Differences in capabilities of different enzyme immunoassays to detect anti-hepatitis E virus immunoglobulin G in pigs infected experimentally with hepatitis E virus genotype 3 or 4 and in pigs with unknown exposure

Hepatitis E virus (HEV), a major cause of acute viral hepatitis in humans in many developing countries, is highly prevalent in the pig population worldwide. The objective of this study was to assess the capability of three porcine prototypes of a human enzyme-linked immunosorbent assay (ELISA), an in-house ELISA and a line-immunoassay (LIA) to detect anti-HEV antibodies in pigs infected experimentally with HEV (n = 57), known to be negative for HEV infection (n = 27), or with unknown exposure to HEV infection (field samples, n = 90). All 27 samples from non-infected pigs were negative with all five assays. The earliest detection of anti-HEV antibodies occurred at 14 days post-inoculation (dpi) with four of five assays. From 42 dpi, all samples from infected pigs were detected correctly as anti-HEV positive. Kappa analysis demonstrated substantial agreement among tests (0.62-1.00) at 14 dpi and complete agreement (1.00) at 56 dpi. The overall area under the curve for all quantitative tests as determined by receiver operator characteristic analysis ranged from 0.794 to 0.831 indicating moderate accuracy. The results showed that all five assays can detect anti-HEV IgG antibodies accurately in pigs infected experimentally with HEV. In field samples, a higher prevalence of anti-HEV IgG was found in breeding herds than in growing pigs (100% versus 66.7-93.9%). These serological assays should be very useful in veterinary diagnostic labs for HEV diagnosis in swine.     

一起戊型肝炎暴发的血清抗体比较研究

目的评价戊型肝炎(戊肝)抗体E2-IgM(抗-HEV E2-IgM)酶联免疫试剂(捕获法)在反映戊肝流行特征和对戊肝早期诊断中的作用.方法在首发病例26 d后对某单位戊肝暴发人群和相邻单位对照人群进行血清抗-HEV E2-IgM、IgG检测;部分人群进行美国Genelabs抗-HEV IgM、IgG的平行检测.结果抗-HEV E2-IgM试剂捕获法在对照人群中仅检出1例阳性(0.11%),且阳性和阴性之间可明显区分,其特异度为99.89%;在暴发流行人群中检出145例阳性(8.66%),显著高于对照人群(P＜0.001);暴发人群中戊肝患者的血清学动态变化为抗-HEV E2-IgM在暴露时间为30～60d时保持较高吸光度(A值),随着时间的延长A值呈明显下降趋势;抗-HEV E2-IgM阳性在该组人群中与性别和年龄无关;在暴发人群抗-HEV E2-IgM(+)的115例患者中,Genelabs抗-HEV IgG检测出88份阳性,检出率为76.52%,漏检27例,漏检率为23.48%.对照人群随机抽样179例患者中有20例Genelabs抗-HEVI IgG(+),阳性率为11.17%.在110份抗-HEV E2-IgM(+)的血样中,Genelabs抗-HEVIgM只检测出76份,检出率为69.09%;有16例患者Genelabs抗-HEV IgG、IgM均未能检出;Genelabs抗-HEV IgG和IgM的不一致率为25.45%.结论抗-HEV E2-IgM具有99%左右的特异度,与在正常人群中检出较高阳性率的Genelabs抗-HEV IgG试剂相比,减少了假阳性;抗-HEV E2-IgM与Genelabs抗-HEV IgM、IgG相比,对急性戊肝感染诊断的灵敏度提高了25%～30%,减少了漏诊;抗-HEV E2-IgM试剂盒操作简单、快速,本底较好,不存在酶结合物不足的问题.     

Development and validation of a genotype 3 recombinant protein-based immunoassay for hepatitis E virus serology in swine

Hepatitis E virus (HEV) is classified within the family Hepeviridae, genusHepevirus. HEV genotype 3 (Gt3) infections are endemic in pigs inWestern Europe and in North and South America and cause zoonotic infections inhumans. Several serological assays to detect HEV antibodies in pigs have beendeveloped, at first mainly based on HEV genotype 1 (Gt1) antigens. To develop asensitive HEV Gt3 ELISA, a recombinant baculovirus expression product of HEV Gt3 openreading frame-2 was produced and coated onto polystyrene ELISA plates. Afterincubation of porcine sera, bound HEV antibodies were detected with anti-porcineanti-IgG and anti-IgM conjugates. For primary estimation of sensitivity andspecificity of the assay, sets of sera were used from pigs experimentally infectedwith HEV Gt3. For further validation of the assay and to set the cutoff value, abatch of 1100 pig sera was used. All pig sera were tested using the developed HEV Gt3assay and two other serologic assays based on HEV Gt1 antigens. Since there is nogold standard available for HEV antibody testing, further validation and a definitesetting of the cutoff of the developed HEV Gt3 assay were performed using astatistical approach based on Bayes'' theorem. The developed and validated HEVantibody assay showed effective detection of HEV-specific antibodies. This assay cancontribute to an improved detection of HEV antibodies and enable more reliableestimates of the prevalence of HEV Gt3 in swine in different regions.     

