Effect of a Histone Demethylase Inhibitor on Equine Herpesvirus-1 Activity In Vitro.

Rebecca L Tallmadge,M Julia B Felippe,Gerlinde R Van De Walle,Emilija Žygelytė,Thomas M Kristie

doi:10.3389/fvets.2018.00034

Abstract

Equine herpesvirus type 1 (EHV-1) is a ubiquitous and highly contagious pathogen that causes a range of disease severities with outbreaks of notable economic impact. Given the limitations in immune protection of current vaccines and the limited effectiveness of antiviral drugs on EHV-1 infections in vivo, improved treatment measures are needed to control disease. The use of drugs that alter the epigenetic state of herpes simplex virus genome has been shown to limit viral primary infection and reactivation both in vitro and in vivo. Therefore, we tested the hypothesis that maintaining a repressive epigenetic state on the EHV-1 genome in the host equine cell would decrease viral load during lytic infection. Equine fetal kidney cells (EFKCs) or isolated peripheral blood leukocytes were treated in vitro with (a) the nucleoside analog ganciclovir; (b) the histone demethylase inhibitor OG-L002; (c) both ganciclovir and OG-L002; or (d) dimethyl sulfoxide (DMSO, vehicle control); and then infected with a clinical EHV-1 isolate. Treatment of EFKCs with ganciclovir (mean 22.3 DNA copies per cell, p = 0.0005), OG-L002 (mean 25.6, p = 0.005) or both ganciclovir and OG-L002 (mean 7.1, p = 0.0001) resulted in decreased EHV-1 viral load at 24 h post-infection (hpi) in comparison with DMSO (mean 42.0), with greater impact using the combined treatment. Further, EHV-1 gene expression at 3 hpi decreased when EFKCs were infected in the presence of ganciclovir (p = 0.04) and combined treatment of ganciclovir and OG-L002 (p = 0.0003). In contrast, under similar conditions, neither ganciclovir nor OG-L002 suppressed EHV-1 infection in leukocytes. Differences between cell types, drug penetrance, or drug turnover, may have contributed to the distinct effects observed in this study.

Highlights

Equine herpesvirus 1 (EHV-1) is a serious threat to horses worldwide [1]
The objective of this work was to measure the effect of inhibition of the histone demethylase lysine-specific demethylase 1 (LSD1) on Equine herpesvirus type 1 (EHV-1) lytic infection in vitro
To quantify EHV-1 viral load in the presence of ganciclovir and/ or OG-L002 during lytic infection of primary Equine fetal kidney cells (EFKCs) in vitro, DNA was harvested at 24 hpi and Quantitative PCR (qPCR) performed for EHV-1 gB and equine SP1 targets

Summary

Introduction

Equine herpesvirus 1 (EHV-1) is a serious threat to horses worldwide [1]. EHV-1 outbreaks have emphasized the potential effects of this virus including: [1] severe respiratory disease, neurological disease, abortion, or death; [2] the highly contagious nature of the virus; [3] incomplete protection from vaccination and antiviral therapy; and [4] substantial economic costs for the equine industry [2,3,4,5,6,7,8,9,10,11]. The prevalence of EHV-1 among 4,228 horses with fever, respiratory signs, and/or. Equine herpesvirus 1 infection is initiated by inhalation of infectious virus, whereupon the virus enters epithelial cells of the upper respiratory tract and replicates, leading to viral shedding via nasal discharge, and further spreading of the infection [16]. EHV-1 upper respiratory tract entry facilitates infection of leukocytes, enabling the virus to circulate and infect endothelial cells of the central nervous system, leading to myeloencephalopathy; or reach the pregnant uterus, causing late-term abortion [17,18,19]

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