Apical membrane antigen 1 is a cross-reactive antigen between Neospora caninum and Toxoplasma gondii, and the anti-NcAMA1 antibody inhibits host cell invasion by both parasites

The cross-reactive antigens of Neospora caninum and Toxoplasma gondii are important in the exploration to determine the common mechanisms of parasite-host interaction. In this study, a gene encoding N. caninum apical membrane antigen 1 (NcAMA1) was identified by immunoscreening of a N. caninum tachyzoite cDNA expression library with antisera from mice immunized with recombinant T. gondii apical membrane antigen 1 (TgAMA1). NcAMA1 was encoded by an open reading frame of 1695 bp, which encoded a protein of 564 amino acids. The single-copy NcAMA1 gene was interrupted by seven introns. NcAMA1 showed 73.6% amino acid identity to TgAMA1. Mouse polyclonal antibodies raised against the recombinant NcAMA1 (rNcAMA1) recognized a 69-kDa native parasite protein by Western blotting. Immunofluorescence analysis showed that NcAMA1 was localized to the apical end of tachyzoites. Two-dimensional electrophoresis and Western blotting indicated that an approximately 57-kDa cleavage product was released into the excretory/secretory products of N. caninum. Preincubation of free tachyzoites with anti-rNcAMA1 IgG antibodies inhibited the invasion into host cells by N. caninum and T. gondii. These results indicated that AMA1 is a cross-reactive antigen between N. caninum and T. gondii and a potential common vaccine candidate to control two parasites.     

Identification and characterization of Neospora caninum tachyzoite antigens useful for diagnosis of neosporosis.

The purpose of the present study was to identify antigens of the protozoan Neospora caninum that could be useful for the diagnosis of neosporosis in domestic animals. As revealed by immunoblotting, immune sera from a wide range of animal species exhibited a similar recognition pattern of four major and several minor N. caninum antigens. In contrast to preinoculation sera, all tested immune sera recognized nonreduced immunodominant 17-, 29-, 30-, and 27-kDa antigens. A 46-kDa protein which showed faint recognition by preimmune sera also exhibited a strong response by immune sera. Immunolocalization of the four immunodominant N. caninum antigens was investigated by immunogold electron microscopy using monospecific polyclonal antisera. The 17-kDa antigen appears to be associated with the body part of the rhoptries, while the 29- and 30-kDa antigens were associated with the dense granules, network, and limiting membrane of the parasitophorous vacuole. Studies were also conducted to compare antibody responses to N. caninum and the related protozoan Toxoplasma gondii. Although N. caninum and T. gondii (RH strain) tachyzoites shared a few cross-reacting antigens, the immunodominant antigens of both parasites were not recognized by heterologous sera. Also, immunogold staining with rabbit anti-Neospora hyperimmune serum exhibited almost no labeling of external membranes of Neospora tachyzoites compared with the very marked labeling seen when Toxoplasma tachyzoites (RH strain) were incubated with rabbit anti-Toxoplasma hyperimmune serum. These unique antigenic differences should be useful in developing a diagnostic assay for N. caninum.     

Identification of ribosomal phosphoprotein P0 of Neospora caninum as a potential common vaccine candidate for the control of both neosporosis and toxoplasmosis

The characterization of the cross-reactive antigens of two closely related apicomplexan parasites, Neospora caninum and Toxoplasma gondii, is important to elucidate the common mechanisms of parasite-host interactions. In this context, a gene encoding N. caninum ribosomal phosphoprotein P0 (NcP0) was identified by immunoscreening of a N. caninum tachyzoite cDNA expression library with antisera from mice immunized with T. gondii tachyzoites. The NcP0 was encoded by a gene with open reading frame of 936 bp, which encoded a protein of 311 amino acids. The NcP0 gene existed as a single copy in the genome and was interrupted by a 432 bp intron. The NcP0 showed 94.5% amino acid identity to T. gondii P0 (TgP0). Anti-recombinant NcP0 (rNcP0) sera recognized a native parasite protein with a molecular mass of 34 kDa in Western blot analysis. Immunofluorescence analysis showed that the NcP0 was localized to the surface of N. caninum tachyzoites. A purified anti-rNcP0 IgG antibody inhibited the growth of N. caninum and T. gondii in vitro in a concentration-dependent manner. These results indicate that P0 is a cross-reactive antigen between N. caninum and T. gondii and a potential common vaccine candidate to control both parasites.     

