Virus Infections In The Eye

我们对病毒和寄生虫在眼睛微环境中复制时发生的各种病毒学和免疫病理过程的研究包括五个方面：(1)病毒诱导的视网膜退化过程；(2)病毒在人类疾病中的可能作用；(3)人类巨细胞病毒(CMV)感染的分子诊断和发病机制；(4)眼睛的疱疹病毒感染；(5)视网膜的弓形虫感染。我们已经建立了一个研究视网膜退行性疾病的模型系统-实验性冠状病毒视网膜病变(EcoR)。该病毒能够在存在轻度视网膜血管炎症的情况下引发急性感染。最初的视网膜损伤之后是感染性病毒的清除和进行性的视网膜变性。这是第一个显示病毒引起的变性、病毒持久性、对病毒引起的组织损伤的遗传易感性和病毒引发的自身免疫反应的视网膜模型。我们的目标是确定视网膜退行性疾病的病理生理机制，并确定与之相关的基因。在过去的一年里，我们取得了以下重要发现。我们进行了EcoR的表征，以检测干扰素-γ在清除视网膜中的传染性病毒方面的潜在贡献。我们发现在EcoR过程中产生了干扰素-γ，并且在视网膜内检测到了干扰素-γ基因的表达。干扰素-γ的存在与宿主对MHV感染的免疫应答的激活有关，而干扰素-γ缺陷小鼠的缺乏与病毒性脑炎和死亡的急剧增加有关。这些研究表明，渗透到视网膜的细胞产生干扰素-γ是免疫机制的重要组成部分，该机制负责将传染性病毒从视网膜上清除出去。在动物模型系统的基础上，我们还启动了评估人类视网膜退行性疾病的研究。通过免疫细胞化学染色和免疫印迹分析，对不明原因视网膜病变患者进行自身抗体检测。用患者血清筛选大鼠视网膜表达文库，鉴定阳性克隆。其中一个克隆与晶状体上皮源性生长因子/转录共激活因子p52和p75/DSF70有88%的同源性。这些数据表明，在该患者中发现的针对p75/p52的抗体可能与她的视网膜病变有关。人类巨细胞病毒是一种疱疹病毒，是先天性感染儿童和免疫功能受损儿童失明的主要原因。人类巨细胞病毒潜伏期的研究比较困难。因此，CMV复制和潜伏期的细胞培养模型可能为替代治疗方式提供理论基础。趋化因子调节白细胞的运输，可能在炎症细胞重新聚集到视网膜中起重要作用。人巨细胞病毒感染hRPE细胞后，引起3种重要的趋化因子MCP-1、MCP-3和IL-8的调节。感染HCMV的hRPE中MCP-1和MCP-3的mRNA和蛋白水平均低于未感染的hRPE。相反，巨细胞病毒感染使IL-8mRNA和蛋白水平升高。由于趋化因子促进白细胞向炎症部位的迁移和激活，病毒对趋化因子产生的调节可能是视网膜炎和免疫恢复性葡萄膜炎中HCMV免疫逃避发病机制的一个可能机制。

Our studies of various virologic and immunopathologic processes that occur when viruses and parasites replicate in the ocular microenvironment comprise five areas: (1) virus induced retinal degenerative processes; (2) the possible roles of viruses in human diseases; (3) molecular diagnosis and pathogenesis of cytomegalovirus (CMV) infections in man; (4) herpesvirus infections of the eye and (5) Toxoplasma gondii infections of the retina. We have established a model system for studying retinal degenerative diseases, experimental coronavirus retinopathy (ECOR). The virus is capable of inducing an acute infection in the presence of mild retinal vascular inflammation. Initial retinal damage is followed by clearance of infectious virus and progressive retinal degeneration. This is the first retinal model to demonstrate a virus induced degeneration, viral persistence, a genetic predisposition to virus induced tissue damage and a virus triggered autoimmune response. Our goal is to determine the pathophysiological mechanisms and to identify genes involved in the retinal degenerative disease. During the past year we have made the following key findings. We undertook the characterization of ECOR to examine the potential contribution of IFN-gamma in the clearance of infectious virus in the retina. We found that IFN-gamma was produced during ECOR, and IFN-gamma gene expression was detected within the retina. The presence of IFN-gamma was asssociated with the activation of host immune response to MHV infection, and the absence of IFN-gamma in IFN-gamma deficient mice was associated with a dramatic increase in viral encephalitis and death. These studies indicate that generation of IFN-gamma by cells infiltrating the retina is an essential part of an immune mechanism responsible for noncytolytic clearance of infectious virus from the retina. Based on the animal model system, we have also initiated studies to evaluate human retinal degenerative diseases. Autoantibodies were detected in patients with retinopathy of unknown origin by immunocytochemical staining and western blot analysis. Using patient sera, a rat retina cDNA expression library was screened and positive clones were identified. One of the clones demonstrated 88% identity to lens epithelium-derived growth factor / transcription coactivators p52 and p75/DSF70. These data suggest that antibodies directed against p75/p52 identified in this patient may contribute to her retinopathy. Human CMV is a herpesvirus that is a major cause of blindness in children born with congenital infections and in immunocompromised individuals. It is difficult to study CMV latency in man. Therefore cell culture models of CMV replication and latency may provide insight into a rationale for alternative treatment modalities. Chemokines regulate leukocyte trafficking and may be important in inflammatory cell recruitment into the retina. HCMV infection in HRPE cells resulted in modulation of three important chemokines, MCP-1, MCP-3 and IL-8. The levels of MCP-1 and MCP-3 mRNA and protein in HCMV infected HRPE were reduced in comparison to uninfected HRPE. In contrast, HCMV infection enhanced IL-8 mRNA and protein levels. Because chemokines facilitate the migration and activation of leukocytes to the sites of inflammation, the modulation of chemokines production by the virus suggests a possible mechanism in immune evasion of immunopathogenesis for HCMV in retinitis and immune recovery uveitis.