Use of enzyme-linked immunoassays for antibody to types C and D botulinum toxins for investigations of botulism in cattle

The development of specific enzyme-linked immunosorbent assays (ELISA) for antibody to types C and D Clostridium botulinum toxins for investigation of botulism in cattle is described. Partially purified type C and D toxins were used as antigens to develop these ELISAs. Specificity of the ELISAs was evaluated on sera from 333 adult beef and dairy cattle from areas with no history or evidence of botulism in animals or water birds. The test was also evaluated on sera from 41 herds that included herds vaccinated against botulism, confirmed botulism cases and herds from areas where the disease is considered endemic. The ELISAs detected the presence of antibody to botulinum toxins in samples from vaccinated cattle and both convalescent and clinically normal animals from unvaccinated herds with outbreaks of botulism. Antibody was also found in unvaccinated animals from herds in which there had been no diagnosed botulism cases in areas where botulism was considered endemic. Sera from some unvaccinated cattle with high ELISA reactivity was shown to be protective for mice in botulinum toxin neutralisation tests. The use of these tests in investigations of botulism in cattle is discussed.     

Characterization of the neurotoxin produced by isolates associated with avian botulism

Several varieties of birds are affected by type C botulism. We conducted neutralization tests of culture supernatants of isolates from cases of avian botulism. Whereas the toxin produced by isolates derived from mammalian botulism was neutralized only with type C antitoxin, the toxins of all isolates related to avian botulism were neutralized with both type C and D antitoxins. An analysis of nucleotide sequences with several strains revealed that the neurotoxin gene in the isolates from avian botulism comprises two thirds of the type C neurotoxin gene and one third of the type D neurotoxin gene. This indicates that the neurotoxin of avian isolates is a mosaic of type C and D neurotoxins. We prepared three sets of primers to differentiate the gene for the mosaic form from the conserved genes of type C and D neurotoxins. The results of polymerase chain reaction with these primers indicated that all avian botulism-related isolates and specimens possess the gene for the mosaic form of the neurotoxin. The toxins purified from avian and mammalian isolates exhibited the same degree of lethality in mice, but the former showed greater toxicity to chickens than the latter. These results indicate that the mosaic neurotoxin is probably a pathogenic agent causing some forms of avian botulism.     

Characterization of the D/C mosaic neurotoxin produced by Clostridium botulinum associated with bovine botulism in Japan

Clostridium botulinum types C and D are related to avian and mammalian botulism. Bovine botulism occurred at various farms from 2004 to 2007 in Japan. Since culture supernatants of isolates from cases of bovine botulism were neutralized completely and partially with type D and C antitoxins, respectively, we attempted to confirm the nucleotide sequences of the neurotoxin gene in isolates. The neurotoxin gene comprised two-thirds of the type D neurotoxin gene and one-third of the type C neurotoxin gene, indicating that the neurotoxin of bovine isolates is a mosaic of type D and C neurotoxins, D/C mosaic neurotoxin. We prepared four sets of primers to differentiate the genes of the mosaic and authentic forms with PCR. The results showed that all bovine botulism-related isolates possess the gene for the D/C mosaic form. Pulsed-field gel electrophoresis analysis demonstrated that isolates from bovine botulism which had occurred between 2004 and 2007 were genetically homologous, except for the isolate from one area. We further examined the biological and antigenic properties of the D/C mosaic neurotoxin, which was found to exhibit the highest lethal activity in mice compared with other types of neurotoxins. In the D/C mosaic neurotoxin, three epitopes recognized by monoclonal antibodies that specifically react to and neutralize the toxin were located in the carboxyl-terminal domain of the heavy chain. These results indicate that D/C mosaic neurotoxin is a pathogenic agent causing bovine botulism and has unique characteristics different from other type C and D neurotoxins.     

