布鲁氏菌胞内存活机制与巨噬细胞极化关系研究进展

布鲁氏菌(Brucella)是一种兼性胞内寄生致病菌,虽无典型的毒力因子却有很强的致病力,且常导致慢性持续感染。布鲁氏菌病被列入世界上严重的人兽共患病之一,直接对畜牧业造成重大经济损失,严重威胁人类健康和公共卫生安全。布鲁氏菌感染的靶细胞主要是巨噬细胞,其发展了更高的策略逃逸宿主免疫细胞的杀伤,甚至在细胞内大量繁殖,削弱巨噬细胞的功能,使巨噬细胞的杀伤作用和抗原递呈功能部分丧失,从而能在宿主细胞内长期持续性感染。文章围绕布鲁氏菌胞内存活机制进行探讨,分析了不同极化类型的巨噬细胞在布鲁氏菌感染过程中的调控作用,以及相关炎症通路对机体炎症发展的作用;揭示了布鲁氏菌胞内生存不仅可适应持续感染期间不同的免疫微环境,也可适应感染期间靶细胞营养物质利用率的差异;证实了在慢性感染的过程中免疫逃避和与宿主细胞代谢的相互作用起关键作用;解释了NF-κB通路是调节M1/M2型巨噬细胞亚型平衡状态的关键因素。布鲁氏菌在宿主细胞中持续感染是国内外学者所面临的巨大难题,其免疫逃逸机制和致病机制仍需进一步研究。     

布鲁氏菌致病及免疫机制研究进展

布鲁氏菌病是由布鲁氏菌属的细菌引起的人畜共患传染病 ,目前布鲁氏菌属的细菌主要有七个种。随着分子生物学技术的发展 ,对布鲁氏菌的致病机制在分子水平上有了更进一步的理解 :布鲁氏菌自身一些与致病有关的基因使得布鲁氏菌逃避了巨噬细胞的杀伤作用 ,在巨噬细胞内存活和定居。在布鲁氏菌病免疫过程中 ,先天性免疫应答主要通过补体、巨噬细胞、天然杀伤细胞来参与 ,获得性免疫应答中 ,CD4 、CD8 、rδT细胞起很重要的作用。文章围绕这些与致病、免疫有关的基因及参与免疫反应细胞的研究进展进行了探讨 ,可为今后进行布鲁氏菌病预防及开发新型基因工程苗提供理论依据。     

NF-κB信号通路调控布鲁氏菌胞内存活分子机制的初步研究

本试验用布鲁氏菌强、弱毒株侵染小鼠巨噬细胞RAW264.7,旨在探讨NF-κB信号通路与布鲁氏菌强、弱毒株在胞内生存的关系。采用光滑型牛布鲁氏菌2308、粗糙型牛布鲁氏菌RB51在不同感染复数下侵染小鼠巨噬细胞RAW264.7,侵染0、4、8、24 h后,裂解细胞收集蛋白,Western blotting检测布鲁氏菌对激活NF-κB信号通路的影响。利用不同浓度的NF-κB信号通路抑制剂处理小鼠巨噬细胞RAW264.7,然后用布鲁氏菌在不同感染复数下侵染小鼠巨噬细胞RAW264.7,ELISA试剂盒检测细胞因子TNF-α、IL-1β、IL-6的表达量;同时对胞内菌CFU进行计数。结果显示粗糙型牛布鲁氏菌RB51可以强烈激活NF-κB信号通路,光滑型牛布鲁氏菌2308对其激活作用较弱;同时对NF-κB信号通路的激活具有浓度依赖性,在感染复数为80:1、侵染时间为8 h时光滑型牛布鲁氏菌2308和粗糙型牛布鲁氏菌RB51对NF-κB激活程度最强,且该通路参与产生TNF-α、IL-1β和IL-6;NF-κB信号通路抑制剂BAY11-7082影响布鲁氏菌在胞内的生存。因此,粗糙型牛布鲁氏菌RB51胞内存活与NF-κB信号通路密切相关,为进一步研究布鲁氏菌的胞内致病机制奠定基础,也为布鲁氏菌新型药物的研发、家畜布鲁氏菌病预防和治疗提供科学依据。     

