Comparison of two antigens for use in an enzyme-linked immunosorbent assay to detect African swine fever antibody

Two African swine fever virus (ASFV) antigens were tested for use in an ELISA to detect antibody to ASFV. Antigens used were the cytoplasmic soluble fraction (CS-P) of infected cells grown in the presence of porcine serum and the semipurified viral structural protein VP73 (SVP73). Both antigens were tested by ELISA against 72 sera obtained during several ASF field episodes and from ASFV-inapparent carriers. Of the 72 sera, only 2.8% has positive results by ELISA against CS-P antigen; 60% of positive-reacting sera (to both antigens) had higher ELISA values when the CS-P antigen was used. Samples (with positive results) that reacted only to CS-P antigen had results confirmed by immunoblot analysis. Such sera reacted against ASFV-infection proteins IP25, IP25.5, and IP30, but not against IP73. In time-course experiments to detect appearance of ASFV-antibodies in infected miniature pigs, antibodies were detected by immunoblot analysis on postinoculation day (PID) 8. At that time, only the polypeptides IP25, IP25.5 IP30, and IP31 were recognized; IP73 and IP12 were first detected 3 and 4 days later, respectively. In the same experiments, ASFV antibodies were detected by ELISA, using CS-P or SVP73 antigens, on PID 7 and 9, respectively. These results could explain the percentage of sera not having positive results by ELISA using SVP73 antigen, if the sera were obtained from ASFV-infected pigs during the first days of infection before induction of antibody response against the IP73 protein. This feature makes the use of CS-P antigen advantageous in early serologic detection of ASFV-infected pigs.     

Comparison of a radioimmunoprecipitation assay to immunoblotting and ELISA for detection of antibody to African swine fever virus

A radioimmunoprecipitation assay (RIPA) has been developed for detection of antibody to African swine fever virus (ASFV) and compared with the immunoblot assay with regard to sensitivity and specificity. Two hundred seven field sera, obtained from pigs in Spain from different geographic areas between 1975 and 1986, that were positive by ASFV enzyme-linked immunosorbent assay (ELISA) were also analysed by immunoblot assay and RIPA. By serum dilution experiments, the RIPA appeared at least as sensitive as the ELISA and immunoblotting tests, although ELISA and RIPA detected antibodies to ASFV earlier in natural infection than did the immunoblot assay, as disclosed by animal inoculation studies. The most antigenic ASFV-induced proteins in natural infection detected by RIPA were the viral proteins p243, p172, p73, p25.5, p15, and p12 and the infection proteins p30 and p23.5. In the immunoblot assay, the proteins that were most reactive with the same sera were the viral protein p25.5 and the infection proteins p30, p25, and p21.5. Only 1 serum, from an animal infected with ASFV, was negative by immunoblot assay but showed a positive result by RIPA. A modification of conventional RIPA was performed using a dot transference of immunoprecipitated proteins to a nitrocellulose filter. This modification simplified the conventional RIPA procedures by eliminating the electrophoresis of immunoprecipitated proteins without affecting sensitivity and specificity. The ease of use, specificity, and the sensitivity comparable to that of the immunoblot assay make the RIPA a useful confirmatory assay for sera that yield conflicting results in other ASFV antibody assays.     

非洲猪瘟病毒p54蛋白单克隆抗体的制备及阻断ELISA方法的建立

旨在建立检测非洲猪瘟病毒(ASFV)血清抗体的阻断ELISA方法.采用原核表达的ASFVp54蛋白作为包被抗原,并制备了针对p54蛋白的单克隆抗体,采用方阵滴定法确定了阻断ELISA方法的最佳反应条件,并对建立的方法进行了敏感性、特异性、重复性和符合性评价.结果显示,抗原最佳包被浓度为2.0 μg·mL-1,抗原包被温...     

Comparison of dot immunobinding assay, enzyme-linked immunosorbent assay and immunodiffusion for serodiagnosis of paratuberculosis.