Detection of Clostridium botulinum types C and D toxin by ELISA

An ELISA to detect Clostridium botulinum type D toxin was developed using polyclonal antibodies to a semi-purified toxic complex of the neurotoxin. Sensitivity of the ELISA for detecting type C and type D toxin compared with mouse inoculation was 70% and specificity 96% on samples from animals with botulism diagnosed on clinical signs and herd history. However, both mouse inoculation and the ELISA failed to detect toxin in many animals with a presumptive diagnosis of botulism. Some cross-reaction was seen with Clostridium novyi type A, but not with other clostridial species. While the ELISA described here cannot replace mouse inoculation for the diagnosis of botulism, it is a useful additional test.     

重组C型肉毒梭菌毒素的表达与免疫保护性分析

本研究旨在获得重组C型肉毒梭菌毒素蛋白,并评价其免疫保护性。将麦芽糖蛋白（MBP）和C型肉毒梭菌毒素重链C末端（CH_C）的编码基因序列进行优化和串联,获得基因片段GMBPCH_C。将GMBPCH_C克隆至pET28a-（＋）后转化大肠杆菌BL21（DE3）感受态细胞,分别在15和37℃两种温度条件下诱导表达。利用Ni-IDA亲和层析方法对可溶性表达的目的蛋白进行纯化,从而获得重组蛋白rMBPCH_C。将rMBPCH_C与Montanide ISA 201佐剂混合制备成疫苗,免疫4只家兔,剂量为100 μg/只。根据《中华人民共和国兽药典》（2015年版）规定的方法检测一免后21 d及二免后14 d家兔血清的中和抗体效价。同时,在二免后14 d对家兔进行攻毒。结果表明,rMBPCH_C在37℃的诱导温度下,主要以包涵体的形式表达;在15℃的诱导温度下,可溶性表达的比例可达50%。一次免疫后,免疫组4只家兔血清对C型肉毒梭菌天然毒素（简称天然毒素）的中和效价均可达到1（0.1 mL血清中和1个小鼠最小致死量（MLD）的天然毒素）。二免后,家兔血清的中和抗体效价可达到4~8。用10个家兔MLD的天然毒素攻毒后,免疫组家兔得到了100%（4/4）的保护,而用1个家兔MLD的天然毒素攻毒后,对照组家兔100%（2/2）死亡。以上结果说明,rMBPCH_C具有良好的免疫原性,从而为C型肉毒梭菌病基因工程亚单位疫苗的研制提供了重要的试验数据。     

Investigation of serology for diagnosis of outbreaks of botulism in cattle

Serology has been used to diagnose retrospectively types C and D outbreaks of botulism in cattle in Australia and this study has investigated whether the approach would be applicable in England and Wales. Three hundred sera from routine surveillance submissions in England and Wales were used as a negative control population. Some stored sera were available from a small number of clinical cases of botulism and 125 samples were collected from cohort groups of clinical cases in four new outbreaks of botulism. Three of these outbreaks were identified as being caused by type D Clostridium botulinum toxin. Sera were tested by antibody ELISA in laboratories in Australia and Germany. There was no increase in the proportion of animals seropositive to type C or D antibody in the botulism-associated cattle. The proportion of samples which were seropositive to type D antibodies was <2% in both the negative control and outbreak populations. It was concluded that single time serology is unlikely to be helpful for retrospective diagnosis of outbreaks of type D botulism in England and Wales.     

Comparative immunogenicity of two bivalent botulinum vaccines

OBJECTIVE: To compare the ability of a new single-dose botulinum vaccine containing a non-mineral oil adjuvant with a single dose of a conventional botulinum vaccine product to produce antibody to Clostridium botulinum types C and D in cattle in Northern Australia. DESIGN AND PROCEDURE: One hundred and fifty Brahman steer weaners were randomly divided into two groups receiving either a single dose of CSL Bivalent Botulinum vaccine or Websters Singvac. Blood samples were collected at 0, 8 and 24 weeks and tested by antibody ELISA. The final samples were also tested by the toxin neutralisation test, to test titres of neutralising antibody. RESULTS: Six months after inoculation, cattle vaccinated with Websters Singvac had ELISA antibody response twice that of CSL conventional product. However, this difference was only evident for neutralising antibody to type C botulinum toxin. Both products produced similar titres of type D neutralising antibody after a single dose. CONCLUSION: Websters' Singvac produces a greater neutralising antibody response to type C botulism upon single inoculation than a conventional vaccine. The product produces an equivalent neutralising antibody response to type D.     

