Discovery of inhibitory materials against PEDV corona virus from medicinal plants

Abstract

Coronaviruses (CoVs) are one type of enveloped viruses with single-stranded RNA genome. They contain the largest genome to date, ranging from approximately 26 to 32 kilobases. During CoVs replication, genes encoding the viral structural proteins, including nucleocapsid (N), membrane (M), spike (S), and envelope (E), are key elements for viral integrity. CoVs infections are a major cause of enteric, respiratory, and central nervous system diseases at both animals and humans. An outbreak of SARS-CoV infections in 2002-2003 caused severe acute respiratory syndrome (SARS) of more than 8,000 individuals and 774 fatalities worldwide. Middle East Respiratory Syndrome coronavirus (MERS-CoV), which were occurred Saudi Arabia in 2012, shows a recent outbreak of a completely novel respiratory virus. MERS on May in 2015 abruptly broke out in Korea and 36 patients of infected 186 persons were died. These experiences in Korea suggest that MERS outbreak or other CoVsinfectious diseases should be prepared to control for the protection of human health. There are four common CoVs infecting animals, including porcine epidemic diarrhea virus (PEDV), canine coronavirus (CCV), avian infectious bronchitis virus (IBV), and transmissible gastroenteritis coronavirus (TGEV). PEDV can spread via vertical transmission through lactation or the fecal-oral route. By targeting the epithelial cells of the small intestine PEDV can cause severe mucosal atrophy and malabsorption, and result in acute and lethal diarrhea in piglets. PEDV infection can cause a high mortality in piglets and fattening swine with almost 100% for one-week old piglets. Recently, new PEDV was noticed in USA for the first time in May 2013, and its outbreak affects 23 US states by the end of January of 2014. PEDV infection in US swine industry caused severe watery diarrhea, variable vomiting, dehydration, and high mortality in affected swine, especially neonatal piglets resulting severe economic loss. In concerning about the control and eradication of PEDV infection, generous efforts have been made with major focus on preventive therapy by vaccination. However, as an oral vaccine for preventing PEDV infections is still not able to significantly alter the duration of virus shedding, an effective control strategy may be the benefit to prevent such infections. Natural products have been regarded as a rich source of novel chemical entities with unique pharmacological activities. During the course of our antiviral screening programs from natural products for PEDV, we screened strong inhibitory materials by using of virus-induced cell death method by PEDV. A CPE assay, RT-PCR analysis, western blot analysis, and immunofluorescence assay supported that some candidates from natural products showed potent and promising inhibitory effects on PEDV replication by targeting key structural protein synthesis and relevant gene expression. These studies provided a new class of natural scaffolds that may be able to be developed as potential anti-PEDV agents via inhibiting viral replication. The clear SARs outlined will facilitate the further structure optimization of this compound class for developing novel antiviral agents. Furthermore, human corona viruses, like SARS or MERS, from the same Coronaviridae family share a similar replication mechanism with PEDV. Therefore, the anti-PEDV molecules obtained in this study will also be used for further investigation against the fatal human coronaviruses, including SARS or MERS.