A rapid, simple and inexpensive dot immunobinding assay (DIA) was evaluated for the serodiagnosis of paratuberculosis in cattle. The assay was performed on nitrocellulose strips which were dotted with purified protoplasmic antigen of Mycobacterium paratuberculosis. After incubation with test serum samples, the bound antibodies were detected using an enzyme-amplified immunostaining procedure. The efficacy of DIA as a screening test for paratuberculosis was compared to that of an enzyme-linked immunosorbent assay (ELISA), a modified agar gel immunodiffusion (mAGID) test, and an AGID test using 329 serum samples from cattle which were examined for M. paratuberculosis infection by a sensitive fecal culture technique. The DIA and ELISA had comparable results and both of the enzyme immunoassays had higher sensitivity than tests based on AGID. The sensitivity of all four tests was influenced by the intensity of fecal bacterial shedding. Preabsorption of sera with Mycobacterium phlei increased the sensitivity of both enzyme immunoassays. the specificity but reduced the sensitivity of both enzyme immunoassays.     

非洲猪瘟病毒p30蛋白单克隆抗体的制备及阻断ELISA抗体检测方法的建立

为建立检测非洲猪瘟病毒(ASFV)抗体的阻断ELISA方法,本研究利用原核表达的ASFV p30重组蛋白免疫BALB/c小鼠制备单克隆抗体。以重组p30蛋白作为包被抗原,以辣根过氧化物酶(HRP)标记的p30单克隆抗体作为检测抗体,经条件优化,建立了一种检测ASFV抗体的阻断ELISA方法。ROC曲线分析显示,该方法最佳阻断率临界值为16.63%。该方法与CSFV、FMDV-O/A、PRRSV、PEDV、SVA的阳性血清均无交叉反应;最低能检出1∶128稀释的阳性血清;批内和批间变异系数(CV)均＜10%。用本方法与商品化试剂盒平行检测208份血清样品,Kappa值为0.96,表明具有高度一致性。上述结果表明,本研究建立的阻断ELISA方法具有较高的特异性和敏感性,可用于血清ASFV抗体的检测,为ASFV流行病学调查及猪群疫情监控提供技术支持。     

检测非洲猪瘟McAb-ELISA竞争试剂盒的建立及初步应用

用基因重组技术制备的非洲猪瘟蛋白P54免疫BALB/C小鼠,将免疫鼠的脾细胞与SP2/0骨髓瘤细胞融合,采用有限稀释法进行克隆,获得能稳定分泌抗ASFV单克隆抗体的杂交瘤细胞株。使用该单克隆抗体,建立了检测血清中非洲猪瘟抗体的竞争法ELISA。实验结果表明：ELISA竞争法特异性高,无交叉反应,灵敏度高于间接免疫荧光法,可用于猪血清的非洲猪瘟抗体检测。该法的建立对非洲猪瘟实验诊断的标准以及流行病学调查具有重要的现实意义。     

非洲猪瘟病毒p22蛋白表达、多克隆抗体制备及间接ELISA方法的建立

【目的】试验旨在表达与纯化非洲猪瘟病毒(African swine fever virus, ASFV)的结构蛋白p22,将其作为包被抗原建立ASFV抗体的间接ELISA检测方法,用于诊断非洲猪瘟。【方法】将ASFV p22编码基因KP177R的截短体(24―145位氨基酸)克隆至原核表达载体pET-32a(+)中,将重组质粒pET-32a-p22转化大肠杆菌BL21(DE3)感受态细胞,经0.1 mmol/L IPTG诱导表达5 h,利用镍柱亲和纯化p22蛋白,并进行Western blotting鉴定。利用p22蛋白免疫BALB/c小鼠制备抗血清,并以含p22全长基因的真核表达质粒pCAGGS-EGFP-fp22转染HEK293T细胞为抗原基质,利用间接免疫荧光(IFA)鉴定抗血清的反应性。以重组p22蛋白为包被抗原,优化最佳抗原包被浓度、待检血清稀释度、封闭条件、抗原抗体反应时间、酶标二抗工作浓度等参数,建立ASFV抗体间接ELISA检测方法,并对临床猪血清样品进行检测。【结果】ASFV p22截短蛋白在大肠杆菌中高水平表达,蛋白产量为0.85 mg/100 g菌体;p22蛋白具...     