羊布鲁氏菌强毒株16M感染小鼠巨噬细胞模型的建立

巨噬细胞是机体抗吞噬能力最强的细胞,但布鲁氏菌不但不能被巨噬细胞杀死,反而能在胞内大量繁殖,因此,本研究建立其感染模型,为下一步继续研究布鲁氏菌与其宿主细胞表面相关膜蛋白之间的作用和胞内寄生机制奠定基础。用羊布鲁氏菌强毒株16M感染巨噬细胞系264.7（细胞和细菌比例为1∶500）,感染时间为4 h,建立布鲁氏菌感染巨噬细胞模型,做间接免疫荧光试验和透射电镜试验。间接免疫荧光试验中一抗与二抗最佳稀释度分别为1∶80和1∶80,电镜下观察到细菌侵入细胞时膜凹陷,形态发生变化,形成内吞小体。本试验减少感染过程所涉及的环境因素,优化了间接免疫荧光试验所需的一抗和二抗浓度比,成功建立感染模型。     

牛种布鲁氏菌clpP基因缺失株的毒力和免疫保护力评价

为研究布鲁氏菌clpP基因与细菌毒力的关系,采用同源重组的方法,构建牛种布鲁氏菌clpP基因缺失株,用巨噬细胞RAW264.7感染模型和小鼠感染模型评价clpP基因缺失株的毒力,同时测定该缺失株免疫小鼠后产生的免疫保护力。研究发现:牛种布鲁氏菌clpP基因缺失后,在细胞感染模型和小鼠感染模型中的毒力显著降低;clpP基因缺失株感染小鼠后,不引起脾脏肿胀,并且在脾脏内的持续期短于A19疫苗株,说明该基因缺失株具有更高的安全性;使用clpP基因缺失株免疫小鼠后,该基因缺失株无法抵御牛种布鲁氏菌2308株和羊种布鲁氏菌M28株的感染。本研究为揭示布鲁氏菌致病机制和新型布病疫苗研发提供了参考。     

羊口疮病毒与宿主的博弈：免疫应答与病毒免疫逃逸机制

羊口疮(orf)是由羊口疮病毒(orf virus, ORFV)感染引起的一种高度接触性、嗜上皮性人兽共患传染病，不但阻碍畜牧业发展，而且危害人类健康。ORFV感染诱导宿主强烈的免疫反应和炎症反应，但宿主仍可被ORFV反复感染，主要是因为ORFV在与宿主的长期相互作用过程中，发展和进化出多种免疫逃逸机制。ORFV主要通过抑制干扰素反应、抑制NF-κB信号通路、抑制炎症反应、调控细胞凋亡、细胞周期、自噬和血管增生等方式实现免疫逃逸。ORFV免疫逃逸主要是通过其编码的多个免疫调控蛋白来实现。本文主要对ORFV感染引起的宿主免疫应答、ORFV免疫逃逸机制的最新研究进展进行综述，旨在为orf疫苗研制及综合防控提供重要参考。     

