寄生虫感染与免疫1

1、1,寄生虫感染与免疫,2,寄生虫组织结构、生活史的特点,1.寄生虫的分类,原生动物亚界,无脊椎动物,肉足鞭毛门,顶复门,纤毛门,扁形动物门,线性动物门,棘头动物门,节肢动物门,蠕虫,原虫,3,2.寄生虫的组织结构：复杂,4,红细胞,核膜,内质,外质,核仁,细胞膜,核丝,核染色质粒,溶组织内阿米巴(E.histolytica) 滋养体,核,食物泡,伪足,5,吸虫结构,6,吸虫（Trematode）,卫氏并殖吸虫P.westermani,日本血吸虫（S.japonicum),7,绦虫（Tapeworm）,猪带绦虫(T.solium),8,绦虫雌雄同体，生殖器官高度发达,每个节片各有雌雄生殖系统各一

2、套。,9,线虫（Nematode）,蛔虫(A.lumbricoides),10,线虫结构,11,医学节肢动物（Medical arthropod）,12,3.寄生虫的生活史： 有多个发育阶段，生活史多样性,13,疟原虫生活史,14,华支睾吸虫生活史,15,猪带绦虫生活史,16,蛔虫生活史,17,4.寄生虫的抗原,多源性: 寄生虫的抗原按虫体结构分：体抗原、表膜抗原、卵抗原、排泄-分泌抗原等。,复杂性（多糖、糖蛋白、糖脂等）: 寄生虫的组织结构和生活史的复杂性，以及虫种的遗传差别等多种原因，决定了寄生虫抗原的复杂性。,特异性（种、期),18,Overview of metabolism and

3、transport in P. falciparum （Nature，2002，419: 498511）,19,寄生虫的免疫应答,体液免疫应答,抗体的生物功能 ： 1.Ab单独作用于寄生虫，使其丧失入侵细胞的能力。 2.Ab与相应的寄生虫Ag结合后，在补体参与下，直接破坏寄生 虫。 3.Ab与相应寄生虫Ag结合后，通过Fc段与巨噬细胞、嗜酸性粒 细胞、NK、中性粒细胞联合诱导ADCC。 4.Ab诱导单核细胞分泌可溶性生物活性物质直接抑制或杀伤虫 体，即ADCI(抗体依赖细胞抑制作用）。,20,细胞免疫应答,1.抗原特异性T细胞可直接发挥效应功能，如 CTL可直接裂解靶细 胞 。 2.抗原活化的

4、T细胞可通过分泌细胞因子进一步作用于其他细胞群体，如TNF和白三烯(LT)可活化中性粒细胞和血管内皮细胞，IL-5活化嗜酸性粒细胞； IFN-活化单核巨噬细胞，IL-2活化NK细胞等 。 3.寄生虫感染的免疫应答中， Th具有关键作用 ： Th1细胞通过分泌IL-2、IFN-和TNF-促进细胞免疫， Th2细胞通过分泌IL-4、IL-5、IL-6、IL-10及IL-13促进体液免疫。 宿主对寄生虫感染的免疫应答机制十分复杂，且存在个体差异，寄生虫不同的发育期和致病期其优势表达的T细胞类型各不相同。,21,(1)遗传性特征 如黑人对P.v不易感 (2)种的特征 如人蛔虫猪蛔虫,(1)消除性免疫

5、如皮肤利什曼原虫病,免 疫作 用,1.非特异性免疫 （天然免疫）,2.特异性免疫 （获得性免疫）,(2)非消除性免疫,a.带虫免疫 如疟原虫,b.伴随免疫如血吸虫,寄生虫感染宿主免疫应答的类型,22,带虫免疫(premunition) 人体感染疟原虫后产生的免疫力，能抵抗同种疟原虫的再感染，但同时其血液内又有低水平的原虫血症。,伴随免疫(concomitant immunity) 宿主感染血吸虫后产生的免疫力，可对再次入侵的童虫具有一定的杀伤力，但对原发感染的成虫不起作用，这种原发感染继续存在，而对再感染具有一定免疫力的现象称伴随免疫。,23,寄生虫的免疫逃避,1.解剖学隔离,寄生于细胞、组织