基于非洲猪瘟病毒p30与p54蛋白表位串联多肽的间接ELISA抗体检测方法的建立

旨在建立检测非洲猪瘟病毒(ASFV)血清抗体的间接ELISA方法。本研究以两株纯化的ASFV p30与p54蛋白单克隆抗体(mAbs)为靶分子,利用噬菌体展示十二肽库进行四轮生物淘选,筛选多肽表位,以氨基酸GGG为接头设计合成表位串联多肽作为包被抗原,通过棋盘滴定法确定间接ELISA的最佳反应条件,利用不同类型血清样本对建立的方法进行特异性分析、敏感度分析、稳定性分析及符合性评价。噬菌体淘选试验结果表明¹⁴⁶PAEPYTT¹⁵²为本实验室保存的mAb所识别的p54蛋白抗原表位核心序列。ELISA条件优化试验结果显示,以鸡卵白蛋白(OVA)作为N端偶联物的表位串联多肽抗原具有较低的非特异性血清反应背景,当多肽以碳酸盐缓冲液包被(2 μg·mL^-1),血清以封闭液(1%明胶溶液)稀释100倍,辣根过氧化物酶(HRP)标记抗体以0.05% PBST溶液稀释5 000倍时,反应效果最佳;以上述优化后的条件确定了血清抗体阳性临界值为0.339。方法评价试验结果显示,该方法与经典猪瘟病毒(CSFV)、猪繁殖与呼吸综合征病毒(PRRSV)、猪圆环病毒2型(PCV2)、猪细小病毒(PPV)及猪伪狂犬病病毒(PRV)的抗体阳性血清均无交叉反应,能检测低至1 600倍稀释的ASFV阳性血清,具有较好的重复性。用该方法与商品化的ASFV抗体检测试剂盒同时检测320份猪血清样本,两种方法的相对特异性和相对敏感性分别为97.6%与97.3%,总体符合率达97.5%(312/320)。综上表明,本研究建立的多肽间接ELISA方法具有良好的特异性、敏感性及重复性,具有发展为临床诊断试剂盒的潜在应用价值。     

非洲猪瘟病毒p62蛋白单克隆抗体的制备及初步应用

为制备非洲猪瘟病毒（ASFV）p62蛋白的特异性单克隆抗体,并初步应用于感染组织样品中ASFV抗原的免疫组化（IHC）检测,本研究以杆状病毒表达的非洲猪瘟病毒重组p62蛋白免疫BALB/c小鼠,取其脾细胞与骨髓瘤细胞进行融合获得杂交瘤细胞。结果显示：基于纯化的p62蛋白建立的间接ELISA方法对杂交瘤细胞进行筛选和亚克隆,获得了18株可稳定分泌抗非洲猪瘟病毒p62蛋白单克隆抗体的杂交瘤细胞株。经IFA检测,制备的单克隆抗体均与非洲猪瘟病毒反应,且不与猪瘟病毒、猪繁殖与呼吸综合征病毒、猪伪狂犬病病毒、猪圆环病毒2型等猪源常见病毒反应,特异性良好。抗体识别蛋白的鉴定结果显示,3株MAbs识别p35蛋白,15株MAbs识别p15蛋白。14株MAbs重链亚类为IgG1型,4株MAbs重链亚类为IgG2a,轻链均为κ链。利用18株MAbs对ASFV感染猪的肺、扁桃体、淋巴结等组织进行IHC检测,结果显示5株MAbs均能够与感染ASFV的组织发生特异性的免疫反应。本研究获得的非洲猪瘟病毒p62蛋白单克隆抗体可为非洲猪瘟病毒免疫学检测方法的建立及p62蛋白的结构功能等基础研究提供重要的生物材料。     

