Abstract: bioRxiv preprint doi: https://doi.org/10.1101/2021.04.27.441512; this version posted April 27, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Iota-carrageenan prevents the replication of SARS-CoV-2 on an in vitro respiratory epithelium model 1 2 Augusto Varese1,†, Ana Ceballos1,†, Carlos Palacios2, Juan Manuel Figueroa2, Andrea Vanesa Dugour2,* 3 4 1 5 6 7 2 8 †These authors have contributed equally to this work. Instituto de Investigaciones Biomédicas en Retrovirus y SIDA (INBIRS), Universidad de Buenos Aires, Buenos Aires, Argentina. Respiratory Research Group, Instituto de Ciencia y Tecnología Dr. César Milstein - (Consejo Nacional de Investigaciones Científicas y Técnicas CONICET- Fundación Pablo Cassará), Saladillo 2468, Ciudad de Buenos Aires, C1440FFX, Argentina. 9 10 11 * Correspondence: Andrea Vanesa Dugour adugour@fundacioncassara.org.ar 12 Keywords: SARS-CoV-21, COVID-192, iota-carrageenan3, respiratory epithelium4, antivirals5. 13 Abstract 14 15 16 17 18 19 There are, except for remdesivir, no approved antivirals for the treatment or prevention of SARSCoV-2 infections. Iota-carrageenan formulated into a nasal spray has already been proven safe and effective in viral respiratory infections. We explored this antiviral activity in Calu-3, a human respiratory model cell line. A formula of iota-carrageenan and sodium chloride, as a nasal spray, already approved for human use, effectively inhibited SARS-CoV-2 infection in vitro, providing a more substantial reference for further clinical studies or developments. 20 1 21 22 23 24 25 26 The severe acute respiratory coronavirus 2 (SARS-CoV-2) is responsible for the currently ongoing pandemic coronavirus disease (COVID-19), counting more than 144.878.978 confirmed cases and more than 3.075.042 deaths worldwide by April 23, 2021 (Dong et al., 2020). There are still no adequate therapeutic or preventive medicines for COVID-19; repurposing established medications with recognized safety profiles is a possible approach for preventing or treating the disease and shortening the time-consuming drug development stages. 27 28 29 During the first days of the infection, the virus replicates mainly in the nasal cavity and the nasopharynx; therefore, nasal sprays with antiviral activity would reduce the viral load in these cavities. 30 31 32 33 34 35 Marine-derived polysaccharides, such as carrageenans, are a family of linear sulfated polysaccharides extracted from red seaweeds, widely used as thickening agents and stabilizers for food. Besides these properties, the iota-carrageenan demonstrated antiviral activity against several viruses, including respiratory viruses such as human rhinovirus, influenza A H1N1, and common cold coronavirus (Grassauer et al., 2008; Leibbrandt et al., 2010; Morokutti-Kurz et al., 2015). Iota-carrageenan inhibits virus infection mainly based on its interaction with the surface of viral particles, preventing