Kim Seong K, Shakya Akhalesh K, O'Callaghan Dennis J
Department of Microbiology and Immunology and Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
Department of Microbiology and Immunology and Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA.
J Virol. 2016 Aug 26;90(18):8090-104. doi: 10.1128/JVI.00986-16. Print 2016 Sep 15.
Equine herpesvirus 1 (EHV-1) is a major pathogen affecting equines worldwide. The virus causes respiratory disease, abortion, and, in some cases, neurological disease. EHV-1 strain KyA is attenuated in the mouse and equine, whereas wild-type strain RacL11 induces severe inflammation of the lung, causing infected mice to succumb at 4 to 6 days postinfection. Our previous results showed that KyA immunization protected CBA mice from pathogenic RacL11 challenge at 2 and 4 weeks postimmunization and that KyA infection elicited protective humoral and cell-mediated immune responses. To investigate the protective mechanisms of innate immune responses to KyA, KyA-immunized mice were challenged with RacL11 at various times postvaccination. KyA immunization protected mice from RacL11 challenge at 1 to 7 days postimmunization. Immunized mice lost less than 10% of their body weight and rapidly regained weight. Virus titers in the lungs of KyA-immunized mice were 1,000-fold lower at 2 days post-RacL11 challenge than virus titers in the lungs of nonimmunized mice, indicating accelerated virus clearance. Affymetrix microarray analysis revealed that gamma interferon (IFN-γ) and 16 antiviral interferon-stimulated genes (ISGs) were upregulated 3.1- to 48.2-fold at 8 h postchallenge in the lungs of RacL11-challenged mice that had been immunized with KyA. Murine IFN-γ inhibited EHV-1 infection of murine alveolar macrophages and protected mice against lethal EHV-1 challenge, suggesting that IFN-γ expression is important in mediating the protection elicited by KyA immunization. These results suggest that EHV-1 KyA may be used as a live attenuated EHV-1 vaccine as well as a prophylactic agent in horses.
Viral infection of cells initiates a signal cascade of events that ultimately attempts to limit viral replication and prevent infection through the expression of host antiviral proteins. In this study, we show that EHV-1 KyA immunization effectively protected CBA mice from pathogenic RacL11 challenge at 1 to 7 days postvaccination and increased the expression of IFN-γ and 16 antiviral interferon-stimulated genes (ISGs). The administration of IFN-γ blocked EHV-1 replication in murine alveolar macrophages and mouse lungs and protected mice from lethal challenge. To our knowledge, this is the first report of an attenuated EHV-1 vaccine that protects the animal at 1 to 7 days postimmunization by innate immune responses. Our findings suggested that IFN-γ serves as a novel prophylactic agent and may offer new strategies for the development of anti-EHV-1 agents in the equine.
马疱疹病毒1型（EHV-1）是一种影响全球马匹的主要病原体。该病毒可引起呼吸道疾病、流产，在某些情况下还会导致神经疾病。EHV-1 KyA株在小鼠和马中具有减毒作用，而野生型RacL11株可诱导严重的肺部炎症，导致感染小鼠在感染后4至6天死亡。我们之前的结果表明，KyA免疫可在免疫后2周和4周保护CBA小鼠免受致病性RacL11的攻击，并且KyA感染可引发保护性体液免疫和细胞介导的免疫反应。为了研究对KyA的固有免疫反应的保护机制，在接种疫苗后的不同时间用RacL11对经KyA免疫的小鼠进行攻击。KyA免疫可在免疫后1至7天保护小鼠免受RacL11的攻击。免疫小鼠体重减轻不到10%，并迅速恢复体重。在RacL11攻击后2天，经KyA免疫的小鼠肺部病毒滴度比未免疫小鼠肺部病毒滴度低1000倍，表明病毒清除加速。Affymetrix微阵列分析显示，在经KyA免疫的RacL11攻击小鼠的肺部，γ干扰素（IFN-γ）和16种抗病毒干扰素刺激基因（ISG）在攻击后8小时上调了3.1至48.2倍。小鼠IFN-γ抑制EHV-1对小鼠肺泡巨噬细胞的感染，并保护小鼠免受致死性EHV-1攻击，这表明IFN-γ的表达在介导KyA免疫引发的保护作用中很重要。这些结果表明，EHV-1 KyA可作为一种减毒活EHV-1疫苗以及马匹的预防剂。
细胞的病毒感染引发一系列信号事件，最终试图通过宿主抗病毒蛋白的表达来限制病毒复制并预防感染。在本研究中，我们表明EHV-1 KyA免疫在接种疫苗后1至7天有效保护CBA小鼠免受致病性RacL11的攻击，并增加了IFN-γ和16种抗病毒干扰素刺激基因（ISG）的表达。IFN-γ的给药可阻断EHV-1在小鼠肺泡巨噬细胞和小鼠肺部的复制，并保护小鼠免受致死性攻击。据我们所知，这是关于一种减毒EHV-1疫苗在免疫后1至7天通过固有免疫反应保护动物的首次报道。我们的发现表明，IFN-γ可作为一种新型预防剂，并可能为马抗EHV-1药物的开发提供新策略。
