锥虫免疫逃避的研究进展

正在寄生虫与宿主长期的适应过程中,有些寄生虫获得了抵制其免疫清除作用的能力,这种能力被称为免疫逃避(immune evasion)~([1])。寄生虫为了在宿主体内存活,进化出了逃避宿主先天性免疫和特异性免疫的能力。锥虫(Trypanosome)寄生于人和动物的血液内引起严重的锥虫病,其免疫逃避机制非常复杂,这也正是锥虫病疫苗研究困难的原因之一,揭示其免疫逃避机制将为锥虫病疫苗的研制奠定理论基础。锥虫有多种复杂的免疫逃避机制,如     

病毒免疫逃避机制

哺乳动物虽然有完整的、高度进化的免疫保护系统 ,有些病毒仍能在其中长期存在。这主要是由于病毒在长期的宿主免疫选择压力下产生了多种对抗宿主免疫系统的机制。一些病毒 ,如流感病毒、ＨＩＶ病毒通过抗原变异 ;疱疹病毒通过隐性感染来逃避宿主的免疫清除。这些病毒有很大的基因组 ,其中有些基因并不是病毒复制所必需的 ,但在其逃避宿主免疫清除却有重要的作用。通过对这些病毒基因组序列分析及其表达产物的鉴定 ,发现病毒编码的蛋白与宿主免疫系统的功能调节分子具有同源性 ,病毒通过这些蛋白来调节宿主的免疫监控系统 ,从而得以复制、增…     

锥虫变异抗原基因的分子生物学

锥虫是单细胞的真核生物,种类很多.寄生于哺乳动物的锥虫,从地域上讲有非洲锥虫、亚洲锥虫和美洲锥虫;从传播方式上讲有唾液传播锥虫(含机械传播锥虫)和粪便传播锥虫.非洲和亚洲锥虫多为唾液传播锥虫,美洲锥虫主要是粪便传播锥虫.能够在哺乳动物体内进行抗原变异的是唾液传播锥虫.唾液锥虫寄生于宿主血液之中,也存在于宿主其他部位,如马媾疫锥虫寄生于马、驴的生殖系统.大部分种类的唾液锥虫能够在昆虫体内发     

血吸虫的抗原伪装研究进展

抗原伪装是包括寄生虫在内的病原体的一种逃避宿主免疫反应方式.血吸虫在宿主间的转移实验证明了血吸虫具有抗原伪装现象.在血吸虫生活史的主要阶段均发现了许多与宿主相同的抗原以及众多的免疫抑制物质.这些物质有些是血吸虫自身表达的,有些是血吸虫结合的宿主抗原.它们通过掩盖血吸虫抗原等多种机理伪装血吸虫进而使血吸虫逃避宿主的免疫攻击.     

一例猪弓形体病的诊疗报告

猪弓形体病是由弓形体寄生于人和多种动物体内引起的人畜共患的原虫病。弓形体为细胞内寄生虫,终末宿主是猫,中间宿主包括哺乳动物、鸟类和冷血动物。本病可在猪场突然暴发,发病急,流行快,死亡率高。不仅严重危害养猪业,也影响人类的健康。近几年来,由于猪无名高热病的流行,许     

寄生虫感染与免疫

本文从寄生虫抗原、宿主对寄生虫和寄生虫对宿主的免疫应答、免疫抑制及免疫不全状态下的寄生虫感染以及免疫学诊断、预防等方面,重点阐明其特征性的免疫现象。寄生虫的抗原非常复杂,包括构成虫体本身物质的虫体抗原和排泄、分泌抗原等。寄生虫感染的重要表现是IgE抗体产生增强和嗜酸白细胞增多。特异性IgE抗体产生,是因为在寄生虫抗原中有诱导IgE抗体生成的抗原即变应原的存在,这种变应原又受特异的辅助T淋巴细胞的诱导。嗜酸白细胞不仅在血中增加,在感染组织中也见显著浸润。它除了在Ⅰ型变态反应中具有调节作用外,对寄生虫也有直接作用。寄生蠕虫类一方面可降低本身的抗原性,朝着与宿主抗原相一致的方向进化着。另一方面虫体可以把感染初期的抗体吸附在自身表面形成封闭抗体。同时蠕虫类还能产生抗补体因子和向外释放抗原物质来干扰宿主的免疫系统,巧妙地逃避宿主的免疫应答而使自身生存下来。     

