PDF(Pubmed)
Abstract：
Herpesviruses establish a well-adapted balance with their host\'s immune system. Despite this co-evolutionary balance, infections can lead to severe disease including neurological disorders in their natural host. In horses, equine herpesvirus 1 (EHV-1) causes respiratory disease, abortions, neonatal foal death and myeloencephalopathy (EHM) in ~10 % of acute infections worldwide. Many aspects of EHM pathogenesis and protection from EHM are still poorly understood. However, it has been shown that the incidence of EHM increases to >70 % in female horses >20 years of age. In this study we used old mares as an experimental equine EHV-1 model of EHM to identify host-specific factors contributing to EHM. Following experimental infection with the neuropathogenic strain EHV-1 Ab4, old mares and yearling horses were studied for 21 days post-infection. Nasal viral shedding and cell-associated viremia were assessed by quantitative PCR. Cytokine/chemokine responses were evaluated in nasal secretions and cerebrospinal fluid (CSF) by Luminex assay and in whole blood by quantitative real-time PCR. EHV-1-specific IgG sub-isotype responses were measured by ELISA. All young horses developed respiratory disease and a bi-phasic fever post-infection, but only 1/9 horses exhibited ataxia. In contrast, respiratory disease was absent in old mares, but all old mares developed EHM that resulted in euthanasia in 6/9 old mares. Old mares also presented significantly decreased nasal viral shedding but higher viremia coinciding with a single fever peak at the onset of viremia. According to clinical disease manifestation, horses were sorted into an EHM group (nine old horses and one young horse) and a non-EHM group (eight young horses) for assessment of host immune responses. Non-EHM horses showed an early upregulation of IFN-α (nasal secretions), IRF7/IRF9, IL-1β, CXCL10 and TBET (blood) in addition to an IFN-γ upregulation during viremia (blood). In contrast, IFN-α levels in nasal secretions of EHM horses were low and peak levels of IRF7, IRF9, CXCL10 and TGF-β (blood) coincided with viremia. Moreover, EHM horses showed significantly higher IL-10 levels in nasal secretions, peripheral blood mononuclear cells and CSF and higher serum IgG3/5 antibody titres compared to non-EHM horses. These results suggest that protection from EHM depends on timely induction of type 1 IFN and upregulation cytokines and chemokines that are representative of cellular immunity. In contrast, induction of regulatory or TH-2 type immunity appeared to correlate with an increased risk for EHM. It is likely that future vaccine development for protection from EHM must target shifting this \'at-risk\' immunophenotype.
摘要：
疱疹病毒与宿主的免疫系统建立了良好的适应性平衡。尽管有这种共同进化的平衡，感染可导致严重的疾病，包括其天然宿主的神经系统疾病。在马,马疱疹病毒1（EHV-1）引起呼吸道疾病，堕胎,在全球约10％的急性感染中，新生儿马驹死亡和骨髓脑病（EHM）。EHM发病机理和对EHM的保护的许多方面仍然知之甚少。然而,已经表明,在>20岁的雌马中,EHM的发病率增加到>70%。在这项研究中，我们使用老母马作为EHM的实验马EHV-1模型，以确定导致EHM的宿主特异性因素。在用神经致病性菌株EHV-1Ab4进行实验性感染后，在感染后21天研究了老马和一岁马。通过定量PCR评估鼻腔病毒脱落和细胞相关病毒血症。通过Luminex测定法在鼻分泌物和脑脊液（CSF）中以及通过定量实时PCR在全血中评估细胞因子/趋化因子反应。通过ELISA测量EHV-1特异性IgG亚同种型应答。所有幼马在感染后出现呼吸道疾病和双相性发热,但只有1/9的马表现出共济失调。相比之下,在老母马中没有呼吸道疾病，但是所有的老母马都发展了EHM，导致6/9的老母马安乐死。老母马也表现出显着减少的鼻病毒脱落，但病毒血症较高，与病毒血症发作时的单个发烧高峰相吻合。根据临床表现,将马分为EHM组(九匹老马和一匹幼马)和非EHM组(八匹幼马)以评估宿主免疫应答。非EHM马显示IFN-α（鼻分泌物）的早期上调，IRF7/IRF9,IL-1β,CXCL10和TBET(血液)以及病毒血症期间的IFN-γ上调(血液)。相比之下,EHM马鼻分泌物中的IFN-α水平较低，IRF7，IRF9，CXCL10和TGF-β（血液）的峰值水平与病毒血症相吻合。此外，EHM马在鼻腔分泌物中显示出显著较高的IL-10水平，与非EHM马相比，外周血单核细胞和CSF以及更高的血清IgG3/5抗体滴度。这些结果表明，对EHM的保护取决于1型IFN的及时诱导以及代表细胞免疫的上调细胞因子和趋化因子。相比之下,调节或TH-2型免疫的诱导似乎与EHM风险增加相关。未来针对EHM的保护疫苗开发可能必须以改变这种“处于危险中”的免疫表型为目标。