大理地区猪源甲型、乙型、戊型肝炎病毒血清流行病学调查

目的:调查大理地区猪体内甲、乙、戊型肝炎病毒的感染情况。方法:采用酶联免疫吸附实验(ELISA)检测屠宰生猪血清标本甲肝血清标志物(HAV-lgG和HAV-lgM)、乙肝血清标记物(HBsAg,HBsAb,HBeAg,HBeAbHBcAb)、戊肝血清标志物(HEV-lgG和HEV-lgM)。结果:HAV、HBV和HEV的感染率分别为:91%(162/178),93.9%(185/197),23.6%(42/178);HAV和HBV二重感染率为67.97%(121/178);HAV、HBV和HEV三重感染率为20.2%(36/178);HAV和HEV二重感染率为1.7%(3/178);HBV和HEV二重感染率为2.2%(4/178)。结论:甲、乙、戊型肝炎病毒在猪体内存在感染,同时发现在猪体内甲、乙型肝炎病毒重叠感染常见。     

乙型肝炎病毒e抗原的纯化及其在人血清抗体检测中的应用

目的方法利用ＺｈｏｕＪｉａｎ教授提供的重组质粒ＤＮＡｐＢＶ２２０／ｅＡｇ，转染ＤＨ５α细胞，经３０℃培养３小时，４２℃培养６小时温度诱导后，提取乙型肝炎病毒ｅ抗原（ＨＢｅＡｇ）。经ＤＥＡＥ－ＳｅｐｈａｒｏｓｅＦａｓｔＦｌｏｗ层折纯化后免疫打点分析，收集阳性蛋白。经ＳＤＳ－ＰＡＧＥ电泳，考马斯亮蓝Ｇ２５０染色，显示为单一的蛋白带，用免疫印迹法（Ｗｅｓｔｅｒｎｂｌｏｔ）和免疫打点（ｌｍｍｕｎｏｄｏｔ）法，确定表达产物的特异性。将纯化的ＨＧｅＡｇ用酶联免疫吸附试验（ＥＬＩＳＡ）和免疫条。方法基检测人血清中的相关抗体。结果经４９例乙型肝炎病毒ｅ抗体（ＨＢｅＡｂ）阳性病人血清检验证实了其特异性。结论免疫条方法较ＥＬＩＳＡ方法更敏感、特异。     

IgM and IgG antibodies to hepatitis E virus (HEV) detected by an enzyme immunoassay based on an HEV-specific artificial recombinant mosaic protein

To develop an enzyme immunoassay (EIA) for IgM antibody to hepatitis E virus (HEV) (IgM anti-HEV) and IgG antibody to HEV (IgG anti-HEV), a synthetic gene encoding several liner immuno-dominant antigenic epitopes from HEV structural proteins was assembled as a chimeric recombinant mosaic protein (Mpr) with glutathione S-transferase and used as an immunodiagnostic target. In addition, a neutralization confirmation test was developed using individual synthetic peptides. Among 614 patients with acute hepatitis from 10 geographically distinct outbreaks, IgG anti-HEV was found in 546 (88.9%), with a range of 77–100% depending on the outbreak. Of 130 patients tested for IgM anti-HEV, 126 (96.9%) were positive. Among patients tested within 4 months of onset of jaundice, 37/37 (100%) were IgG anti-HEV positive. For patients from whom sera were collected 1–16 days after onset of jaundice, the geometric mean IgG titer (GMT) was 1:47,000; the GMT increased to 1:70,710 30–40 days after onset of jaundice and decreased to 1:1,778 3–4 months after the onset of jaundice. For patients tested 6–8 months after onset of jaundice, 11/12 (92%) were IgG anti-HEV positive, and the GMT was 1:2,908. IgM anti-HEV was detected in 43/43 (100%) sera collected 1–40 days after onset of jaundice, and the GMT for IgM anti-HEV was 1:10,000 at that time. For sera collected 3–4 and 6–12 months after onset of jaundice, 7/14 (50%) and 5/12 (40%) respectively, were IgM anti-HEV positive. In conclusion, an artificial mosaic protein composed of linear antigenic epitopes from open reading frame 2 (ORF2) and ORF3 of HEV has been successfully applied to the development of a sensitive and specific EIA for the detection of IgG and IgM anti-HEV activity. These assays were used for the verification of HEV infection in outbreak settings and for the diagnosis of HEV infection in sporadic cases. © 1996 Wiley-Liss, Inc.     

