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，在面对完全启动的免疫系统时可能会重新激活。这种病毒策略需要逃避宿主免疫反应。对于人巨细胞病毒（HCMV），在独特的短（US）区域的一组基因编码在所有可能性结构相似的I型膜糖蛋白的集合。这些基因中的几个，特别是US 2、US 3、US 6和US 11，已知在组织培养系统中分析时干扰MHC I类限制性抗原呈递。为了补充最近对I-US 2类结构的测定，我们已经启动了HCMV US 3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HHV 7编码的免疫evasin，也下调MHC I类分子。 由于没有HCMV感染的动物模型，因此对HCMV US簇中编码的免疫evasins的生物学作用的建议仍然是不确定的。将产生配备有US基因（单独或组合）的鼠CMV重组体，连同流感基质蛋白一起沿着，流感基质蛋白将充当“过客”抗原以允许计数抗原特异性T细胞。用这些病毒，我们将感染HLA-A2和I-ILA-B7转基因小鼠，其中内源性H-2K和H-2D基因已经通过基因靶向被破坏。这些动物必须依赖于人限制性元件来产生CD 8 T细胞，其存在和频率将用适当的HLA-I类肽四聚体来确定。考虑到US基因产物和MHC I类抗原之间的密切联系，将确定许多临床HCMV分离物的US 2、US 3、US 6和US 11基因的核苷酸序列，所述临床HCMV分离物优选从具有不同MHC I类等位基因组和分布的不同种族群体获得。这种分析应该揭示人类群体中的MHC等位基因是否以及在多大程度上有助于形成免疫evasins的“库”。

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.