Antiviral therapies against Ebola and other emerging viral diseases using existing medicines that block virus entry

Abstract

Emerging viral diseases pose a threat to the global population as intervention strategies are mainly limited to basic containment due to the lack of efficacious and approved vaccines and antiviral drugs. The former was the only available intervention when the current unprecedented Ebolavirus (EBOV) outbreak in West Africa began. Prior to this, the development of EBOV vaccines and anti-viral therapies required time and resources that were not available. Therefore, focus has turned to re-purposing of existing, licenced medicines that may limit the morbidity and mortality rates of EBOV and could be used immediately. Here we test three such medicines and measure their ability to inhibit pseudotype viruses (PVs) of two EBOV species, Marburg virus (MARV) and avian influenza H5 (FLU-H5). We confirm the ability of chloroquine (CQ) to inhibit viral entry in a pH specific manner. The commonly used proton pump inhibitors, Omeprazole and Esomeprazole were also able to inhibit entry of all PVs tested but at higher drug concentrations than may be achieved in vivo. We propose CQ as a priority candidate to consider for treatment of EBOV.

Keywords: H5N1; Marburg; avian influenze; chloroquine; ebola; emerging viral disease; esomeprazole; omemprazole.

Figure 1.. Inhibition of pseudotype virus entry by existing FDA-approved drugs

293T cells previously transfected with a Renilla expression plasmid were treated with differing concentrations of drug before being transduced with PV (carried out in triplicate). Data are the percent of infection compared to untreated cells. EBOV-Z, EBOV-B, MARV, FLU-H5 and GALV inhibition was measured for each drug compound. Cells were harvested and firefly and Renilla activity measured after 48 h incubation. A. Cells were treated with 10, 3.33 and 1.11nM of BafA1. B. Cells were treated with 30, 10, 3.33 and 1.11µM of CQ. C and D. Cells were treated with 100, 50 and 25µM of OM and ESOM, respectively. Statistical analysis of these data are shown in Table 1.

Figure 2.. Correlation of decreased pH with inhibitory effect on entry.

A549 cells were treated with drug for 1 h before 75nM Lysotracker ^® Red DND-99 was added to each well. DMSO (drug vehicle) only was diluted at 30mM, 3mM, 0.3mM and 0.03mM. ( A–D). CQ was diluted 30, 10, 3.33 and 1.11µM ( E–H), BafA1 was diluted to 10, 3.33 and 1.11nM ( I–L) and OM and ESOM were diluted to 100, 50 and 25µM ( M–P) and ( Q–T) respectively. The level of fluorescence was imaged by confocal microscopy (x50 magnification).