Comparison of a chemiluminescence immunoassay and an enzyme immunoassay for detection of IgM antibodies against measles,mumps, rubella,cytomegalovirus (CMV), Epstein Barr virus (EBV), and human herpes virus (HHV) -1 and -2 infections

PurposeOutbreaks of vaccine-preventable viral diseases have been increasingly reported globally over the past few years. The burden of congenital viral infections, their impact on physical and mental development and the resulting economic loss to the family and the community are also well known. IgM antibody detection has been convenient in the diagnosis of acute viral infections, particularly in settings with limited resources where molecular tests are not feasible.MethodsThis is a comparative study between a chemiluminescence immunoassay (Liaison, DiaSorin, Saluggia, Italy) and an enzyme linked immunosorbent assay (ELISA) (Euroimmun, Lubeck, Germany) for the detection of IgM antibody against measles, mumps, rubella, CMV, EBV and HHV-1 and -2 viruses using a total of 345 samples. Results are expressed as agreement using kappa statistics.ResultsIn this study, CLIA is perfectly comparable to ELISA for the detection of IgM antibodies against measles (0.86) and mumps (0.92) with a moderate agreement for rubella (0.52), CMV (0.57), EBV (0.50), and HHV-1 and -2 (0.47) assays. However, a PABAK (prevalence-adjusted bias-adjusted kappa) showed improved agreement for rubella (0.64), CMV (0.65), EBV (0.60), and HHV-1 and -2 (0.88) assays.ConclusionsIgM antibody assays (CLIA and ELISA) against measles and mumps virus can be comparably used depending on the laboratory setup, throughput and expertise.     

我国汉、回和藏族部分人群HEV感染的血清学调查

目的了解我国不同民族的健康人群戊型肝炎病毒感染情况。方法采用ELISA方法检测人群血清中戊型肝炎病毒（戊肝,HEV）IgG抗体。汉族人群血清分别来自于四川、北京、黑龙江和山东,回族和藏族人群血清来自于甘肃、宁夏和青海,总共10448份血清采集于2006—2008年。结果七省市人群HEV抗体总阳性率为17．97％（1878／10448）。汉、回和藏不同民族人群HEV抗体阳性率分别为24．32％（1794／7376）、3．59％（81／2258）和0．37％（3／814）。不同地区人群HEV抗体阳性率分布,四川、北京、黑龙江和山东汉族人群阳性率分别为27．45％、20．30％、22．89％和22．68％,甘肃汉和回族分别为24．63％（184／747）和6．12％（77／1258）,宁夏回族和青海藏族分别0．40％和0．37％。汉回藏不同民族各年龄组人群HEV感染分布,汉族各年龄组人群HEV抗体阳性率,在≤10岁年龄组为5．19％,11～20岁组为11．64％,21～30岁组为20．08％,31～40岁组为34．17％,41—50岁为41．75％,51～60岁组为48．58％,≥61岁组为57．43％。回族人群各年龄组人群HEV抗体阳性率依次为3．11％,3．96％,2．11％,3．98％,2．52％,4．57％和6．67％。藏族人群3份阳性者分布在21—30岁组、31—40岁组和51～60岁组各1份,阳性率为0．63％、0．58％和1．01％。结论汉族人群戊肝病毒感染明显高于回族和藏族,感染率随年龄增长而升高。回藏族人群HEV抗体阳性率低下,应加强对HEV感染的监测。     