非洲猪瘟病毒环介导恒温扩增快速检测技术的建立及应用

本研究基于非洲猪瘟病毒（African swine fever virus, ASFV）vp72基因设计引物,建立了能够快速检测非洲猪瘟病毒的环介导恒温扩增技术（loop-mediated isothermal amplification, LAMP）。将LAMP与OIE参考的PCR检测方法进行比较,并且应用LAMP对非洲猪瘟参考实验室提供的非洲猪瘟病毒17个毒株的基因组以及国内收集的50份猪的基因组、30份蜱的基因组进行检测。结果显示,本研究设计的引物具有良好的特异性和敏感性,所建立的LAMP能够成功扩增非洲猪瘟病毒17个毒株的基因组,而野外收集的猪和蜱的基因组检测均为阴性。因此,本研究所建立的方法能够用于非洲猪瘟的快速诊断以及防控。     

非洲猪瘟病毒p30基因的原核表达及间接ELISA抗体检测方法的建立

为建立检测血清中非洲猪瘟病毒（African swine fever virus,ASFV）抗体的间接ELISA方法,本试验将ASFV p30基因进行原核表达,采用SDS-PAGE和Western blotting方法对重组蛋白进行表达鉴定和免疫原性分析,随后以纯化的重组蛋白为包被抗原,经条件优化、特异性试验、敏感性试验和重复性试验,建立一种血清中ASFV抗体的检测方法。结果显示,ASFV p30基因成功克隆到原核表达载体pET-32a （+）中,获得pET-32a-p30重组质粒;转化大肠杆菌BL21（DE3）感受态细胞进行诱导表达,得到P30重组蛋白,重组蛋白大小约为42 ku,主要以包涵体形式存在;Western blotting结果显示,纯化后的蛋白具有良好的免疫原性;以纯化的P30重组蛋白为包被抗原,建立了检测ASFV抗体的间接ELISA方法,通过方阵试验对间接ELISA方法进行优化,最终确定了抗原最佳包被浓度为1.2 μg/mL,待检血清最佳稀释倍数为1：100,最佳封闭液为1% BSA,酶标抗体最佳稀释度为1：4 000,以此建立的ASFV间接ELISA方法临界值为0.322。本方法仅与ASFV阳性血清发生特异性反应,与猪瘟病毒、猪繁殖与呼吸综合征病毒、口蹄疫病毒、伪狂犬病病毒、猪圆环病毒2型及猪流行性腹泻病毒阳性血清均无交叉反应,具有较强的特异性。该方法检测ASFV阳性血清灵敏度可达到1：1 600;批内重复性和批间重复性变异系数均<10%。本试验建立的间接ELISA方法具有良好的特异性、灵敏度和重复性,可初步应用于ASFV抗体的检测。     

非洲猪瘟病毒p72蛋白阻断ELISA检测方法的建立

本研究旨在建立一种非洲猪瘟病毒(ASFV)p72蛋白阻断ELISA抗体检测方法。以纯化的重组p72蛋白作为包被抗原,HRP标记的6E5抗体作为阻断抗体,通过对反应条件进行优化,建立了基于ASFV p72蛋白的阻断ELISA方法。用建立的阻断ELISA方法检测119份临床阴性血清,计算血清阻断率确定临界值,确定了该方法的判定标准：当阻断率PI≥50%时判定为ASFV抗体阳性;PI≤40%时判定为ASFV抗体阴性;当阻断率介于两者之间时,判定为可疑。该方法与猪伪狂犬病病毒、猪繁殖与呼吸综合征病毒、猪瘟病毒、猪圆环病毒2型、A型塞内卡病毒、猪口蹄疫病毒、猪大肠杆菌、猪多杀性巴氏杆菌、副猪格拉瑟菌和猪胸膜肺炎放线杆菌的抗体阳性血清无交叉反应,批间、批内试验的变异系数均小于15%。用该方法与商品化ASFV抗体检测试剂盒同时检测447份猪临床血清样品,两种方法的相对敏感性和相对特异性分别为95.3%和94.5%,符合率为94.9%。本研究建立的阻断ELISA方法具有较高的敏感性和良好的特异性,可用于ASFV感染诊断和流行病学调查。     

