Hot Water Extracts of Spirulina (Arthrospira Maxima) Demonstrate Antiviral Activity Against Respiratory Syncytial Virus

Abstract

Background: There are currently no effective antivirals to treat RSV infection. Therefore, the development of safe and novel anti-RSV drugs is urgent and necessary.

Purpose: Spirulina (Arthrospira maxima) extracts can exert antiviral effects against several viruses, but their effectiveness against respiratory syncytial virus (RSV) is not known. We purposed to explore the anti-RSV activity of spirulina hot water extracts.

Study Design: Anti-RSV activity of spirulina hot water extracts was assessed in vitro. The potential mechanism and the composition of spirulina hot water extracts was characterized.

Methods: Cytotoxicity and anti-RSV activity of spirulina hot water extracts were measured using MTT and neutralization assays, respectively. Potential mechanisms and components were assessed using time of addition, attachment, internalization, pull-down assays, and composition analysis.

Results: Spirulina hot water extracts showed no toxicity toward HEp-2 cells but demonstrated anti-RSV activity. The polysaccharide-enriched high-molecular weight fraction (>100 KDa, SHD1) had an EC50 of 0.0915 mg/mL and a selective index of >261.5 against RSV. SHD1 significantly reduced viral yield in a dose-dependent manner during the RSV attachment stage. SHD1 disrupted RSV internalization and inhibited RSV G protein binding to heparan sulfate receptors on the host cell surface, thus preventing RSV attachment and entry. SHD1 had a high total sugar content, with rhamnose accounting for as much as 60 mol% of total monosaccharides. The main glycosyl linkages included 3-, 4-, and 2,3-rhamnopyranosyl linkages.

Conclusion: Spirulina hot water extracts serve as effective candidates for novel drug development against RSV infection.

Note:

Funding Information: This study was supported by Chang Gung Memorial Hospital [grant number CMRPD1H0231-33] to S.-R.S.

Declaration of Interests: The authors declare no competing interests.

Keywords: Antiviral activity, Arthrospira maxima, water extract, respiratory syncytial virus