广西优势血清西优势血清型IBV代表株M基因在杆状病毒系统中的表达

采用RT-PCR扩增鸡传染性支气管炎病毒(IBV)广西优势血清型代表性毒株GX-YL5的膜(M)蛋白基因,将其克隆至pFastBac~(TM)/HBM-TOPO杆状病毒转移载体,转化大肠杆菌DH10Bac感受态细胞,获得重组杆粒rHBM-M;将重组杆粒转染Sf9昆虫细胞,获得重组杆状病毒;利用间接免疫荧光试验(IFA)和蛋白质免疫印迹(Western-blot)鉴定表达的M蛋白。IFA检测可见重组杆状病毒感染后72h细胞出现特异性荧光,Westernblot检测可见大小约为26ku的特异性蛋白带,表明该重组M蛋白在Sf9昆虫细胞中成功获得表达。研究为IBVM蛋白的生物学功能、IBV诊断试剂和新型疫苗制备等奠定基础。     

鸡传染性支气管炎病毒GX-YL5株N蛋白在昆虫杆状病毒系统中的分泌表达

以鸡传染性支气管炎病毒(IBV)广西优势血清型代表株GX-YL5为研究对象,利用RT-PCR扩增出其核蛋白(N)基因,引入昆虫细胞识别的蜂素(Honeybee melittin,HBM)信号肽,同时在C端加入6个组氨酸标签以利于纯化,将其定向克隆到转座载体pFast Bac~(TM)dual中,转化DH10Bac~(TM)感受态细胞进行同源重组获得重组杆粒r HBM-N;利用脂质体介导转染Sf9昆虫细胞,获得重组杆状病毒,通过间接免疫荧光(IFA)和Western-blot鉴定表达的N蛋白。结果显示:IFA出现特异性荧光,Western-blot中细胞上清和细胞沉淀均出现51 ku的特异性条带。结果表明N蛋白获得了分泌表达且具有良好的免疫原性。研究首次引入昆虫细胞识别的HBM信号肽进行N蛋白的表达,不仅为N蛋白的生物学功能、诊断试剂以及IBV新型亚单位疫苗研究奠定了基础,也为其它蛋白的表达提供参考。     

施马伦贝格病毒核衣壳蛋白的表达及单克隆抗体制备

为表达与纯化具有天然构象的施马伦贝格病毒(Schmallenberg virus,SBV)核衣壳(N)蛋白,并制备其单抗(McAb),本研究在SBV-N基因的N端加入6个组氨酸(6×His)标签后,将其克隆至杆状病毒表达载体pFastBac~(TM)1中,构建重组供体质粒pFastBac-His-SBV-N。将pFastBac-His-SBV-N转化DH10Bac E.coli,通过蓝白斑筛选获得重组杆粒rBacmid-His-SBV-N。将rBacmid-His-SBV-N转染Sf9昆虫细胞制备表达His-SBV-N融合蛋白的重组杆状病毒,借助Ni-NTA琼脂糖纯化重组杆状病毒感染Sf9细胞中的His-SBV-N蛋白。以纯化的HisSBV-N免疫BALB/c小鼠制备McAb,利用ELISA叠加试验检测McAb抗原识别位点的异同,并采用高碘酸钠法对识别不同抗原表位的McAb进行辣根过氧化物酶(HRP)标记。最终获得了4株识别不同抗原表位的McAb(2A11、2E1、4H11和6E12)并进行了HRP标记;亚型鉴定表明,2A11为IgG1亚型,2E1、4H11和6E12均为IgG2b亚型;间接免疫荧光试验证实,4株McAb均能够识别稳定表达SBV-N蛋白的BHK-21细胞系;Western blot进一步表明,HRP标记的4株McAb均与His-SBV-N蛋白发生特异性反应。His-SBV-N融合蛋白及其McAb的成功制备,为施马伦贝格病血清学检测方法的建立提供了良好的生物材料。     

狂犬病病毒磷蛋白在杆状病毒系统的表达及鉴定

为了建立狂犬病毒磷蛋白(phosphoprotein,P)的体外表达系统,本研究将RT-PCR扩增的狂犬病病毒ERA株P蛋白基因克隆于杆状病毒转移载体pFastBacHTA,构建重组质粒pFastBacHTA-P,并转染昆虫细胞Sf9包装形成重组杆状病毒。SDS-PAGE分析显示重组质粒pFastBacHTA-P转染的Sf9细胞中出现了分子量约为42 kDa的蛋白条带,Western blot证实分子量约为42 kDa的蛋白能与抗His的单克隆抗体发生特异性反应,间接免疫荧光(indirect immunofluorescence assay,IFA)分析进一步显示Sf9细胞表达的P蛋白与抗P蛋白单克隆抗体能特异性结合。这些实验证明,狂犬病病毒P蛋白不仅在Sf9细胞中获得表达,而且具有良好的免疫反应性。狂犬病病毒P蛋白杆状病毒表达体系的建立,为蛋白结构的解析和诊断试剂的研制奠定了基础。     

