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

人类疱疹病毒引起终身潜伏感染，在完全启动的免疫系统面前可能发生重新激活。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），一组独特的短（US）区域的基因编码了一组在所有可能的结构上相似的I型膜糖蛋白。在组织培养系统中分析，其中一些基因，特别是US2、US3、US6和us11，已知会干扰MHC I类限制性抗原呈递。为了补充最近确定的I-US2类结构，我们启动了HCMV US3产品的结构研究。我们将进一步分析U21的作用模式和结构，U21是一种hhv7编码的免疫逃避蛋白，也下调MHC I类分子。由于没有HCMV感染的动物模型，关于HCMV US簇中编码的免疫逃避素的生物学作用的建议仍然是推测性的。携带US基因的小鼠巨细胞病毒重组体（单独或联合）将与流感基质蛋白一起产生，后者将作为“乘客”抗原，以便枚举抗原特异性T细胞。我们将用这些病毒感染HLA-A2和I-ILA-B7转基因小鼠，这些小鼠的内源性H-2K和H-2D基因通过基因靶向被破坏。这些动物必须依靠人类限制因子来产生CD8 T细胞，其存在和频率将通过适当的hla - I类肽四聚体来确定。鉴于US基因产物与MHC I类抗原之间的密切联系，将对一些临床HCMV分离株进行US2、US3、US6和us11基因的核苷酸序列测定，优选从不同民族、不同MHC I类等位基因集合和分布的人群中获得。这一分析将揭示人群中MHC等位基因是否以及在多大程度上帮助形成免疫逃避素的“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.