恶性疟原虫FCC1/HN株环子孢子蛋白的原核表达、纯化及其对肝细胞靶向作用的观察

目的从恶性疟原虫FCC1／HN株基因组中扩增得到环子孢子蛋白(circumsporozoite protein,CSP)的全长编码基因,克隆至原核表达载体pET-32c中进行表达纯化,观察重组环子孢子蛋白对肝细胞的结合能力,探讨其作为原发性肝癌基因治疗的靶向分子的可行性。方法根据恶性疟原虫3D7株环子孢子蛋白的编码序列设计一对引物,利用聚合酶链反应(PCR)技术从恶性疟原虫FCC1／HN株基因组中扩增出CSP的全长编码基因,将其克隆到载体pGEM-T中,通过基因测序加以证实;进一步亚克隆至原核表达载体pET-32c中,在大肠杆菌BL21中用IPTG诱导表达,表达产物用Ni2+螯合柱亲和纯化,采用免疫印迹技术(WB)对纯化的融合蛋白进行免疫反应性检测;采用免疫组化(IHC)技术观察重组环子孢子蛋白对不同组织细胞的结合能力。结果从恶性疟原虫FCC1／HN株基因组中成功扩增到1263 bp的全长CSP基因,该基因在原核系统中经诱导表达出一相对分子质量(Mr)约62×103大小的融合蛋白,表达产物以包涵体的形式存在;通过Ni2+亲和柱纯化获得重组CSP融合蛋白;WB表明,重组CSP融合蛋白能被疟原虫阳性血清特异性识别;免疫组化结果显示重组CSP融合蛋白能够与肝癌和正常肝细胞特异性地结合,与其他组织来源的细胞则未见反应。结论CSP是疟原虫子孢子表面主要的蛋白,重组环子孢子蛋白作为原发性肝癌基因治疗的靶向分子具有一定的潜在应用价值。     

A component of an antigenic rhoptry complex of Plasmodium falciparum is modified after merozoite invasion

Human antibodies affinity purified on an adsorbent prepared from a cDNA clone (Ag44) expressing a portion of a rhoptry antigen were used to characterize the synthesis and fate of the antigen in the asexual blood stages of Plasmodium falcipartum. The rhoptry antigen is synthesized in the mature trophozoite-stage parasites as a 103 kDa polypeptide, is present in the schizonts and merozoites as a 105 kDa polypeptide, is discharged from the rhoptries and found in the newly invaded red cells as a 110 kDa polypeptide. Anti-Ag44 antibodies immunoprecipitate the antigen and two additional polypeptides of 135 and 150 kDa from lysates of infected cells and from culture supernatants. The three polypeptides are associated in a non-covalent complex that persists in the newly invaded red cells. All the components of the high molecular weight rhoptry complex are antigenic and can be precipitated with immune human serum. The 135 kDa polypeptide is identical to a 140 kDa rhoptry antigen previously identified by a monoclonal antibody.     

恶性疟原虫113肽抗原基因重组的减毒鼠伤寒沙门菌在家兔中免疫应答的研究

我们已经在减毒鼠伤寒沙门菌ＳＬ３２６１以融合蛋白的形式表达了人工合成的恶性疟原虫杂合１１３肽基因ＡＢ（ＧＺ－ＡＢ）。活菌以２×１０９ＣＦＵ经口服免疫新西兰家兔，用ＥＬＩＳＡ测定抗体水平，结果于首次免疫或加强免疫后都可检测到一定水平的特异性抗体。所免疫的家免可以诱发针对恶性疟原虫抗原及ＧＺ－ＡＢ的迟发性超敏反应（ＤＴＨ）。我们的研究表明，含有多个恶性疟原虫抗原表位的人工合成基因可以在减毒鼠伤寒沙门菌中表达，活菌可诱发家兔产生特异的体液免疫及细胞免疫，为恶性疟口服活菌苗的制备打下基础。     

Modulation of the cellular immune response during Plasmodium falciparum infections in sickle cell trait individuals.

Plasma and peripheral blood mononuclear cells (PBMC) were obtained from P. falciparum-infected individuals with and without the sickle cell trait at diagnosis and 7 days after treatment. HbAA and HbAS patients were compared for levels of plasma soluble IL-2 receptors (IL-2R) and the in vitro cellular reactivity to affinity-purified soluble P. falciparum antigens (SPAg), PPD and phytohaemagglutinin (PHA). At diagnosis, HbAS patients with clinical disease had lower plasma-soluble IL-2R levels and parasite counts than the corresponding HbAA patients, whereas HbAS and HbAA patients with asymptomatic infections had comparable soluble IL-2R levels and parasite counts. PBMC from HbAS patients had higher proliferation and IFN-gamma production in response to SPAg than PBMC from HbAA patients. The difference in the lymphoproliferative responses to SPAg between the two groups was evident in patients with asymptomatic infections. In all patients, the clinical severity, the soluble IL-2R levels and the parasite counts were directly related. The former two were inversely related to the proliferative responses to SPAg. After treatment, all the studied parameters were comparable in the two groups. The study indicates that during P. falciparum infection, HbAS compared with HbAA patients had lower in vivo cellular activation and higher in vitro cellular reactivity in response to soluble malaria antigens.     

