Capture and neutralization of SARS-CoV-2 and influenza virus by algae-derived lectins with high-mannose and core fucose specificities.

We first investigated the interactions between several algae-derived lectins and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We created lectin columns using high-mannose (HM)-type glycan-specific lectins OAA and KAA-1 or core fucose-specific lectin hypninA-2 and conducted binding experiments with SARS-CoV-2. The results showed that these lectins were capable of binding to the virus. Furthermore, when examining the neutralization ability of nine different lectins, it was found that KAA-1, ESA-2, and hypninA-2 were effective in neutralizing SARS-CoV-2. In competitive inhibition experiments with glycoproteins, neutralization was confirmed to occur through HM-type or core fucose-type glycans. However, neutralization was not observed with other lectins, such as OAA. This trend of KAA-1 and ESA-2 having the neutralizing ability and OAA not having it was also similar to influenza viruses. Electron microscopy observations revealed that KAA-1 and hypninA-2 strongly aggregated SARS-CoV-2 particles, while OAA showed a low degree of aggregation. It is believed that the neutralization of SARS-CoV-2 involves multiple factors, such as glycan attachment sites on the S protein, the size of lectins, and their propensity to aggregate, which cause inhibition of receptor binding or aggregation of virus particles. This study demonstrated that several algae-derived lectins could neutralize SARS-CoV-2 and that lectin columns can effectively recover and concentrate the virus.

Ethanol Susceptibility of SARS-CoV-2 and Other Enveloped Viruses.

Ethanol is an effective disinfectant against the novel coronavirus SARS-CoV-2. However, its effective concentration has not been shown, and we therefore analyzed the effects of different concentrations of ethanol on SARS-CoV-2. When SARS-CoV-2 was treated with varying ethanol concentrations and examined for changes in infectivity, the ethanol concentration at which 99% of the infectious titers were reduced was 24.1% (w/w) [29.3% (v/v)]. For reference, ethanol susceptibility was also examined with other envelope viruses, including influenza virus, vesicular stomatitis virus in the family Rhabdoviridae, and Newcastle disease virus in the family Paramyxoviridae, and the 99% inhibitory concentrations were found to be 28.8%(w/w) [34.8% (v/v)], 24.0% (w/w) [29.2% (v/v)], and 13.3% (w/w) [16.4% (v/v)], respectively. Some differences from SARS-CoV-2 were observed, but the differences were not significant. It was concluded that ethanol at a concentration of 30%(w/w) [36.2% (v/v)] almost completely inactivates SARS-CoV-2.