School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, United Kingdom.
J Virol. 2011 Jul;85(14):7321-32. doi: 10.1128/JVI.00021-11. Epub 2011 May 4.
Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS), an endothelial cell (EC) neoplasm characterized by dysregulated angiogenesis and inflammation. KSHV infection of EC causes production of proinflammatory mediators, regarded as possible initiators of the substantial mononuclear leukocyte recruitment seen in KS. Conversely, KSHV immune evasion strategies exist, such as degradation of EC leukocyte adhesion receptors by viral proteins. Here, we report the effects of KSHV infection of primary EC on recruitment of flowing leukocytes. Infection did not initiate adhesion of any leukocyte subset per se. However, on cytokine-stimulated EC, KSHV specifically inhibited neutrophil, but not PBL or monocyte, transmigration, an observation consistent with the inflammatory cell profile found in KS lesions in vivo. This inhibition could be recapitulated on uninfected EC using supernatant from infected cultures. These supernatants contained elevated levels of human interleukin 6 (hIL-6), and both the KSHV- and the supernatant-induced inhibitions of neutrophil transmigration were abrogated in the presence of a hIL-6 neutralizing antibody. Furthermore, preconditioning of EC with hIL-6 mimicked the effect of KSHV. Using RNA interference (RNAi), we show that upregulation of suppressor of cytokine signaling 3 (SOCS3) was necessary for this effect of hIL-6. These studies reveal a novel paracrine mode of KSHV immune evasion, resulting in reduced recruitment of neutrophils, a cell type whose antiviral and antitumor roles are becoming increasingly appreciated. Moreover, the findings have implications for our understanding of the contribution of hIL-6 to the pathogenesis of other inflammatory disorders and tumors in which this cytokine is abundant.
卡波西肉瘤相关疱疹病毒(KSHV)是卡波西肉瘤(KS)的病原体,KS 是一种内皮细胞(EC)肿瘤,其特征是血管生成和炎症失调。KSHV 感染 EC 会导致促炎介质的产生,这些介质被认为是 KS 中大量单核白细胞募集的可能启动子。相反,KSHV 存在免疫逃避策略,例如病毒蛋白降解 EC 白细胞黏附受体。在这里,我们报告了 KSHV 感染原代 EC 对流动白细胞募集的影响。感染本身不会引发任何白细胞亚群的黏附。然而,在细胞因子刺激的 EC 上,KSHV 特异性抑制中性粒细胞,但不抑制 PBL 或单核细胞的迁移,这一观察结果与体内 KS 病变中发现的炎症细胞特征一致。在用感染培养物的上清液处理未感染的 EC 时,可以重现这种抑制作用。这些上清液中含有高水平的人白细胞介素 6(hIL-6),并且 KSHV 和上清液诱导的中性粒细胞迁移抑制作用均可在 hIL-6 中和抗体存在下被消除。此外,hIL-6 预处理 EC 可模拟 KSHV 的作用。通过 RNA 干扰(RNAi),我们表明,细胞因子信号转导抑制剂 3(SOCS3)的上调对于 hIL-6 的这种作用是必需的。这些研究揭示了 KSHV 免疫逃避的一种新的旁分泌模式,导致中性粒细胞募集减少,而这种细胞类型的抗病毒和抗肿瘤作用正越来越受到重视。此外,这些发现对于我们理解 hIL-6 对其他富含这种细胞因子的炎症性疾病和肿瘤发病机制的贡献具有重要意义。