6、和腔道的寄生虫，特有的生 理屏障使之与免疫系统隔离。 某些寄生虫在宿主体内可形成保护层。 某些寄生虫寄生于细胞内，可形成纳虫空泡,24,纳虫空泡,棘球蚴被纤维组织包裹,25,、表面抗原的改变,寄生虫抗原的阶段特异性 宿主体内寄生虫不同发育阶段表面抗原特异性发生改变。 如疟疾获得性免疫有严格的阶段特异性。,26,（2）抗原变异,表型改变是病原生物逃避宿主免疫反应杀伤的主要方法，表达变异的表面分子逃避免疫系统的清除，造成宿主持续性感染，这一过程称为抗原变异。 寄生虫抗原变异可表现为随机突变，如果突变率高，会给治疗造成很大的困难。另一方面寄生虫也有规律地改变暴露于宿主免疫系统的抗原。,27,Plas

7、modium falciparum erythrocyte membrane 1(PfEMP1)位于感染恶性疟原虫的红细胞表面,不是位于疟原虫虫体表面。是由恶性疟原虫分泌，然后转移到感染的红细胞膜上，并在红细胞表面蓄积而形成结节 。 大量研究表明 PfEMP1具有调节抗原变异和细胞黏附的双重作用。 恶性疟原虫将PfEMP1插入感染的红细胞膜，使其不能呈递抗原，从而逃避宿主免疫系统的攻击 。,Example 1,28,Genome sequence of the human malaria Parasite P. falciparum. Nature,2002,419: 498511,29,Al

8、ignment of P.falciparum and P. reichenowi Msp2 alleles is shown here. Amino-acid alignment of representatives of the 3D7/Camp (3D7) and Fc27 (OKS) allelic families with the P. reichenowi Msp2.,S.M. Rich, M.U. Ferreira and F.J. Ayala.The Origin of Antigenic Diversity in Plasmodium falciparum. Parasit

9、ology,2000.9:390-396,Example 2,30,(3)分子模拟与伪装 分子模拟：虫体体表能表达与宿主组织抗原 相似的成分。 伪 装：虫体体表镶嵌或包被宿主抗原。,如 :S.mansoni童虫体表可获得宿主的血型抗原和MHC,The similarity between host and microbial antigens may suppress the immune system and protect invading parasites and other infectious agents from being eliminated by the immune s

10、ystem.,31,马来布鲁线虫能够编码哺乳动物细胞因子 TGF-的同源物Bm-TGH-1 和Bm-TGH-2, 后者在体外由成虫所分泌并能和宿主的TGF-受体相结合；也能表达在功能和结构上与宿主MIF（macrophage migration inhibitory factor) 极相似的蛋白, 尽管二者只有28%的同源性。,Example 1,32,Maizels RM , Gomez- Escobar N, Gregory WF, et al. Immun evasion genes f rom f ilarial nematodes J . Int J Parasitol, 2001,

11、31( 9) : 889- 898.,33,Example 2,Schistosoma mansoni Excretory Circulating Cathodic Antigen Shares Lewisx Epitopes With a Human Granulocyte Surface Antigen and Evokes Host Antibodies Mediating Complement-Dependent Lysis of Granulocytes,34,35,华支睾吸虫LysoPLA氨基酸序列比对，与人的LysoPLA1同源性为47%,较高浓度的溶血磷脂可破坏生物膜的构象，甚

12、至引起细胞死亡。溶血磷脂的降解主要通过溶血磷脂酶I (lysophospholipase I, LysoPLA I）。,Example 3,36,（）表膜脱落与更新 虫体表膜脱落与更新，与表膜结合的抗体随之脱落。,如： S.mansoni成虫在有特异抗体存在时能脱去部分表 皮，然后再修复； S.mansoni尾蚴钻入皮肤时脱去其体表的糖萼，皮肤 中的童虫也能脱去表面抗原而保持完整形态。 肝片吸虫幼虫膜外层可不断被剥脱并再生。,37,、抑制宿主的免疫应答,（1）细胞因子的免疫调节,通过主动调整Th1细胞因子与Th2细胞因子的平衡，使寄生虫逃避宿主对其进行免疫杀伤，同时又不使宿主产生严重的免疫抑制

