SARS-CoV-2 in-vitro neutralization assay reveals inhibition of virus entry by iota-carrageenan

In the absence of a vaccine and other effective prophylactic or therapeutic countermeasures the severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) remains a significant public health threat. Attachment and entry of coronaviruses including SARS-CoV-2 is mediated by the spike glycoprotein (SGP). Recently, a SARS-CoV-2 Spike Pseudotyped Lentivirus (SSPL) was developed that allows studying spike-mediated cell entry via luciferase reporter activity in a BSL2 environment. Here, we show that iota-carrageenan can inhibit the cell entry of SSPL in a dose dependent manner. SSPL particles were efficiently neutralized with an IC ₅₀ value of 2.6 µg/ml iota-carrageenan. In vitro data on iota-carrageenan against various Rhino- and Coronaviruses showed similar IC ₅₀ values and translated readily into clinical effectiveness when a nasal spray containing iota-carrageenan demonstrated a reduction in severity and duration of symptoms of common cold caused by various respiratory viruses. Accordingly, our in vitro data on SSPL suggest that administration of iota-carrageenan may be an effective and safe prophylaxis or treatment for SARS-CoV-2 infections.