Development of Virus-Specific CD4+ and CD8+ Regulatory T Cells Induced by Human Herpesvirus 6 Infection

Human herpesvirus 6 (HHV-6) is an important immunosuppressive and immunomodulatory virus. The mechanisms by which HHV-6 establishes latency and immunosuppression in its host are not well understood. Here we characterized HHV-6-specific T cells in peripheral blood mononuclear cells (PBMCs) from HHV-6-infected donors. Our results showed that HHV-6 infection could induce both CD4⁺ and CD8⁺ HHV-6-specific regulatory T (Treg) cells. These HHV-6-specific Treg cells had potent suppressive activity and expressed high levels of Treg-associated molecules CD25, FoxP3, and GITR. Both CD4⁺ and CD8⁺ Treg cells secreted gamma interferon (IFN-γ) and interleukin-10 (IL-10) but little or no IL-2, IL-4, or transforming growth factor β (TGF-β). Furthermore, HHV-6-specifc Treg cells not only could suppress naive and HHV-6-specific CD4⁺ effector T cell immune responses but also could impair dendritic cell (DC) maturation and functions. In addition, the suppressive effects mediated by HHV-6-specific Treg cells were mainly through a cell-to-cell contact-dependent mechanism but not through the identified cytokines. These results suggest that HHV-6 may utilize the induction of Treg cells as a strategy to escape antivirus immune responses and maintain the latency and immunosuppression in infected hosts.     

Determinants of Human CD134 Essential for Entry of Human Herpesvirus 6B

We identified two key amino acid residues within human CD134 (hCD134) that are required for its interaction with human herpesvirus 6B (HHV-6B) and for HHV-6B entry into cells. One of the residues (K79) allows access of the HHV-6B ligand to hCD134. Murine CD134 (mCD134) functioned as an HHV-6B receptor when these two amino acid residues were replaced with homologous human residues. This study identifies both the HHV-6B receptor-ligand interaction and the species-specific determinants of hCD134 essential for HHV-6B entry.     

人疱疹病毒6型的研究进展

人疱疹病毒6型(HHV-6)是一种新发现的疱疹病毒,属于β亚科。HHV-6感染与一些疾病的发生相关。如幼儿急疹、器官移植后并发症、AIDS以及人类某些肿瘤等。就HHV-6的生物学特性、流行病学以及与人类疾病的关系等作一综述。     

Human Herpesvirus 6 and Measles Virus Employ Distinct CD46 Domains for Receptor Function

We employed a quantitative cell fusion assay to identify structural domains of CD46 required for its function as a receptor for human herpesvirus 6 (HHV-6). We examined the activities of recombinant variants of CD46, including different isoforms as well as engineered truncations and molecular chimeras with decay-accelerating factor, a related protein in the family of regulators of complement activation (RCA). We observed strong receptor activity for all four CD46 isoforms, which differ in the membrane-proximal extracellular and cytoplasmic domains, indicating that the critical determinants for HHV-6 receptor activity reside outside the C-terminal portion of CD46. Analysis of the short consensus repeat (SCR) regions that comprise most of the extracellular portion of CD46 indicated a strong dependence on SCRs 2 and 3 and no requirement for SCRs 1 or 4. Fusion-inhibition studies with SCR-specific monoclonal antibodies supported the essential role of SCRs 2 and 3 in HHV-6 receptor activity. These findings contrast markedly with fusion mediated by measles virus glycoproteins for which we observed a strict dependence on SCRs 1 and 2, consistent with previous reports. These results expand the emerging notion that CD46 and other members of the RCA family are co-opted in distinct manners by different infectious pathogens.     

