昆虫天然免疫反应研究前沿

昆虫天然免疫反应分为体液免疫和细胞免疫两种,二者共同作用抵御细菌、真菌、病毒等外源病原物的侵染。体液免疫反应主要包括黑色素形成和抗菌肽产生两种机制,细胞免疫反应包括吞噬、集结和包囊等作用类型。在昆虫天然免疫反应中,昆虫模式识别蛋白负责识别并结合外源物表面特有的模式分子,丝氨酸蛋白酶、丝氨酸蛋白酶抑制剂、各种配体、受体等负责级联信号途径的激活和调控,抗菌肽、黑色素等效应分子则负责对入侵物的杀灭和清除。本文根据国外和作者自己的研究,综述了昆虫天然免疫反应的研究进展,并针对该领域最新的研究动态展望了昆虫肠道免疫、昆虫免疫致敏以及不完全变态昆虫免疫学等这些研究前沿。     

Toll样受体对病原真菌的天然免疫识别

天然免疫系统是宿主抵御病原入侵的第一道防线,在机体抗感染免疫中发挥重要作用。Toll样受体(Toll-like receptors,TLRs)是天然免疫系统最重要的模式识别受体(pattern recognitionreceptors,PRRs)之一,通过识别病原真菌的病原相关分子模式(pathogen-associated molecularpatterns,PAMPs),招募特异接头蛋白,激活一系列信号级联反应,引发炎症因子、趋化因子等的释放和树突状细胞(dendritic cells,DCs)的成熟,发挥抗真菌感染作用。通过简要介绍宿主的TLRs及信号通路的研究进展,总结了目前TLRs对不同病原真菌PAMPs的天然免疫识别及信号通路研究现状,以期对进一步研究宿主天然免疫系统与病原真菌相互作用的分子机制提供参考。     

小菜蛾Gloverin like抗菌肽对蝉拟青霉侵染的响应研究

抗菌肽是昆虫天然免疫的重要成分,在抵御病原物的侵染中发挥着重要的作用。昆虫Gloverin抗菌肽是一类仅在鳞翅目昆虫中存在的富含甘氨酸抗菌肽。本研究在转录组测序的基础上对小菜蛾抗菌肽gloverin like基因进行了克隆,其开放阅读框序列全长519 bp,编码172 aa,信号肽为1-17 aa。序列分析表明其序列中甘氨酸的比例为15%,与鳞翅目昆虫Gloverin抗菌肽具有较高的同源性。qRT-PCR结果表明小菜蛾抗菌肽gloverin like基因在脂肪体和血细胞组织中表达量较高。蝉拟青霉、金黄色葡萄球菌及大肠杆菌均可诱导小菜蛾抗菌肽gloverin like基因上调表达,蝉拟青霉诱导12 h后表达量达到最高。利用LC-MS方法在蝉拟青霉侵染的小菜蛾幼虫血淋巴中鉴定出小菜蛾Gloverin like、Gloverin抗菌肽以及Lysozyme II、Transferrin、Prophenoloxidase等抗菌效应蛋白。与对照相比,蝉拟青霉侵染后小菜蛾Toll通路4个免疫基因(βGBP、Toll、Cactus和Dorsal)表达量上升。本研究在抗菌肽方面为进一步研究小菜蛾抵御病原真菌入侵的分子机制提供基础信息,也为新的害虫防治方法提供了思路和靶标。     

丝氨酸蛋白酶抑制剂Serpins对昆虫免疫调控作用的研究进展

丝氨酸蛋白酶抑制剂Serpins是一类参与调控多种生理过程的蛋白酶抑制剂,广泛存在于所有生命体中.本文以黑腹果蝇Drosophila melanogaster、黄粉虫Tenebrio molitor、烟草天蛾Manduca sexta为例,阐述Serpins在昆虫体内诱导抗菌肽产生的Toll信号通路和诱导黑化反应的酚氧化酶酶原(Prophenoloxidase,PPO)激活通路中的调控作用,并以病毒、线虫、细菌和真菌及寄生蜂为例,明确它们产生的Serpins对昆虫宿主免疫系统的调控作用,全面总结和综述了近年来具有Serpin domain结构域的典型Serpins对昆虫免疫的调控作用的研究进展.     