A longitudinal study of rotavirus antibody titers in swine in a closed specific pathogen-free herd.

In a newly established closed specific pathogen-free (SPF) swine herd, gilt/sow suckling and weaned pig rotavirus specific antibody titers were followed for three lactations by enzyme-linked immunosorbent assay (ELISA) to gain insight into the dynamics of herd antibody titers to group A rotavirus. Among gilts/sows, serum antirotavirus IgG titers increased during each lactation with a subsequent drop in titer between farrowings. Serum antirotavirus IgM titers declined during each lactation and with subsequent parity. Serum antirotavirus IgA titers remained constant during lactations and among parities. In colostrum and milk, antirotavirus IgA antibody was abundant. Differences in titer were not noticed between gilts and second litter sows but third litter sows had significantly higher titers than the first two groups. Antirotavirus IgG was high in colostrum but nearly nonexistent in milk. This titer did not vary significantly within or among parities. There was a linear regression in the titers of baby pig serum antirotavirus IgG from the post colostral sample through to seven weeks old, after which titer began to increase. No difference in baby pig serum antirotavirus IgG was noted among the three litters. Serum antirotavirus IgA and IgM were undetectable in baby pig sera after 2-3 weeks of age. Coproantibody to rotavirus was sporadically present in pig feces for 2-3 weeks after birth with highest titers in the IgA fraction. We conclude that although it is probable that age resistance of pigs to rotavirus diarrhea occurs, humoral immunity as measured by ELISA rotavirus antibody titers may not be intimately involved in virus clearance since in our studies baby pigs passively received large amounts of antibody but still excreted pathogenic virus. The finding of increasing levels of serum antirotavirus IgG in gilt/sow serum suggest that exposure to antigen of dams occur without significant increases in antirotavirus IgG titers in either colostrum, milk, or baby pig serum.     

Determination of IgM and IgG antibodies to Toxoplasma using the IFA test, ELISA, and Dot-ELISA procedures

The dot enzyme-linked immunosorbent assay (Dot-ELISA) and the enzyme-linked immunosorbent assay (ELISA) were compared with the immunofluorescent antibody test (IFA) for detection of IgM- and IgG-specific antibodies to human toxoplasmosis. Reciprocal titers were determined in all three assays using sera from 56 patients with suspected toxoplasmosis or with symptoms and diseases requiring exclusion of toxoplasmosis and control sera from 56 healthy persons. Using the Dot-ELISA, six patient sera (10.7%) were positive at titers of greater than equal to 1024 for IgM antibodies (titer range 1024-16 384) and 47 sera (84%) were positive for IgG antibodies (titer range 16-262 144) at a titer of greater than or equal to 16. One control serum was reactive for IgM (titer 1024) and 10 control sera (18%) were positive for IgG in the Dot-ELISA. In the ELISA, at titers of greater than or equal to 128, five sera (9%) were reactive for IgM (titer range 128-512) and 52 sera (92.8%) were reactive for IgG (titer range 32-8192) at a titer of greater than or equal to 32; no control sera gave positive reactions for IgM while 10 sera (18%) were positive for IgG in the ELISA. Using the IFA test at reciprocal titers of greater than or equal to 16, four sera (7.1%) were positive for IgM (titer range 32-512), and 51 sera (91%) were positive for IgG (titer range 16-8192). None was reactive for IgM, and eight sera (14%) were positive for IgG (titer range 32-128) in the IFA test. The Dot-ELISA correlated well with the IFA test (correlation coefficient = 0.895) and the ELISA correlated slightly higher with the IFA test (correlation coefficient = 0.910) for detection of IgG antibodies to Toxoplasma gondii.     

