Establishment of a screening platform based on human coronavirus OC43 for the identification of microbial natural products with antiviral activity

Human coronaviruses (HCoVs) cause respiratory tract infections and are of great importance due to the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Human betacoronavirus OC43 (HCoV-OC43) is an adequate surrogate for SARS-CoV-2 because it infects the human respiratory system, presents a comparable biology, and is transmitted in a similar way. Its use is advantageous since it only requires biosafety level (BSL)-2 infrastructure which minimizes costs and biosafety associated limitations. In this report, we describe a high-throughput screening (HTS) platform to identify compounds that inhibit the propagation of HCoV-OC43. Optimization of assays based on inhibition of the cytopathic effect and virus immunodetection with a specific antibody, has provided a robust methodology for the screening of a selection of microbial natural product extracts from the Fundación MEDINA collection. Using this approach, a subset of 1280 extracts has been explored. Of these, upon hit confirmation and early LC-MS dereplication, 10 extracts were identified that contain potential new compounds. In addition, we report on the novel antiviral activity of some previously described natural products whose presence in bioactive extracts was confirmed by LC/MS analysis.