甘露聚糖结合凝集素相关丝氨酸蛋白酶

甘露聚糖结合凝集素（MBL）是一种重要的天然免疫防御分子,通过激活MBL相关丝氨酸蛋白酶（MAST）而启动补体激活凝集素途径来清除病原体。本文就MASP的基因、分子结构及功能等方面研究概况作一介绍。     

昆虫天然免疫相关基因研究进展

在长期进化过程中,昆虫形成了强大的天然免疫防御系统,即体液免疫和细胞免疫。体液免疫主要包括Toll、IMD和JAK/STAT 3条信号通路,通过信号转导及免疫途径调控免疫相关基因的表达,诱导产生抗菌肽和其他效应分子。细胞免疫由血细胞介导,主要完成对病原物的包裹、吞噬和集结等。近年来,昆虫基因组学快速发展,通过生物信息学等方法从昆虫基因组数据中已鉴定到大量免疫相关基因,对这些基因的研究加深了人们对昆虫天然免疫分子机制的认识和理解。根据基因功能,免疫相关基因分为识别、信号转导、调制器、效应分子、黑化反应、RNA干扰和其他基因等7类,这些基因通过互作来调控体液免疫和细胞免疫。本文对昆虫免疫相关基因的分类、功能及家族进化等方面的研究成果进行总结,并对今后昆虫免疫的研究重点进行了展望,以期为昆虫免疫分子机制的研究及开发新的害虫防治策略提供依据。     

食线虫真菌致病相关丝氨酸蛋白酶的研究进展

食线虫真菌是一类土壤微生物,作为线虫的天敌,它们对于维持线虫在土壤生态环境中的种群动态平衡发挥着十分重要的作用。食线虫真菌通过形成特殊的捕食器官或产生毒素等方式来捕捉和杀死线虫。丝氨酸蛋白酶是食线虫真菌侵染线虫的重要毒力因子,近年来,研究人员对不同食线虫真菌来源的致病相关丝氨酸蛋白酶进行了大量的研究,尤其在丝氨酸蛋白酶的晶体结构和分子进化方面的研究取得了较大的进展。本文对食线虫真菌致病相关丝氨酸蛋白酶的生物化学性质和功能进行了系统的总结,对丝氨酸蛋白酶的晶体结构、催化机制及分子进化等最新的进展进行了评述。     

多种病原物混合侵染的昆虫流行病模型

两种或两种以上的病原物同时侵染昆虫寄主时,病原物之间的相互作用表现为偏利、偏害、中性及竞争等类型,寄生群体的病症可呈多种形式．根据单种病菌的重叠侵染原理,建立了多种病原物混合侵染时以温度、病原接种量、虫龄及湿度为因子的昆虫流行病模型．由模型可计算寄生群体中不同病原物的致病比率,及寄主群体的总发病率,给出了模型的参数求解算法,以及病原物相互作用类型的判定准则．这类模型可用于多种病原物混合侵染的昆虫流行病预测,也可作为多种病原物混合施用防治害虫的最优化模型．     

虫生真菌分子致病机理及基因工程改造研究进展

虫生真菌侵染寄主昆虫的复杂过程可分为体表附着、体壁穿透及体内定殖和致死等不同阶段。近年来, 以金龟子绿僵菌(Metarhizium anisopliae)和球孢白僵菌(Beauveria bassiana)为代表的基因功能研究取得了长足的进展, 从不同角度阐明了虫生真菌的分子致病机理; 同时, 基因工程技术的应用为昆虫病原真菌的遗传改良和选育高毒力杀虫菌株开辟了新的途径。对近年来昆虫病原真菌侵染寄主的分子对策及基因工程改造的研究进展进行了综述, 并就进一步研究虫生真菌的毒力基因及功能进行了探讨。     

虫生真菌分子致病机理及基因工程改造研究进展

虫生真菌侵染寄主昆虫的复杂过程可分为体表附着、体壁穿透及体内定殖和致死等不同阶段.近年来,以金龟子绿僵茵(Metarhizium anisopliae)和球孢白僵菌(Beauveria bassiana)为代表的基因功能研究取得了长足的进展,从不同角度阐明了虫生真菌的分子致病机理;同时,基因工程技术的应用为昆虫病原真菌的遗传改良和选育高毒力杀虫菌株开辟了新的途径.对近年来昆虫病原真菌侵染寄主的分子对策及基因工程改造的研究进展进行了综述,并就进一步研究虫生真菌的毒力基因及功能进行了探讨.     

