Lieber A, He C Y, Meuse L, Himeda C, Wilson C, Kay M A
Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, Washington 98115, USA.
J Virol. 1998 Nov;72(11):9267-77. doi: 10.1128/JVI.72.11.9267-9277.1998.
NF-kappaB is a key regulator of the innate antiviral immune response, due in part to its transcriptional activation of cytokines and adhesion molecules, which, in turn, function in chemotaxis and activation of inflammatory cells. We reported earlier that viral gene expression in hepatocytes transduced with first-generation (E1-deleted) adenoviruses induced NF-kappaB activation, elevation of serum cytokines, and hepatocellular apoptosis during the first days postinfusion. These events did not occur in mice infused with an adenovirus vector deleted for E1, E2, E3, and late gene expression. In the present study, we used an adenovirus expressing an IkappaBalpha supersuppressor (Ad.IkappaBM) and bcl-2 transgenic mice to unravel the role of virus-induced NF-kappaB activation and apoptosis in the clearance of recombinant adenovirus vectors from the liver. The combined action of IkappaBM and Bcl-2 allowed for vector persistence in livers of C57BL/6 x C3H mice. In the absence of Bcl-2, IkappaBM expression in mouse livers significantly reduced NF-kappaB activation, cytokine expression, leukocyte infiltration, and the humoral immune response against the transgene product; however, this was not sufficient to prevent the decline of vector DNA in transduced cells. Infusion of Ad.IkappaBM caused extended apoptosis predominantly in periportal liver regions, indicating that NF-kappaB activation may protect transduced hepatocytes from apoptosis induced by adenovirus gene products. To confer vector persistence, bcl-2 transgene expression was required to block virus-induced apoptosis if NF-kappaB protection was inactivated by IkappaBM. Expression of gene products involved in early stages of apoptotic pathways was up-regulated in response to virus infusion in bcl-2 transgenic mice, which may represent a compensatory effect. Our study supports the idea that the suppression of innate defense mechanisms improves vector persistence.
核因子κB是先天性抗病毒免疫反应的关键调节因子，部分原因在于其对细胞因子和黏附分子的转录激活作用，而这些细胞因子和黏附分子反过来又在趋化作用以及炎症细胞的激活中发挥作用。我们之前报道过，在输注第一代（E1缺失）腺病毒转导的肝细胞中，病毒基因表达在输注后的头几天会诱导核因子κB激活、血清细胞因子升高以及肝细胞凋亡。而在输注缺失E1、E2、E3和晚期基因表达的腺病毒载体的小鼠中，这些情况并未发生。在本研究中，我们使用了一种表达IκBα超抑制剂（Ad.IκB M）的腺病毒和bcl-2转基因小鼠，以阐明病毒诱导的核因子κB激活和凋亡在重组腺病毒载体从肝脏清除过程中的作用。IκB M和Bcl-2的联合作用使得载体能够在C57BL/6×C3H小鼠肝脏中持续存在。在没有Bcl-2的情况下，小鼠肝脏中IκB M的表达显著降低了核因子κB激活、细胞因子表达、白细胞浸润以及针对转基因产物的体液免疫反应；然而，这并不足以阻止转导细胞中载体DNA的减少。输注Ad.IκB M主要在肝门周围区域导致广泛的凋亡，这表明核因子κB激活可能保护转导的肝细胞免受腺病毒基因产物诱导的凋亡。为了使载体持续存在，如果核因子κB的保护作用被IκB M灭活，则需要bcl-2转基因表达来阻断病毒诱导的凋亡。在bcl-2转基因小鼠中，响应病毒输注，凋亡途径早期阶段涉及的基因产物表达上调，这可能代表一种补偿效应。我们的研究支持了先天防御机制的抑制可提高载体持久性这一观点。