13、，使其在宿主体内长期寄生。,38,Major components of the granulomatous response to schistosome eggs in the host liver and the main cytokines and chemokines that regulate this response. Legend: Egg, Neutrophil, Eosinophil, Macrophage, Hepatic Stellate Cell，Fibroblast, Collagen Fibres, CD4+T-cell/B-cells, Hepatocytes

14、.,39,日本血吸虫虫卵肉芽肿及其纤维化,40,Possible involvement of immune cells and mediators in the helminth-induced immunomodulation on T helper subsets. Substances contained in the bodies of helminths or their excretory secretory (ES) products are recognized by innate immune cells via PAMPs receptors like TLRs. The

15、reafter, various changes occur in the immune cells, for example, down-modulation of IL-12/23p40 expression (DC), alternative activation (macrophages), proliferation and/or IL-10 production (Treg, Tr1, and B cells), and IL-4 production (basophils). We can observe suppression of immune disorders with

16、down-regulation of pathogenic T helper subsets (Th1, Th17, and allergic Th2) as consequence of mixed effects of such immunological changes.,41,（2）激活Treg细胞 如:感染血吸虫的小鼠的Treg细胞（抑制免疫活性细胞的分化和增殖）激活，产生免疫抑制。,42,The expression of IFN- (a) and IL-10 (b) in spleen cell culture supernatant in BALB/c mice. *P0.05

17、, versus normal group. *P0.01, versus normal group. #P0.05, versus infected group,43,Parasitol Res ，2011， 108:477480,44,（3）虫源性淋巴细胞毒性因子,寄生虫的分泌、排泄物中某些成分具有直接的淋巴细胞毒性作用或抑制淋巴细胞激活。,Example : T. cruzi cDNA encoding a parasite released protein (named Tc52) completely inhibited human and mice lymphocyte proli

18、feration in response to mitogens.,45,Tc52 synergizes with IFN- to stimulate NO production by macrophages,It is likely that NO production during the initial phase of acute T. cruzi infection might participate in the clearance of parasites by macrophages whereas its overproduction during the late phas

19、e of acute infection would account for the immunosuppression observed.,46,S.mansoni童虫表面 的糖蛋白抗原,有共同的碳水化合物表位,（4）封闭抗体,虫卵的大分子多糖抗原,47,蠕虫感染的免疫特点,In both humans and animals, this canonical response is of the Th2 type and involves -IL-3, IL-4, IL-5, IL-9, IL-10 and IL-13, the antibody isotypes IgG1, IgG4 an

20、d IgE, and expanded populations of eosinophils, basophils, mast cells and alternatively activated macrophages . The innate immune system not only anticipates and initiates the adaptive Th2 cell response but, importantly, continues to provide companying and mutually reinforcing pathways of Th2-type i

21、mmunity throughout infection .,48,Figure ： IL-4Ris the central role of type 2 immunity,1、Th2的免疫应答,YM1,YM2:chitinase 3-like protein 3 and 4 RELM: resistin-like molecular TSLP : thymic stromal lymphopoietin MBP: eosinophil granule major basic protein MUC5AC: mucin 5AC,49,2、蠕虫感染引起的Th2免疫应答,Effector Th2

22、immunity in mucosal tissues,Effector Th2 immunity in peripheral tissues,in which the cells impose a slow death by compromising worm vitality rather than providing an immediate lethal hit.,In non-mucosal tissues, parasites must be destroyed rather than excluded, and the type 2 response is consequentl

23、y very different.,50,Epithelial cells are also one of the principal targets of Th2 cytokines,as IL-13 increases cell turnover and induces the differentiation of goblet cells, which produce mucins and the anti-nematode protein resistin-like molecule-) . Fluid transfer into the gut is raised by the ac

24、tion of mast cell proteases, which degrade tight junctions in the epithelial cell layer. Antibodies from B cells contribute by diminishing worm fitness and fecundity.,51,IL-13 induces Muc5ac as part of the normal response to worm expulsion. (A) Levels of Muc5ac were determined using immunofluorescen

25、ce microscopy with the 45M1 antibody in WT and IL-4 and IL-4Rdeficient mice (BALB/c background) at days 18 and 35 with T. muris. Results are representative of three individual experiments and are presented as the mean value of five mice per group SEM. ND, none detected. *, P 0.05 compared with nave