小反刍兽疫病毒Nigeria 75/1株病毒样颗粒的构建及其免疫原性

为了构建具有天然构象的小反刍兽疫病毒Nigeria 75/1株病毒样颗粒,本试验扩增了Nigeria 75/1株M、F和H基因,并分别克隆至双启动子载体pFastBac~(TM) Dual中,构建含有双目的基因的重组供体质粒pFastBac~(TM) Dual-2M、pFastBac~(TM) Dual-2F和pFastBac~(TM) Dual-2H;测序正确后转化至DH10Bac~(TM) 感受态细胞,同源重组获得穿梭质粒rBacmid-2M、rBacmid-2F和rBacmid-2H;将其分别转染昆虫细胞Sf9获得重组杆状病毒rpFB-2M、rpFB-2F和rpFB-2H。以鼠抗M、H蛋白的主要抗原表位区多克隆抗体与绵羊抗PPRV阳性血清对重组杆状病毒感染细胞进行间接免疫荧光(IFA)鉴定,可见特异性荧光;以3种重组杆状病毒共感染昆虫细胞Sf9的方式组装病毒样颗粒,放大培养后进行病毒样颗粒纯化。Western blot检测纯化后样品可见相对分子质量为38 000,59 000,68 000左右的条带,表明基质膜蛋白与2种囊膜糖蛋白成功组装出病毒样颗粒,且免疫小鼠可诱导产生保护性中和抗体。本试验为后续小反刍兽疫病毒(PPRV)病毒样颗粒疫苗的进一步研发奠定了基础。     

猪瘟病毒石门株E2蛋白在杆状病毒系统中的表达

以杆状病毒Bac-to-Bac表达系统表达猪瘟病毒(CSFV)石门株的E2蛋白,将CSFV石门株的E2囊膜糖蛋白基因亚克隆到杆状病毒转移载体pFastBacHTA中,获得重组转移质粒pFastBacHTA-E2。转化大肠埃希菌DH10Bac感受态细胞,获得重组Bacmid质粒后转染Sf9昆虫细胞,获得重组病毒。传毒3代后对表达蛋白进行Western blot和间接免疫荧光试验检测。结果显示,E2蛋白获得高效表达,能被抗E2蛋白的单克隆抗体2B10和6×His-单克隆抗体特异性识别,表明CSFV石门株E2囊膜糖蛋白在Sf9昆虫细胞中得到成功表达,具有良好的抗原反应性。     

鸡传染性支气管炎病毒GX-YL5株S蛋白在昆虫杆状病毒表达系统的表达及其免疫原性

为了对鸡传染性支气管炎病毒(avian infectious bronchitis virus,IBV)广西优势血清型代表株GX-YL5的S蛋白进行真核表达并研究其免疫原性,设计GX-YL5毒株S基因特异引物,扩增出目的片段后,构建重组表达载体pFastBacTM/HBM-TOPO-S,转化DH10Bac细胞获得重组杆状病毒rHBM-S;重组S蛋白鉴定正确后,大量表达、纯化并免疫新西兰大白兔制备兔抗血清,应用IFA、Western blot以及间接ELISA、气管环(TOC)中和试验对该重组蛋白的反应原性及免疫原性进行分析。结果显示,成功获得重组S蛋白;制备的抗S蛋白多抗血清具有良好的特异性,ELISA效价可达1∶25600,TOC中和试验滴度为1∶512。结果表明,应用昆虫杆状病毒表达系统成功表达了具有很好免疫原性的GX-YL5株的S蛋白。本试验为研究IBV S蛋白的生物学功能、研发诊断试剂和制备新型疫苗等奠定了基础,为利用昆虫杆状病毒表达系统进行IBV或其他冠状病毒结构蛋白的表达及多抗的制备提供了借鉴和参考。     

狂犬病毒HEP-Flury株基质蛋白的原核表达及纯化

为原核表达狂犬病毒(RV)基质蛋白(M),本研究以RV的HEP-Flury株全长重组质粒为模板扩增M基因,双酶切后定向克隆至原核表达载体pQE30,构建重组质粒pQE-M并转化至宿主菌E.coli M15(pREP4),在IPTG的诱导下表达。SDS-PAGE电泳分析显示M蛋白为25ku。Western blot检测证明,重组蛋白可被鼠抗His单克隆抗体及鼠抗狂犬病毒多克隆抗体特异识别。本研究为狂犬病诊断方法的建立奠定了基础。     

