Alkyl-imino sugars inhibit the pro-oncogenic ion channel function of human papillomavirus (HPV) E5

Despite the availability of prophylactic vaccines the burden of human papillomavirus (HPV) associated malignancy remains high and there is a need to develop additional therapeutic strategies to complement vaccination. We have previously shown that the poorly characterised E5 oncoprotein forms a virus-coded ion channel or viroporin that was sensitive to the amantadine derivative rimantadine. We now demonstrate that alkylated imino sugars, which have antiviral activity against a number of viruses, inhibit E5 channel activity in vitro. Using molecular modelling we predict that imino sugars intercalate between E5 protomers to prevent channel oligomerisation. We explored the ability of these viroporin inhibitors to block E5-mediated activation of mitogenic signalling in keratinocytes. Treatment with either rimantadine or imino sugars prevented ERK-MAPK phosphorylation and reduced cyclin B1 expression in cells expressing E5 from a number of high-risk HPV types. Moreover, viroporin inhibitors also reduced ERK-MAPK activation and cyclin B1 expression in differentiating primary human keratinocytes containing high-risk HPV18. These observations provide evidence of a key role for E5 viroporin function during the HPV life cycle. Viroporin inhibitors could be utilised for stratified treatment of HPV associated tumours prior to virus integration, or as true antiviral therapies to eliminate virus prior to malignant transformation.