Identification of a major surface protein on Neospora caninum tachyzoites

Neospora caninum is a recently identified coccidian parasite that is closely related to Toxoplasma gondii. Molecules associated with the surface of N. caninum tachyzoites are likely to be involved in the process of adhesion and invasion of host cells. They probably also participate in the interaction of the parasite with the immune system, and they could play an important role in the pathogenesis of the parasite. To identify such surface molecules, we performed subcellular fractionation studies of isolated N. caninum tachyzoites. Employing the nonionic detergent Triton-X-114, we prepared a membrane fraction. Immunoblot analysis of this fraction using polyclonal antisera directed against tachyzoites of N. caninum and T. gondii resulted in the identification of a protein of approximately 43 kDa (Nc-p43). This molecule was present in two isolates of Neospora (Nc-1 and Liverpool) but was absent in Toxoplasma (RH-strain) tachyzoites. Further immunofluorescence and immunogold transmission electron microscopy (TEM) studies using affinity-purified anti-Nc-p43 antibodies demonstrated the presence of this molecule on the surface of N. caninum tachyzoites.     

In vitro induction of Neospora caninum bradyzoites in vero cells reveals differential antigen expression, localization, and host-cell recognition of tachyzoites and bradyzoites

We report on an optimized method for the in vitro culture of tissue cyst-forming Neospora caninum bradyzoites in Vero cells and the separation of viable parasites from host cells. Treatment of tachyzoite-infected Vero cell cultures with 17 microM sodium nitroprusside for 8 days severely scaled down parasite proliferation, led to reduced expression of tachyzoite surface antigens, and induced the expression of the bradyzoite marker NcBAG1 and the cyst wall antigen recognized by the monoclonal antibody MAbCC2. Transmission electron microscopy demonstrated that intracellular parasites were located within parasitophorous vacuoles that were surrounded by a cyst wall-like structure, and the dense granule antigens NcGRA1, NcGRA2, and NcGRA7 were incorporated into the cyst wall. Adhesion-invasion assays employing purified tachyzoites and bradyzoites showed that tachyzoites adhered to, and invaded, Vero cells with higher efficiency than bradyzoites. However, removal of terminal sialic acid residues from either the host cell or the parasite surface increased the invasion of Vero cells by bradyzoites, but not tachyzoites.     

兔抗人唾液酸转运蛋白抗体的制备及特性鉴定

目的：制备兔抗人唾液酸转运蛋白（sialin）的抗体，并进行特性鉴定。方法：应用RT—PCR从培养的人颌下腺细胞系HSG中扩增编码sialin N端1～38氨基酸的DNA序列，构建重组表达质粒pGEX-5X-1-sialin，测序鉴定后，转化大肠杆菌JM109，在0．1 mmol／L IPTG的诱导下表达GST—sialin融合蛋白。经SDS-PAGE鉴定后，利用GSTrap FF^TM柱纯化融合蛋白，并以其免疫家兔制备抗人sialin抗体。用ELISA法测定兔抗sialin血清的效价；用Western blot及免疫细胞化学等方法鉴定抗血清的特异性。结果：构建了重组表达质粒pGEX-5X-1-sialin；以其转化大肠杆菌在IPTG诱导下，获得以可溶性形式表达的GST-sialin融合蛋白；表达的GST—sialin经GSTrap FF^TM柱纯化后，免疫家兔制备出抗sialin抗血清，ELISA法测定抗血清的效价为1：32000。Western blot鉴定表明，制备的抗sialin抗体可特异地识别HSG细胞中相对分子质量（Mr）约55000的sialin蛋白。免疫细胞化学检测表明，sialin抗血清识别的抗原定位于HSG细胞的细胞质和胞核。结论：成功地制备出兔抗人sialin抗血清，为进一步研究sialin在涎腺组织的功能奠定了基础。     

Monoclonal rat antibodies directed against Toxoplasma gondii suitable for studying tachyzoite-bradyzoite interconversion in vivo.