HHV6感染激活卡波济肉瘤相关疱疹病毒(KSHV)的溶解性周期复制

运用细胞融合、细胞混合培养、条件培养基培养和病毒直接刺激等方法,研究人类疱疹病毒6型(HHV6)对卡波济肉瘤相关疱疹病毒(KSHV)溶解性周期复制的影响。①将HHV6感染的JJhan细胞(T淋巴细胞系)与BCBL-1细胞(原发性渗出性淋巴瘤,PEL)进行细胞融合形成异核体细胞。②将HHV6感染的JJhan细胞与BcBL-1细胞进行混合培养。③收集HHV6感染的JJhan细胞培养上清液作为条件培养基进行灭活处理,以灭活前后的条件培养基培养BcBL-1细胞。进一步离心纯化HHV6病毒颗粒,并感染BCBL-1细胞,分别设紫外线和热灭活的HHV6病毒颗粒感染BCBL-1细胞为对照。提取上述的实验细胞总RNA,RT-PCR和／或实时定量(Real-time)PCR检测卡波济肉瘤相关疱疹病毒(KSHV)次要衣壳蛋白编码基因ORF26 mRNA转录。结果显示：①细胞融合后15h开始出现明显细胞病变,RT-PCR检测不同时间的实验组ORF26 mRNA转录水平均明显高于对照组;Real-time PCR检测各时间ORF26 mRNA转录水平是对照组的2．3倍以上;②细胞混合培养72h时,实验组ORF26 mRNA转录水平是对照组的1．8倍;混合培养5天时,实验组KSHV裂解周期蛋白K8．1表达水平是对照组的2．46倍;③灭活前后的HHV6感染细胞培养上清液培养BCBL-1细胞96h时,ORF26 mRNA转录水平分别是对照组的2．73倍和2．22倍;④灭活前后的HHV6均可增强BCBL-1细胞中KStHV ORF26 mRNA转录水平。提示：KHV6感染可激活KSHV的溶解性周期复制。     

人类疱疹病毒6型及其与某些疾病的关系

人类疱疹病毒6型(human herpes virus type 6,HHV-6)是1986年从淋巴增殖异常患者及艾滋病病人外周血单核细胞中,首先分离到的一种具有疱疹病毒形态和嗜淋巴细胞的新病毒。人类感染HHV-6十分普遍,多为隐性感染。可在60%～80%儿童及成人血清中查到HHV-6抗体。HHV-6是婴儿急疹(玫瑰疹)的病原体,并证实与淋巴增殖性疾病、自身免疫病和免疫缺陷病人的感染等有关。随着器官移植的发展和艾滋病病人的增多,HHV-6感染变得日益重要。     

Human herpesvirus 6 infection of CD4+ T-cell subsets

The immune system includes CD4+ regulatory T (T reg) cells that play a role in self-tolerance and demonstrate functional variations that govern immune responses. HHV-6 is an important immunosuppressive virus that completely replicates in vivo and in vitro in only CD4+ T cells. However, there have been no reports of the specific T-cell subpopulation that permits the replication of this virus. Here, we evaluated the infectivity of HHV-6 to specific T-cell populations such as CD4+CD25 high, which includes the majority of T reg cells, and CD4+CD25(-). These cells were isolated from peripheral blood and then expanded. The expanded cell fractions were then infected with the HHV-6 variant B strain, and the spreads of infected cells were evaluated by immunofluorescence. Viral growth was also quantified by real-time PCR. The effects of virus infection on cytokine production from these T-cell subsets were examined using ELISA. Our results revealed that both these fractions permitted complete HHV-6 replication. Virus infection enhanced the production of both Th1- and Th2-type cytokines from CD4+CD25(-) T cells; however, only Th2-type cytokine release was augmented from viral-infected CD4+CD25 high T cells. Further, while virusinfected CD4+CD25 high T cells shift their antiviral immunity toward Th2 dominance by producing IL-10, the role of virus-infected CD4+CD25(-) T cells remains obscure.     

人FUT4基因近端启动子结构的初步分析

LeY是一种双岩藻糖化寡糖,在大多数上皮来源的肿瘤细胞（包括乳腺癌、卵巢癌等）中高表达.岩藻糖基转移酶Ⅳ（fucosyltransferase Ⅳ, FUT4）是合成LeY的关键酶. 前期工作发现,FUT4通过增加LeY糖的合成来促进细胞的增殖. 但有关FUT4的转录调控机制尚不清楚. 本文通过对人FUT4基因近端启动子进行生物信息学分析,并构建不同长度启动子序列荧光虫荧光素酶报告基因表达载体,分析其转录活性. 使用First EF程序分析并获得FUT4近端启动子序列,采用PCR 法扩增FUT4基因近端不同长度的启动子序列,定向克隆,获得不同长度的启动子重组质粒. 重组质粒经双酶切及测序鉴定正确. 荧光素酶活性分析不同长度的FUT4 基因启动子片段的转录活性.结果显示,pGL6-FUT4-1.2 kb在MCF-7和MDA- MB-231细胞中转录活性明显升高（P<0.05）.说明FUT4基因启动子区域定位于转 录起始位点上游的-800～-1 600 bp的区域内.     