Detection of serum antibodies against Ehrlichia risticii in Potomac horse fever by enzyme-linked immunosorbent assay

An indirect enzyme-linked immunosorbent assay (ELISA) was developed which was specific and sensitive in detecting antibodies to Ehrlichia risticii in Potomac horse fever (PHF). The ELISA antibody titers were correlated with the indirect fluorescent antibody (IFA) titers. E. risticii propagated in human histiocyte culture was purified on renografin gradient and the band of the organisms at a density of 1.182 g/ml was used as antigen. ELISA antibody titers were determined through computer assisted analysis, the observed antibody titers were derived by serial serum dilutions and using a resultant standard curve the predicted antibody titers were obtained from a single serum dilution. The standard curve had a correlation coefficient of 0.8975. The observed and predicted antibody titers were in good agreement, as the respective titers fell within a two-fold range. There was a good correlation between ELISA and IFA test results, but the ELISA titers were several times higher. In experimental infections of horses produced with the infected equine whole blood and the Ehrlichia infected macrophage culture, the antibodies were first detected in two weeks and one week postinoculation (PI), respectively. In both cases the titers reached a peak in about 4 weeks PI with a mean titer of 1:16558 and 1:4030, respectively. The antibody titers of the convalescent sera of field cases of PHF were comparatively lower than the experimentally infected horses.     

Serological distinction of bovine Salmonella carriers from vaccinated and acutely infected cows.

Identification of Salmonella carriers using lipopolysaccharide (LPS) ELISA serology in a Salmonella-infected herd requires distinction of chronically infected cattle from convalescent and vaccinated cows. Cows responding to Salmonella infection and vaccination produce titers to Salmonella LPS that overlap with the lower titers of some Salmonella carriers. The objective of this study was to determine if the LPS antigen specificity of the bovine humoral immune response to Salmonella LPS antigens differs following vaccination and acute and chronic Salmonella infection. The study focused on the nondiscriminatory area of Salmonella ELISA serology, specifically, peak-titered sera from Salmonella bacterin-vaccinated and experimentally infected cows and low-titered sera from Salmonella carriers. The LPS serogroup specificity of the IgG1 and IgG2 response following acute and chronic Salmonella serotype Dublin infection and Salmonella bacterin vaccination was evaluated using 5 Salmonella serogroup (B, D, E1, C3, and C1) LPS ELISA assays. IgG, titers of carriers, vaccinated, and acutely infected cows were predominantly O antigen specific. Similarly, the IgG2 titers of acutely infected cows were also O antigen specific. In contrast, Salmonella carriers produced an IgG2 response to each of the heterologous LPS antigens (B, E1, C3, and C1) examined. The results of this study indicate that the bovine IgG1 isotype response to Salmonella LPS is serogroup specific. Conversely, production of IgG2 antibodies to core Salmonella LPS antigens shared across Salmonella serogroups is a feature of chronic Salmonella infections.     