运用伊氏锥虫抗原变异规律进行免疫的初步研究

为了克服锥虫抗原变异对宿主免疫反应的干扰，探索伊氏锥虫病高效保护性抗原，根据伊氏锥虫在宿主体内第一次发生变异产生的变异抗原免疫原性相同的规律，设计了伊氏锥虫变异前抗原（VSG1）和第二次变异所产生的抗原（VSG2）复合物作免疫原，对小鼠进行免疫与单用变异前抗原免疫鼠相比较，两组鼠都用带变异前抗原的虫攻击，另以未免疫的鼠作对照，结果VSG1＋VSG2免疫组小鼠8只全部获得保护，单用VSG1免疫组小鼠10只和未免疫组小鼠10只血中全部出虫而死亡，前者比后者出虫时间和存活时间延长，提示运用伊氏锥虫抗原变异这一规律设计的这种免疫复合物，能激收缩主克服虫体抗原变异对免疫保护的干扰。     

非洲锥虫的非变异表面糖蛋白

非洲锥虫的非变异表面糖蛋白蔡建平沈永林汪志楷（南京农业大学动物医学院２１００９５）众所周知，锥虫可通过其表面变异糖蛋白（ＶＳＧ）的时序性改变而逃避宿主的免疫［１］。现已知每个锥虫携带的ＶＳＧ基因大约有１０００种之多［２］，这些基因以时序表达的方式合成...     

鸡虱病的具体防治方法

鸡虱是寄生在家禽体表的一种昆虫,也是家禽的一种最普通的外寄生虫。属节肢动物门、昆虫纲、食毛目的一种体外寄生虫。寄生于家禽体表的羽虱种类很多,且各具严格的宿主,寄生部位也较恒定。     

核酸疫苗的研究进展

核酸疫苗又称基因疫苗，包括DNA疫苗和RNA疫苗。目前研究最多的是DNA疫苗，由于其不需要任何化学载体，又称裸DNA疫苗，主要是利用基因重组技术直接将编码抗原蛋白的外源抗原基因导入动物体细胞内，在宿主细胞中表达外源抗原基因，诱导宿主产生对该抗原的免疫应答，从而使被接种动物获得免疫保护。     

Antigenic variation as an exploitable weakness of babesial parasites

Babesia bovis and its bovine host interact in many ways, resulting in a range of disease and infection phenotypes. Host responses to the parasite elicit or select for a variety of responses on the part of the parasite, the full range of which is not yet known. One well-established phenomenon, thought to aid parasite survival by evasion of host adaptive immune responses, is the sequential expansion of antigenically variant populations during an infection, a phenomenon referred to as "antigenic variation". Antigenic variation in B. bovis, like that in the human malarial parasite, Plasmodium falciparum, is intimately linked to a second survival mechanism, cytoadhesion. In cytoadhesion, mature parasite-containing erythrocytes bind to the capillary and post-capillary venous endothelium through parasite-derived ligands. The reliance of these parasites on both functions, and on their linkage, may provide opportunities to develop anti-babesial and, perhaps, anti-malarial protection strategies. The development of inhibitors of DNA metabolism in B. bovis may be used to abrogate the process of antigenic variation, whereas small molecular mimics may provide the means to vaccinate against a wide range of variants or to prevent the surface export of variant antigen ligands. In this article, aspects of antigenic variation and cytoadhesion in bovine babesiosis are explored, with a discussion of opportunities for prophylactic or therapeutic intervention in these intertwined processes.     

African trypanosomosis: from immune escape and immunopathology to immune intervention

African trypanosomes can cause prolonged chronic infections through a mechanism of antigen variation whereby they manipulate the humoral immune system of their hosts. However, besides antigenic variation these extracellular parasites exert other immunoregulatory activities mainly mediated by innate cells in particular macrophage-like (M) cells. In this review, the modulation of M cells through parasite factors and host cytokines as well as their role in parasite control and immunopathology will be examined. The concept of M cell polarization into distinct activation states (M1, M2) that may contribute to trypanosusceptibility or resistance will be discussed. Finally, the possibility to interfere with such activation states hereby providing new therapeutical modalities in the treatment of this infectious disease will be illustrated.     

寄生虫蛋白酶体的研究进展

近年来,蛋白酶体的分子组成、亚基、生化机理、胞内功能等方面的研究受到广泛关注,发展迅速.蛋白酶体的主要生物学功能包括:降解细胞内蛋白质、调节细胞周期、促进细胞凋亡、调节转录因子、增加抗原提呈等.在寄生虫中,蛋白酶体不仅参与胞内寄生虫的生长发育调节,同时对宿主造成损伤,并可诱导宿主产生对其的免疫应答.对寄生虫蛋白酶体的研究有助于深入了解寄生虫的入侵机制,为寄生虫病的防治提供新思路.作者对蛋白酶体的结构、功能及寄生虫蛋白酶体的研究进展作一综述.     

