Cargo, biogenesis and functions of extracellular vesicles released during HSV-1 infection

单纯疱疹病毒-1(HSV-1)在位于人体入口处的粘膜上皮细胞中产生裂解感染后，在感觉神经元中建立了终生的、沉默的感染。由于免疫反应减弱或压力导致的疾病，从良性唇疱疹到脑炎，病毒偶尔会被重新激活。单纯疱疹病毒1型有助于阿尔茨海默氏症等神经退行性疾病的恶化，并促进艾滋病毒-1等其他病原体的感染。细胞外小泡(EV)由所有类型的细胞释放，因为它们构成了细胞间通讯的主要机制，并且它们可以影响受体细胞的功能。在HSV-1感染期间，很容易检测到两种EV群体。第一个种群是通过Tetraspanins生物发生途径产生的。这些是HSV-1感染细胞释放的最丰富的EV，富含CD63 Tetraspan，并携带宿主因子，如干扰素基因刺激物(STING)，胞浆中DNA的传感器。这些CD63EV可以激活未感染的受体细胞的先天免疫反应，并抑制随后的HSV-1感染。第二类EV是通过转运途径所需的内体分选复合体(ESCRT)产生的，因此我们将其命名为ESCRT EV。这些EV携带ESCRT组件以及选定的病毒被膜和包膜蛋白，它们似乎具有前病毒作用。除了这两种EV外，早期的研究已经报道了在HSV-1感染过程中产生无衣壳颗粒，由被膜和包膜蛋白组成，但缺乏病毒基因组。这些粒子比单纯疱疹病毒1型病毒粒子轻，被称为L粒子。L-颗粒与ESCRT EVS相似，因为它们携带病毒蛋白并具有前病毒作用，但比ESCRT EVS密度更大，并富含病毒蛋白。我们假设，在HSV-1感染期间，不同的EV群体被释放，对感染产生不同的影响。为了检验我们的假设，我们制定了三个目标。在目标1中，我们建议用质谱学方法比较ESCRT电动汽车和CD63型电动汽车与单纯疱疹病毒1型感染期间产生的L颗粒的货物。这一分析的结果将产生有关受感染细胞传递的信息的重要信息。在目标2中，我们建议确定在HSV-1感染过程中EV的生物发生途径，这些EV参与了ESCRT EV、CD63EV和L颗粒的产生。为此，我们将使用基因沉默的方法来影响选定的EV生物发生途径，或者我们将使用突变病毒来确定选定的病毒基因对EV生物发生的影响。在目标3中，我们建议确定CD63EVS、ESCRT EVS和L颗粒在受体细胞中触发的反应类型，并确定感染的后果。这些研究将提供关于HSV-1感染细胞释放的EV的生物发生、货物和功能的重要信息，这些信息对于确定它们对HSV-1致病机制的影响是必不可少的。

Following productive, lytic infection in mucosal epithelial cells located at the portal of entry in the body, herpes simplex virus-1 (HSV-1) establishes a lifelong, silent infection in sensory neurons. The virus is occasionally reactivated due to weakened immune response or stress causing diseases that range in severity from benign cold sores to encephalitis. HSV-1 contributes to exacerbation of neurodegenerative diseases such as Alzheimer's and facilitates infection by other pathogens such as HIV-1. Extracellular vesicles (EVs) are released by all types of cells, as they constitute a major mechanism of intercellular communication, and they can influence recipient cell functions. During HSV-1 infection two populations of EVs are readily detectable. The first population is produced through a tetraspanins biogenesis pathway. These are the most abundant EVs released from HSV-1 infected cells, which are enriched in CD63 tetraspanin and carry host factors such as the STimulator of INterferon Genes (STING), a sensor of DNA in the cytosol. These CD63+ EVs can activate innate immune responses in uninfected recipient cells and suppress a subsequent HSV-1 infection. The second population of EVs is produced through the endosomal sorting complex required for the transport (ESCRT) pathway, thus we named them ESCRT+ EVs. These EVs carry ESCRT components along with selected viral tegument and envelope protein and they appear to have a proviral role. In addition to these two population of EVs, earlier studies have reported the production of capsidless particles during HSV-1 infection composed of tegument and envelope proteins but lacking viral genome. These particles are lighter than HSV-1 virions and are known as L-particles. L-particles resemble the ESCRT+ EVs in that they carry viral proteins and have a proviral effect but are denser than ESCRT+ EVs and enriched in viral proteins. We hypothesize that distinct populations of EVs are released during HSV- 1 infection with different effects on the infection. To test our hypothesis, we have formulated three Aims. In Aim 1, we propose to compare the cargo of ESCRT+ EVs and CD63+ EVs with L-particles produced during HSV-1 infection using a mass spectrometry approach. The results of this analysis will generate important information about messages communicated by infected cells. In Aim 2, we propose to determine EV biogenesis pathways involved in the production of ESCRT+ EVs, CD63+ EVs and L-particles during HSV-1 infection. For this, we will use a gene silencing approach to compromise selected EV biogenesis pathways or we will use mutant viruses to determine the impact of selected viral genes on EV biogenesis. In Aim 3, we propose to determine the type of responses that CD63+ EVs, ESCRT+ EVs and L-particles trigger in recipient cells and determine the consequences to the infection. These studies will provide important information on the biogenesis, cargo, and functions of EVs released by HSV-1 infected cells, which are essential to determine their impact on HSV-1 pathogenesis.