丙型肝炎病毒抗原检测方法的建立

目的以特异性单克隆抗体为基础建立丙型肝炎病毒(HCV)抗原检测的酶联免疫吸附(ELISA)法,探索从血浆或血清中检测HCV抗原的可能性.方法利用我们制备的抗-HCV核心及NS3区单克隆抗体(McAbs),进行多种交叉组合模式的分析,确立实验室模式,并测定348份义务献血员血样,确定此方法的Cutofff值,并分析146份抗-HCV阳性及225份抗-HCV阴性血浆,阳性结果用套式PCR试剂盒确证.结果构建了以抗-HCV核心区单抗C39及NS3区单抗C7-6为包被抗体,以C39及NS3区C7-57为标记抗体的夹心ELISA检测模型,以C7为抗原,其检出灵敏度为5ng/ml,其Cutoff值为阴性对照均值±0.25.146份抗-HCV阳性样本中,11份为抗原反应阳性,225份抗-HCV阴性样本中,16份为抗原阳性,这些阳性样本经PCR检测后,23份为HCVRNA阳性.结论用单抗构建的HCV抗原检测方法分别从抗-HCV阳性及阴性样本中检测出HCV抗原反应阳性样本,并经PCR确证,表明直接从血浆样本中检测HCV抗原是可能的,这将对于HCV和基础研究及控制HCV的传播有重要意义.     

Incidence and seroprevalence of hepatitis E virus infection in pregnant women infected with hepatitis B virus and antibody placental transfer in infants

BackgroundHepatitis E has poor outcomes in pregnant women. Superinfection of hepatitis E virus (HEV) in patients infected with hepatitis B virus (HBV) may worsen liver disease.ObjectivesTo estimate the incidence and seroprevalence of HEV infection among HBV-infected pregnant women, to investigate the transplacental transfer of maternal anti-HEV IgG, and to compare the maternal and neonatal outcomes in anti-HEV positive and negative pregnant women.Study designTotally 391 HBV-infected pregnant women were recruited from April 2012 to October 2014. Paired mothers and infants were followed up at an average 9.8 months postpartum. Anti-HEV IgG and IgM were tested by ELISA.ResultsOf the pregnant women, none was anti-HEV IgM positive and 42 (10.7%) were IgG positive. At the follow-up, 3 seronegative women converted to anti-HEV IgG positive, with an estimated incidence of 17 per 1000 person-years. No significant differences of gestational age, preterm birth rate, Apgar score and birthweight were observed between newborns of anti-HEV IgG positive and negative mothers. Of the 42 neonates born to anti-HEV IgG positive mothers, 38 (90.5%) had anti-HEV IgG in their cord blood. The neonatal and maternal anti-HEV IgG levels were positively correlated (r = 0.827, p < 0.05). All infants were negative for both anti-HEV IgM and IgG at the follow-up.ConclusionsHBV-infected pregnant women rarely have novel HEV infection during late pregnancy in Jiangsu, China. Maternal anti-HEV IgG efficiently transfers into the fetuses, and disappears in infants before 10 months old.     

Cross-species infection of specific-pathogen-free pigs by a genotype 4 strain of human hepatitis E virus

Hepatitis E virus (HEV) is an important pathogen. The animal strain of HEV, swine HEV, is related to human HEV. The genotype 3 swine HEV can infect humans and genotype 3 human HEV can infect pigs. The genotype 4 swine and human HEV strains are genetically related, but it is unknown whether genotype 4 human HEV can infect pigs. A swine bioassay was utilized in this study to determine whether genotype 4 human HEV can infect pigs. Fifteen, 4-week-old, specific-pathogen-free pigs were divided into three groups of five each. Group 1 pigs were each inoculated intravenously with PBS buffer as negative controls, group 2 pigs similarly with genotype 3 human HEV (strain US-2), and group 3 pigs similarly with genotype 4 human HEV (strain TW6196E). Serum and fecal samples were collected at 0, 7, 14, 21, 28, 35, 42, 49, and 56 days postinoculation (dpi) and tested for evidence of HEV infection. All pigs were necropsied at 56 dpi. As expected, the negative control pigs remained negative. The positive control pigs inoculated with genotype 3 human HEV all became infected as evidenced by detection of HEV antibodies, viremia and fecal virus shedding. All five pigs in group 3 inoculated with genotype 4 human HEV also became infected: fecal virus shedding and viremia were detected variably from 7 to 56 dpi, and seroconversion occurred by 28 dpi. The data indicated that genotype 4 human HEV has an expanded host range, and the results have important implications for understanding the natural history and zoonosis of HEV.     