昆虫肽聚糖识别蛋白研究进展

在脊椎动物和非脊椎动物中,识别非己是天生免疫反应中的第一步。肽聚糖是细菌细胞壁的必需成分,属于进化上保守的微生物表面病原相关分子模式(pathogen-associated molecular pattern, PAMP),可以被模式识别蛋白(pattern recognition proteins, PRRs)如肽聚糖识别蛋白(peptidoglycan recognition proteins, PGRPs)识别。 在昆虫的天生免疫系统中,有些PGRPs能够利用细菌独有的肽聚糖识别入侵细菌,并将细菌入侵信号传递给下游的抗菌肽(antimicrobial peptide, AMP)合成途径,启动抗菌肽基因的转录及合成;PGRPs对肽聚糖的识别也会启动酚氧化酶原途径的激活,引起黑化反应。有些具有酰胺酶活性的PGRPs可以促进吞噬作用;有些可以抑制抗菌肽合成以减弱过度免疫反应带来的损伤。还有一些PGRPs作为效应因子直接作用于细菌将细菌杀死。本文主要从昆虫PGRPs作为识别受体(recognition receptor)、调节子(regulator)和效应因子(effector) 3个方面进行了综述,并分析了目前PGRPs研究中仍不清楚的问题和未来研究的方向。     

Mechanisms and functions of guanylate‐binding proteins and related interferon‐inducible GTPases: Roles in intracellular lysis of pathogens

Guanylate‐binding proteins (GBPs) are a group interferon‐inducible GTPases within the constellation of the dynamin GTPase superfamily. These proteins restrict the replication of intracellular pathogens in both immune and non‐immune cells. GBPs and their related family members immunity‐related GTPases target and lyse the membrane of the pathogen‐containing vacuole, destroying the residential niche of vacuolar protozoal and bacterial pathogens. They also prevent virion infectivity and target replication complexes of ribonucleic acid viruses. The exciting concept that GBPs and immunity‐related GTPases can directly target the membrane of bacteria and protozoa has emerged. Rupture and lysis of the pathogen membrane mediates liberation of concealed microbial ligands for activation of innate immune sensing pathways and the inflammasome. Further studies have demonstrated a capacity of GBPs to recruit additional antimicrobial factors, highlighting the complexity of the molecular mechanisms involved in pathogen killing. In this mini‐review, we discuss recent advances describing the localisation and functions of GBPs on the host and pathogen membrane. We also highlight unresolved questions related to the regulation of GBPs in cell‐autonomous immunity to intracellular pathogens.     

抗菌肽在宿主防御中作用

抗菌肽广泛地存在于自然界中,其中许多抗菌肽具有直接抗微生物活性,能作用于G-、 G+细菌、真菌、寄生虫甚至是包膜病毒,并且在宿主先天免疫和适应性反应中有重要的调节作用。近来,越来越多的证据表明抗菌肽是有效的免疫辅助因子,能够与其他的众多免疫效应子协同作用,从而起始适应性免疫,促进伤口愈合,抑制前炎症反应以及诱导和调节细胞因子和趋化因子的产生。另外,随着抗菌肽作用机理逐渐被揭开,将这些内源性肽及其衍生物制成抗感染治疗药剂将会有广阔的应用前景。     

Intracellular innate resistance to bacterial pathogens

Mammalian innate immunity stimulates antigen-specific immune responses and acts to control infection prior to the onset of adaptive immunity. Some bacterial pathogens replicate within the host cell and are therefore sheltered from some protective aspects of innate immunity such as complement. Here we focus on mechanisms of innate intracellular resistance encountered by bacterial pathogens and how some bacteria can evade destruction by the innate immune system. Major strategies of intracellular antibacterial defence include pathogen compartmentalization and iron limitation. Compartmentalization of pathogens within the host endocytic pathway is critical for generating high local concentrations of antimicrobial molecules, such as reactive oxygen species, and regulating concentrations of divalent cations that are essential for microbial growth. Cytosolic sensing, autophagy, sequestration of essential nutrients and membrane attack by antimicrobial peptides are also discussed.     