布鲁菌16M感染后宿主免疫相关蛋白质泛素化修饰的差异分析

为探究布鲁菌感染宿主细胞早期泛素化修饰蛋白质组表达变化并筛选出影响免疫应答的关键调控蛋白,通过Label-free和泛素化富集技术以及高分辨率LC-MS/MS联用的定量蛋白质组学研究策略,对布鲁菌16M感染11 h (感染5 h,胞内复制6 h)后的巨噬细胞和未感染布鲁菌16M的巨噬细胞进行了泛素化蛋白质组学定量研究,数据库检索分析了16M感染后的巨噬细胞和未感染的巨噬细胞差异表达的泛素化位点对应的蛋白质,并应用生物信息学方法筛选出16M感染巨噬细胞后可造成宿主免疫抑制的关键蛋白质。结果显示,共鉴定出349个蛋白质上580个泛素化位点。布鲁菌16M感染组相对于未感染组167个蛋白质上259个位点泛素化修饰水平发生上调,212个蛋白质上321个位点泛素化修饰水平发生下调(差异倍数1.5,P0.05);35个泛素化修饰差异表达的蛋白质可能与布鲁菌感染后宿主的免疫应答有关,其中27个泛素化修饰的下调蛋白质(如Bcap31、Btk、Faf1和Akap31等),1个泛素化修饰上调蛋白质Ubqln1可能是布鲁菌感染宿主后造成免疫抑制的关键蛋白。本研究筛选获得了布鲁菌16M感染宿主细胞免疫相关差异表达的泛素化修饰蛋白质,初步揭示布鲁菌能够调控宿主免疫信号通路、自噬和凋亡等免疫应答过程中相关蛋白质的泛素化修饰,为进一步研究布鲁菌感染后调节宿主泛素化修饰进而形成免疫逃逸的分子机制提供理论基础。     

深度测序技术分析布鲁菌感染巨噬细胞RAW264.7早期转录组学变化

本研究试图寻找参与布鲁菌胞内感染相关的宿主相关基因,为从感染宿主角度阐述布鲁菌的致病机制奠定基础.布鲁菌感染小鼠巨噬细胞后,利用数字基因表达谱技术筛选小鼠巨噬细胞感染布鲁菌16M株的差异表达基因,并利用荧光定量PCR对差异表达基因进行验证.差异表达基因经GO Term、KEGG分析,识别感染后显著富集的信号通路.在感染后4h,筛选出差异表达基因3 576个,其中58％的基因表现上调.并且NOD凋亡信号通路、溶酶体信号通路、NOD受体信号通路、FcγR-介导的吞噬通路、p53信号通路、内质网蛋白处理相关通路被显著富集.利用数字基因表达谱技术成功分析巨噬细胞感染布鲁菌后转录组学变化,为布鲁菌致病机制的逐步阐述奠定基础.     

抗病毒免疫中宿主细胞的自溶作用以及病毒的进化

多种病原体能够侵害宿主细胞并从宿主的机体免疫系统的防御下得以逃逸。在宿主细胞中,病原体利用一些复杂的方法和途径避免了细胞对入侵者强有力的攻击。近年来的研究表明,自噬作用是细胞内宿主细胞杀灭入侵病原微生物的防御结构中最显著的工具之一,有些病原体却可以在分子水平阻滞这种自噬通路而使持续感染成为可能。宿主抗病毒反应中自噬作用与先天免疫和获得性免疫之间,以及病毒与自噬作用之间存在着复杂的相互关系,这些关系主导了自噬作用和病原菌之间的相互作用。     

泛素相关修饰蛋白SUMO-2对RAW264.7细胞内布鲁氏菌16M存活的影响

为探究泛素相关修饰蛋白SUMO-2对布鲁氏菌16M的影响，本试验构建了SUMO-2基因干扰和过表达小鼠巨噬细胞RAW264.7模型，并用布鲁氏菌16M进行侵染。参照GenBank中SUMO-2基因序列设计特异性干扰片段和过表达引物，克隆成功后连接至相应的慢病毒载体，转化大肠杆菌DH5α感受态细胞，选取阳性克隆菌提取质粒转染HEK-293FT细胞，将重组的慢病毒感染小鼠巨噬细胞RAW264.7，利用布鲁氏菌16M分别侵染构建成功的干扰和过表达细胞模型。通过实时荧光定量PCR检测SUMO-2 mRNA的转录水平，Western blotting检测SUMO-2蛋白的表达，ELISA检测IFN-γ和TNF-α水平，菌落计数来确定布鲁氏菌在细胞中的存活能力。结果显示，与对照组相比，干扰组SUMO-2 mRNA水平极显著降低（P<0.01），过表达组SUMO-2 mRNA水平极显著升高（P<0.01），成功构建了SUMO-2干扰和过表达细胞模型。Western blotting结果显示，布鲁氏菌16M感染能以时间依赖的方式下调SUMO-2蛋白的表达。经菌落计数后发现，SUMO-2过表达后布鲁氏菌的数量极显著减少（P<0.01），抑制布鲁氏菌16M的细胞内繁殖。而SUMO-2干扰后布鲁氏菌的数量显著或极显著增加（P<0.05；P<0.01），促进布鲁氏菌16M的细胞内繁殖。同时，经SUMO-2过表达后，IFN-γ和TNF-α水平极显著升高（P<0.01）。经SUMO-2干扰后，TNF-α水平显著降低（P<0.05），IFN-γ水平极显著降低（P<0.01），SUMO-2在RAW264.7细胞中的表达变化也影响IFN-γ和TNF-α的产生。综上所述，SUMO-2蛋白在布鲁氏菌胞内存活中起着重要作用，可能有助于阐明布鲁氏菌感染的致病机制。     

