence of proteinaceous material. The findings suggest that the application of 1.0% NCT could be a comprehensive clinical strategy for the prevention and treatment of acute viral respiratory tract infections.