寄生虫半胱氨酸蛋白酶研究进展

半胱氨酸蛋白酶(Cysteine protease,CP)是一类在酶的活性中心含有半胱氨酸残基的蛋白水解酶.CP属于木瓜蛋白酶家族,广泛分布于从病毒至脊椎动物的生物体中.对人体半胱氨酸蛋白酶的研究主要集中在细胞凋亡分子机制和恶性肿瘤的基因诊断与治疗等方面.而对寄生虫半胱氨酸蛋白酶研究的内容则更为广泛,其中包含半胱氨酸蛋...     

核酸疫苗的应用研究进展

核酸疫苗不仅引起体液免疫反应,而且诱导高水平的细胞免疫应答,尤其是细胞毒T淋巴细胞(CTL)反应,被认为在病毒、胞内菌、寄生虫等病原体感染的防治中具有更大的优势。核酸疫苗作为近年来发展起来的一项新的生物技术,已经成为疫苗研究领域的热点之一,并获得了迅速的发展。实验结果表明,核酸疫苗既可作为病毒、细菌或寄生虫的预防疫苗,也可作为非感染性疾病如肿瘤病的治疗用疫苗。通过介绍近年来核酸疫苗在病毒、细菌、寄生虫等感染性疾病的预防和治疗等领域的研究进展情况,表明随着分子生物技术的不断发展,核酸疫苗的进一步研究和实践为改善人类和动物健康显示出新的希望。     

蜱半胱氨酸蛋白酶抑制分子研究进展

蜱是以吸血为生的体外寄生虫,能传播多种病原体。控制蜱的传统方法是使用杀虫剂,但会产生药物残留等问题。为了找到控制蜱及蜱传病的新方法,必须在分子水平上了解蜱的相关生理过程。蜱半胱氨酸蛋白酶抑制分子是一类抗蛋白酶分子,主要作用于半胱氨酸蛋白酶的抑制调控。论文介绍了蜱半胱氨酸蛋白酶抑制分子的结构和分类,以及在蜱的吸血、血液消化、蜱的先天免疫及对宿主免疫调节等生理过程的重要作用,同时也综述了半胱氨酸蛋白酶抑制分子具有抗寄生虫和抗癌的作用,为全面了解蜱半胱氨酸蛋白酶抑制分子提供参考。     

寄生虫半胱氨酸蛋白酶抑制剂的研究进展

半胱氨酸蛋白酶抑制剂是一类在进化相关的蛋白质,能够抑制半胱氨酸蛋白酶类的活性。根据氨基酸序列和一级结构特征,将半胱氨酸蛋白酶抑制剂分为stefins家族,cystatins家族,kininogens家族和fetuin家族四个亚家族。本文通过结合半胱氨酸蛋白酶抑制剂功能的研究进展,对吸虫、绦虫、线虫和原虫半胱氨酸蛋白酶抑制剂的结构、种类、免疫调节和免疫逃避功能进行综述,以期对寄生虫半胱氨酸蛋白酶抑制剂的应用和深入研究提供参考。     

寄生虫半胱氨酸蛋白酶生物学功能研究进展

半胱氨酸蛋白酶(CP)是广泛存在于动物和植物以及寄生虫中的一类含有半胱氨酸残基的蛋白水解酶,是蛋白酶家族中最重要的成员之一.目前,对人CP的研究宅要集中在凋亡和肿瘤两个方面,而对寄生虫CP的研究则相对比较广泛.     