非洲猪瘟病毒全长与截短p72蛋白的抗原性比较

比较非洲猪瘟病毒(African swine fever virus,ASFV)全长p72与截短p72蛋白(p72s)的抗原性,为ASFV特异性抗体检测技术研究提供试验依据.应用大肠杆菌表达系统表达p72和p72s蛋白,应用Western blot和液相色谱—质谱联用(LC-MS/MS)技术鉴定表达的蛋白,分析蛋白的抗...     

非洲猪瘟病毒强免疫原性重组CD2v抗原的制备与初步应用

旨在获得非洲猪瘟病毒（ASFV）强免疫原性重组CD2v抗原,利用生物信息学软件进行CD2v抗原指数分析,将其细胞质内免疫显性区与类弹性蛋白多肽（ELP）在重组大肠杆菌中进行融合表达,对ELP-CD2v融合蛋白的相变循环（ITC）条件进行优化,在优化条件下进行融合蛋白纯化,利用烟草蚀纹病毒（TEV）蛋白酶活性包涵体切除ELP标签,通过免疫转印法对重组CD2v抗原进行鉴定,利用重组CD2v抗原建立ELISA抗体检测方法,与多抗原ELISA对ASFV抗体阳性和阴性血清进行平行检测。结果显示,ELP-CD2v融合蛋白获得正确、可溶性表达,ITC条件为28℃和1.5 mol·L^-1 NaCl,在0.2% Triton X-100存在下进行ITC,纯化的融合蛋白纯度为76.3%;TEV蛋白酶活性包涵体能有效切割ELP标签,再次ITC回收的重组CD2v抗原纯度为91.7%,能被ASFV抗体识别;根据多抗原ELISA检测结果选择血清样品,用重组CD2v抗原ELISA进行检测,结果显示,15份ASFV抗体阴性血清均为CD2v抗体检测阴性,15份ASFV抗体阳性血清均为CD2v抗体检测阳性。这些研究结果表明,ASFV的CD2v蛋白胞内区存在强免疫原性表位,其重组抗原有望用于CD2v的抗体检测。     

Preparation and Preliminary Application of Highly Immunogenic Recombinant CD2v Antigen of African Swine Fever Virus

To obtain the highly immunogenic recombinant CD2v antigen of African swine fever virus (ASFV), the amino acid sequence of CD2v was analyzed for antigenic index using bioinformatics software and the intracytoplasmic region with high antigenic index was expressed in E. coli as an elastin-like polypeptide (ELP) fusion protein. After optimization of the conditions for inverse transition cycling (ITC), ELP-CD2v fusion protein was purified by ITC in the presence of different concentrations of Triton X-100 and the ELP tag was cleaved with active inclusion bodies of tobacco etch virus (TEV) protease. The tag-free recombinant CD2v antigen was recovered by an additional round of ITC and identified by Western blotting. By using the recombinant CD2v antigen, an indirect ELISA was established and used to detect ASFV antibody-positive and antibody-negative sera in parallel with the multi-antigen ELISA. The results showed that ELP-CD2v fusion protein was expressed correctly in E. coli with an optimal transition temperature of 28 ℃ at 1.5 mol·L^-1 NaCl. After one cycle of ITC in the presence of 0.2% Triton X-100, ELP-CD2v fusion protein was purified to 76.3% purity. The ELP tag was cleaved efficiently with the TEV protease and removed after an additional round of ITC. The recovered recombinant CD2v protein had a purity of 91.7%, which was recognized by pig anti-ASFV serum. For 30 serum samples detected by ASFV multi-antigen ELISA, recombinant CD2v ELISA showed that all of 15 antibody-negative sera were CD2v antibody negative and all of 15 antibody-positive sera were CD2v antibody positive. These data suggest that the presence of immune dominant epitopes in the intracytoplasmic region of CD2v protein and the potential application of the recombinant CD2v antigen for ASFV antibody detection.     