The innate immune response against Brucella in humans

Pathogens have developed different strategies to survive and multiply within their host. Among them is the ability to control phagocyte apoptosis while another is to affect the expression of cytokines which is necessary for a normal protective function of the immune response. To establish themselves and cause chronic disease in humans and animals, Brucella spp. invade and proliferate within monocytic phagocytes. We have established that in humans, Brucella suis impairs the apoptosis of monocytes and macrophages, thus preventing its host cell elimination. In mice, which are not naturally colonized by the bacteria, Brucella infection results in Type1 (Th1) cellular immune response which promotes a clearance of the bacterial organism. The development of this response is under the control of major cytokines like TNF-alpha, IFN-gamma and IL-12 produced at the onset of infection. We have observed that in humans, B. suis-infected macrophages which produce IL-1, IL-6, IL-10 and several chemokines including IL-8, do not secrete TNF-alpha. By constructing null mutants, we demonstrated that this inhibition involves the outer membrane protein Omp25 of Brucella, however the mechanism regulating the inhibition has not yet been clearly defined. It is likely that the Omp25-induced effect on TNF-alpha production assists bacterial evasion of antimicrobial defences at different levels. Firstly, by preventing the autocrine activation of macrophages thus inhibiting innate immunity and secondly by impairing the production of IL-12 and the development of a Th1 type specific immunity. In addition to the central role of the macrophage in Brucella infection, others cells of the innate immune response are recruited and influenced by the interactions between bacteria and host. For instance, human Vgamma9Vdelta2 T-cells play an important role in the early response to infection with intracellular pathogens. Evidence has been presented that their number dramatically increased in the peripheral blood of patients with acute brucellosis. We have shown that human Vgamma9Vdelta2 T-cells can be specifically activated by non-peptidic low molecular weight compound(s) from B. suis lysate or by soluble factors produced by B. suis-infected macrophages. Under these conditions, they produce TNF-alpha and IFN-gamma and reduce the bacterial multiplication inside infected autologous macrophages. This impairment of B. suis multiplication is due to both soluble factors released from activated gammadeltaT-cells (including TNF-alpha and IFN-gamma) and to a contact-dependent cytotoxicity directed against the infected cells. The interactions between the bacteria and these cells can counteract the intramacrophagic development of the bacteria and finally influence the further development of the host defense. We hypothesize that the chronicity or the elimination of the infection will depend on the balance between contradictory effects induced by the bacteria which favor either the host or the pathogen. Moreover, the interrelationship between the different cells must be taken into account in the analysis of the virulence of the bacteria and in the development of in vitro models of human macrophage infection.     

布鲁氏菌病病原学研究进展

布鲁氏菌病是由布鲁氏茵引起的危害严重的人畜共患病,主要危害人畜生殖系统,患病动物是主要的传染源,其流行地域在不断变化,每年都有新发和复发地区的报道。布鲁氏菌的感染主要缘于其有效的宿主免疫逃避机制,论文对近几年国内外布鲁氏菌抗原和毒力因子等病原学研究进展予以综述,为布鲁氏菌病防治提供参考。     