寄生虫核酸疫苗的研究概况

核酸疫苗是一种将某种保护性抗原的编码基因克隆到真核细胞表达调控序列的质粒中 ,制成 DNA的重组质粒 ,直接给动物注射后质粒 DNA在组织内扩散 ,被宿主细胞摄取 ,随后通过宿主细胞的转录翻译系统 ,表达保护性抗原蛋白 ,在抗原蛋白释放分泌的同时 ,诱导机体发生免疫应答 ,产生对该抗原的保护性免疫 ,以达到治疗和预防疾病的目的。因此核酸疫苗又称基因疫苗 [1]。其包括 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 DNA疫苗。本文就寄生虫核酸疫苗的研究作一综述。1　核酸疫苗的研究概况1 994年 5…     

蜱半胱氨酸蛋白酶分子研究进展

蜱作为体表吸血节肢动物,可通过采食宿主血液传播多种病原体,是一种重要媒介。半胱氨酸蛋白酶是一类分布广泛具有一定保守性的蛋白酶,在蜱生理学中发挥重要作用。本文对蜱半胱氨酸蛋白酶的研究进展进行了综述,重点介绍了组织蛋白酶、天冬酰胺内肽酶和半胱天冬氨酸蛋白酶,及参与自噬反应的半胱氨酸蛋白酶的功能及相互作用。     

核酸技术在禽病研究中的应用

核酸限制内切酶指印和酶谱分析是用特异限制性酶分解核酸,然后用电泳分离核酸片段的技术。该技术可鉴别出血败血性巴氏杆菌野毒和疫苗株;把肠炎沙门氏菌分为3组;把衣原体分为7组和清楚地鉴别出牛痘、鹌鹑痘和禽痘。核酸探针是一些用来检     

鸡球虫病疫苗研究进展

鸡球虫病广泛分布于世界各地,是危害养鸡业的重要寄生虫疫病之一。对鸡球虫病疫苗的研究已成为广大动物医学工作者关注和研究的热点之一。文章对鸡球虫病疫苗的研究现状以及核酸疫苗在鸡球虫病防制中的应用等研究新进展作简要综述。     

巨型艾美耳球虫gam82基因核酸疫苗的构建与免疫原性分析

以重组质粒pGEM-T-gam82为模板,构建巨型艾美耳球虫gam82基因核酸疫苗.采用MTT法与ELISA对该核酸疫苗接种鸡体后淋巴细胞增殖与抗体水平的变化进行检测,结果显示,该核酸疫苗具有一定的免疫原性.     

Immunodiagnostic/protective role of cathepsin L cysteine proteinases secreted by Fasciola species

Cathepsin L, a major cysteine proteinase secreted by the parasite plays a pivotal role in various aspects of its pathogenecity. The enzyme takes part in nutrient acquisition by catabolizing host proteins to absorbable peptides, facilitates the migration of the parasite through the host intestine and liver by cleaving interstitial matrix proteins such as fibronectin, laminin and native collagen and is implicated in the inactivation of host immune defenses by cleaving immunoglobulins. Recently, Cathepsin L has been shown to suppress Th1 immune response in infected laboratory animals making them susceptible to concurrent bacterial infections. Accordingly, the protease has been recognized as an important target at which parasite intervention strategies should be directed. Fluke Cathepsin L cysteine proteinases are also reported as sensitive and specific markers for the immunodiagnosis of fasciolosis in ruminants. Further, vaccination of laboratory or large animals with these proteases resulted in a significant reduction in fluke burden and/or fecundity.     

Proteases in helminthic parasites

Proteases catalyse the cleavage of internal peptide bonds within peptides and proteins. They are classified into four major classes and are involved in a broad range of eukaryotic processes. Proteases have also been found to play a number of critical roles in the virulence of pathogenic agents, particularly of nematode parasites. Parasitic proteases are involved in different aspects of host-parasite interactions. They facilitate the invasion of host tissues and allow nutrition as well as the survival of the parasite in its host. Proteases also participate in the parasite's evasion from the host's immune response. The functional diversity and complexity of these enzymes are described in this review, with a particular focus on the principally identified proteases of four helminths: Schistosoma sp., Fasciola sp., Taenia sp. and Haemonchus sp. Some of these proteases, especially the cysteine proteases secreted by the parasitic trematode Fasciola hepatica, have been successfully tested in experimental immunodiagnosis. Proteases identified in different parasites are currently under study for a use as recombinant vaccines. In this respect, proteases are proposed as major potential targets for immunotherapy and chemotherapy against parasitic diseases.     

