Molecular and cellular mechanisms of synapse-mediated spread of Epstein Barr virus: overcoming the CD21-restricted cellular tropism.

爱泼斯坦巴尔病毒（EBV）是一种常见的口腔传播病毒，感染大多数人群。EBV通过隐藏在被称为B细胞的淋巴细胞亚群中，在宿主的一生中保持沉默感染。eb病毒感染的B细胞在实验室中已被广泛研究。在实验室中，受感染的B细胞被有效地转化为具有致癌潜力的持续生长的细胞。这种情况在体内很少发生，但一旦发生，就会导致包括霍奇金淋巴瘤在内的B细胞癌。B细胞癌如此罕见的一个原因是，感染是由包括T细胞和自然杀伤细胞（NK）在内的其他细胞的免疫反应控制的。EBV进入B细胞的机制已被广泛研究。病毒上的蛋白（gp350和gp42）与细胞表面的病毒受体（分别为CD21和HLA II类）相互作用，将EBV与B细胞结合。此后，进一步的病毒蛋白（gp82, gp25）触发病毒内化。然而，不表达CD21的其他细胞类型，包括上皮细胞、T细胞和NK细胞的感染也被观察到。这些感染要么与病毒传播到新的易感宿主（上皮细胞）有关，要么与上皮细胞、T细胞和NK细胞的疾病和恶性肿瘤有关。上皮细胞排列在口腔（口咽部）上，为EBV进入未感染宿主和从感染宿主逃逸到新的易感宿主形成屏障。上皮细胞被认为是eb病毒在口咽部复制的主要部位；然而，它们不表达CD21，并且在实验室中EBV对上皮细胞的感染很差。我之前已经证明，通过首先将病毒与B细胞结合，可以大大增强上皮细胞的感染。EBV与CD21的结合触发粘附分子和B细胞表面的EBV极化，然后“粘附”到上皮细胞上，使EBV与上皮细胞密切接触，从而实现有效感染。这个过程可能与口咽部的情况类似，上皮细胞和淋巴细胞，包括B细胞，彼此密切接触。在我们的eb病毒感染上皮细胞的模型中，我们认为B细胞上的eb病毒可能来自完全成熟的B细胞，称为浆细胞，当eb病毒感染时产生新的感染性病毒。这种EBV可能从浆细胞中释放出来，与静止的B细胞相互作用。或者，正如越来越多的其他感染淋巴细胞的病毒（如HIV）所观察到的那样，浆细胞可能直接与上皮细胞相互作用，导致浆细胞内的EBV重新定位到细胞间接触点，并直接从浆细胞传播到上皮细胞，从而逃避抗EBV抗体。在这里，我打算扩展我的研究，了解EBV如何使用浆细胞作为病毒供体感染上皮细胞，并确定上皮细胞和EBV有效感染的分子要求，以便我们了解如何用疫苗破坏EBV的传播。EBV相关的T和NK细胞疾病的范围从看起来是免疫系统过度活跃的结果的疾病（EBV相关的噬血细胞淋巴组织细胞增多症，慢性活动性EBV）到侵袭性恶性肿瘤（结外T/NK细胞淋巴瘤，侵袭性NK细胞白血病）。T细胞和NK细胞不表达CD21，我们不清楚这些细胞是如何被EBV感染的。使用两种不同的方法，我的目标是确定如何感染这些细胞：(1)使用浆细胞与T和NK细胞相互作用，(2)感染cd21阳性的未成熟T和NK细胞。有了这些新信息，我们将能够了解病毒是如何引起T细胞和NK细胞疾病的，并开始开发针对这些耐药疾病的新疗法。

Epstein Barr Virus (EBV) is a common, orally-transmitted virus, infecting most of the human population. EBV maintains a silent infection for the lifetime of the host by hiding in a subset of lymphocytes called B cells. EBV infection of B cells in the laboratory has been extensively studied. In the laboratory, infected B cells are efficiently transformed into continuously growing cells with the potential to cause cancer. This happens only rarely in the body, but when it does can cause B cell cancers including Hodgkin lymphoma. One reason why B cell cancers are so rare is because infection is kept under control by immune responses involving other cells, including T and natural killer (NK) cells.The mechanisms of EBV entry into B cells have been extensively studied. Proteins on the virus (gp350 and gp42) interact with virus receptors on the cell surface (CD21, HLA class II respectively) to bind the EBV to the B cell. Thereafter further virus proteins (gp82, gp25) trigger virus internalisation. However, infection of other cell types, including epithelial, T and NK cells that do not express the CD21 are also observed. These infections are associated with either virus transmission to a new susceptible host (epithelial), or are associated with diseases and malignancies of epithelial, T and NK cells.Epithelial cells line the oral cavity (oropharynx) and create a barrier for entry of EBV into an uninfected host, and for escape of EBV from an infected host for transmission to a new susceptible host. Epithelial cells are thought to be the major site of EBV replication in the oropharynx; however they do not express CD21, and EBV infection of epithelial cells in the laboratory is poor. I have previously shown that infection of epithelial cells can be greatly enhanced by first binding the virus to B cells. EBV binding to CD21 triggers adhesion molecules and EBV on the B cell surface to polarise then 'adhere' to the epithelial cells, bringing EBV into close contact with epithelial cells and enabling efficient infection. This process is probably similar to the situation in the oropharynx, where epithelial cells and lymphocytes, including B cells, are in close contact with each other.In our model of EBV infection of epithelial cells, we suggest EBV on the B cells may come from fully matured B cells, called plasma cells, which when infected with EBV produce new infectious virus. This EBV may be released from the plasma cell to interact with the resting B cell as above. Or, as increasingly observed with other viruses that infect lymphocytes (like HIV), the plasma cell may interact directly with the epithelial cell, cause EBV inside the plasma cell to relocate to the point of cell-to-cell contact and transmit directly from the plasma cell to the epithelial cell, thereby evading anti-EBV antibodies. Here, I intend to extend my studies to understand how EBV can infect epithelial cells using plasma cells as the virus donor, and determine the molecular requirements of epithelial cells and EBV for efficient infection, so we can understand how to disrupt EBV transmission with vaccines.EBV associated T and NK cell diseases range from illnesses that appear to be a consequence of an over-active immune system (EBV-associated haemophagocytic lymphohistiocytosis, chronic active EBV), to aggressive malignancies (extranodal T/NK cell lymphoma, aggressive NK cell leukaemia).T and NK cells do not express CD21 and we do not understand how these cells can be infected with EBV. Using two different methods, I aim to determine how infection of these cells is achieved: (1) Using plasma cell interaction with T and NK cells, and (2) infecting CD21-positive immature T and NK cells. With this new information, we will be able to develop ideas of how the virus may be causing the T and NK cell diseases, and begin develop new treatments for these treatment-resistant diseases.