Genetic Modifiers of Immune Evasion by Cytomegalovirus in Glioblastoma

描述（由申请人提供）：越来越多的证据表明人巨细胞病毒（HCMV）与胶质母细胞瘤（GBM）的病因有关：HCMV蛋白在胶质瘤发生中被认为是肿瘤促进剂;胶质瘤分级以及患者生存率与HCMV基因产物的水平直接相关。在这项提案中，我们试图了解为什么这种常见的疱疹病毒只在一部分感染者中引起疾病：HCMV血清阳性率为80%，而GBM的患病率为0.025%。HCMV已经进化出高度复杂的免疫逃避策略。一种策略涉及产生两种蛋白质编码的基因TRL 11/IRL 11和UL 119-UL 118-具有功能特性的Fc？R，这可能使病毒逃避宿主免疫监视逃避抗体结合的效应后果，如ADCC。我们实验室最近的研究表明，免疫系统的一个主要基因复合物的等位基因GM同种异型编码的三个高度多态性IGHG基因座14号染色体上调节这种病毒的战略：HCMV TRL 11/IRL 11编码的Fc？R对表达GM 3+，1-，2-同种异型的IgG 1蛋白的亲和力显著高于对表达等位基因GM 17+，1+，2+同种异型的IgG 1蛋白的亲和力（p = 0.0005）。这些观察使我们假设GM基因是HCMV-GBM关联的效应调节剂，其潜在机制包括它们对抗HCMV抗体应答的贡献和它们对病毒免疫逃避策略的调节影响。以下具体目标将检验我们的假设：1）确定GBM患者中GM决定簇的分布是否与对照组不同。将对GBM患者和对照的DNA进行几种GM等位基因的基因分型。由于它们对HCMV编码的Fc？表达GM 3+，1-，2-同种异型的R，抗HCMV IgG 1抗体更可能使其Fc结构域被清除，从而降低其通过ADCC和其他Fc介导的效应器机制消除病毒的免疫能力。因此，这些同种异型的频率预计将在患者中高于对照组; 2）比较GBM患者和对照组中的抗HCMV抗体水平，并确定它们是否与特定的GM等位基因相关。将通过ELISA定量测定患者和对照血清/血浆中的HCMV糖蛋白B（gB）抗体，并比较两组之间的水平。我们还将确定抗体水平是否与特定的GM等位基因相关; 3）确定是否HCMV编码的Fc？在GBM患者中，R蛋白与抗HCMV IgG抗体的遗传上不同的Fc（GM）区域差异结合。HCMV编码的Fc？Rs将被克隆和表达。我们将从GBM患者的血清中纯化针对HCMV gB的IgG抗体。不同GM同种异型IgG分子与HCMV Fc？将通过表面等离子体共振监测Rs。从拟议的调查结果可能会打开一个新的途径，调查恶性肿瘤，每年约有13000人死亡，仅在美国。 公共卫生相关性：胶质母细胞瘤是一种高度致命的脑癌。巨细胞病毒，一种常见的疱疹病毒，已被牵连在这种恶性肿瘤的病因。本研究旨在探讨免疫系统主要基因在巨细胞病毒诱发的胶质母细胞瘤发病机制中的作用。这些研究的结果可以帮助设计针对这种癌症的新免疫策略。

DESCRIPTION (provided by applicant): Increasing evidence implicates human cytomegalovirus (HCMV) in the etiology of glioblastoma (GBM): HCMV proteins have been implicated as tumor promoters in gliomagenesis; glioma grade-as well as patient survival-directly correlates with the level of HCMV gene products. In this proposal, we seek to understand why this common herpesvirus causes disease in only a subset of those infected: HCMV seroprevalence, 80% vs. the prevalence of GBM, 0.025%. HCMV has evolved highly sophisticated immune evasion strategies. One strategy involves generating two proteins-encoded by genes TRL11/IRL11 and UL119-UL118-that have functional properties of the Fc?R, which may enable the virus to evade host immunosurveillance by evading the effector consequences of antibody binding, such as ADCC. Recent studies from our laboratory show that alleles of a major gene complex of the immune system-GM allotypes encoded by three highly polymorphic IGHG loci on chromosome 14-modulate this viral strategy: The HCMV TRL11/IRL11-encoded Fc?R has significantly higher affinity for IgG1 proteins expressing the GM 3+,1-,2- allotypes than for those expressing the allelic GM 17+,1+,2+ allotypes (p = 0.0005). These observations led us to hypothesize that GM genes are effect modifiers of HCMV-GBM association and the underlying mechanisms include their contribution to anti-HCMV antibody responses and their modulating influence on the viral immune-evasion strategies. The following specific aims will test our hypothesis: 1) Determine if the distribution of GM determinants in GBM patients is different from that in controls. DNA from GBM patients and controls will be genotyped for several GM alleles. Because of their higher affinity to the HCMV-encoded Fc?R, anti-HCMV IgG1 antibodies expressing the GM 3+,1-,2- allotypes would be more likely to have their Fc domains scavenged, thereby reducing their immunological competence to eliminate the virus through ADCC and other Fc-mediated effector mechanisms. Consequently, the frequency of these allotypes would be expected to be higher in patients than in controls; 2) Compare the levels of anti-HCMV antibodies in GBM patients and in controls, and determine if they are associated with particular GM alleles. Antibodies to HCMV glycoprotein B (gB) in the sera/plasma of patients and controls will be quantitated by an ELISA and the levels will be compared between the two groups. We will also determine whether the antibody levels are associated with particular GM alleles; 3) Determine if HCMV-encoded Fc?R proteins bind differentially with genetically disparate Fc (GM) regions of anti-HCMV IgG antibodies in GBM patients. Ectodomains of HCMV-encoded Fc?Rs will be cloned and expressed. We will purify IgG antibodies directed against HCMV gB from the sera of GBM patients. Binding and comparative affinities of IgG molecules of different GM allotypes to the HCMV Fc?Rs will be monitored by surface plasmon resonance. Results from the proposed investigation are likely to open a new avenue of investigation in a malignancy that kills approximately 13000 people every year in the U.S. alone. PUBLIC HEALTH RELEVANCE: Glioblastoma is a highly lethal brain cancer. Cytomegalovirus, a common herpesvirus, has been implicated in the etiology of this malignancy. This project investigates the role of a major gene of the immune system in the etiopathogenesis of cytomegalovirus-spurred glioblastoma. Results from these investigations could help devise novel immunotherapeutic strategies against this cancer.