Development of metacyclic Leishmania promastigotes is associated with the increasing expression of GP65, the major surface antigen

Using immunofluorescence techniques and flow microfluorometry analysis, we have demonstrated that the binding of a monoclonal antibody (VD5/25) produced against GP65, the major surface antigen of Leishmania braziliensis, increased on the surface of stationary-phase promastigotes from all the New World Leishmania species causing mucocutaneous or cutaneous disease as compared with the log-phase parasites. In addition, a sequential development of Leishmania amazonensis promastigotes from a non-infective to an infective stage was demonstrated. Indeed, promastigotes in the stationary phase (days 6-7) were found to be far more infective than those in the logarithmic phase of growth (day 3) both in vitro for mouse peritoneal macrophages and in vivo for BALB/c mice. The intracellular survival and multiplication of L. amazonensis were significantly inhibited when infective promastigotes were treated with the VD5/25 monoclonal antibody. The increasing expression of GP65 on the promastigote surface may thus contribute to Leishmania infectivity. This seems to represent a characteristic mechanism applicable to all New World Leishmania species studied.     

用含霍乱毒素A2/B的载体在大肠杆菌中表达弓形虫主要表面抗原P30

目的：克隆并表达含有弓形虫P30抗原及霍乱毒素A2／B亚基基因的原核表达载体，为弓形虫疫苗的研究奠定基础。方法：应用PCR方法扩增出P30基因片段后，克隆入含有霍乱毒素A2／B亚基基因的表达质粒pUAB024，在大肠杆菌JM109(DE3)中表达融合蛋白。通过SDS-PAGE电泳及Western blotting进行检测鉴定。结果：电泳证明质粒构建正确，SDS-PAGE显示经IPTG诱导可以产生特异性条带，Western blotting进一步证实该条带为P30-CTA2／B融合蛋白。结论：表达载体pUAB024-P30可有效表达特异性的融合弓形虫抗原蛋白P30-CTA2B。     

猪链球菌2型毒力因子部分片段的克隆与表达

根据猪链球菌2型(Streptococcussuistype2)胞外蛋白因子(extracellularfactorprotein,EF)的基因(epf)序列,设计合成一对引物,以猪链球菌2型江苏分离株SS2-H的基因组为模板,扩增epf基因1585-2547位序列,进行T/A克隆,转化入宿主菌DH5α中。提取阳性克隆质粒进行双酶切并纯化,将目的片段向克隆到表达载体pET-32a中组氨酸的下游,将重组质粒转化入大肠杆菌BL21中,经IPTG诱导可表达分子量约为53000的融合蛋白。免疫转印分析表明,该融合蛋白具有EF的抗原表位。     

结核分枝杆菌Rv1884基因的克隆、表达及亲和层析纯化

目的　克隆表达结核分枝杆菌Rv1884基因 ,序列测定正确后进行融合表达、纯化。方法　采用聚合酶链反应(PCR)从结核分枝杆菌H37Rv基因组中扩增出Rv1884编码基因 ,用限制性内切酶消化后插入到pGEM Teasy中 ,序列测定正确后 ,再亚克隆到融合表达载体 pPro EXHT中 ,转化大肠杆菌DH5α ,目的基因经IPTG诱导 ,由T7启动子调控表达了氨基端带 6个连续组氨酸残基的Rv1884蛋白 ,在变性条件下对目的蛋白进行纯化。结果　获得了结核分枝杆菌H37Rv株Rv1884蛋白基因 ,得到融合 6个组氨酸残基的Rv1884蛋白纯度大于 85 %。结论　构建了结核分枝杆菌Rv1884基因的重组表达载体 ,并获得了高纯度的融合表达蛋白 ,为以后的深入研究奠定了基础。     

pOVEX vector: prokaryotic expression and purification of onchocerciasis vaccine candidate antigens as fusion proteins with the 24 kD Onchocerca volvulus glutathione S-transferase

Summary An expression vector, pOVEX, has been designed and constructed, combining the advantages of the expression vectors pGEX-3X and pJC20. The pOVEX vector produces a fusion protein with the 24kD Onchocerca volvulus glutathione S-transferase (OvGST2) which is easy to purify in one step from bacterial extracts under non-denaturing conditions using glutathione-sepharose chromatography. High yields of fusion protein were produced from this T7 RNA polymerase-dependent expression vector, which were then cleaved by digestion with the factor Xa protease to separate the OVGST2 polypeptide from the expressed protein of interest. This vector will be particularly useful to O. volvulus investigators for the production of O. volvulus antigens for the analyses of host humoural and cellular responses to these proteins and for immunization studies.     

细粒棘球蚴转化生长因子βI型受体胞内域原核表达载体的构建及蛋白纯化

目的构建细粒棘球蚴（Echinococcus granulosus,Eg）转化生长因子βI型受体胞内域（transforming growth factor—β type I receptor intracellular domain,TβRI—I）原核表达载体,诱导表达并纯化EgTβRI—I蛋白。方法采集感染Eg的羊源原头蚴,Trizol法提取原头蚴总RNA,RT—PCR扩增EgTβRI—I基因片段,克隆至原核表达载体pET28a（＋）,经限制性内切酶双酶切和序列鉴定正确的重组质粒转化至大肠埃希菌感受态细胞BL21,异丙基-β-D-硫代半乳糖苷（IPTG）诱导表达,经镍柱亲和层析纯化蛋白,SDS—PAGE检测目的蛋白的表达。结果pET28a—EgβIRI—I原核表达载体构建成功,经IPTG诱导可表达EgTβRI—I蛋白（分子质量单位为48ku）,纯化后获得大量纯度较高的可溶性蛋白。结论成功构建pET28a—EgTβRI—I原核表达载体,并获得纯化的可溶性目的蛋白,为研究EgTβRI—I在Eg体内的生物学作用及其作用方式奠定了基础。