Antiviral activity of lambda-carrageenan against influenza viruses and severe acute respiratory syndrome coronavirus 2

Abstract

Influenza virus and coronavirus, belonging to enveloped RNA viruses, are major causes of human respiratory diseases. The aim of this study was to investigate the broad spectrum antiviral activity of a naturally existing sulfated polysaccharide, lambda-carrageenan (λ-CGN), purified from marine red algae. Cell culture-based assays revealed that the macromolecule efficiently inhibited both influenza A and B viruses with EC50 values ranging from 0.3 to 1.4 μg/ml, as well as currently circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with an EC50 value of 0.9 ± 1.1 μg/ml. No toxicity to the host cells was observed at concentrations up to 300 μg/ml. Plaque titration and western blot analysis verified that λ-CGN reduced expression of viral proteins in cell lysates and suppressed progeny virus production in culture supernatants in a dose-dependent manner. This polyanionic compound exerts antiviral activity by targeting viral attachment to cell surface receptors and preventing virus entry. Moreover, its intranasal administration to mice during influenza A viral challenge not only alleviated infection-mediated reductions in body weight but also protected 60% of mice from virus-induced mortality. Thus, λ-CGN could be a promising antiviral agent for preventing infection with several respiratory viruses.

Carrageenan-containing over-the-counter nasal and oral sprays inhibit SARS-CoV-2 infection of airway epithelial cultures

“…Products A and B contain carrageenans (Table 1), which are sulfated polysaccharides isolated from red seaweeds previously shown to exert antiviral activity (14,(21)(22)(23)(24)(25). Product A contains i-carrageenan (1.2 mg/mL) and κ-carrageenan (0.4 mg/mL), and product B contains i-carrageenan only (1.2 mg/mL).…”

Quinine Inhibits Infection of Human Cell Lines with SARS-CoV-2

“…In the early face of a pandemic where only hygienic measures and confinements are the options to stop the spread of infections among the affected population, either repurposed synthetic drugs or natural substances with a broadly acting antiviral capacity are the only options for therapeutic intervention. Similar to quinine, the natural substance iota-carrageenan was shown to interfere with SARS-CoV-2 replication in vitro [56][57][58]. For this polysaccharide isolated from red algae, which can be used as a prophylactic nasal and throat spray or as a lozenge, first clinical trials in Austria, the United States, Argentina, and Great Britain have been reported, and first positive results have been published [56,59,60].…”

Seaweed Sulfated Polysaccharides against Respiratory Viral Infections

“…Furthermore, Bansal et al confirmed the antiviral activity of iota-carrageenan nasal spray in vitro using Vero E6 cells [67]. Lambda-carrageenan showed the potent inhibition of SARS-COV-2 in vitro in Vero cells, preventing the viral attachment to cell receptors [64].…”

“…Lambda-carrageenan inhibited both influenza A and B viruses in vitro on MDCK cells along with infected mouse models. This molecule has shown its effect by preventing the viral attachment to cell receptors [64].…”