昆虫先天性免疫信号通路研究进展

昆虫体内形成了强大的免疫防御系统,其被各种微生物攻击时能依靠病原相关分子模式识别蛋白对感染进行区分和激活体内信号通路诱导如抗菌肽之类的效应分子.昆虫体内控制先天性免疫的信号通路分别是:Toll通路、IMD通路和JAS/STAT通路,这3条通路在信号传递过程中存在协作,并且,这些通路与脊椎动物体内某些通路存在惊人相似、在免疫调控通路方面存在共同的进化起源.这揭示了先天性免疫在动物体内存在的普遍性和机体抵御病原感染的重要性.     

Regulators and signalling in insect antimicrobial innate immunity: Functional molecules and cellular pathways

Insects possess an immune system that protects them from attacks by various pathogenic microorganisms that would otherwise threaten their survival. Immune mechanisms may deal directly with the pathogens by eliminating them from the host organism or disarm them by suppressing the synthesis of toxins and virulence factors that promote the invasion and destructive action of the intruder within the host. Insects have been established as outstanding models for studying immune system regulation because innate immunity can be explored as an integrated system at the level of the whole organism. Innate immunity in insects consists of basal immunity that controls the constitutive synthesis of effector molecules such as antimicrobial peptides, and inducible immunity that is activated after detection of a microbe or its product(s). Activation and coordination of innate immune defenses in insects involve evolutionary conserved immune factors. Previous research in insects has led to the identification and characterization of distinct immune signalling pathways that modulate the response to microbial infections. This work has not only advanced the field of insect immunology, but it has also rekindled interest in the innate immune system of mammals. Here we review the current knowledge on key molecular components of insect immunity and discuss the opportunities they present for confronting infectious diseases in humans.     

Establishment of ex vivo systems to identify compounds acting on innate immune responses and to determine their target molecules using transgenic Drosophila

Innate immunity is an evolutionarily conserved self-defense mechanism against microbial infections. In Drosophila, induction of antimicrobial peptides is a major immune response that is regulated by two distinct signaling pathways called the IMD pathway and the Toll pathway, similar to the tumor necrosis factor-alpha signaling and Toll-like receptor/interleukin-1 signaling pathways, respectively, in mammals. In mammals, innate immunity interacts with adaptive immunity and has a key role in the regulated immune response. Therefore, innate immunity is a pharmaceutical target for the development of immune regulators. Previously, based on the striking conservation between the mechanisms that regulate Drosophila immunity and human innate immunity, we established an ex vivo culture in which compounds acting on innate immunity can be evaluated using a reporter gene that reflects activation of the IMD pathway [Yajima et al. [Yajima, M., Takada, M., Takahashi, N., Kikuchi, H., Natori, S., Oshima, Y., Kurata, S., 2003. A newly established in vitro culture using transgenic Drosophila reveals functional coupling between the phospholipase A2-generated fatty acid cascade and lipopolysaccharide-dependent activation of the immune deficiency (imd) pathway in insect immunity. The Biochemical Journal 371(Pt 1), 205-210] Biochem J 371, 205-210]. Here, we combined the ex vivo culture with a reporter gene that reflects the heat shock response and demonstrated that the resulting systems are useful for screening compounds that act specifically on innate immunity, including mammalian innate immune responses. Identification of target molecules is essential for the development of more potent medicines with fewer side effects. In this study, we also established ex vivo systems capable of identifying target molecules of the identified compounds using targeted activation of the IMD pathway.     

Positive and negative regulation of the Drosophila immune response

Insects mount a robust innate immune response against a wide array of microbial pathogens. The hallmark of the Drosophila humoral immune response is the rapid production of antimicrobial peptides in the fat body and their release into the circulation. Two recognition and signaling cascades regulate expression of these antimicrobial peptide genes. The Toll pathway is activated by fungal and many Gram-positive bacterial infections, whereas the immune deficiency (IMD) pathway responds to Gram-negative bacteria. Recent work has shown that the intensity and duration of the Drosophila immune response is tightly regulated. As in mammals, hyperactivated immune responses are detrimental, and the proper down-modulation of immunity is critical for protective immunity and health. In order to keep the immune response properly modulated, the Toll and IMD pathways are controlled at multiple levels by a series of negative regulators. In this review, we focus on recent advances identifying and characterizing the negative regulators of these pathways.