The role of molecular biology in veterinary parasitology

The tools of molecular biology are increasingly relevant to veterinary parasitology. The sequencing of the complete genomes of Caenorhabditis elegans and other helminths and protozoa is allowing great advances in studying the biology, and improving diagnosis and control of parasites. Unique DNA sequences provide very high levels of specificity for the diagnosis and identification of parasite species and strains, and PCR allows extremely high levels of sensitivity. New techniques, such as the use of uniquely designed molecular beacons and DNA microarrays will eventually allow rapid screening for specific parasite genotypes and assist in diagnostic and epidemiological studies of veterinary parasites. The ability to use genome data to clone and sequence genes which when expressed will provide antigens for vaccine screening and receptors and enzymes for mechanism-based chemotherapy screening will increase our options for parasite control. In addition, DNA vaccines can have desirable characteristics, such as sustained stimulation of the host immune system compared with protein based vaccines. One of the greatest threats to parasite control has been the development of drug resistance in parasites. Our knowledge of the basis of drug resistance and our ability to monitor its development with highly sensitive and specific DNA-based assays for 'resistance'-alleles will help maintain the effectiveness of existing antiparasitic drugs and provide hope that we can maintain control of parasitic disease outbreaks.     

The highly antigenic 53/25 kDa Taenia solium protein fraction with cathepsin-L like activity is present in the oncosphere/cysticercus and induces non-protective IgG antibodies in pigs

Cathepsin L-like proteases are secreted by several parasites including Taenia solium. The mechanism used by T. solium oncospheres to degrade and penetrate the intestine and infect the host is incompletely understood. It is assumed that intestinal degradation is driven by the proteolytic activity of enzymes secreted by the oncosphere. Blocking the proteolytic activity by an antibody response would prevent the oncosphere penetration and further infection. Serine and cysteine proteases including chymotrypsin, trypsin, elastase, and cathepsin L, are secreted by T. solium and Taenia saginata oncospheres when cultured in vitro, being potential vaccine candidates. However, the purification of a sufficient quantity of proteases secreted by oncospheres to conduct a vaccine trial is costly and lengthy. A 53/25 kDa cathepsin L-like fraction partially purified from T. solium cyst fluid was described previously as an important antigen for immunodiagnostics. In this study we found that this antigen is present in the T. solium oncosphere and is also secreted by the cysticercus. This protein fraction was tested for its ability to protect pigs against an oral challenge with T. solium oncospheres in a vaccine trial. IgG antibodies against the 53/25 kDa cathepsin L-like protein fraction were elicited in the vaccinated animals but did not confer protection.     

Infectious bovine keratoconjunctivitis vaccine development

Infectious bovine keratoconjunctivitis is a common and highly contagious ocular disease affecting cattle worldwide. The tremendous economic losses attributable to this disease warrant continued investigation into methods of prevention. Multiple virulence factors have been linked to the primary aetiologic agent, Moraxella bovis. Efforts to develop an efficacious vaccine have primarily focused upon the use of surface pili or cytolysin to stimulate host immunity; however, M. bovis possesses other virulence determinants that include proteases, fibrinolysins, phospholipases and other cell surface components such as outer membrane proteins. These potentially conserved antigens provide additional possibilities for vaccine development. Examination of appropriate antigen presentation is necessary to attain an adequate immune response. Further, the potential for antigenic diversity as well as epitope conversion requires continuous epidemiological surveillance of isolates recovered from outbreaks. Current work targeting conserved immunogens provides hope for efficacious vaccines that when used in tandem with proper management may control, if not prevent, infectious bovine keratoconjunctivitis.     