26、controls; , P 0.05 compared with WT.,52,Muc5ac deficiency renders resistant mice susceptible to chronic T. muris infection. Muc5ac-deficient mice and the WT C57BL/6 mice were infected with a high dose of T. muris eggs, and worm burdens were assessed on days 14, 23, and 45 p.i. Results are representa

27、tive of three individual experiments and are presented as the mean value of three to five mice per group SEM. *, P 0.01 compared with day 14; , P 0.01 compared with Muc5ac-deficient mice.,53,A dose-dependent decrease in the nematodes ATP levels was observed when they were treated with an increasing

28、concentration of MUC5AC.,J. Exp. Med. 2011，208 ： 893-900,54,In the tissues, parasites are open to attack by the full range of host innate effectors, including macrophages, neutrophils, eosinophils, basophils and. The ability of these effector cells to kill helminths is often dependent on one or more

29、 isotypes of specific antibody (often IgE, but IgM in the bloodstream) and complement. Armed granulocytes or macrophages can release damaging metabolic oxygen and nitrogen intermediates onto helminths, but in vivo killing methods are not yet fully understood.,55,3.Th2 immunity in the repair of paras

30、ite-induced damage,56,Parasites such as hookworms repeatedly breach the gut wall, and the resulting cell death leads to the release of alarmins, such as interleukin33 (IL33). These molecules, along with parasite products, promote a type 2 response, either directly by acting on innate cells or indire

31、ctly through APCs that induce Th2 cells. Macrophages in this setting may be predominantly anti-inflammatory, suppressing T cell responses through arginase 1 production and inhibiting classical macrophage inflammation and recruitment through the production of arginase 1, triggering receptor expressed

32、 on myeloid cells 2 (TREM2) and other molecules. Epithelial cells stimulated by Th2type cytokines can induce resistin-like molecule- (RELM) or RELM, which contribute to wound repair, while arginase 1 from fibroblasts may promote extracellular matrix (ECM) deposition that can either repair damage or

33、encapsulate worms.,57,4. Foxp3+ Tregs 调节蠕虫感染的免疫应答,58,Foxp3+ Treg responses to helminths encompass cells of both natural and adaptive origins. Evidence indicates that natural Foxp3+ Tregs respond rapidly to infection, forming the first line of regulation, whereas adaptive Foxp3+ Treg responses develo

34、p with slower kinetics. To limit immune pathology, Tregs must dampen infection-induced inflammation; however, activated Tregs can inhibit protective immunity, opening an exploitable avenue for parasites. Reflecting this, both host and helminth can create adaptive Foxp3+ Tregs, because helminths secr

35、ete a TGF- mimic to hijack the TGF- pathway used to convert naive T cells towards a regulatory phenotype.,59,自身免疫性疾病(autoimmune diseases，AID): 指自身耐受机制遭到破坏，自身免疫应答的质和(或)量发生异常，自身抗体和自身反应性淋巴细胞攻击并破坏自身组织细胞，机体出现的病理改变和相应临床表现。在自身耐受(self tolerance)机制正常的情况下，机体免疫系统对自身组织成分保持无应答或低应答状态。自身耐受的产生和维持有赖于中枢和外周耐受机制的共同作用，其

36、异常和破坏是导致AID发生的根本原因。,寄生虫感染对自身免疫性疾病的保护作用,60,流行病学调查表明在许多国家寄生虫感染率和自身免疫性疾病的发病率往往呈负相关，提示寄生虫感染对自身免疫性疾病可能有保护作用。早期的研究表明，ThlTh2细胞活性的相对平衡对机体局部和全身的免疫及病理状况都有直接影响。自身免疫性疾病往往伴随着Thl细胞的过度活动；而蠕虫感染却常可诱导一个偏向于 Th2细胞的反应。,61,The immune system has evolved to operate optimally in the presence of helminth downmodulation, so t

37、hat the level of immune reactivity has been calibrated by evolution to compensate for parasite induced dampening of immune responses, while minimizing the risk of incurring life threatening helminth generated pathology from either uncontrolled worm loads or overzealous inflammatory reactions .,62,In contemporary societies without endemic helminth infections, proinflammatory alleles that evolved to maintain immune fitness are now seen as responsible for immunopathologies in the human population.,63,Cooke等在NOD小鼠上进行了曼氏血吸虫 感染与工型糖尿病(insulindependent diabetes m