We previously reported the in vitro analysis of stage differentiation of Toxoplasma gondii in murine bone marrow-derived macrophages. The purpose of this study was to generate monoclonal rat antibodies that might be suitable for investigating tachyzoite-bradyzoite interconversion in vivo with the murine model. Immunization of Fischer rats with cysts of T. gondii NTE resulted in the generation of seven monoclonal antibodies of the immunoglobulin G2a, G2b, or M isotype, which were further characterized by the immunoblot technique, immunofluorescence assay, immunohistology, and immunoelectron microscopy. Immunoblots demonstrated specific reactivity of five monoclonal antibodies with proteins with molecular masses of 40, 52, 55, 60, 64, 65, and 115 kDa. One antibody (CC2) appeared to recognize a differently expressed antigen depending on the parasite stage, reacting with a 40-kDa molecule in tachyzoites and a 115-kDa antigen in bradyzoites and oocysts. Several other monoclonal antibodies were shown to be stage specific and to react in immunofluorescence assays or in immunoblots with either tachyzoites or bradyzoites. Kinetics of stage conversion in vitro could be monitored by immunofluorescence with two of these monoclonal antibodies. Preliminary immunohistological investigations of tissue sections from infected mice demonstrated the possible usefulness of these monoclonal antibodies for future in vivo studies on stage differentiation of T. gondii in the murine system.     

Characterization of anti-Neospora caninum hyperimmune rabbit serum by Western blot analysis and immunoelectron microscopy

The antigens recognized by hyperimmune rabbit serum raised against tachyzoites of the NC-1 isolate ofNeospora caninum were characterized using chemiluminescent Western blotting, immunogold-silver staining and immunoelectron microscopy. Approximately 20 immunodominant antigens whose relative rates of migration were 16–80 kDa were recognized by the serum in Western blots using reduced or nonreduced parasite antigen preparations. The nonreduced parasite antigens were more strongly recognized by the serum than were the reduced antigen preparations. Immunoelectron microscopy revealed that the rabbit-serum-labeled antigens were localized to some organelles ofN. caninum tachyzoites and to the parasitophorous vacuole surrounding them. In particular, antigens found in the dense granules, in the micronemes, and in the posterior portion of the rhoptries were strongly labeled by an indirect immunogold-labeling technique     

兔抗人PON2抗体的制备与初步应用

目的:制备兔抗人PON2(paraoxonase-2)的多克隆抗体并进行初步鉴定.方法:生物信息学方法分析人PON2蛋白序列,选取人兔同源性较低,亲水性及免疫原性较强的片段,通过大肠杆菌原核表达系统进行重组表达,获得GST-PON2融合蛋白用于免疫新西兰大耳白兔获得多克隆抗体,通过XX方法分离纯化得到的抗PON2多克隆抗体,用West-ern blot、间接免疫荧光对其进行特异性及灵敏度鉴定.结果:成功获得了高表达的相对分子质量(Mr)为46 000的PON2重组融合蛋白;Western blot鉴定结果显示此多克隆抗体可特异识别肝脏总蛋白、HeLa细胞及U937细胞中Mr为39 000的天然PON2蛋白;间接免疫荧光结果显示此多克隆抗体所识别的蛋白定位于SY5Y细胞胞质中.结论:抗人PON2的多克隆抗体特异识别肝总蛋白、HeLa细胞及U937细胞中的天然蛋白,可用于PON2的研究及临床检测.     

鸡MHC Ⅰ类分子的多抗制备及其在不同MD抗性MHC单倍型鸡脾脏中的差异表达

目的制备能检测不同MHC-B单倍型MHC I类蛋白的多抗血清,并对马立克氏病(MD)抗性较强的BW/G3系鸡群(MHC B2单倍型)和敏感性较强的BW/G7系鸡群(B19单倍型)接种马立克氏病毒(MDV)后,利用Western blot技术半定量分析MHC I类蛋白表达量的差异。方法从BW/G3系鸡脾组织cDNA中PCR扩增BF基因的保守序列第4～8外显子,克隆入原核表达载体pET-30a,构建重组质粒。转化大肠杆菌BL21(DE3),经IPTG诱导获得表达,经SDS-PAGE初步纯化,免疫新西兰兔,制备兔抗血清。以高效价的兔抗血清为一抗,对BW/G3和BW/G7系健康鸡和MDV攻毒后11周的脾组织进行Western blot,利用ImageQuant 5.2软件半定量分析其中MHC Ⅰ类蛋白含量的变化。结果含BF部分基因的重组质粒在大肠杆菌中表达,其特异性兔抗血清能检测到不同MHC-B单倍型鸡的MHC Ⅰ类蛋白。BW/G3和BW/G7系鸡群感染MDV后,MHC Ⅰ类蛋白含量全部上调,正常组和攻毒组中BW/G7系的表达量均极显著高于BW/G3系(P≤0.01,P≤0.001)。结论成功制备了能检测MHC B2、B6和B19单倍型鸡的MHC I类蛋白特异性多抗血清;MDV攻毒后期,抗性鸡BW/G3和敏感鸡BW/G7脾组织中MHC I类蛋白的表达量都发生上调,且易感鸡中的表达量高于抗性鸡,为进一步揭示病毒性肿瘤病的致病机理提供了思路。     

Serological diagnosis of bovine neosporosis by Neospora caninum monoclonal antibody-based competitive inhibition enzyme-linked immunosorbent assay.