Immune response of pregnant cows to bovine rotavirus immunization

Fifteen pregnant Holstein cows were freely assigned to 3 experimental groups (5 cows in each group). Cows in group I were inoculated IM and intramammarily (IMm) with Ohio Agricultural Research and Development Center (OARDC) tissue culture-propagated modified-live Nebraska calf diarrhea bovine rotavirus with added adjuvant (OARDC vaccine-immunized cows). Group II cows were given IM injections of a commercial modified-live rotavirus-coronavirus vaccine (commercial vaccine-immunized cows), and the remaining 5 cows were noninoculated controls (group III). Rotavirus antibody in colostrum and milk was mainly associated with immunoglobulin (Ig)G1, and less so with IgG2, IgA, and IgM, as analyzed by the enzyme-linked immunosorbent assay (ELISA), using monospecific anti-bovine IgG1, IgG2, IgM, and IgA sera. In serum, the rotavirus antibody was distributed almost equally between IgG1 and IgG2. The same relationships appeared in both immunized and nonvaccinated cows. All OARDC vaccine-injected cows had virus-neutralization (VN) and ELISA IgG1 rotavirus antibody titers in serum and mammary secretions at significantly increased levels (at least 100-fold; P less than 0.05) compared with the titers in groups II (commercial vaccine-immunized cows) and III (controls). Serum, colostrum, and milk antibody titers from these latter 2 groups did not differ statistically. The ELISA IgG2, IgA, and IgM rotavirus antibody titers also were significantly greater in mammary secretions from OARDC vaccine-immunized cows than in groups II and III cows. There was a high correlation between ELISA IgG1 and VN rotavirus antibody titers for all samples tested (r = 0.97, P less than 0.001), but ELISA IgG1 antibody titers were consistently higher than VN titers. The ELISA IgG1 and VN antibody titers of milk samples collected from cows 30 days after parturition were higher from the OARDC vaccine-immunized cows (ELISA IgG1, geometric mean titer (GMT) = 3,511; VN GMT = 1,689) than were titers from the group II cows (ELISA IgG1 GMT = 39; VN GMT = 33) or group III cows (ELISA IgG1 GMT = 21; VN GMT = 19). These results indicate that IM plus IMm immunization of pregnant cows, using modified-live bovine rotavirus with added adjuvant, may significantly enhance serum, colostrum, and milk rotavirus antibody titers, whereas IM vaccinal inoculation of pregnant cows with a commercial modified-live rotavirus-coronavirus vaccine may not.     

新城疫病毒M蛋白单克隆抗体的制备与鉴定

为获得新城疫病毒（Newcastle disease virus,NDV） M蛋白单克隆抗体,本研究将编码该蛋白的基因克隆、表达并纯化重组蛋白,作为免疫原免疫小鼠,同时建立ELISA筛选方法对小鼠血清效价进行测定,筛选出血清抗体效价最高的小鼠脾细胞与SP2/0细胞融合,最终获得能稳定产生NDV M蛋白单克隆抗体的杂交瘤细胞株,并进行了抗体的免疫荧光、Western blotting、亚类的鉴定、杂交瘤细胞染色体计数、小鼠腹水制备及腹水内单克隆抗体效价测定。结果显示,PCR、重组质粒测序及双酶切鉴定正确,M基因大小约为1 095 bp。SDS-PAGE和Western blotting检测显示,试验成功表达了重组M蛋白,分子质量约为60 ku,且可与NDV阳性血清反应。建立的ELISA筛选方法中,重组M蛋白、His标签蛋白和抗体的最佳工作浓度分别为0.5 μg/mL、0.5 μg/mL和1∶256 000。抗体的免疫荧光、Western blotting、亚类的鉴定显示,杂交瘤细胞产生的抗体可与NDV SG10株及重组M蛋白特异性结合,其轻链为κ,重链为IgG2A。C9-G2、D3-F2杂交瘤细胞染色体计数结果分别为97和101条;杂交瘤细胞上清的ELISA检测效价均为1∶6 400,腹水的ELISA检测效价分别为1∶409 600和1∶102 400。本研究成功制备了NDV M蛋白的单克隆抗体,可为进一步研究M蛋白的功能提供工具。     

An enzyme-linked immunosorbent assay for coccidiosis in chickens: correlation of antibody levels with prior exposure to coccidia in the laboratory and in the field

An enzyme-linked immunosorbent assay was developed for detecting antibody to coccidia to facilitate the survey of laboratory and field infections. Serum antibody levels in chickens were measured against soluble Eimeria tenella oocyst antigen. Sera from breeders aged 10, 23, 37, and 43 weeks were positive with uniformly high antibody titers. Broiler chick sera showed high maternal antibody titer at hatch, decreasing to an almost negligible response at 3 weeks of age. Two-week-old broiler chicks had variable responses to a single infection of E. tenella: titers were elevated at 8 to 10 days postinfection and generally increased through day 24. Weekly reinfection of 2-week-old broiler chickens produced an antibody titer in proportion to the number of oocysts per dose and stimulated protection against challenge with 2 x 10(5) E. tenella. Inbred birds raised in a pathogen-free environment for 6 weeks had no detectable antibody titers.     

