VIRAL EVASION STRATEGIES: ANALYSIS OF HERPES VIRUSES HSV, VZV AND HHV-6-7

人类疱疹病毒会导致终身潜伏感染，在完全启动的免疫系统面前，可能会发生重新激活。这种病毒策略需要逃避宿主的免疫反应。对于人类巨细胞病毒(HCMV)来说，独特的短(US)区的一组基因编码一组结构上非常相似的I型膜糖蛋白。其中几个基因，特别是US2、US3、US6和US11，在组织培养系统中分析时，已知干扰MHC I类限制性抗原提呈。为了补充最近对I-US2类结构的确定，我们启动了对HCMV US3产物的结构研究。我们将进一步分析U21的作用模式和结构，U21是一种HHV7编码的免疫血管蛋白，也下调MHC I类分子。由于目前还没有人巨细胞病毒感染的动物模型，因此关于巨细胞病毒US簇中编码的免疫因子的生物学作用的建议仍然是推测的。将产生单独或组合配备US基因的小鼠CMV重组体，以及流感基质蛋白，该蛋白将作为“乘客”抗原，允许计数抗原特异性T细胞。用这些病毒感染内源性H-2K和H-2D基因已被基因打靶打乱的人类白细胞抗原A2和I-ILA-B7转基因小鼠。这些动物必须依靠人类的限制因素来产生CD8T细胞，CD8T细胞的存在和频率将由适当的人类白细胞抗原-I类多肽四聚体来确定。鉴于US基因产物与MHC I类抗原之间的密切联系，将确定一些临床分离株的US2、US3、US6和US11基因的核苷酸序列，最好从具有不同MHC I类等位基因集合和分布的不同种族中获得。这项分析应该会揭示人类群体中的MHC等位基因是否以及在多大程度上帮助形成了免疫球蛋白的“曲目”。

Human Herpesviruses cause a life-long latent infection, from which reactivation can occur in the face of a fully primed immune system. This viral strategy necessitates evasion of host immune reactions. For human cytomegalovirus (HCMV), a set of genes in the unique short (US) region encode a collection of in all likelihood structurally similar-type I membrane glycoproteins. Several of these genes, notably US2, US3, US6 and US 11, are known to interfere with MHC class I restricted antigen presentation when analyzed in tissue culture systems. To complement the recent determination of the Class I-US2 structure we have initiated structural studies of the HCMV US3 product. We shall further analyze the mode of action and structure of U21, an HHV7-encoded immunoevasin that also down-regulates MHC class I molecules. Because there is no animal model for HCMV infection, the suggestions for the biological role of the immunoevasins encoded in the HCMV US cluster remain conjectural. Murine CMV recombinants equipped with the US genes, alone or in combination, will be generated, along with the flu matrix protein, which will serve as the "passenger" antigen to allow enumeration of antigen-specific T cells. With these viruses we shall infect HLA-A2 and I-ILA-B7 transgenic mice in which the endogenous H-2K and H-2D genes have been disrupted through gene targeting. These animals must rely on the human restriction elements for the generation of CD8 T cells, the presence and frequency of which will be determined with the appropriate HLA-Class I peptide tetramers. In view of the intimate connection between the US gene products and MHC class I antigens, the nucleotide sequence of the US2, US3, US6 and US 11 genes will be determined for a number of clinical HCMV isolates, to be obtained preferably from different ethnic groups with different sets and distributions of MHC class I alleles. This analysis should reveal if and to what extent the MHC alleles in the human population help shape the "repertoire" of immunoevasins.