Functional analysis of the chemokine and chemokine receptors encoded by human herpesvirus 6.

人肝炎病毒6型(HHV-6)属于β疱疹病毒亚科，在体外主要感染T细胞和单个核细胞，可引起急性和潜伏性感染。HHV-6的两个变种是根据几种特性的不同而区分出来的。我们测定了HHV-6变异株B株(HHV-6B)的DNA全序列，并与A变异株U1102的DNA序列进行了比较。在HHV-6全基因组161,573个碱基的连续序列中，共有115个潜在的开放阅读框(ORF)，其中包括一些氨基酸同源性显著不同的基因。HST株U83编码一种趋化因子，对单核细胞具有趋化作用。同样，菌株U1102的U83编码趋化因子同系物，但不包含信号肽序列。因此，U1102菌株U83可能不能分泌，从而不能发挥其趋化活性。如果U83在v…中起化学诱导剂的作用更多的是，HHV-6可能很容易通过细胞间感染传播，即使在存在中性抗体的情况下也是如此。Z29株的U12基因被截短，不编码由HST株编码的CC趋化因子的钙动员受体。Z29株的致病机理尚不清楚。这些结果提示，U12的产物可能通过与CC-趋化因子结合的跨膜信号在HHV-6的致病过程中发挥重要作用。U83基因包含一个编码113个氨基酸的ORF，从第一个蛋氨酸开始，含有一个可能的信号肽和典型的半胱氨酸残基，具有趋化因子的特征。逆转录-聚合酶链式反应和感染细胞的免疫荧光抗体检测均表明该编码蛋白为晚期蛋白。将与Fc基因融合的ORF U83基因在COS-7细胞中以融合蛋白的形式表达，并从细胞培养上清液中纯化融合蛋白，检测其生物学功能。纯化的蛋白能够诱导THP-1细胞的瞬时钙动员，并对THP-1细胞具有化学激活作用。这些发现表明，U83蛋白可能通过激活和运输单个核细胞到病毒复制部位而在HHV-6体内传播中发挥重要作用，从而有助于发展高效的病毒生产机制。较少

Human henpesvirus 6(HHV-6), which belongs to the betaherpesvirus subfamily and infects mainly T cells and mononuclear cells in vitro, causes acute and latent infections. Two variants of HHV-6 have been distinguished on the basis of differences in several properties. We have determined the complete DNA sequence of HHV-6 variant B(HHV-6B)strain HST, the causative agent of exanthem subitum, and compared the sequence with that of variant A strain U1102. A total of 115 potential open reading frames(ORFs)were identified within the 161,573-bp contiguous sequence of the entire HHV-6 genome, including some genes with remarkable differences in amino acid identity. U83 of strain HST encodes a chemokine, which functions as a chemoattractant for monocytes. Similarly, U83 of strain U1102 encodes a chemokine homolog, but it does not contain a signal peptide sequence. Thus, U83 of strain U1102 may not be secreted and thus cnnot exert its chemotactic activity. If U83 functions as a chemoattractant in v … More ivo, it is possible that HHV-6 can easily spread through cell-to-cell infection, even in the presence of neutral antibodies. U12 of strain Z29 is truncated and dose not encode a calcium-mobilizing receptor for CC-chemokines which is encoded by that of strain HST.Nobody know the pathogenesis of strain Z29. These findigns suggested that the product of U12 may play an important role in the pathogenesis of HHV-6 through transmembrane signaling by binding with CC-chemokines.We have cloned the U83 gene and analyzed the biological function of this gene. The U83 gene contained an ORF encoding a 113-amino-acid peptide, starting at the first methionine and containing a possible signal peptide and the typical cysteine residues chanacteristic of the chemokines. Reverse transcription-PCR analysis of mRNA and immunofluorescent-antibody testing of infected cells both indicated that the encoded protein was a late protein. The ORF U83 gene fused to the FC gene was expressed as a fusion protcin in COS-7 cells by tnansfection, and the fusion protein was purified from the supernatant of transfected cells to test its biological function. The purified protein was capable of inducing transient calcium mobilization in THP-1 cells and of chemotactically activating THP-1 cells. These findings suggested that the U83 protein might play an important role in HHV-6 propagation in vivo by activating and trafficking mononuclear cells to sites of vira replication, thus aiding the development of superbly efficient virus production mechanisms. Less