An oligothiophene compound neutralized influenza A viruses by interfering with hemagglutinin

Background and ObjectivesRecently influenza pandemic outbreaks were caused by emerging H5N1, H7N9 and H1N1 viruses. However, virucidal disinfectants are mainly unspecific and toxic. It is tactical to discover specific virucidal compounds.MethodsThe inhibitory potency was determined in H5N1 pseudovirus system; Interactions of compounds with hemagglutinin (HA) were detected with surface plasmon resonance (SPR) and further calculated with molecular docking. Virucidal effect was also estimated in influenza virus A/Puerto Rico/8/34(H1N1). Prevention efficacy was further estimated in mice model.ResultsOligothiophene compound 4sc was potently virucidal against H5N1 pseudovirus with selective index > 1169 (IC₅₀ = 0.17 ± 0.01 μM). Pseudovirus assay revealed 4sc may interact with HA. However, HA inhibition test indicated 4sc did not interact with receptor pocket in HA. SPR detection revealed 4sc interacted directly with HA and its HA2 subunits. Molecular docking analysis revealed that 4sc interacted with the cavity of HA2 stem region and HA1-HA2 interface which consist of 7 residues: L2₂, K26₂, G47₂ and F110₂ in HA2; M24₁, E25₁ and N27₁ in HA1. 4sc also potently and irreversibly neutralized PR8 (H1N1) virus, causing 10^{5.06 ± 0.26} fold decrease of virus titer after exposure for 10 min. 4sc blocked PR8 transmission to MDCK cells. Amazingly, virucidal effect of 4sc was not significantly reduced even at 4 °C. Furthermore, 4sc blocked viral transmission to mice.ConclusionOligothiophene compound 4sc is a novel selective virucide of influenza virus, which blocks entry by interfering viral hemagglutinin. Due to promising safety profile and stable virucidal effect at 4 °C, 4sc may be useful in disinfecting H5N1 and H1N1 influenza virus.