Functional Analysis of FIV ORF-A

描述（由申请人提供）：猫免疫缺陷病毒（FIV），猫的一种慢病毒，引起类似于人类免疫缺陷病毒（HIV）的艾滋病。FIV感染的临床过程与人类的HIV感染相似。在实验性感染FIV几周后，猫会出现类似HIV感染的急性临床综合征，包括低烧和短暂的全身淋巴结肿大。随后是一段较长的无症状期，由于CD4+细胞逐渐减少，CD8+细胞也逐渐增加，CD4+:CD8+细胞比例下降。与HIV类似，FIV基因组除了编码结构蛋白的基因外，还包含几个开放阅读框（orf）。ORF-A基因产物在体外激活FIV启动子依赖基因的表达。对ORF-A缺陷FIV的感染研究表明，病毒在体外和体内的复制都减少了。在感染ORF-A缺陷FIV的猫中，外周血CD4:CD8比值降低的发病延迟。胸腺细胞亚群的比较表明，在ORF-A缺陷FIV感染的猫中，单个阳性CD4-CD8+胸腺细胞的扩增减少。观察到感染ORF-A缺陷突变体的猫的病毒复制减少和测量免疫缺陷参数的延迟，表明该蛋白在FIV引起的疾病进展中很重要。通过测定ORF-A存在和不存在时不同原代细胞中病毒基因的表达水平，我们将确定ORF-A在控制细胞向性和细胞病理中的作用。这些研究结合ORF-A功能特征的解剖将阐明ORF-A在FIV发病机制中的作用。

DESCRIPTION (provided by applicant):Feline immunodeficiency virus (FIV), a lentivirus of cats, causes an AIDS similar to what is seen in humans with human immunodeficiency virus (HIV). The clinical course of FIV infection parallels HIV infection in humans. A few weeks after experimental infection with FIV, cats develop an acute clinical syndrome like the HIV infection, including low-grade fever and transient generalized lymph node enlargement. This is followed by a long asymptomatic period in which the CD4+:CD8+ cell ratio declines because of a gradual decrease in CD4+ cells, and an increase in CD8+ cells as well. Similar to HIV, the FIV genome contains several open reading frames (ORFs) in addition to genes encoding for the structural proteins. The ORF-A gene product transactivates FIV promoter-dependent gene expression in vitro. Infection studies with ORF-A defective FIV show that virus replication is reduced both in vitro and in vivo. In cats infected with ORF-A defective FIV the onset of reduced peripheral blood CD4:CD8 ratio is delayed. Comparison of thymocyte subpopulations demonstrated a reduced expansion of single positive CD4-CD8+ thymocytes in ORF-A defective FIV infected cats. The observation that there is a reduction in virus replication and delay of the onset of parameters that measure immunodeficiency in cats infected with an ORF-A defective mutant suggests that this protein is important in the progress of disease caused by FIV. By determining the level of viral gene expression in different primary cells in the presence and absence of ORF- A, we will define the role of ORF-A in controlling the cell tropism and cytopathology. These studies in combination with dissection of functional characterization of the ORF-A will clarify the role of ORF-A in FIV pathogenesis.