(-)-Epigallocatechin-3-Gallate Inhibits the Life Cycle of Pseudorabies Virus In Vitro and Protects Mice Against Fatal Infection.

Haochun Pan,Song Gao,Hengyue Zou,Tingting Guo,Luyao Jiang,Changchao Huan,Weiyin Xu,Chengmin Li

doi:10.3389/fcimb.2020.616895

Abstract

A newly emerged pseudorabies virus (PRV) variant with enhanced pathogenicity has been identiﬁed in many PRV-vaccinated swine in China since 2011. The PRV variant has caused great economic cost to the swine industry, and measures for the effective prevention and treatment of this PRV variant are still lacking. (–)-Epigallocatechin-3-gallate (EGCG) exhibits antiviral activity against diverse viruses and thus in this study, we investigated the anti-PRV activity of EGCG in vitro and in vivo. EGCG significantly inhibited infectivity of PRV Ra and PRV XJ5 strains in PK15 B6 cells and Vero cells. The anti-PRV activity of EGCG was dose-dependent, and 50 μM EGCG could completely block viral infection at different multiplicities of infection. We next revealed that EGCG blocked PRV adsorption and entry to PK15 B6 cells in a dose-dependent manner, but inhibition of PRV entry by EGCG was not as efficient as its inhibition of PRV adsorption. PRV replication was suppressed in PK15 B6 cells treated with EGCG post-infection. However, EGCG did not affect PRV assembly and could promote PRV release. Furthermore, 40 mg/kg EGCG provided 100% protection in BALB/c mice challenged with PRV XJ5, when EGCG was administrated both pre- and post-challenge. These results revealed that EGCG exhibits antiviral activity against PRV mainly by inhibiting virus adsorption, entry and replication in vitro. Meanwhile, EGCG increased the survival of mice challenged with PRV. Therefore, EGCG might be a potential antiviral agent against PRV infection.

Highlights

Pseudorabies, a disease caused by pseudorabies virus (PRV) which infects both domestic and wild animals, is characterized by fever, severe itching, respiratory and nervous system disorders, and encephalomyelitis (Brittle et al, 2004)
PK15 B6 cells were infected with PRV XJ5 (MOI=0.1) at 4°C for 1 h, infected cells were treated with 10, 20, or 50 mM EGCG for 1 h, before removal of the EGCG medium and culture in EGCG-free Dulbecco’s modified Eagle medium (DMEM). (A) At 24 hpi, PRV gE, UL42, and b-actin protein expression were quantified by Western blot. (B) PRV gB DNA was quantified by qRT-PCR, (C) virus titer was evaluated by 50% tissue culture infective dose (TCID50) and (D) immunofluorescent assay (IFA) for internalized virus was performed. **p < 0.01
EGCG is a polyphenolic compound found in green tea extracts and possesses many beneficial properties, including antiviral activities (Xu et al, 2017)

Summary

INTRODUCTION

Pseudorabies, a disease caused by pseudorabies virus (PRV) which infects both domestic and wild animals, is characterized by fever, severe itching (except in pigs), respiratory and nervous system disorders, and encephalomyelitis (Brittle et al, 2004). (–)-Epigallocatechin-3-gallate (EGCG) is the most abundant bioactive polyphenol found in solid green tea extracts and has a variety of physiological and pharmacological effects on human health (McKay and Blumberg, 2002; Chacko et al, 2010) It has antibacterial, antiviral, antioxidant, antiarthritic, antiangiogenic, anti-inflammatory and antitumor activities (Haqqi et al, 1999; Osada et al, 2001; Sartippour et al, 2002; Dona et al, 2003; Weber et al, 2003; Sudano Roccaro et al, 2004). In vivo studies demonstrated antiviral activity of EGCG in BALB/c mice challenged intraperitoneally with a lethal dose of PRV These results suggested that EGCG could be further developed as an antiviral agent against PRV infection

MATERIALS AND METHODS

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DISCUSSION