Valuable antibody detection method for classifying hepatitis E virus genotypes

Nucleotide‐based methods are conventionally used to classify the hepatitis E virus (HEV) genotypes. A serological enzyme immunoassay (EIA) using open reading frame 3 (ORF3) C‐terminal peptides was developed to conveniently and accurately classify and evaluate the genotypes of HEV. The sera of mice immunized with HEV genotype 1, 3, and 4 reacted highly specifically to the peptides of the corresponding genotypes. Most (84.2%) clinical sera infected with HEV genotype 4 were positive for anti‐HEV antibodies when tested with the ORF3 peptides of genotype 4, but were negative for genotypes 1 and 3. Monkey and clinical serial sera infected with HEV reacted strongly to the homologous genotype ORF3 peptides. The indirect EIAs were more sensitive, with stronger reactivity, than commercial anti‐HEV immunoglobulin G assays when serial sera from monkeys infected with HEV genotype 1 or 4 were tested. All our results indicate that the serological typing EIA assays described in this study are more effective and convenient for the classification of HEV genotypes than molecular approaches, and can be used to screen large numbers of serum samples and differentiate genotypes for the diagnosis of HEV infections.     

丙型肝炎病毒不同基因型NS3蛋白的抗原异质性分析

目的探讨不同基因型丙型肝炎病毒(HCV)NS3蛋白的抗原特性及其用于抗-HCV检测的意义。方法分别构建和表达含有HCV1型和6型NS3基因片段的重组质粒和重组蛋白，以EIJSA法和Western blot分析不同基因型重组蛋白与已知抗-HCV阳性血清的抗原反应性。结果HCV1型和6型NS3重组蛋白氨基酸序列的同源性为83．2％；85份抗-HCV阳性血清以此不同基因型HCV NS3单片段抗原检测，阳性检出率分别为61．2％(1型)和58．8％(6型)，其中有7份标本以NS3-1型抗原检测阴性，但可被NS3-6型抗原检出，反之，有9份血清以NS3-6型重组蛋白检测为阴性，而NS3．1型检测阳性；54份大学生体检血清和39份阴性质控血清以此两种抗原检测均为阴性。结论HCV1型和6型NS3重组蛋白存在抗原异质性，在发展HCV抗体检测试剂时需考虑加入不同基因型的NS3抗原。     

化学发光酶免疫分析法在乙肝病毒及核心抗体定性检测中的应用分析

目的 通过对比,探讨了化学发光酶免疫分析法在乙肝病毒及核心抗体定性检测中的应用价值.方法 选取2013年5月至2015年5月在我院的疑似乙型肝炎患者80例,抽取空腹血液样本后都分别进行乙肝病毒以及核心抗体的化学发光酶免疫分析法及ELISA法检测,并对其检测结果进行分析.结果 化学发光酶免疫分析法检出乙型肝炎病毒阳性78例,检出率为97.5％;而ELISA检出乙型肝炎病毒阳性76例,检出率为95.0％,两种方法的检出率对比差异无统计学意义(P＞0.05).化学发光酶免疫分析法对于乙肝病毒核心抗体IgM与IgG的检测阳性率分别为80.0％和70.0％,而ELISA法检测两种抗体的阳性率则分别为18.8％和20.0％,化学发光酶免疫分析法对乙肝核心抗体IgM与IgG的检测阳性率明显高于ELISA法(P＜0.05).ELISA法检出HBc-IgM的最低限为0.135 IU/ml,检出HBc-IgM最低限为0.143 IU/ml;化学发光酶免疫分析法检出HBc-IgM最低限为0.032 IU/ml,检出HBc-IgG最低限为0.038 IU/ml.结论 化学发光酶免疫分析法在乙型肝炎检测中具有高的检出率,尤其对乙肝病毒的核心抗体的检测敏感度较高,值得在临床推广应用.     

Enzyme-linked immunosorbent assay for the detection and identification of coxsackie B antigen in tissue cultures and clinical specimens

An enzyme-linked immunosorbent assay (ELISA) has been developed for the identification of Coxsackie B antigens. This assay was capable of identifying and distinguishing all six Coxsackie B serotypes at concentrations one hundredfold to ten thousandfold less than could be detected by complement fixation (CF) systems. In addition, the Coxsackie B ELISA correctly identified the presence of Coxsackie B antigen in 19 of 21 tissue culture fluids and five of nine rectal swab specimens. Two additional rectal swab specimens reacted with Coxsackie B antisera but could not be conclusively serotyped. Tissue culture fluids and rectal swab specimens containing other viruses such as ECHO virus, Coxsackie virus A, rhinovirus, rotavirus and Norwalk virus were consistently negative in the assay. The Coxsackie B ELISA offers potential for the rapid identification of Coxsackie B antigens in clinical specimens and tissue culture systems.     