Comparison of the dot-immunobinding assay with the complement fixation test for the detection of Brucella antibodies in sheep

A dot-immunobinding assay (DIA), using as antigen a sonic extract of Brucella abortus dotted on nitrocellulose bound to a plastic strip, was employed for the detection of Brucella antibodies in 666 sheep sera. The results were compared with the complement fixation test (CFT). All the 242 sera belonging to two flocks were found to be negative by DIA. CFT was negative in 239 cases, whereas three samples showed anti-complementary activity. Of the 424 sera from the remaining three flocks, 98 were positive by both tests and six were positive in DIA, but negative in CFT. In addition, 14 of the 19 anti-complementary sera were also positive by DIA.     

Detection of antibodies against African swine fever virus using infected monolayers and monoclonal antibodies

Three monoclonal antibodies, specific for porcine IgG, IgM and IgA, were used to develop isotype-specific immunoperoxidase monolayer assays for the detection of antibodies against African swine fever virus. A mixture of anti-IgM and anti-IgG monoclonal antibodies was used in an assay designed for screening sera. This test was compared with a commercially available ELISA by using experimental sera and field sera obtained after an outbreak of African swine fever on two farms in the Netherlands in 1986. Although the ELISA was less sensitive than the immunoperoxidase monolayer assay on sera taken early after infection, the tests were equally useful for screening purposes. The isotype-specific assays gave epizootiological information about the stage of infection on the two farms.     

某养殖场的病死野猪ASFV实时荧光PCR检测

为了进一步做好非洲猪瘟疫情防控工作,研究用实时荧光PCR法对武威市某养殖场病死野猪的猪耳朵和猪鼻拭子样品进行了非洲猪瘟病毒检测。结果显示该养殖场病死猪耳样品和猪鼻拭子样品均无Ct值,线形为直线,表明所有被检测样品均为ASFV抗原阴性。研究为严防非洲猪瘟进入威武市奠定了坚实的技术储备,也为威武市非洲猪瘟疫情防控提供了一定参考。     

Comparison of the dot-immunobinding assay with the serum agglutination test, the rose bengal plate test and the milk ring test for the detection of Brucella antibodies in bovine sera and milk.

In this study, Brucella antibodies in bovine sera and milk were detected using the dot-immunobinding assay (DIA), the serum agglutination test (SAT), the Rose Bengal plate test (RBPT) and the milk ring test (MRT). For this purpose, a total of 116 paired blood and milk samples collected at the same time from 56 aborted and from 60 healthy dairy cows was examined. In DIA, a nitrocellulose membrane (NCM) was used as the solid phase. Antigen adsorbed on the NCM was extracted from Brucella abortus S99 by heat treatment. The results obtained by DIA were compared with those of SAT, RBPT and MRT. Of the 116 paired blood and milk samples, 24 were positive and 72 were negative by all tests used. Serum samples of six aborted cows were positive by DIA, SAT and RBPT but the milk samples were negative by DIA and MRT. Serum and milk samples of four aborted cows gave positive reaction only by DIA tests. The remaining six aborted cows were negative only by MRT and two of them were negative by both RBPT and MRT. Four sera of healthy cows were found to be positive only by SAT.     

Comparison of three serotests for the detection of pseudorabies antibodies in pigs

The serum-neutralization test (SN), enzyme-linked immunosorbent assay (ELISA) and the radial immunodiffusion enzyme assay (RIDEA) were compared for the detection of pseudorabies (PRV) antibodies in swine sera. A total of 1285 serum samples were tested. All three tests were considered useful in determining the PRV antibody status of swine on a herd basis, but available evidence supports the continued use of SN as the definitive test because of possible false positive reactions associated with ELISA and RIDEA.