Neospora caninum, a protozoan parasite closely related to Toxoplasma gondii, causes abortion and congenital infection in cattle. To investigate specific methods of antemortem diagnosis, the antibody responses of infected cows were evaluated by immunoblot assay and competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) by using a monoclonal antibody (MAb), MAb 4A4-2, against N. caninum tachyzoites. MAb 4A4-2 bound diffusely to the exterior surface of N. caninum tachyzoites and recognized a single 65-kDa band in immunoblots. MAb 4A4-2 was unreactive to antigens of two closely related apicomplexan protozoa, Toxoplasma gondii and Sarcocystis cruzi. Binding of MAb 4A4-2 was inhibited by mild periodate treatment of N. caninum antigen, demonstrating the carbohydrate nature of the epitope. Immunoblot analysis of N. caninum tachyzoite antigens with sera from cows with confirmed Neospora-induced abortion revealed at minimum 14 major antigens ranging from 11 to 175 kDa. Although the recognized antigens varied from cow to cow, antigens of 116, 65, and 25 kDa were detected in all cows with abortion confirmed to be caused by N. caninum. The binding of MAb 4A4-2 to N. caninum tachyzoite antigen was consistently inhibited by sera from Neospora-infected cows in a CI-ELISA format and was not inhibited by sera from Neospora antibody-negative cows. Furthermore, sera from cattle experimentally infected with T. gondii, S. cruzi, Sarcocystis hominis, or Sarcocystis hirsuta, which had cross-reactive antibodies recognizing multiple N. caninum antigens by immunoblot assay, did not inhibit binding of MAb 4A4-2 in the CI-ELISA. Thus, MAb 4A4-2 binds a carbohydrate epitope on a single N. caninum tachyzoite surface antigen that is recognized consistently and specifically by Neospora-infected cattle.     

Structures of Toxoplasma gondii Tachyzoites, Bradyzoites, and Sporozoites and Biology and Development of Tissue Cysts

Infections by the protozoan parasite Toxoplasma gondii are widely prevalent worldwide in animals and humans. This paper reviews the life cycle; the structure of tachyzoites, bradyzoites, oocysts, sporocysts, sporozoites and enteroepithelial stages of T. gondii; and the mode of penetration of T. gondii. The review provides a detailed account of the biology of tissue cysts and bradyzoites including in vivo and in vitro development, methods of separation from host tissue, tissue cyst rupture, and relapse. The mechanism of in vivo and in vitro stage conversion from sporozoites to tachyzoites to bradyzoites and from bradyzoites to tachyzoites to bradyzoites is also discussed.     

Characterization of microneme proteins of Toxoplasma gondii

Three microneme proteins of Toxoplasma gondii have been characterized using 3 monoclonal antibodies and a recombinant protein specific antiserum. In all cases, apical labeling of tachyzoites and bradyzoites was observed by indirect immunofluorescence assay. Immunogold localization on ultrathin sections of bradyzoites or tachyzoites showed a specific labeling of micronemes. The following proteins were characterized using 2-dimensional gel electrophoresis and Western immunoblotting: Mic 1 (60 kDa, Pi 6.5), Mic 2 (120 kDa, Pi 5) and Mic 3 (90 kDa, Pi 6.75). The 90-kDa protein (Mic 3) is a heterodimer of two 38-kDa polypeptides (Pi 6.7 and 6.75 respectively) linked by disulfide bridges. Metabolic labeling and immunoprecipitation assays showed that at least one of the 38-kDa polypeptides was processed from a 40-kDa precursor. No processing was observed during the biosynthesis of the 120- and 60-kDa polypeptides.     

PIWIL4的克隆及其抗体制备和初步应用

目的 制备兔抗人PIWIL4的多克隆抗体,鉴定其特异性,并应用该抗体检测内源性PIWIL4在人各细胞系中的表达差异及细胞定位.方法 构建原核表达质粒pGEX-5X-1-PIWIL4,转化大肠杆菌BL21,PIWIL4蛋白经异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达.融合蛋白通过切胶纯化后免疫家兔制备抗体血清.以间接酶联免疫吸附试验(ELISA)检测抗体效价,Western blot鉴定抗体特异性及检测PIWILA在各细胞系中的表达差异,免疫荧光染色观察PIWIL4的细胞定位.结果 成功构建原核表达质粒,表达并纯化PIWIL4蛋白.免疫大白兔后得到PIWIL4多克隆抗体,ELISA检测抗体效价为1:20 000,Western blot和免疫组化确定抗体具有高度特异性,并成功地应用该抗体检测到PIWIL4在人多种细胞系中的表达差异及细胞定位.结论 PIWIL4蛋白及其多克隆抗体的成功制备,为进一步研究PIWILA的生物学功能奠定了基础.     