The 18 kDa Antigen of Theileria equi is a Specific but Less Abundant Protein Also Expressed by Parasites Cultured In Vitro

A universally applicable test has not yet been developed for the reliable diagnosis of equine theileriosis, mainly because of the paucity of specific antigens and antigenic variation between different isolates. In this study, we used Theileria equi parasites cultured in vitro to identify potential diagnostic antigens. Using preparative isoelectric focusing to resolve the proteins in a lysate of infected erythrocytes, we identified an 18 kDa component of the parasite as a specific but poorly expressed antigen. This antigen also appears to have conserved epitope(s) between the isolates from the New and the Old World, as positive sera from both European and South American horses recognize it. The recombinant replica of this antigen might be a valuable tool for inclusion in the development strategy for a diagnostic test.     

Antigenic alteration in major piroplasm surface proteins of Theileria sergenti during infection

Theileria sergenti piroplasms were purified from different parasitemia peaks of cattle infected with parasitized erythrocytes or sporozoites during persistent infection. Their activities with monoclonal antibodies 13F5 and C9, which recognize 23 kDa and 32 kDa piroplasm surface proteins, respectively, were analyzed. Antigenic differences were observed among parasites from different parasitemia peaks during persistent infection when cattle were infected with sporozoites. Results of two-dimensional polyacrylamide gel electrophoresis showed that the 23 and 32 kDa proteins were expressed in all samples tested, regardless of their reactivities with the monoclonal antobodies. In contrast, parasites obtained from cattle inoculated with parasitized erythrocytes showed no antigenic alteration over a 2 month observation period. The results suggest that antigenic alteration of T. sergenti during persistent infection is related to whether the parasites proliferate through extraerythorocytic schizont stage in cattle or sporozoite and other sexual stages in tick vector.     

Immunologic structures and functions of the gut

The intestine is richly populated with lymphoid tissue capable of initiating and effecting a wide variety of immunologic reactions. These reactions have consequences not only for the gut itself but for the body in general, and have established the importance of the gut as an immunologic organ. Among the outer and inner surfaces of our body, the 200 to 300 m2 of the gut contrast with the 2 m2 of the skin, and the 80 m2 of the lung. At the inner surface of the intestine, our organism contacts intimately bacteria, parasites, enzymes, toxins, a wide variety of dietary substances and their breakdown products. The essential barrier against the permanent antigenic burden is the mucosa. Its integrity depends on the continual replication, maturation, and metabolism of its constituents. Additional defense functions are exerted by the mucus, lysozyme, phagocytes, other cells, humoral factors and biological response modifiers involved in inflammatory and immune reactions. Some of these factors are being produced very close to the surface at which they act. The sum of the mechanical, humoral, cellular, immunologic and non-immunologic defense factors of the intestinal mucosa constitutes the mucosal block. However, the block is not complete. Rather, a continuous antigenic uptake through the epithelial layer takes place. The specialized structures of Peyer's patches, solitary lymph follicles, appendix vermiformis and their associated epithelium allow a controlled antigen uptake (sampling). Because of the heavy antigenic load, the intestine can be described as the most important immunologic contact organ of our body. The antigens may give rise to local and systemic immune reactions with antibody production, or the suppression of systemic immunologic responses to ingested antigens ("oral tolerance").     

An update of the isolation and characterization of culture-derived soluble antigens of Babesia bovis

In this paper recent progress concerning the identification of soluble antigens from cultures of Babesia bovis parasites is reviewed. Soluble antigens present in the supernatant of B. bovis cultures have been shown to be efficient immunogens for induction of protective immunity against bovine babesiosis. Immunochemical analysis of culture supernatants has demonstrated that at least 3 parasite antigens are released in vitro. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that at least 2 of these antigens have molecular weights within the range of 37 000-40 000 daltons. Crossed immunoelectrophoretic studies have further revealed an antigenic spectrum consisting of 1 major and 2 minor antigens with mobilities in the albumin and alpha 1 regions. Within the infected erythrocyte, 2 antigens have been localized on or near the erythrocytic membrane, while the third antigen appears to be directly associated with the parasite.     

Antigenic comparison of Lelystad virus and swine infertility and respiratory syndrome (SIRS) virus.

This study reports the antigenic relatedness of isolates of Lelystad virus collected in the Netherlands, Germany, and the United States. The binding of antibodies directed against these isolates was tested in a set of field sera collected during outbreaks of porcine epidemic abortion and respiratory syndrome in Europe and outbreaks of swine infertility and respiratory syndrome (SIRS) in North America. Two sets of sera from pigs experimentally infected with Lelystad virus or SIRS virus were also tested. Although all 7 isolates reacted with anti-Lelystad virus sera, antigenic variation was considerable. The 4 European isolates resembled each other closely, but differed from the American isolates, and the 3 American isolates differed antigenically from each other. To reliably diagnose Lelystad virus infection, a common antigen must first be identified.