Assessment of the antiviral properties of recombinant surfactant protein D against influenza B virus in vitro

•Influenza B viruses are highly sensitive to the neutralizing activity of recombinant porcine SP-D (RpSP-D).•RpSP-D efficiently inhibits agglutination of red blood cells by influenza B viruses and reduces infection of MDCK cells with influenza B viruses.•RpSP-D blocks binding of influenza B viruses to epithelial cells of ferret and human respiratory tract.

The armamentarium of antiviral drugs against influenza viruses is limited. Furthermore, influenza viruses emerge that are resistant to existing antiviral drugs like the M2 and NA inhibitors. Therefore, there is an urgent need for the development of novel classes of antiviral drugs. Here we investigated the antiviral properties of recombinant porcine surfactant protein D (RpSP-D), an innate defense molecule with lectin properties, against influenza B viruses. We have previously shown that porcine SP-D has more potent neutralizing activity against influenza A viruses than human SP-D. Here we show that RpSP-D neutralizes influenza B viruses efficiently and inhibited the binding of these viruses to epithelial cells of the human trachea.