PIWIL4的克隆及其抗体制备和初步应用

目的 制备兔抗人PIWIL4的多克隆抗体,鉴定其特异性,并应用该抗体检测内源性PIWIL4在人各细胞系中的表达差异及细胞定位.方法 构建原核表达质粒pGEX-5X-1-PIWIL4,转化大肠杆菌BL21,PIWIL4蛋白经异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达.融合蛋白通过切胶纯化后免疫家兔制备抗体血清.以间接酶联免疫吸附试验(ELISA)检测抗体效价,Western blot鉴定抗体特异性及检测PIWILA在各细胞系中的表达差异,免疫荧光染色观察PIWIL4的细胞定位.结果 成功构建原核表达质粒,表达并纯化PIWIL4蛋白.免疫大白兔后得到PIWIL4多克隆抗体,ELISA检测抗体效价为1:20 000,Western blot和免疫组化确定抗体具有高度特异性,并成功地应用该抗体检测到PIWIL4在人多种细胞系中的表达差异及细胞定位.结论 PIWIL4蛋白及其多克隆抗体的成功制备,为进一步研究PIWILA的生物学功能奠定了基础.     

PIWIL4的克隆及其抗体制备和初步应用

目的制备兔抗人PIWIL4的多克隆抗体,鉴定其特异性,并应用该抗体检测内源性PIWIL4在人各细胞系中的表达差异及细胞定位。方法构建原核表达质粒pGEX-5X-1．PIWIL4,转化大肠杆菌BL21,PIWIL4蛋白经异丙基-β-D-硫代半乳糖苷（IPTG）诱导表达。融合蛋白通过切胶纯化后免疫家兔制备抗体血清。以间接酶联免疫吸附试验（ELISA）检测抗体效价,Westernblot鉴定抗体特异性及检测PIWIL4在各细胞系中的表达差异,免疫荧光染色观察PIWIL4的细胞定位。结果成功构建原核表达质粒,表达并纯化PIWIL4蛋白。免疫大白兔后得到PIWIL4多克隆抗体,ELISA检测抗体效价为1：20000,Westernblot和免疫组化确定抗体具有高度特异性,并成功地应用该抗体检测到PIWIL4在人多种细胞系中的表达差异及细胞定位。结论PIWIL4蛋白及其多克隆抗体的成功制备,为进一步研究PIWIL4的生物学功能奠定了基础。     

Preparation and application of polyclonal antibodiesagainst KSHV v-cyclin

We prepared rabbit polyclonal antibodies against Kaposi''s sarcoma-associated herpesvirus (KSHV)-encoded v-cyclin (ORF 72) and detected the natural viral protein using these polyclonal antibodies. Three antigenic polypeptides of v-cyclin were designed and synthesized. A fragment of the v-cyclin gene was cloned into a eukaryotic expression vector pEF-MCS-Flag-IRES/Puro to construct a recombinant vector, pEF v-cyclin. Then, pEF v-cyclin was transfected into 293T and EA.hy926 cells to obtain v-cyclin-Flag fusion proteins. Six New Zealand white rabbits were immunized with KLH-conjugated peptides to generate polyclonal antibodies against v-cyclin. The polyclonal antibodies were then characterized by ELISA and Western blotting assays. Finally, the polyclonal antibodies against v-cyclin were used to detect natural viral protein expressed in BCBL-1, BC-3, and JSC-1 cells. The results showed that using the Flag antibody, v-cyclin-Flag fusion protein was detected in 293T and EA.hy926 cells transfected with pEF-v-cyclin. Furthermore, ELISA showed that the titer of the induced polyclonal rabbit anti-v-cyclin antibodies was higher than 1:8,000. In Western blotting assays, the antibodies reacted specifically with the v-cyclin-Flag fusion protein as well as the natural viral protein. The recombinant expression vector pEF-v-cyclin was constructed successfully, and the polyclonal antibodies prepared can be used for various biological tests including ELISA and Western blotting assays.