The limited treatment options for the increasing occurrence of Lassa hemorrhagic fever in West Africa poses an urgent need for the discovery and development of novel therapeutics.Dietary supplements,especially natural products that are edible and safe for human use,are a good source of drug discovery with potential for uncovering novel applications,In this study,we tested 40 natural products of dietary supplements and identified capsaicin,a common dietary supplement abundant in chili peppers,as an inhibitor of Lassa virus(LASV)entry with EC5,of 6.9-10.0μmol/L using an HIV based pseudo virus platform.Capsaicin inhibits the entry of five LASV strains but not against the Old World arenavirus lymphocytic choriomeningitis virus(LCMV),showing a preferential activity against LASV.Capsaicin inhibits LASV entry by blocking the pH dependent viral fusion through affecting the stable signal peptide(SSP)-GP2 transmembrane(GP2TM)region of the LASV surface glycoprotein.Mutational study revealed the key residues Ala25,Val431,Phe434 and Val435 in SsP-CP2TM region in capsaicin’s antiviral effect.This study for the first time reveals a direct acting antiviral effect of capsaicin against the hemorrhagic fever causing LASV,providing detailed interaction hot spots in the unique SSP-GP2TMinterface of LASV glycoprotein that is crucial in fusion inhibition,and offering a new strategy in discovering and developing antivirals from natural products that are safe for human use.
Filoviruses cause severe and fatal viral hemorrhagic fever in humans. Filovirus research has been extensive since the 2014 Ebola outbreak. Due to their high pathogenicity and mortality, live filoviruses require Biosafety Level-4(BSL-4) facilities, which have restricted the development of anti-filovirus vaccines and drugs.An HIV-based pseudovirus cell infection assay is widely used for viral entry studies in BSL-2 conditions. Here,we successfully constructed nine in vitro pseudo-filovirus models covering all filovirus genera and three in vivo pseudo-filovirus-infection mouse models using Ebola virus, Marburg virus, and Lloviu virus as representative viruses. The pseudo-filovirus-infected mice showed visualizing bioluminescence in a dose-dependent manner. A bioluminescence peak in mice was reached on day 5 post-infection for Ebola virus and Marburg virus and on day4 post-infection for Lloviu virus. Two known filovirus entry inhibitors, clomiphene and toremiphene, were used to validate the model. Collectively, our study shows that all genera of filoviruses can be well-pseudotyped and are infectious in vitro. The pseudo-filovirus-infection mouse models can be used for in vivo activity evaluation of anti-filovirus drugs. This sequential in vitro and in vivo evaluation system of filovirus entry inhibitors provides a secure and efficient platform for screening and assessing anti-filovirus agents in BSL-2 facilities.