Induction of immune responses in sheep by vaccination with liposome-entrapped DNA complexes encoding Toxoplasma gondii MIC3 gene

Toxoplasma gondii is a parasite that has been extensively studied due to its medical and veterinary importance in terminating pregnancies. Consequently, a satisfactory vaccine is required to control its adverse effects on pregnant animals. The microneme protein, MIC3, is a major adhesion protein that binds to the surface of host cells and parasites, and is therefore a potential vaccine against T. gondii. The viability of MIC3 as a vaccine is investigated in this study. Sheep were injected twice, intramuscularly, with plasmids containing DNA encoding for the mature form of MIC3 protein formulated into liposomes. Control sheep were injected with an empty vector or received no injections. The injection of sheep with DNA plasmids encoding for MIC3 elicited an immune response after the first and second injections as indicated by antibody responses and the production of IFN-gamma. The immune response, as measured by the IgG2 and IgG1 serum levels, was boosted after the injection of the MIC3 DNA vaccine together with high anti-MIC3 antibodies. The results demonstrate that the intramuscular injection of sheep with a plasmid containing DNA coding for MIC3 protein induces a significant and effective immune response against T. gondii.     

Preliminary development of a live drug-controlled vaccine against bovine babesiosis using the Mongolian gerbil, Meriones unguiculatus.

This study investigated the practicality and potential of the gerbil, Meriones unguiculatus, as a source of live Babesia divergens vaccine and also as a model for the use of the vaccine in cattle. A series of experiments with gerbils concerning vaccine infectivity, immunogenicity and safety were carried out. It was concluded that the use of RPMI medium/40% foetal calf serum as a diluent improved vaccine infectivity, but that the parasitaemia of the blood obtained from donor gerbils had little or no effect. The immunostimulants levamisole and killed Corynebacterium parvum improved vaccine immunogenicity and it was also shown that the subcutaneous route of infection resulted in the greatest host response. Control of vaccine virulence with drugs was only possible when drugs with prophylactic properties, such as imidocarb and long-acting oxytetracycline, were used. More studies are required on all these topics, particularly with regard to their applicability to cattle, and also concerning the possible attenuation of the parasite by manipulation in the gerbil host.     

Immunoprotective effect of cysteine proteinase fractions from two Haemonchus contortus strains adapted to sheep and goats

A preliminary analysis of the significance of genetic diversity in cysteine proteinase genes has been performed simultaneously in sheep and goats, with regard to the immunological control using these enzymes against haemonchosis. For this purpose, we have studied the cross-immunoprotective effect of cysteine protease-enriched protein fractions (CPFs) in adult worms of two Haemonchus contortus strains from North America and Spain that are adapted to sheep and goats, respectively. Previous genetic analysis of cysteine proteinase genes in both strains has shown that some of loci are polymorphic and these differences are translated into changes in the amino acid sequences. However, our results show that CPFs from H. contortus adult worms have a protective effect against the parasite in both sheep and goats. These results are similar regardless of whether they were obtained from sheep or goat-adapted H. contortus strains, which could be very important in case H. contortus CPFs were commercially used in different countries, as vaccines to prevent the negative effects of this parasite. Interestingly, this experimental inoculation of both species with a heterologous strain of H. contortus contributes to the idea shown in previous studies about how difficult is the interpretation and the comparison of vaccination where strains not adapted to a specific host are used. Therefore, the challenger of using heterologous strains could provide similar results to those observed in immunised animals. This study suggests the possibility of exploring the mechanisms involved in natural protection against non-adapted strains, in order to develop strategies to control haemonchosis.     

顶复门原虫含苹果结构域蛋白的研究进展

苹果结构域在弓形虫和艾美耳球虫中的研究较深入,其不但具有高度的保守性而且在虫体粘附和入侵宿主的过程中起着重要作用。为此,本文对苹果结构域的结构和功能,及其在弓形虫、艾美耳球虫、肉孢子虫中的研究进展做以综述,以期为开发新一代顶复门原虫的抗虫药物和重组疫苗奠定理论基础[1]。