Genotypic characterization of symptomatic hepatitis E virus (HEV) infections in Egypt

BackgroundHepatitis E virus (HEV) is a common cause of acute viral hepatitis (AVH) in many developing countries. In Egypt, HEV seroprevalence is among the highest in the world; however, only a very limited number of Egyptian HEV sequences are currently available.ObjectivesThe objectives were to determine the HEV genotype(s) currently circulating in Egypt.Study designAVH patients without serologic evidence of hepatitis A, B, and C viruses were evaluated for possible HEV infection using serologic assays for anti-HEV IgM and anti-HEV IgG and real-time PCR for HEV RNA. Stool suspensions from suspected cases were inoculated into rhesus macaques to confirm the presence of HEV. Sequence analysis was utilized to determine HEV genotype.ResultsOf 287 subjects with AVH enrolled, 58 had serologic evidence of acute HEV infection. Stool samples for two of these patients were repeatedly positive for HEV RNA by real-time PCR. Macaques experimentally inoculated with these human stools also developed viremia. Sequence analysis of open reading frame (ORF) 1 demonstrated that these isolates belonged to HEV genotype 1 and were 3.9–9.5% divergent from other genotype 1 isolates. ORF2 was 5.3–8.7% divergent from previously reported Egyptian isolates.ConclusionsThis study strongly suggests that genotype 1 HEV related to other North African isolates is circulating in acute symptomatic patients in Egypt. Further evaluation of genotypic variability is underway in this highly endemic cohort and is considered an important component of our increased understanding of HEV pathogenesis.     

Molecular characterization and phylogenetic analysis of the complete genome of a hepatitis E virus from European swine

Hepatitis E virus (HEV) has been detected in humans and in a broad range of animals, including pigs. For the first time the full-length genomic sequence of a HEV of European porcine origin, termed swX07-E1, was determined. Comparative analysis of 76 complete or nearly complete nucleotide sequences showed that swX07-E1 shares the highest nucleotide identity with Japanese swine HEV swJ8-5 and swJ12-4. The whole-genome phylogenetic analysis showed that swX07-E1 from Europe belongs to genotype-3 HEV, clusters with variants from Japan, Mongolia and Kyrgyzstan in subgroup 3c, but it is divergent from the prototype US HEV. Our analysis indicates that swX07-E1 represents a new subgroup of genotype-3 and that analysis of full-length sequences is necessary to discover new subgroups of HEV. According to our knowledge, swX07-E1 is the first full-length genome sequence of HEV from European swine. Knowledge about the full length HEV sequence from European swine is very important for understanding the HEV evolutionary events and the molecular mechanism of infection in human and in animals.     

Complete or near-complete nucleotide sequences of hepatitis E virus genome recovered from a wild boar, a deer, and four patients who ate the deer

Zoonosis has been implicated in hepatitis E virus (HEV) transmission. We examined wild boar living in a forest of Hyogo prefecture, Japan, and found HEV RNA in three of seven boars. A full-genome HEV isolate from one of them was revealed to be 99.7% identical to a previous isolate from a wild deer hunted in the same forest and to those from four patients who contracted hepatitis E after eating raw meat of the deer. These findings suggest an interspecies HEV transmission between boar and deer in their wild life, and that both animals might serve as an infection source for human beings as suggested previously.     

Rapid enzyme-linked immunosorbent assay of whole blood for detection of antibodies to japanese encephalitis virus

The application of the rapid system of enzyme-linked immunosorbent assay (ELISA) was studied to quantify antibodies to Japanese encephalitis virus in large-scale epidemiological surveys, especially by testing under field conditions. The assay system, with 15 min for the first reaction and 30 min each for the second and the third reactions, was highly reproducible (coefficients of variation with swine positive sera were less than 5.8%) and was significantly correlated with the routine assay system with 1 h for each reaction (correlation coefficient was 0.960). Compared with the haemagglutination inhibition test, the rapid system gave a correlation coefficient of 0.916 and qualitative agreeement of 96.1%. The substitution of whole blood for serum in the first reaction was also examined not only to avoid serum separation but also to apply this system to antibody quantification in animals from which sufficient amounts of sera cannot be easily obtained: only 2 μl were needed for the test. The results obtained with 51-fold diluted whole blood had a linear relationship to those obtained with 100-fold diluted sera in swine and humans.