Investigating the role of salivary gland NK cells in controlling CMV infection

描述（由申请人提供）：人巨细胞病毒（HCMV）是一种广泛存在的人类病原体，感染全球50-95%的成年人群。在健康个体中，原发性HCMV感染从除下颌下唾液腺（SMG）之外的所有组织中清除，在那里它可以持续数月。经过这段时间的持续存在，HCMV最终成为宿主生命的潜伏者。潜伏HCMV的再激活在具有健康免疫系统的个体中是罕见的，但在具有受损免疫系统的个体中更为常见。这些包括先天性或获得性免疫缺陷的人，器官移植接受者或任何服用免疫抑制药物的患者。在免疫受损的个体中，原发性HCMV感染或潜伏感染的再激活可引起严重甚至致命的健康并发症。即使不是致命的，唾液腺中HCMV的重新激活也会导致几种严重限制生活质量的口腔疾病，如增加的蛀牙，牙周感染和慢性口干。HCMV也可以在怀孕期间从母亲传给胎儿，由此产生的新生儿HCMV感染可导致严重的出生缺陷。由于CMV家族成员的严格种属嗜性，HCMV不能在动物模型中进行研究。然而，鼠巨细胞病毒（MCMV）在遗传学、结构和感染机制方面与HCMV非常相似。因此，MCMV是研究HCMV感染的合适动物模型。与HCMV一样，MCMV在变为潜伏性之前持续存在于宿主的SMG中。与人类一样，小鼠自然杀伤（NK）细胞对于MCMV的早期遏制至关重要。NK细胞是先天性免疫细胞，其通过直接杀死受感染的细胞和通过释放促炎细胞因子如IFN-？刺激进一步的免疫反应。最近，Brossay实验室发现SMG的NK细胞对MCMV感染反应迟钝：它们在感染后被激活，但它们的IFN-？与脾、肝和血液的NK细胞相比，免疫应答减弱。SMG是一种脆弱的组织，容易受到未经检查的病毒复制或广泛的炎症免疫反应的不可逆损伤。我的假设是，SMG NK细胞的效应反应减弱，使MCMV在该器官中持续存在，其水平太低而不会造成直接损伤，同时保护SMG组织免受广泛的炎症损伤。在目标1中，我将确定SMG NK细胞是否将MCMV复制控制到低水平。在目标2中，我将确定SMG NK细胞是否可以被诱导对MCMV感染产生应答，或者它们的低应答表型是否是内在的和不可逆的。本提案中描述的研究将阐明允许MCMV在哺乳动物宿主SMG中持续存在的因素。这些知识最终可能导致开发出针对这种无处不在的人类病原体的更有效的疗法。

DESCRIPTION (provided by applicant): Human cytomegalovirus (HCMV) is a widespread human pathogen that infects 50-95% of the adult population worldwide. In healthy individuals, primary HCMV infection is cleared from all tissues except the submandibular salivary gland (SMG), where it can persist for several months. After this period of persistence, HCMV eventually becomes latent for the life of the host. Reactivation of latent HCMV is rare in individuals with healthy immune systems, but is far more common in individuals with compromised immune systems. These include people with congenital or acquired immune deficiencies, organ transplant recipients, or any patients taking immunosuppressive drugs. In immune compromised individuals, primary HCMV infection or reactivation of latent infection can cause serious and even fatal health complications. Even when it is not fatal, reactivation of HCMV in the salivary gland can cause several oral pathologies that greatly limit quality of life, such as increased dental cavities, periodontal infections, and chronic dry mouth. HCMV can also be passed from mother to fetus during pregnancy, and the resulting neonatal HCMV infection can result in severe birth defects. Due to the strict species tropism of the CMV family members, HCMV cannot be studied in an animal model. However, murine cytomegalovirus (MCMV) is very similar to HCMV in terms of genetics, structure, and mechanisms of infection. Thus, MCMV is an appropriate animal model to study HCMV infection. Like HCMV, MCMV persists in the SMG of the host before becoming latent. Also like in humans, murine natural killer (NK) cells are crucial for the early containment of MCMV. NK cells are innate immune cells that respond to MCMV infection by directly killing infected cells, and by releasing pro-inflammatory cytokines such as IFN-? that stimulate further immune responses. Recently, the Brossay laboratory has discovered that the NK cells of the SMG are hyporesponsive to MCMV infection: they are activated upon infection, but their IFN-? response is diminished compared to NK cells of the spleen, liver, and blood. The SMG is a delicate tissue, vulnerable to irreversible damage by either unchecked viral replication or an extensive inflammatory immune response. My hypothesis is that the diminished effector response of the SMG NK cells allows MCMV to persist in this organ at levels too low to cause direct damage, while at the same time preserving the SMG tissues from extensive inflammatory damage. In Aim 1, I will determine whether SMG NK cells control MCMV replication to low levels. In Aim 2, I will determine whether SMG NK cells can be induced to respond to MCMV infection, or whether their hyporesponsive phenotype is intrinsic and irreversible. The research described in this proposal will elucidate the factors allowing MCMV to persist in the SMG of the mammalian host. This knowledge could eventually lead to the development of more effective therapies against this ubiquitous human pathogen.