Pan-antiviral effects of a PIKfyve inhibitor on respiratory virus infection in human nasal epithelium and mice

ABSTRACT Endocytosis, or internalization through endosomes is a major cell entry mechanism used by respiratory viruses. Phosphoinositide 5-kinase (PIKfyve) is a critical enzyme for the synthesis of Phosphatidylinositol (3,5)biphosphate (PtdIns(3,5)P2), and has been implicated in virus trafficking via the endocytic pathway. In fact, antiviral effects of PIKfyve inhibitors against SARS-CoV-2 and Ebola have been reported, but there is little evidence regarding other respiratory viruses. In this study we demonstrated the antiviral effects of PIKfyve inhibitors on influenza virus and respiratory syncytial virus in vitro and in vivo . PIKfyve inhibitors, Apilimod mesylate (AM) and YM201636 concentration-dependently inhibited several influenza strains in a MDCK cell-cytopathic assay. AM also reduced the viral load and cytokine release, whilst improving the cell integrity of human nasal air liquid interface cultured epithelium infected with influenza PR8. In PR8-infected mice, AM (2mg/ml), when intranasally treated, exhibited significant reduction of viral load and inflammation and inhibited weight loss caused by influenza infection, with effects being similar to oral oseltamivir (10 mg/kg). In addition, AM demonstrated anti-viral effects in RSV A2 infected human nasal epithelium in vitro and mouse in vivo , with equivalent effect to that of ribavirin. AM also showed anti-viral effects against human rhinovirus and seasonal coronavirus in vitro . Thus, PIKfyve is found to be involved in influenza and RSV infection, and PIKfyve inhibitor is a promising molecule for pan-viral approach against respiratory viruses.