Modification of Host Chemokine Responses by Human Cytomegalovirus

描述（由申请方提供）：人巨细胞病毒（HCMV）是疱疹病毒科的一个成员，可操纵宿主免疫系统并建立终身潜伏感染。这种与宿主的成功共存是由病毒蛋白质的产生介导的，所述病毒蛋白质模拟正常的免疫调节剂，如细胞因子、趋化因子和趋化因子受体。HCMV编码四种与人趋化因子受体相似的蛋白，US 27、US 28、UL 33和UL 78。US 28和UL 33均表现出配体非依赖性组成型信号传导活性，并且US 28也已显示响应于细胞趋化因子而发出信号。相比之下，对于US 27没有识别出配体或信号传导结果，并且它仍然是孤儿受体。先前开发了表达US 27的稳定细胞系，以筛选US 27的可能的趋化因子配体。虽然未鉴定出配体，但我们意外地观察到US 27显著增强了人趋化因子受体CXCR 4对其天然配体CXCL 12/SDF-1？的信号传导。CXCR 4的许多重要生理作用之一涉及将免疫细胞引导至骨髓，骨髓是HCMV潜伏期的主要部位。通过US 27增强CXCR 4信号传导可能代表HCMV将病毒感染的细胞靶向骨髓以启动新一轮感染并扩大潜伏感染细胞的储存库的策略。具体 正在测试的假设是US 27与CXCR 4形成异聚体，刺激感染细胞向趋化因子CXCL 12/SDF-1？的运动增加。这一假设得到了强有力的初步数据的支持，表明表达US 27和CXCR 4的细胞表现出更大的钙动员和增强的趋化性响应CXCL 12/SDF-1？比对照组。此外，通过免疫荧光染色和共聚焦显微镜发现US 27和CXCR 4共定位于细胞中的离散位置。该提案的具体目标是确定在US 27存在下增加CXCR 4信号传导的机制，并确定在病毒感染的细胞中是否发生增强的CXCR 4应答。该项目的总体目标是阐明US 27在病毒发病机制中的作用，预计结果将揭示孤儿受体的新调节功能，可能影响HCMV潜伏期的维持。

DESCRIPTION (provided by applicant): Human cytomegalovirus (HCMV) is a member of the Herpesviridae family that manipulates the host immune system and establishes life-long latent infection. This successful co-existence with the host is mediated by the production of viral proteins that mimic normal immune modulators like cytokines, chemokines, and chemokine receptors. HCMV encodes four proteins with similarity to human chemokine receptors, US27, US28, UL33, and UL78. US28 and UL33 both exhibit ligand-independent constitutive signaling activity, and US28 has also been shown to signal in response to cellular chemokines. In contrast, no ligands or signaling outcomes have been identified for US27, and it remains an orphan receptor. A stable cell line expressing US27 was developed previously in order to screen for possible chemokine ligands for US27. While no ligands were identified, we made the unexpected observation that US27 significantly enhanced the signaling of a human chemokine receptor, CXCR4, in response to its natural ligand, CXCL12/SDF-1?. One of the many important physiological roles of CXCR4 involves directing immune cells to the bone marrow, which is the primary site of HCMV latency. Potentiation of CXCR4 signaling by US27 could represent a strategy by which HCMV targets virus-infected cells to the bone marrow in order to initiate a new round of infection and expand the reservoir of latently infected cells. The specific hypothesis being tested is that US27 forms heteromers with CXCR4 that stimulate increased movement of infected cells toward the chemokine CXCL12/SDF-1?. This hypothesis is supported by strong preliminary data demonstrating that cells expressing both US27 and CXCR4 exhibit greater calcium mobilization and enhanced chemotaxis in response to CXCL12/SDF-1? than controls. In addition, US27 and CXCR4 were found to co-localize to discrete locations in the cell by immunofluorescence staining and confocal microscopy. The specific goals of this proposal are to identify the mechanism for increased CXCR4 signaling in the presence of US27 and to determine whether enhanced CXCR4 responses occur in virus-infected cells. The overall goal of the project is to clarify the role of US27 in viral pathogenesi, and the results are expected to reveal a novel regulatory function for an orphan receptor with possible implications for the maintenance of HCMV latency.