Intracellular survival of Brucella: defining the link with persistence

Brucellosis is caused by a facultative intracellular pathogen that invades both professional and non-professional phagocytic cells. Resistance to killing in professional phagocytic cells controls survival and chronic infection. Resistance of the organism to killing appears to derive from altered intracellular trafficking of Brucella containing vacuoles to the endoplasmic reticulum via the autophagic pathway. Acute infection is observed in pregnant ruminants in which invasion of the chorionic trophoblasts results in abortion. Following abortion persistence of the organism is observed in the mammary gland and lymph nodes of ruminants. The risk of multiple abortions and subsequent shedding of the organism in the milk has resulted in the culling of infected animals. Persistence of the organism in the reticuloendothelial system is a primary symptom in human infection and may persist over several decades. We have employed the mouse model of brucellosis to characterize genes responsible for persistent infection in an effort to identify potential drug targets for elimination of infection or to attenuate potential vaccine candidates. The results suggest that Brucella utilizes a battery of metabolic functions to sustain itself in intracellular environments in conjunction with altering the intracellular course of infection.     

The pathology of brucellosis reflects the outcome of the battle between the host genome and the Brucella genome

The successful co-existence of each Brucella spp. with its preferred host is the outcome of ancient co-evolutionary relationships and selection pressures that often result in a stalemate where the pathogen has evolved to survive within the biological systems of the host, and the host has evolved innate and acquired immune systems which allow controlled survival of infection by the pathogen, ultimately supporting the survival of the host-pathogen system. In general, Brucella spp. have evolved a similar fundamental pathogenesis of facultative intracellular parasitism though the predominant route of natural exposure varies from oropharynx to genital tract, as does the preferred tissue and cellular tropism, e.g. non-professional placental trophoblasts, fetal lung, professional macrophages of reticulendothelial system, and the male and female reproductive tracts. The morphogenesis of the pyogranulomatous lesions stimulated by Brucella reflects the nature of the persistent parasitism, i.e. genome versus genome. The question is, how can this perplexing array of survival mechanisms be unraveled? Fortunately, the integration of real-time image analysis, cell biology, genome-wide analysis, proteomics and bioinformatics holds the most promise ever for the global analysis of the Brucella infectious process and the host:pathogen interface leading to a clearer understanding of the interactions of these biological systems. These discoveries will be expected to provide a frameshift in rationales for interrupting and/or controlling brucellosis at host and/or pathogen levels.     

Hepatic and splenic immune response during acute vs. chronic Brucella melitensis infection using in situ microscopy

Brucella melitensis is an intracellular bacteria causing disease in humans as an incidental host. The infection initiates as acute flu-like symptoms and may transform into a chronic cyclic infection. This cyclic infection may be partly due to the bacteria’s ability to persist within antigen presenting cells and evade the CD8 + T cell response over long periods of time. This research aims to characterize the immune response of the acute and chronic forms of brucellosis in the murine liver and spleen. We also sought to determine if the exhaustion of the CD8 + T cells was a permanent or temporary change. This was accomplished by using adoptive transfer of acutely infected CD8 + T cells and chronically infected CD8 + T cells into a naïve host followed by re-infection. The histological examination presented supports the concept that exhausted T-cells can regain function through evidence of granulomatous inflammation after virulent challenge in a new host environment.     

Update on the role of innate immune receptors during Brucella abortus infection

The innate immune system constitutes an efficient defense mechanism against invading microbial pathogens. Recent studies have revealed the intracellular signaling cascades involved in the TLR-initiated immune response to Brucella spp. infection. However, there is a piece of the puzzle missing that is the role of non-TLR receptors in innate immunity. The involvement of TLR receptors in brucellosis has been investigated by different research groups. It was demonstrated that TLR2 clearly does not play any role in controlling Brucella abortus infection in vivo, whereas TLR9 has been shown to be required for clearance of this bacterium in infected mice. The participation of adaptor molecules, such as MyD88 and TRIF has also been discussed. Recently, we and others have reported the critical role of MyD88- and not TRIF-mediated signaling in dendritic cell maturation and in vivo resistance during B. abortus infection. However, the relationship between specific Brucella molecules and non-TLR receptors and signal transduction pathways needs to be better understood. It is now clear that the interaction between TLRs and recently identified cytosolic innate immune sensors is crucial for mounting effective immune responses. Finally, this review discusses the mechanisms used by Brucella to escape detection by the host innate immune system.     

