Abstract
Influenza viruses cause a significant public health burden each year despite the availability of anti-influenza drugs and vaccines. Therefore, new anti-influenza virus agents are needed. Rhamnan sulfate (RS) is a sulfated polysaccharide derived from the green alga Monostroma nitidum. Here, we aimed to demonstrate the antiviral activity of RS, especially against influenza A virus (IFV) infection, in vitro and in vivo. RS showed inhibitory effects on viral proliferation of enveloped viruses in vitro. Evaluation of the anti-IFV activity of RS in vitro showed that it inhibited both virus adsorption and entry steps. The oral administration of RS in IFV-infected immunocompetent and immunocompromised mice suppressed viral proliferation in both mouse types. The oral administration of RS also had stimulatory effects on neutralizing antibody production. Fluorescent analysis showed that RS colocalized with M cells in Peyer’s patches, suggesting that RS bound to the M cells and may be incorporated into the Peyer’s patches, which are essential to intestinal immunity. In summary, RS inhibits influenza virus infection and promotes antibody production, suggesting that RS is a potential candidate for the treatment of influenza virus infections.
Highlights
Influenza viruses are disease-causing agents belonging to the Orthomyxoviridae family
To assess the antiviral spectrum of Rhamnan sulfate (RS), we examined its effects on the growth of different host cells and on the replication of different viruses
Representative enveloped viruses and non-enveloped viruses from different taxonomical groups were used in this study
Summary
Influenza viruses are disease-causing agents belonging to the Orthomyxoviridae family. Influenza A viruses (IFVs) infect a broad range of hosts, including humans, pigs, dogs, horses, and birds, and they are known to evolve into highly pathogenic strains. The emergence of novel IFVs have been known to cause pandemics in recent history, such as the influenza pandemic of 2009, and the potential emergence of a highly pathogenic avian influenza virus strain into a pandemic remains a global health concern [1]. In addition to influenza viruses, coronaviruses, such as the causative agents of severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the new SARS-CoV-2 have recently emerged as threats to global health, thereby necessitating new control strategies against emerging viral infections
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