Viral Immunology Center, Department of Biology, Georgia State University, Atlanta, Georgia, USA.
Department of Ophthalmology, Emory University School of Medicine, Atlanta, Georgia, USA.
J Virol. 2018 Aug 29;92(18). doi: 10.1128/JVI.00526-18. Print 2018 Sep 15.
AIDS-related human cytomegalovirus retinitis remains the leading cause of blindness among untreated HIV/AIDS patients worldwide. To study mechanisms of this disease, we used a clinically relevant animal model of murine cytomegalovirus (MCMV) retinitis with retrovirus-induced murine AIDS (MAIDS) that mimics the progression of AIDS in humans. We found in this model that MCMV infection significantly stimulates ocular suppressor of cytokine signaling 1 (SOCS1) and SOCS3, host proteins which hinder immune-related signaling by cytokines, including antiviral type I and type II interferons. The present study demonstrates that in the absence of retinal disease, systemic MCMV infection of mice without MAIDS, but not in mice with MAIDS, leads to mild stimulation of splenic SOCS1 mRNA. In sharp contrast, when MCMV is directly inoculated into the eyes of retinitis-susceptible MAIDS mice, high levels of intraocular SOCS1 and SOCS3 mRNA and protein are produced which are associated with significant intraocular upregulation of gamma interferon (IFN-γ) and interleukin-6 (IL-6) mRNA expression. We also show that infiltrating macrophages, granulocytes, and resident retinal cells are sources of intraocular SOCS1 and SOCS3 protein production during development of MAIDS-related MCMV retinitis, and SOCS1 and SOCS3 mRNA transcripts are detected in retinal areas histologically characteristic of MCMV retinitis. Furthermore, SOCS1 and SOCS3 are found in both MCMV-infected cells and uninfected cells, suggesting that these SOCS proteins are stimulated via a bystander mechanism during MCMV retinitis. Taken together, our findings suggest a role for MCMV-related stimulation of SOCS1 and SOCS3 in the progression of retinal disease during ocular, but not systemic, MCMV infection. Cytomegalovirus infection frequently causes blindness in untreated HIV/AIDS patients. This virus manipulates host cells to dysregulate immune functions and drive disease. Here, we use an animal model of this disease to demonstrate that cytomegalovirus infection within eyes during retinitis causes massive upregulation of immunosuppressive host proteins called SOCS. As viral overexpression of SOCS proteins exacerbates infection with other viruses, they may also enhance cytomegalovirus infection. Alternatively, the immunosuppressive effect of SOCS proteins may be protective against immunopathology during cytomegalovirus retinitis, and in such a case SOCS mimetics or overexpression treatment strategies might be used to combat this disease. The results of this work therefore provide crucial basic knowledge that contributes to our understanding of the mechanisms of AIDS-related cytomegalovirus retinitis and, together with future studies, may contribute to the development of novel therapeutic targets that could improve the treatment or management of this sight-threatening disease.
艾滋病相关的人巨细胞病毒视网膜炎仍然是全球未经治疗的艾滋病毒/艾滋病患者失明的主要原因。为了研究这种疾病的机制,我们使用了一种具有临床相关性的鼠巨细胞病毒 (MCMV) 视网膜炎动物模型,该模型通过逆转录病毒诱导的鼠艾滋病 (MAIDS) 模拟了人类艾滋病的进展。我们在该模型中发现,MCMV 感染显著刺激眼部细胞因子信号转导抑制因子 1 (SOCS1) 和 SOCS3,这些宿主蛋白通过细胞因子阻碍免疫相关信号,包括抗病毒的 I 型和 II 型干扰素。本研究表明,在没有视网膜疾病的情况下,无 MAIDS 的小鼠全身性 MCMV 感染而非 MAIDS 小鼠的 MCMV 感染会导致脾脏 SOCS1 mRNA 的轻度刺激。相比之下,当 MCMV 直接接种到易发生视网膜炎的 MAIDS 小鼠的眼睛中时,眼内会产生高水平的 SOCS1 和 SOCS3 mRNA 和蛋白,这与眼内 γ干扰素 (IFN-γ) 和白细胞介素-6 (IL-6) mRNA 表达的显著上调相关。我们还表明,在 MAIDS 相关 MCMV 视网膜炎发展过程中,浸润的巨噬细胞、粒细胞和固有视网膜细胞是眼内 SOCS1 和 SOCS3 蛋白产生的来源,并且在组织学上具有 MCMV 视网膜炎特征的视网膜区域检测到 SOCS1 和 SOCS3 mRNA 转录本。此外,在 MCMV 感染的细胞和未感染的细胞中均发现 SOCS1 和 SOCS3,这表明在 MCMV 视网膜炎期间,这些 SOCS 蛋白通过旁观者机制被刺激。综上所述,我们的发现表明,在眼部而非全身性 MCMV 感染期间,MCMV 相关刺激 SOCS1 和 SOCS3 在视网膜疾病的进展中发挥作用。巨细胞病毒感染常导致未经治疗的艾滋病毒/艾滋病患者失明。该病毒操纵宿主细胞以失调免疫功能并引发疾病。在这里,我们使用该疾病的动物模型证明,在视网膜炎期间,眼内的巨细胞病毒感染会导致大量免疫抑制宿主蛋白 SOCS 的上调。由于 SOCS 蛋白的病毒过度表达会加剧其他病毒的感染,因此它们也可能增强巨细胞病毒的感染。或者,SOCS 蛋白的免疫抑制作用可能对巨细胞病毒视网膜炎期间的免疫病理学具有保护作用,在这种情况下,SOCS 模拟物或过表达治疗策略可能被用于对抗这种疾病。这项工作的结果因此提供了至关重要的基础知识,有助于我们理解与艾滋病相关的巨细胞病毒视网膜炎的机制,并且结合未来的研究,可能有助于开发新的治疗靶点,从而改善这种威胁视力的疾病的治疗或管理。