Arimilli Subhashini, Johnson John B, Alexander-Miller Martha A, Parks Griffith D
Department of Microbiology and Immunology, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157-1064, USA.
Virology. 2007 Aug 15;365(1):144-56. doi: 10.1016/j.virol.2007.02.035. Epub 2007 Apr 24.
Infection of primary cultures of human immature monocyte-derived dendritic cells (moDC) with the paramyxovirus Simian Virus 5 (SV5) results in extensive cytopathic effect (CPE) and induction of apoptosis, but DC maturation pathways are not activated. In this study, we investigated the relationship between SV5-induced apoptosis and the lack of DC maturation. Reducing CPE and apoptosis in SV5-infected immature DC by the addition of a pancaspase inhibitor resulted in only low level expression of maturation markers CD40, CD80 and CD86, suggesting that SV5 infection either actively blocked maturation pathways or failed to provide sufficient signals to activate maturation. To distinguish between these hypotheses, SV5-infected immature DC were challenged with agonists that stimulate toll-like receptors (TLRs). Treatment with the TLR-4 agonist LPS or TLR-6 agonist FSL1 enhanced cell surface expression of CD40, CD80 and CD86 on SV5-infected cells to levels approaching that of mock-infected TLR-treated moDC, but treatment with agonists for TLR-2, -3, -5 or -8 had little effect. Addition of TLR-4 or -6 agonists to SV5-infected DC also dramatically reduced CPE and apoptosis, but the levels of viral protein and virus yield were not affected. Similarly, SV5-infected immature moDC were matured by treatment with IL-1beta, and these mature infected cells also showed reduced CPE and apoptosis. In the presence of NFkB inhibitors, TLR-4 and -6 agonists did not promote maturation or reduce apoptosis of SV5-infected DC, indicating that maturation and cell survival were both dependent on signaling through NFkB-dependent pathways. Our results suggest a model whereby SV5 replication induces apoptosis in immature DC but fails to provide strong maturation signals, while activation of NFkB-dependent pathways by exogenous ligands can lead to moDC maturation and override SV5-induced cell death.
用人未成熟单核细胞衍生的树突状细胞（moDC）的原代培养物感染副粘病毒猴病毒5（SV5）会导致广泛的细胞病变效应（CPE）并诱导细胞凋亡，但DC成熟途径未被激活。在本研究中，我们调查了SV5诱导的细胞凋亡与DC成熟缺失之间的关系。通过添加泛半胱天冬酶抑制剂来减少SV5感染的未成熟DC中的CPE和细胞凋亡，结果仅导致成熟标志物CD40、CD80和CD86的低水平表达，这表明SV5感染要么主动阻断成熟途径，要么未能提供足够的信号来激活成熟。为了区分这些假设，用刺激Toll样受体（TLR）的激动剂对SV5感染的未成熟DC进行刺激。用TLR-4激动剂LPS或TLR-6激动剂FSL1处理可将SV5感染细胞上CD40、CD80和CD86的细胞表面表达提高到接近 mock感染的TLR处理的moDC的水平，但用TLR-2、-3、-5或-8的激动剂处理几乎没有效果。向SV5感染的DC中添加TLR-4或-6激动剂也显著降低了CPE和细胞凋亡，但病毒蛋白水平和病毒产量不受影响。同样，用IL-1β处理可使SV5感染的未成熟moDC成熟，这些成熟的感染细胞也显示出CPE和细胞凋亡减少。在存在NFkB抑制剂的情况下，TLR-4和-6激动剂不会促进SV5感染的DC成熟或减少细胞凋亡，这表明成熟和细胞存活均依赖于通过NFkB依赖性途径的信号传导。我们的结果提出了一个模型，即SV5复制在未成熟DC中诱导细胞凋亡，但未能提供强烈的成熟信号，而外源性配体激活NFkB依赖性途径可导致moDC成熟并克服SV5诱导的细胞死亡。