Development of an enzyme-linked immunosorbent assay for Bordetella avium

A Bordetella avium enzyme-linked immunosorbent assay (ELISA) was developed to detect serum antibodies in 1-day-old poults, experimentally infected turkeys, and naturally infected turkeys. The optimized procedure included use of a suspension of whole bacteria coated onto plastic microtiter plates, a 1:200 serum dilution, a 1:3200 dilution of commercially available goat anti-turkey IgG (heavy and light chain) conjugated with horseradish peroxidase, and 0.04% orthophenylenediamine as substrate. A sample/negative (S/N) ratio method of analysis was used to estimate antibody titer from absorbance values. The regression equation used to estimate antibody titers was derived from the testing of naturally infected turkey sera. The equation was derived by plotting the log10 titer of the sera against the S/N ratio at a 1:200 serum dilution. The ELISA was an effective method for detecting antibody to B. avium, and the procedure should prove useful for laboratories equipped for high-volume ELISA testing.     

鸡传染性支气管炎ELISA抗体检测试剂盒的研制

采用加蔗糖垫离心纯化鸡传染性支气管炎病毒(IBV)制备抗原，用提纯的IBV抗原包被微量板，建立了检测鸡传染性支气管炎(IB)抗体的ELISA试剂盒。抗原、被检血清和酶标结合物的最佳工作浓度分别为10ug／ml、1：200和1：3200。与IDEXX试剂盒相比，其敏感性、重复性、特异性均接近国外同类产品水平。对SPF鸡血清、实验免疫与攻毒的SPF鸡血清进行检测，结果表明所建立的ELISA特异性为95．6％，与IDEXX试剂盒符合率为95．6％。用于检测抗IBV特异性IgG抗体发现在免疫接种IB弱毒苗后，第4天即可检测到IgG抗体，峰值在第3周。试验鸡在通过滴鼻、点眼途径人工感染IBV强毒后，第5天抗体滴度明显上升。我们认为，该法是目前我国SPF鸡质量监测、养鸡生产中进行IB监测较好的方法。     

副猪嗜血杆菌OMP5单克隆抗体的制备与鉴定

用副猪嗜血杆菌（HPS）血清5型灭活菌液免疫BALB/c小鼠,取其脾细胞与Sp2/0骨髓瘤细胞融合,以HPS外膜蛋白5（OMP5）为抗原,经间接ELISA法筛选阳性融合孔,并用有限稀释法对筛选的阳性孔进行亚克隆,获得2株分泌抗HPS OMP5单克隆抗体的杂交瘤细胞株1E2和8D9;间接ELISA法效价检测,1E2和8D9细胞培养上清抗体效价均为1∶2 560,纯化后腹水抗体效价分别为1∶204 800和1∶51 200;抗体型别鉴定,1E2和8D9分别分泌IgG2b、IgG2a型抗体;特异性检测表明,2株单抗均能特异识别OMP5。将2株杂交瘤细胞反复冻融3次复苏后仍能稳定分泌抗体。2株抗HPS OMP5单克隆抗体的成功制备,将为HPS感染快速检测方法的建立以及检测试剂的研制奠定基础。     

猪抗克伦特罗(CL)抗血清的制备及其IgG纯化与鉴定

为了获得高特异性、高纯度的猪抗克伦特罗 (CL)IgG ,将克伦特罗跟牛血清白蛋白 (BSA)偶联后 ,选取 1 0头大×大×约三元杂交猪 (5头为免疫组 ,5头为对照组 ) ,用偶联物BSA CL对其进行免疫 ,来制备猪抗CL抗血清。以卵清蛋白 (OVA)跟CL的偶联物OVA CL为包被抗原 ,采用ELISA法测定抗血清效价和血清阻断率。结果表明 ,有 4头猪体内产生了抗CL抗体 ,且在第 2次加强免疫后达到最大 ,效价为 1∶2 0 0 0 0 ;而当血清稀释率为 1∶40 0 ,CL的PBS液浓度在 1 8× 1 0 - 4 ～ 7 0× 1 0 - 7之间时 ,其阻断率为 80 %～ 1 8%。随后用正辛酸 硫酸铵法对血清抗体进行纯化 ,经紫外吸收法测定和SDS PAGE电泳试验结果表明IgG成份得到了纯化 ,可用于进一步的免疫试验     

