乙型脑炎病毒吸附与进入细胞的分子机制研究

流行性乙型脑炎病毒(Japanese encephalitis virus, JEV)为蚊媒传播的黄病毒家族成员之一,是流行性乙型脑炎(简称乙脑)的病原体,其遍布整个东南亚和南亚地区,且感染后会引起严重神经系统症状,因而对人类生命健康造成巨大威胁。JEV吸附与进入宿主细胞是其感染靶细胞的关键步骤,参与这一过程的分子主要是JEV表面的包膜蛋白以及宿主细胞表面的10余种黏附分子或病毒受体,包括被多种病毒使用的细胞表面分子、热休克蛋白以及特异性结合病毒的分子。明确参与JEV吸附与进入宿主细胞的分子,不仅能为阐明JEV与宿主细胞相互作用关系和发病机制提供新的线索,还将对乙脑的预防以及治疗提供重要信息。现对参与JEV吸附与进入细胞的相关分子作一概述。     

乙型脑炎病毒及其疫苗最新研究进展

流行性乙型脑炎(Japanese encephalitis,JE)简称乙脑,是由乙脑病毒感染,流行在亚洲和太平洋地区重要的病毒脑炎,近年乙脑流行地区在不断扩大。目前尚无特效的治疗流行性乙型脑炎的方法,控制蚊虫传播和免疫接种是当前的主要防御手段。随着对乙脑病毒研究的深入,利用基因工程技术研制新型候选疫苗已成为预防乙脑新的发展方向。简要综述了乙型脑炎病毒的基因组结构及其蛋白功能,以及国内外乙型脑炎疫苗的最新研究进展。     

抗病毒感染固有免疫应答的信号转导

入侵病毒的探知和适应性免疫应答启动均依靠固有免疫系统。三种模式识别受体(PRRs)在宿主防御系统第一线占据极其重要地位:Toll样受体、维甲酸诱导基因I样受体、核苷酸结合寡聚化结构域样受体。PRRs识别病原相关分子模式(PAMP)或危险信号分子模式(DAMPs)启动和调节固有免疫和适应性免疫应答。每种PRR都有单独的识别配体和细胞定位。激活的PRRs将信号分子传递给其配体分子(MyD88,TRIF,IRAK,IPS-1),配体活化后作为信使激活信号途径下游激酶(IKK复合物,MAPKs,TBK1,RIP-1)和转录因子(NF-κB,AP-1,IRF3),最终产生细胞因子、趋化因子、促炎细胞因子和I型干扰素。本文重点讨论PRRs信号通路及该领域取得的成果,以期为人类健康和免疫疾病防治提供策略。     

抗病毒免疫中干扰素与炎症信号通路的交互调控：防御反应与维持稳态

天然免疫是机体通过识别自身或外部危险信号后,为维持体内稳态而逐步建立起来的一系列防御反应,当宿主细胞内的模式识别受体识别胞内病原相关分子模式后激活干扰素(interferon, IFN)、核因子-kappa B (nuclear factor-kappa B, NF-κB)和炎性小体等信号通路。IFNs在天然免疫应答中发挥重要作用,它诱导的抗病毒基因能够通过多种方式抵御病毒的感染,炎症反应则是机体自动的防御反应,能够在病毒感染机体时释放促炎性细胞因子以调控机体的免疫反应,进而发挥抗病毒作用。在病毒感染过程中,IFN信号通路与炎症反应调控网络中的关键分子如NF-κB/RelA、PKR等存在一定的交互作用,此外,IFN信号通路及其产生的细胞因子又影响其他信号通路的活化,进而调控机体的免疫应答以维持自身稳态,它们之间的交互调控失衡将会引起过度炎症反应,导致组织器官的免疫病理损伤,例如SARS-CoV-2感染机体时产生的过度炎症反应。本文综述了机体抗病毒免疫过程中干扰素信号通路与炎症反应之间的交互调控,为研发抗病毒策略提供新思路。     

黏膜上皮细胞:病毒侵染与机体免疫的初始交汇处

黏膜上皮细胞构成了包括呼吸道、消化道、泌尿生殖道在内的一个广阔的黏膜界面。黏膜上皮细胞、免疫细胞、免疫分子共同组成黏膜相关淋巴组织,构成了一个完整的黏膜免疫防御系统。黏膜上皮细胞通常是病毒感染的初始靶细胞。大多数DNA和RNA病毒都能直接感染黏膜上皮细胞。黏膜上皮细胞在病毒复制过程中可通过各种模式识别受体感应病毒的病原相关分子模式,从而识别病毒,并启动抗病毒固有免疫应答。近10年来,巨噬细胞炎症小体和caspase-1信号通路激活及其相应的抗感染效应成为固有免疫研究一个热点。病原相关分子模式被巨噬细胞识别,启动形成不同类型的炎症小体,激活caspase-1信号通路,诱导炎性细胞因子IL-1β和IL-18产生,造成细胞焦亡。对巨噬细胞炎症小体的研究,加深了人们对固有免疫的理解,促进了免疫识别、免疫信号转导、免疫应答、免疫调节、免疫病理等各个方面的研究。与固有免疫细胞一样,黏膜上皮细胞具有自身特征性的模式识别受体表达和分布。黏膜上皮细胞通过模式识别受体识别病毒病原相关分子模式,并激活NF-κB信号通路,产生炎性细胞因子、I型和III型干扰素,实现快速的炎性应答和发挥抗病毒作用。黏膜上皮细胞的这种快速应答释放出的各类细胞因子共同招募、激活和协调固有免疫细胞发挥固有免疫应答,并进一步调节、诱导特异性免疫细胞产生特异性抗体和T细胞应答。可见,黏膜上皮细胞是病毒侵染与机体免疫的一个最初的重要交汇处。在这个初始交汇处,黏膜上皮细胞不仅对局部黏膜免疫应答起作用,而且对系统免疫应答起着决定性调节作用。然而,黏膜上皮细胞对病原相关分子模式的识别以及相关炎症通路的激活尚处于启蒙时期。黏膜上皮细胞与炎症小体的关系值得进一步研究。新发现的III型干扰素及其在黏膜上皮细胞的独特表达分布,以及其在固有免疫应答中的抗病毒功能近年逐渐得到关注,详细机制需深入研究。此外,黏膜上皮细胞还是黏膜免疫应答特异效应因子Ig A抗体分泌和发挥功能的平台。Ig A特异性抗病毒功能,尤其是Ig A独特的上皮细胞内中和病毒复制的功能机制值得进一步探讨。现将概述病毒入侵黏膜上皮细胞并起始病毒复制过程,以及黏膜上皮细胞识别病毒感染启动固有免疫应答,调节特异免疫应答的研究进展,并探讨部分研究的交叉前沿。     