The long-term culture of bovine monocyte-derived macrophages and their use in the study of intracellular proliferation of Brucella abortus.

Although the immune response to Brucella abortus is multifaceted, the key event in contending with this pathogen appears to be the interaction of the organism with cells of the mononuclear phagocyte system. A cell culture system was developed which allowed the long-term maintenance of blood monocyte-derived macrophages in Teflon culture vessels in a relatively unstimulated state. The assay system was optimized for timing of bacteria-macrophage interaction and numbers of bacteria and macrophages used in each assay. Interaction of B. abortus strain 2308 with bovine mononuclear phagocytes from animals phenotypically resistant and susceptible to infection with B. abortus was investigated. This cell culture and assay system should provide a useful model for the investigation of intracellular parasitism in cattle.     

Brucella: a pathogen without classic virulence genes

The first species of Brucella was isolated and characterized almost 120 years ago and recently the complete nucleotide sequences of the genomes of a number of well-characterized Brucella strains have been determined. However, compared to other bacterial pathogens relatively little is known about the factors contributing to its persistence in the host and multiplication within phagocytic cells. Also, many aspects of interaction between Brucella and their host remain unclear. Molecular characterization of intracellular survival process of Brucella is important as it will provide guidance for prevention and control. One of the features that distinguish Brucella is that they do not express classical virulence factors. Thus identification of virulence factors has been elusive and some of the identifications are putative. Disruption of putative virulence genes and studying their effect on attenuation in cell lines or mouse models is a widely used method. However, in most cases it is not apparent whether the mutated genes encode virulence factors or merely affect metabolic pathways of the pathogen. In addition, some mutations in Brucella can be compensated by redundancy or backup mechanisms. This review will examine known virulence genes (real and putative) identified to date and the mechanisms that contribute to the intracellular survival of Brucella and its ability to establish chronic infection.     

How the bovine viral diarrhea virus outwits the immune system

The interaction of bovine viral diarrhea virus (BVD virus) with its host has several unique features, most notably the capacity to infect its host either transiently or persistently. The transient infection stimulates an antiviral immune reaction similar to that seen in other transient viral infections. In contrast, being associated with immunotolerance specific for the infecting BVD viral strain, the persistent infection differs fundamentally from other persistent infections like those caused by lentiviruses. Whereas the latter are characterized by complex viral evasion of the host's adaptive immune response by mechanisms such as antigenic drift and interference with presentation of T cell epitopes, BVD virus avoids the immune response altogether by inducing both humoral and cellular immune tolerance. This is made possible by invasion of the fetus at an early stage of development. In addition to adaptive immunity, BVD virus also manipulates key elements of the host's innate immune response. The non-cytopathic biotype of BVD virus, which is capable of persistently infecting its host, fails to induce type I interferon. In addition, persistently infected cells are resistant to the induction of apoptosis by double-stranded RNA and do not produce interferon when treated with this pathogen-associated molecular pattern (PAMP) that signals viral infection. Moreover, when treated with interferon, cells persistently infected with non-cytopathic BVD virus do not clear the virus. Surprisingly, however, despite this lack of effect on persistent infection, interferon readily induces an antiviral state in these cells, as shown by the protection against infection by unrelated viruses. Overall, BVD virus manipulates the host's interferon defense in a manner that optimises its chances of maintaining the persistent infection as well as decreasing the risks that heterologous viral infections may carry for the host. Thus, since not all potential host cells are infected in animals persistently infected with BVD virus, heterologous viruses replicating in cells uninfected with BVD virus will still trigger production of interferon. Interferon produced by such cells will curtail the replication of heterologous viruses only, be that in cells already infected with BVD virus, or in cells in which the heterologous virus may replicate alone. From an evolutionary viewpoint, this strategy clearly enhances the chances of transmission of BVD virus to new hosts, as it attenuates the negative effects that a global immunosuppression would have on the survival of persistently infected animals.