恶性疟原虫抗原基因在鼠伤寒沙门氏菌中的表达及免疫原性的初步鉴定

将人工合成的恶性疟原虫杂合７４肽抗原基因克隆到表达载体ｐＷＲ４５０－１中，获得了重组质粒ｐＷＲＣ，将其先转化到减毒伤寒沙门氏菌ＬＢ５０００修饰后，再转化到ＳＬ３２６１，得到重组减毒鼠伤寒沙门氏菌ＳＬ３２６１（ｐＷＲＣ）。ｐＷＲＣ在ＳＬ３２６１中以β－半乳糖苷酶－杂合多肽抗原Ｃ融合蛋白（ＧＺ－Ｃ）形式表达，表达量约占菌体蛋白总量的１１．３％．Ｗｅｓｔｅｒｎｂｌｏｔ及免疫双扩散显示ＧＺ－Ｃ可与兔抗ＧＺ－Ｃ抗原的免疫血清发生特异反应。ＧＺ－Ｃ识别兔抗ＧＺ－Ｃ及鼠抗恶性疟原虫抗血清的ＥＬＩＳＡ滴度分别为１：３２００及１：５１２０。初步结果表明ＳＬ３２６１（ｐＷＲＣ）表达的ＧＺ－Ｃ具有抗原性。连续传代ＳＬ３２６１（ｐＷＲＣ）未见质粒ｐＷＲＣ丢失及对宿主有明显的毒性。     

伯氏疟原虫对青蒿素抗药性的研究

仿Peters剂量递增法用伯氏疟原虫ANKA株及N株对QHS进行了抗药性的研究。经14个月的培育至第58代,QHS im注射“4日抑制性实验”的ED₅₀在RQ/ANKA系及RQ/N系分别为其亲代系的53.4及54.6倍,但经蚊传未获成功。在第40代(I₅₀=25)时,其50%的治愈剂量为其亲代系的5.4倍。停药传代其抗性会逐渐消失。该虫系对青蒿酯钠及蒿甲醚有明显的交叉抗性,其ED₅₀分别为其亲代系的13.1及11.7倍,对伯喹的抗性为2.9倍,对氯喹未见明显交叉抗性。     

恶性疟原虫pGST—HTl融合表达载体的构建及在大肠杆菌中的高效表达

目的 构建pGST—HT1融合表达载体,并观察其在大肠杆菌中的表达情况。方法 基因扩增,融合表达载体的构建,SDS—PAGE电泳和Western blot分析。结果 对重组质粒进行酶切鉴定证实HT11片段已克隆到pGSTag的EcoRI和Sall位点之间。表达产物经SDS—PAGE电泳后显示在相对分子质量82000处出一条新生蛋白带,与HT1／GST(56／26)融合蛋白大小一致,提示成功表达HT1融合蛋白。Western印迹杂交结果也显示在相对分子质量82000处出现阳性着色条带。结论 本实验成功构建pGST—HTl表达载体,并诱导表达出HTl融合蛋白,为HTl蛋白功能和免疫原性的进一步研究奠定了基础。     

Synthesis of merozoite proteins and glycoproteins during the schizogony of Plasmodium falciparum

We have investigated the protein and glycoprotein content of Plasmodium falciparum merozoites by metabolically labeling cultures of schizont-stage parasites with [³⁵S]methionine or with [³H]glucosamine followed by incubation in nonradioactive medium to allow the schizonts to mature into merozoites, infect new erythrocytes, and develop into ring-stage parasites. The ring stages were separated from schizonts by sedimentation through Percoll. Labeled proteins were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by fluorography. Using [³⁵S]methionine, four major proteins (p) with apparent relative molecular weights (M_r) = 202k, 136k, 82k, and 46k and two proteins of intermediate labeling (M_r = 185k and 142k) were observed in the schizont-labeled ring-stage parasites. Because corresponding proteins were also observed in the schizont stage, we conclude that they had been present in the invading merozoite. In contrast, prominent proteins which were generally labeled during the ring stage and some major schizont-stage proteins were virtually absent in the schizont-labeled ring-stage. By labeling the parasite proteins with [³H]glucosamine followed by separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, five major glycoproteins (gp) of apparent M_r = 185k, 88k, 56k, 46k, and 34k were identified. Their presence in both the schizont and the schizont-labeled ring stage demonstrated that the merozoite contains glycoproteins. Immune owl monkey serum recognized all five glycoproteins. A comparison of proteins by two-dimensional gel electrophoresis (isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis) suggested that p185 and gp185 were identical, as were p46 and gp46.     

Structure and expression of the gene for Pv200, a major blood-stage surface antigen of Plasmodium vivax.

Molecular cloning and structure analysis of the gene encoding the Pv200 protein of the Sal-1 strain of Plasmodium vivax revealed an overall identity of 34–37% when the deduced amino acid sequence was compared with the sequences of various major merozoite surface antigens of Plasmodium falciparum, Plasmodium yoelii and Plasmodium chabaudi. When the Sal-1 Pv200 sequence was compared with the corresponding sequence from the Belèm strain of P. vivax, it was found that the two merozoite surface antigens were relatively well conserved with an overall amino acid sequence identity of 81%. A region of 23 repeated glutamine residues, found in the sequence of the Belèm isolate was not found, however, in the Sal-1 sequence. Amino-and carboxy-terminal domains of the Pv200 protein were expressed in the yeast Saccharomyces cerevisiae. Each recombinant protein was shown to react with antibodies in sera from splenectomized Bolivian Saimiri monkeys that had been infected previously with P. vivax, and in human sera from individuals with a history of exposure to vivax malaria. The availability of recombinant DNA-derived Pv200 proteins will now allow a full assessment of their utility in the diagnosis and immunoprophylaxis of the benign tertian malaria associated with P. vivax infection.