Marek's disease avian herpesvirus - Learning from differences

疱疹病毒是一种大型双链DNA病毒，可在不同动物中引起疾病。马立克病病毒（MDV）是一种高致癌性的禽甲疱疹病毒。马立克病（MD）的特点是潜伏感染的鸡细胞中出现CD4+ t细胞淋巴瘤。MD是家禽业最严重的慢性疾病之一，每年在全球范围内造成10 - 20亿美元的损失。MDV具有许多疱疹病毒的特征，但其感染和疫苗作用有几个独特的特点。利用这些独特的特征，我的长期目标是获得对疱疹病毒发病机制和疫苗预防的机制见解。我的短期目标是：1)研究MDV如何从潜伏期产生子代病毒，以更好地了解疱疹病毒如何复制；2)阐明MD疫苗如何在不消除毒性病毒感染的情况下预防淋巴瘤。所有疱疹病毒都能在宿主细胞中建立潜伏感染。在刺激后，潜伏感染的疱疹病毒被重新激活，并使用环状基因组作为复制滚动循环模型的模板恢复子代病毒的生产。然而，这个提出的模型并没有解释如何产生足够数量的循环模板来支持病毒繁殖的爆炸性。目的1：与大多数其他疱疹病毒不同，MDV基因组在潜伏期整合到宿主染色体中。笔者假设端粒交替延长（ALT）是整合MDV基因组在复制前被切除的机制。肿瘤细胞利用ALT延长端粒序列，防止衰老。在ALT端粒延伸过程中，一个环状的部分双链DNA被切除。我将使用RNAi和FISH等分子生物学方法来检查ALT是否切除并循环整合的MDV基因组。如果是这样，ALT可能与滚动圈模型协同工作，为MDV和非整合疱疹病毒创造更多的环状病毒基因组模板拷贝。目的2：虽然其他病毒疫苗通过诱导适应性免疫反应来消除病毒来预防疾病，但MD疫苗预防淋巴瘤而不消除毒性病毒感染。MD疫苗阻止潜伏感染淋巴细胞表达一种病毒蛋白MEQ。MEQ是一种mdv编码的癌基因，其表达对肿瘤的发生至关重要。我假设MD疫苗通过为MDV MEQ的表达提供核内环境来消除能够进行转化的t细胞亚群。我将结合重组病毒和蛋白质组学技术来测试MD疫苗是否在致命的MDV攻击之前通过免疫刺激消除这些细胞，使它们无法在潜伏期表达MEQ。阐明MDV的发病机制和MD疫苗的作用机制将为预测未来MD疫苗破裂的风险和开发新的抗疱疹病毒药物提供必要的证据。

Herpesviruses are large double-strand DNA viruses that cause disease in different animals. Marek's disease virus (MDV) is a highly oncogenic avian alphaherpesvirus. Marek's disease (MD) is characterized by CD4+ T-cell lymphomas in latently infected chicken cells. At $1-2B/year in worldwide costs, MD is one of the most significant chronic disease problem for the poultry industry. MDV shares many characteristics of herpesviruses, but its infection and vaccine action have several unique features. Taking advantage of these unique features, my long-term goal is to gain mechanistic insights into herpesvirus pathogenesis and vaccine prevention. My short-term goals are: 1) to investigate how MDV generates progeny virus from latency to better understand how herpesviruses replicate, and 2) elucidate how MD vaccines prevent lymphoma without eliminating virulent virus infection. All herpesviruses are able to establish latent infection in host cells. Upon stimulation, the latently infected herpesvirus is reactivated and resumes progeny virus production using a circularized genome as a template for the rolling-circle model of replication. This proposed model does not, however, explain how sufficient numbers of circularized templates are generated to support the explosive nature of virus reproduction. Aim 1: Unlike most other herpesviruses, the MDV genome integrates into host chromosomes during latency. I hypothesize alternate lengthening of telomere (ALT) is the mechanism by which the integrated MDV genome is excised prior to replication. Tumor cells use ALT to elongate telomere sequence to prevent senescence. During ALT telomere elongation, a circular partially double strand DNA is excised. I will use molecular biology methods such as RNAi and FISH to examine if ALT excises and circularizes the integrated MDV genome. If so, ALT may work in tandem with the rolling-circle model to create additional copies of circular virus genome templates for MDV as well as non-integrating herpesviruses. Aim 2: While other viral vaccines prevent disease by inducing adaptive immune responses to eliminate the virus, MD vaccines prevent lymphoma without eliminating virulent viral infection. MD vaccines prevent latently infected lymphocytes from expressing a viral protein, MEQ. MEQ is an MDV-encoded oncogene whose expression is essential for the oncogenesis. I hypothesize the MD vaccine eliminates the subset of T-cells that are capable of undergoing transformation by providing intranuclear environment for the expression of MDV MEQ. I will combine recombinant virus and proteomics techniques to test if MD vaccine eliminates these cells by immunologically stimulating prior to the virulent MDV challenge, rendering them incapable of expressing MEQ in latency. Elucidation of MDV pathogenesis and MD vaccine action mechanisms will provide essential evidence to make informed predictions regarding risk of future MD vaccine breaks and develop new anti-herpesvirus drugs.