鸡传染性支气管炎病毒S1基因抗原区的原核表达及鉴定

本研究以鸡传染性支气管炎病毒(infectious bronchitis virus,IBV)S1基因为研究对象,设计特异性引物扩增S1抗原集中区目的基因,长度为198 bp,亚克隆至原核表达载体pGEX-6P-1,构建重组原核表达质粒pGEX-6P-1-S1,转化至宿主菌Rosetta(DE3)后进行诱导表达。SDS-PAGE分析结果显示,表达获得1条特异性蛋白条带,其分子质量大小为33.0 ku,与预期蛋白大小一致。可溶性分析结果表明目的蛋白以包涵体形式存在。Western blotting结果显示,重组蛋白能与IBV鸡阳性高免血清反应,被GST标签单抗识别,结果表明该融合蛋白正确表达并具有良好的抗原性。本研究为制备IBV单克隆抗体奠定了抗原基础。     

犬瘟热病毒囊膜糖蛋白在杆状病毒-昆虫细胞系统中的表达及鉴定

为表达具有天然构象的犬瘟热病毒(CDV)囊膜糖蛋白融合蛋白(F)和血凝素蛋白(H),本研究扩增小熊猫源CDV驯化致弱株LP的F、H基因,克隆至pFastBacTM1载体中,测序验证后转化至DH10BacTM感受态细胞,同源重组获得穿梭质粒rBacmid-F、rBacmid-H,将其分别转染Sf9细胞获得重组杆状病毒rpFB-F、rpFB-H,并将表达的重组融合蛋白(rF)和血凝素蛋白(rH)进行IFA和Western blot鉴定。以犬抗CDV高免血清对重组杆状病毒感染细胞进行IFA鉴定,在感染细胞的细胞膜上可见特异性荧光反应;以鼠抗F、H蛋白的主要抗原表位区多克隆抗体对重组杆状病毒感染细胞进行Western blot检测,可见相对分子质量为63和68ku左右的条带,分别为重组融合蛋白(rF)和血凝素蛋白(rH),大小与预期相符。两种囊膜糖蛋白在杆状病毒-昆虫细胞系统中均成功表达,且具有良好的反应原性。本研究为CDV病毒样颗粒疫苗的开发等工作奠定了基础。     

猪瘟病毒EO蛋白的原核表达及其重组蛋白活性测定

通过重叠PCR合成猪瘟病毒EO基因,将该片段定向插入到pET-22b载体中,构建原核表达载体pET-22b／EO,转化大肠杆菌BL21 (DE3),IPTG诱导表达,比较不同诱导条件下的蛋白表达,确定其最佳表达条件。重组蛋白主要以包涵体的形式表达,Ni2 亲和层析柱纯化蛋白,逐步透析法复性。通过方阵试验确定包被抗原的最适工作浓度,为了测定EO蛋白的活性,本文初步建立了检测猪瘟血清抗体水平的间接 ELISA方法,为开发检测猪瘟抗体诊断试荆奠定基础。     

Adaptation of protein oxidation to protein intake in the domestic cat

It is well-accepted that cats require more dietary protein than omnivores and herbivores. Work on hepatic enzyme activities showed that cats lack the ability to regulate the urea cycle enzymes in response to the dietary supply of protein. It was thus hypothesized that the high protein requirement of cats is due to an inability to regulate these enzymes, limiting adaptation to a low protein diet. We used indirect respiration calorimetry to assess the in vivo ability of cats to adapt substrate oxidation to different levels of dietary protein, including one below their protein requirement. In random order, eight cats consumed each of four semi-purified diets containing 7.7% (LP), 14.6% (AP), 27.3% (MP) and 51.1% (HP) of ME from protein. Cats consumed each diet for at least 14 days and then completed a 5-day nitrogen balance trial and at least 2, 12-hour indirect calorimetry measurements. The data were analyzed by anova using the Mixed procedure of SAS and are expressed as mean ± SEM. There was a significant effect of diet on protein oxidation (p < 0.0001), measuring 9.8 ± 0.5%, 13.4 ± 0.9%, 23.5 ± 0.8% and 49.0 ± 1.8% of total energy expenditure on the LP, AP, MP and HP diets, respectively. The ratio of protein oxidation/protein intake was significantly higher with the LP diet (1.27 ± 0.07) than the other three diets (AP, 0.92 ± 0.06; MP, 0.86 ± 0.03; HP, 0.96 ± 0.04; p < 0.0001), indicating a net loss of protein on the LP diet. Thus, cats adapted to a wide range of dietary protein concentrations, but were unable to fully adapt to the LP diet.     

大豆浓缩蛋白是乳猪饲料的优势蛋白源

乳猪能否顺利断奶是养猪业成功的关键.乳猪消化系统的发育尚未完善,需要易消化、质量高的蛋白原料.因此,高质量、易消化的乳蛋白和血浆蛋白等常被用作乳猪开食料的蛋白原料.     