脂筏在人类疱疹病毒6型装配中的作用

为了探讨脂筏在人类疱疹病毒6型(HHV-6)装配中的作用,用HHV-6 GS株感染HSB2细胞,用非离子去污剂Triton X-100提取脂筏成分,利用Western blot分析HHV-6包膜糖蛋白与脂筏的相关性.并用免疫荧光双标记的方法,从分子共定位的角度研究HHV-6糖蛋白B(gB)与GPI(glycosyl-phosphatidyl inosital)锚固蛋白CD59分子以及神经节苷脂GMI(monosialotetrahexosyl ganglioside)分子之间的表达与分布关系.结果发现HHV-6包膜糖蛋白B、H、L、Q1和Q2(gB、gH、gL、gQ1和gQ2)分布在脂筏部位.激光共聚焦显微镜可观察到CD59分子及GM1均与HHV-6包膜糖蛋白B有着相同的分布,即脂筏提供HHV-6装配的平台.关于脂筏在人类疱疹病毒6型装配中的作用,这是第一次报道.     

Evolutionary History of Endogenous Human Herpesvirus 6 Reflects Human Migration out of Africa

Human herpesvirus 6A and 6B (HHV-6) can integrate into the germline, and as a result, ∼70 million people harbor the genome of one of these viruses in every cell of their body. Until now, it has been largely unknown if 1) these integrations are ancient, 2) if they still occur, and 3) whether circulating virus strains differ from integrated ones. Here, we used next-generation sequencing and mining of public human genome data sets to generate the largest and most diverse collection of circulating and integrated HHV-6 genomes studied to date. In genomes of geographically dispersed, only distantly related people, we identified clades of integrated viruses that originated from a single ancestral event, confirming this with fluorescent in situ hybridization to directly observe the integration locus. In contrast to HHV-6B, circulating and integrated HHV-6A sequences form distinct clades, arguing against ongoing integration of circulating HHV-6A or “reactivation” of integrated HHV-6A. Taken together, our study provides the first comprehensive picture of the evolution of HHV-6, and reveals that integration of heritable HHV-6 has occurred since the time of, if not before, human migrations out of Africa.     

Human CD4+ T cell response to human herpesvirus 6

Following primary infection, human herpesvirus 6 (HHV-6) establishes a persistent infection for life. HHV-6 reactivation has been associated with transplant rejection, delayed engraftment, encephalitis, muscular dystrophy, and drug-induced hypersensitivity syndrome. The poor understanding of the targets and outcome of the cellular immune response to HHV-6 makes it difficult to outline the role of HHV-6 in human disease. To fill in this gap, we characterized CD4 T cell responses to HHV-6 using peripheral blood mononuclear cell (PBMC) and T cell lines generated from healthy donors. CD4(+) T cells responding to HHV-6 in peripheral blood were observed at frequencies below 0.1% of total T cells but could be expanded easily in vitro. Analysis of cytokines in supernatants of PBMC and T cell cultures challenged with HHV-6 preparations indicated that gamma interferon (IFN-γ) and interleukin-10 (IL-10) were appropriate markers of the HHV-6 cellular response. Eleven CD4(+) T cell epitopes, all but one derived from abundant virion components, were identified. The response was highly cross-reactive between HHV-6A and HHV-6B variants. Seven of the CD4(+) T cell epitopes do not share significant homologies with other known human pathogens, including the closely related human viruses human herpesvirus 7 (HHV-7) and human cytomegalovirus (HCMV). Major histocompatibility complex (MHC) tetramers generated with these epitopes were able to detect HHV-6-specific T cell populations. These findings provide a window into the immune response to HHV-6 and provide a basis for tracking HHV-6 cellular immune responses.