Gene Polymorphisms Associated with Infectious Disease

宿主-病毒相互作用由宿主编码的免疫反应元件和完成病毒生命周期所需的蛋白质调节。一种候选基因方法正被用于确定在与人类癌症相关的四种病毒的病毒感染和发病机制中发挥作用的基因：乙肝病毒(乙肝病毒)和丙型肝炎病毒(丙型肝炎病毒)；肝细胞癌(肝癌)；爱泼斯坦-巴尔病毒(EBV)；鼻咽癌(NPC)；人类免疫缺陷病毒(HIV-1)；卡波西肉瘤(KS)；以及淋巴瘤。明确宿主因素限制病毒疾病过程的机制将促进我们对病毒发病机制的理解，并可能导致可能的治疗干预。种族之间和病毒株之间的等位基因和单倍型频率的差异，加上环境因素，可能解释了观察到的艾滋病毒-1、EBV和乙肝病毒和丙型肝炎病毒的感染率和结果的地理差异。 我们正在研究宿主基因变异在疾病进展中的作用，研究对象是11,000多名参与者，这些参与者参加了美国和中国的艾滋病毒-1、乙肝和丙型肝炎自然病史队列和横断面研究。我们还利用一项病例对照研究来确定影响中国EBV感染患者鼻咽癌发展的宿主因素。我们的方法是：1)建立来自研究参与者的细胞系作为DNA的可再生来源；2)确定候选基因中的单核苷酸多态(SNPs)或插入/缺失突变；3)使用高通量基因分型方法筛选SNPs；以及4)使用分类和生存分析来测试基因类型和疾病表型之间的关联。 重要的进展包括(1)在编码趋化因子RANTES的基因的内含子1内鉴定出一个强调节区，RANTES是HIV-1辅助受体CCR5的配体。在调节区域内的SNP(命名为In1.1T/C)的等位基因被发现差异地结合核蛋白并调节转录：In1.1T等位基因强烈促进RANTES的转录，而In1.1C等位基因显著抑制这种增强。在37%的非裔美国人中发现的1.1C单倍型与加速发展为艾滋病和艾滋病相关死亡的速度有关。感染1.1C病毒的欧洲人和非洲裔美国人感染HIV-1的风险也更大。(2)STRL3-3K等位基因对非裔美国人具有保护作用，可延缓感染HIV-1的卡氏肺孢子虫肺炎患者的死亡。 干扰素-g在对细胞内病原体的免疫反应中的关键作用促使我们在这个高度保守的基因的调节区寻找功能变体。我们在启动子区域发现了SNP干扰素-g-179 G/T，在2-4%的非洲血统或后裔中发现，但在高加索人中没有。使用报告分析，我们已经证明了-179T等位基因可以被肿瘤坏死因子-α诱导。在非裔美国人中，干扰素-g-179G/T基因型与艾滋病的加速进展相关(RH=2.34；p=0.009)，可能是因为-179T等位基因在肿瘤坏死因子-a存在的情况下通过凋亡诱导CD+4+细胞枯竭。我们现在正在研究这种变异对HIV-1感染者和未感染者细胞内和分泌的干扰素-γ水平的影响。 在研究EBV相关鼻咽癌的作用方面取得了重大进展。我们招募了400多例鼻咽癌患者，他们的未受影响的配偶作为对照，加上父母或孩子进行单倍型推断。还建立了第二项病例对照研究，以调查EB病毒持续存在的作用，这是由病毒衣壳抗原IgA抗体的存在所确定的。该抗体的存在是鼻咽癌发生的重要危险因素。每个研究对象都获得了冷冻保存的外周血单个核细胞(PBMC)和不可再生的DNA。在这个队列中，我们已经对20多个与免疫反应和炎症有关的候选基因进行了基因分型。未来的计划是进行基因组扫描，努力确定与NPC和IgA/血管细胞黏附(VCA)抗体表型相关的单倍型。

Host-viral interactions are modulated by host-encoding immune response elements and proteins required for the completion of the viral life cycle. A candidate gene approach is being used to identify genes that have a role in viral infection and pathogenesis for four viruses associated with human cancers: the hepatitis viruses B (HBV) and C (HCV); hepatocellular carcinoma (HCC); Epstein-Barr virus (EBV); nasopharyngeal carcinoma (NPC); the human immune deficiency virus (HIV-1); Kaposi sarcoma (KS); and lymphoma. Defining the mechanisms by which host factors restrict viral disease processes will advance our understanding of viral pathogenesis and may lead to possible therapeutic interventions. Differences in allele and haplotype frequencies between racial groups and between viral strains, together with environmental factors, may explain the geographical variation in infection rates and outcomes observed for HIV-1, EBV, and the hepatitis viruses B and C. We are investigating the role of host genetic variation on disease progression in over 11,000 participants enrolled in HIV-1, HBV and HCV natural history cohort and cross-sectional studies in the USA and China. We are also utilizing a case-control study to identify host factors that influence the development of NPC in Chinese patients infected with EBV. Our approach has been to: 1) establish cell lines from study participants as a renewable source of DNA; 2) identify single nucleotide polymorphisms (SNPs) or insertion/deletion mutations in candidate genes; 3) screen SNPs using high throughput genotyping methods; and 4) use of categorical and survival analyses to test for associations between genotypes and disease phenotypes. Important advances include (1) the identification of a strong regulatory region within intron 1 in the gene encoding the chemokine RANTES, a ligand for the HIV-1 coreceptor, CCR5. Alleles of a SNP (named In1.1 T/C) within the regulator region were found to differentially bind nuclear proteins and regulate transcription: the In1.1 T allele strongly enhanced RANTES transcription, and In1.1 C allele significantly reduced this enhancement. In1.1 C-containing haplotypes, found in 37% of African-Americans, were associated with an accelerated rate of progression to AIDS and AIDS-related death. Both European- and African-American carriers for In1.1 C were also at greater risk for HIV-1 infection. (2) The STRL3-3K allele was found to have a protective effect in African-Americans by delaying death in HIV-1-infected individuals with Pneumocystis carinii pneumonia. The pivotal role of IFN-g in immune responses to intracellular pathogens prompted us to look for functional variants in regulatory regions of this highly conserved gene. We identified a SNP IFN-g -179 G/T, in the promoter region that is found in 2-4% of people of African origin or descent but is absent from Caucasians. Using a reporter assay, we have shown that the -179T allele is inducible by TNF-a. The IFN-g -179 G/T genotype was associated with accelerated progression to AIDS (RH=2.34; p=0.009) in African-Americans, possibly because the -179T allele induces CD4+ cell depletion by apoptosis in the presence of TNF-a. We are now investigating the role of this variant on intracelluar and secreted INF-gamma levels in HIV-1 infected and uninfected individuals. Significant progress has been made in the study investigating the role of EBV-associated NPC. We have recruited more than 400 NPC cases, their unaffected spouses who serve as a control, plus a parent or child for haplotype inference. A second case-control study to investigate the role of EBV persistence as determined by the presence of IgA antibody to viral capsid antigen has also been established. The presence of this antibody is a significant risk factor for the development of NPC. Cryopreserved Peripheral Blood Mononuclear Cells (PBMC) and non-renewable DNA has been obtained for each study subject. We have genotyped more that 20 candidate genes involved in immune response and inflammation in this cohort. Future plans are to perform a genome scan in an effort to identify haplotypes associated with the NPC and IgA/Vascular Cell Adhesion (VCA) antibody phenotypes.