猪乳中抗猪瘟IgA、IgG、IgM抗体动态变化规律研究

以猪瘟弱毒疫苗免疫空怀母猪,待母猪分娩后,分别收集10 d内的乳汁,以建立的间接ELISA方法检测猪瘟IgA、IgG、IgM水平,并观察各种抗体动态变化规律。试验结果表明,猪初乳中的IgA、IgG、IgM抗体效价均在分娩当天达到最高值,随后迅速下降,7 d后抗体水平与常乳基本一致。对照组母猪仅在分娩当天检测到较低的抗体水平。     

Preparation of Cathepsin L1 Monoclonal Antibody Against Fasclala gigantica and Establishment of Double Antibody Sandwich ELISA

【Objective】 This study was intend to obtain cathepsin L1(rFgCat L1) specific monoclonal antibody and construct the double antibody sandwich ELISA.【Method】 Five BALB/c mice were immunized with 1 mg/mL rFgCat L1 protein for four times.Mouse splenocytes were isolated and fused with SP2/0 cells to construct hybridoma cells.Strong positive hybridoma cell lines were screened, 1×10⁶ cells were injected intraperitoneally per mouse to prepare monoclonal antibodies.Antibody titer and antigenic epitope were detected using ELISA method, antibody subtype and specificity were identified using Western blotting method.The double antibody sandwich ELISA was constructed by combining the anti-rFgCat L1 polyclonal antibody, and its sensitivity and specificity were tested.The positive and negative critical value was screened by 20 negative sera with positive control, and the constructed double antibody sandwich ELISA was verified by 47 goat positive sera and 47 dairy cow positive sera.【Result】 After immunization, the antibody titers in serum of 4 mice were all more than 10⁴.After isolated mouse with the highest immune response spleen cells were fused with SP2/0 cells total of 8 of them were positive cell lines were obtained after selective culture.5D5 and 7G6 were identified as strong positive strains with stable antibody secretion.After multiple subcloning screens and subcultures, the antibodies secreted in the cell supernatant were stable, with titers of 2⁹ and 2¹⁰ respectively, with ascites titers of 10⁷ and 10⁸.Western blotting and antibody subtype identification kits identified that the two antibodies were IgG1 type and the light chain was kappa type, both of which could specifically bind FgESP.According to the same antigen site was recognized by the two kinds of antibodies, the antigen titer of the two monoclonal antibodies were comparied, 7G6 was used as the coating antibody, and anti-rFgCat L1 was used as the enzyme-labeled secondary antibody.The optimized condition of method was that 7G6 was coated at a concentration of 2 μg/mL, the dilution concentration of anti-rFgCat L1 polyclonal antibody was 25 μg/mL, the dilution of Don-HRP-conjugated was 1∶4 000, 5% skimmed milk powder was selected as the blocking solution and the color development time was 25 min.The method was proved that could recognize the lowest antigen concentration of 0.625 μg/mL, also could specifically recognize antigen of Fasciola fasciatus.The constructed sandwich ELISA method was used for antigen detection of 47 dairy cow positive serum and 47 goat positive serum infective samples kept in the laboratory and the positive antigen rate were 72.3% and 78.7%, respectively.【Conclusion】 Anti-rFgCat L1 monoclonal antibody was successfully prepared and the double-sheet sandwich ELISA method for fascioliasis was constructed, which provided a good theoretical basis and material basis for the development of low-cost and rapid diagnostic kits.