Level of supplemental protein does not influence the ruminally undegradable protein value

Two experiments were conducted to determine whether elevating the percentage of ruminally undegradable protein (RUP) in the diet would influence the RUP value of the protein feedstuff. A single-effluent, continuous-culture study was designed to test the effect of RUP inclusion rate in the diet on ruminal degradability of the protein. Treatments consisted (DM basis) of a control diet with no supplemental protein, control + 2.5% bloodmeal (BM-L), control + 5% bloodmeal (BM-H), control + 4.45% soybean meal (SBM-L), and control + 8.89% soybean meal (SBM-H). Proteolytic activity and total VFA concentration were not affected (P = 0.73 and P = 0.13) by treatment. Within protein source, dietary RUP value was not affected (P = 0.94) by level of inclusion. When corrected for control diet RUP flow, the RUP value of the blood meal (BM) protein was higher (P = 0.01) than soybean meal (SBM); however, level of supplementation did not affect (P = 0.07) the RUP value of BM or SBM. In Exp. 2, 32 British x Continental crossbred steers (276 +/- 26.3 kg) were fed for 72 d to examine the effects of balancing the AA:energy ratio, using BM as a RUP source, on ADG, G:F, and lean tissue deposition. Diets were formulated to provide increasing levels of arginine, while ruminally degradable protein and energy were held constant. Four dietary treatments provided 0.5, 1, 1.5, and 2x the required amount of arginine, whereas the control diet had no BM included. Daily DMI averaged 7.6 kg/steer and did not differ (P = 0.71) among treatments. Steers gained an average of 1.9 kg/d and average G:F was 0.260, with no differences (P = 0.60 and P = 0.97, respectively) among treatments. There was no difference (P = 0.48) in the change in 12th-rib fat depth during the study; however, change in LM area was affected quadratically as the level of BM increased in the diet, with the greatest increase in LM area occurring in steers fed the 1x and 1.5x required arginine treatments. Balancing the AA:energy ratio did not affect G:F, DMI, or ADG; however, it increased deposition of lean in the LM quadratically. Level of dietary inclusion of BM as an RUP source does not affect its RUP value or efficacy of providing postruminal AA in growing steers.     

Displaying the protein of Mycoplasma gallisepticum agglutinin on the cell surface of Bacillus thuringiensis with the S-layer protein

The S-layer protein CTC surface-display system of Bacillus thuringiensis (Bt) was used to test the possibility of displaying the protein of Mycoplasma gallisepticum (MG) agglutinin (pMGA) on the Bt cell surface. By fusing part of pmga1.2 (pmga1.2p) with the surface-anchoring motif of ctc, two recombinant plasmids, pCTC-PMGA1.2P and pCSPMGA1.2P, were constructed. They harboured the fusion genes ctc-pmga1.2p and csa-ctc-pmga1.2p (csa represents csaAB operon, important in anchoring the S-layer protein on the cell surface), respectively. Two recombinant Bt strains were constructed by electro-transferring recombinant plasmids to a Bt plasmid-free derivative strain BMB171. Strains obtained were BCCG (bearing pCTC-PMGA1.2P and the csaAB operon-carrying plasmid pMIL-CSA) and CG (pCSPMGA1.2P). The vegetative cells of both strains were used as antigens for haemagglutination (HA) and haemagglutination inhibition (HI) assays. HA and HI assays showed that recombinant PMGA1.2P proteins were not only displayed on the cell surface of BCCG and CG, but also specific to MG-positive serum. After oral immunization of chickens with spores, both BCCG and CG elicited a humoral response to PMGA1.2P and exhibited immunogenicity, as indicated by serum plate agglutination (SPA) assays. This study suggests the possibility of generating heat-stable and oral vaccines against infectious diseases of fowl with Bt surface-display system.     

In vitro evaluation of protein degradability in the rumen and digestibility of undegraded protein

A three-phase laboratory procedure suitable for predicting protein degradability in the rumen and digestibility of undegraded protein is reported. In the first phase the feed was incubated with starch and buffered rumen fluid. In the incubation mixture the viability of protease-active bacteria was checked by anaerobic culturing, whereas changes in protease activity were monitored by azocasein degradation. In the second and third phase rumen undegradable protein (UDP) was digested with pepsin and pancreatin, respectively. The measurements showed that 63.2, 5.2 and 4.7% of the crude protein of green lucerne was decomposed by rumen fluid, pepsin and pancreatin, respectively. Degradability of the crude protein of extracted sunflower meal was 68.3, 17.7 and 5.5% in the three phases, respectively. Repeated determination yielded crude protein degradabilities of 66.7, 27.1 and 5.1% for the three phases, respectively.