TANK结合激酶1在固有免疫应答中的作用及其泛素化调控

固有免疫系统通过模式识别受体识别病原微生物表面的病原相关分子模式启动固有免疫反应,经级联信号转导,激活下游转录因子NF-κB和干扰素调节因子IRFs,进而产生炎性细胞因子以及Ⅰ型干扰素,抵抗病原微生物感染。TANK结合激酶1 (TANK binding kinase 1,TBK1) 作为一个中心节点蛋白,参与多条固有免疫信号通路的传导,可同时激活NF-κB和IRFs,是机体抗感染过程中关键的蛋白激酶。TBK1的精准调控对维持机体免疫稳态、抵抗病原体入侵至关重要。文中综述了TBK1在固有免疫应答中的作用及其泛素化调控机制,以期为病原体感染及自身免疫病的临床治疗提供理论基础。     

长链非编码RNANRAV在抗病毒应答中对干扰素刺激基因(ISG)转录的调控作用

<正>天然免疫是宿主抵抗病毒的第一道防线。病毒侵染宿主后,宿主的病原识别受体(PRR)鉴别出病毒的核酸或蛋白质组分,激活抗病毒天然免疫应答。一系列天然免疫信号通路被PRR激活,通路下游的转录因子随之活化并进入细胞核,核内各种免疫相关基因依次开始转录调控。首先,干扰素大量表达并被分泌至细胞外,随后上百种干扰素刺激基因(ISG)转录表达。这些ISG蛋白分布至细胞内外,通过多种机制抵御病毒的感染复制,以清除机体内的病毒。长链非编码RNA(Long non-coding RNA,lnc RNA)是一类长度大于200nt、不具有蛋白编码特性的RNA分子。近年来大量实验证据表明,长链非编码RNA在细胞     

病毒感染对宿主TLRs模式识别与免疫应答信号的影响

TLRs是一类古老的天然模式识别分子,通过识别病毒的PAMPs,活化依赖和非依赖于MyD88的信号通路,诱导IFNs、促炎性细胞因子和趋化因子等分子的释放和表达,清除病毒的感染;同时,病毒为了感染宿主,采用多种免疫逃避策略干扰机体TLRs的信号,尤其调节MyD88、NF-κB、TRIF和IRFs等重要信号分子,以逃避机体天然PRRs的监视、识别和清除。因此,本文重点以VACV、HCV和HIV为例,介绍病毒感染对宿主TLRs模式识别与免疫应答信号的调节,以进一步理解病毒与宿主相互作用的复杂性,为病毒病的有效防治提供理论依据。     

线粒体抗病毒蛋白对先天免疫的影响

病毒感染启动宿主先天免疫反应是通过激活转录因子NF-κB和干扰素调节因子3（IRF-3）,它们协同调控Ⅰ型干扰素的表达。病毒在复制过程中产生的复制中间体双链RNA作为一个病原相关分子模式,被细胞内具有RNA解旋酶活性的维甲酸诱导基因Ⅰ（RIG-1）编码蛋白检测到。线粒体抗病毒蛋白（MAVS）作为一个接头蛋白,在RIG-1信号通路的下游和NF-κB、IRF-3信号通路的上游扮演着重要的角色。MAVS通过其疏水跨膜结构域定位在线粒体外膜上,是线粒体中发现的第一个与先天免疫相关的蛋白质,将线粒体和先天免疫联系在一起。     

干扰素调节因子家族和免疫调控

干扰素(IFN)是一类能够抵抗病毒感染、抑制细胞周期和行使免疫调节功能的细胞因子。干扰素调节因子家族(IRF)成员因在病毒感染时能够结合到IFN启动子上诱导、调节IFN的表达而得名。最近的研究表明:IRF是一类多功能的转录因子,在干扰素转录调控,病原体免疫反应,细胞因子信号转导,细胞增殖调控;以及造血干细胞的发育、淋巴细胞的分化,自稳平衡,先天性免疫和适应性免疫调控等方面都有着重要的作用。IRF的功能及其分子机制的揭示将对抗病毒,免疫疾病和恶性肿瘤的治疗提供新的靶向策略。     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

Changes in lactate dehydrogenase activity in chicken tissues in hyperthyreosis in ontogenesis

The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration.     

Scurvy in capybaras bred in captivity in Argentine

In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.