IN SILICO EVALUATION OF SILVESTROL, ROCAGLAMIDE AND OTHER FLAVAGLINE COMPOUNDS AS POSSIBLE HEPATITIS E VIRUS INHIBITORS

Hepatitis E Virus (HEV) is a small positive sense single stranded RNA virus member of the Hepiviridae family, particularly of the Orthohepevirus genus. It leads to 20 million HEV estimated infections/year worldwide and 3.3 million symptomatic cases of Hepatitis E, according to the World Health Organization [1]. While the fatality rate usually ranges from 0.2% to 4%, it significantly increases for pregnant women [2]. The virus spreads via waterborne, zoonotic and foodborne transmission depending both on the considered country and on the considered HEV genotype [3, 4]. Pigs are the main reservoirs but even game and livestock, with all the related meat-based products, are a major source of infection [5-9]. Unfortunately, HEV in vitro culture and analysis are still difficult, resulting in a poor understanding of its molecular biology [10]. Moreover, HEV encodes for only one non-structural protein (ORF1): a multifunctional, multidomain, non-cleaved polyprotein which could be a potential druggable target but whose crystallization results unfeasible due to size-related reasons (185 kDa) [11]. In this context, an in-silico approach succeeded at overcoming the lack of HEV ORF1 structural data, allowing the identification of potential anti-viral compounds. Based on previous studies showing the inhibitory activity of the natural plant secondary metabolite silvestrol against HEV [12], our study provided a reliable model to: I) investigate the underpinning mechanisms; and II) provide a predictive framework to estimate the activity of silvestrol analogues for further dedicated investigations. The HEV RNA Helicase domain was modelled and refined via a homology modelling approach based on an innovative, crystallome-based strategy. Then the interaction with 9 silvestrol-related compounds, including rocaglamide and silvestrol, and 2 virtual decoys recovered from the DUD-E database, was computed via docking and molecular dynamics simulations. Overall, our study presented mechanistic insights on HEV RNA Helicases and silvestrol dependent inhibition, expanded the current understanding of the structure-activity relationship for Silvestrol-related compounds and provided a blueprint for further analysis targeting the HEV RNA Helicase. Eventually, in-depth investigation is warmly sought to possibly extend the usage of either silvestrol, rocaglamide or some of the related natural compounds as feed additives in order to reduce the HEV diffusion in livestock. Notably, silvestrol has already been proven to be well tolerated in animals [13].