Preparation and diagnostic utility of a hemagglutination inhibition test antigen derived from the baculovirus-expressed hemagglutinin-neuraminidase protein gene of Newcastle disease virus

A recombinant hemagglutinin-neuraminidase (rHN) protein from Newcastle disease virus (NDV) with hemagglutination (HA) activity was expressed in Spodoptera frugiperda cells using a baculovirus expression system. The rHN protein extracted from infected cells was used as an antigen in a hemagglutination inhibition (HI) test for the detection and titration of NDV-specific antibodies present in chicken sera. The rHN antigen produced high HA titers of 2(13) per 25 microL, which were similar to those of the NDV antigen produced using chicken eggs, and it remained stable without significant loss of the HA activity for at least 12 weeks at 4degrees C. The rHN-based HI assay specifically detected NDV antibodies, but not the sera of other avian pathogens, with a specificity and sensitivity of 100% and 98.0%, respectively, in known positive and negative chicken sera (n = 430). Compared with an NDV-based HI assay, the rHN-based HI assay had a relative sensitivity and specificity of 96.1% and 95.5%, respectively, when applied to field chicken sera. The HI titers of the rHN-based HI assay were highly correlated with those in an NDV-based HI assay (r = 0.927). Overall, these results indicate that rHN protein provides a useful alternative to NDV antigen in HI assays.

Development of an attenuated vaccine strain from a korean respiratory type infectious bronchitis virus / 대한수의학회지

An attenuated vaccine strain AVR1/08 of Korean respiratory type of infectious bronchitis virus (IBV) was developed by 89th passages of IBV D85/06 strain in chicken eggs. The AVR1/08 strain had higher virus titer at least 20 times (10(1.3)) than the parent virus D85/06 by egg inoculation method. The AVR1/08 strain had a single point mutation (S to Y) at position 56 of spike protein of IBV compared to parent virus IBV D85/06 strain. The mutation was observed consistently at viruses after 47th passage in chicken eggs. The AVR1/08 strain showed no virulence even after 6 passages in chickens and all chickens inoculated induced anti-IBV antibody 14 days after vaccination. The AVR1/08 strain had broad protective efficacy against QX type Korean nephropathogenic virus (Q43/06 strain), KM91 type Korean nephropathogenic virus (KM91 strain) and Korean respiratory virus (D85/06 strain). In contrast, Massachusetts (Mass) type attenuated vaccine strain H120 showed protection of 37.5 to 50% against these three viruses. Our results indicate that the AVR1/08 strain has potential as an attenuated vaccine effective in controlling IBVs circulating in Korea.

Antigenic and immunogenic investigation of the virulence motif of the Newcastle disease virus fusion protein

Newcastle disease (ND) caused by virulent Newcastle disease virus (NDV) is a highly contagious viral disease of poultry. Virulent NDVs characteristically have a multibasic amino acid sequence (virulence motif) such as (112)RRQKRF(117) at the cleavage site of the precusor fusion (F0) protein. The antigenic and immunogenic characteristics of the virulence motif (112)RRQKRF(117) in the F0 protein of virulent NDVs were investigated. Epitope mapping analysis revealed that a RRQKRF-specific monoclonal antibody 4G2 recognized the KRF section of the motif. A synthetic peptide bearing the RRQKRF motif reacted strongly with sera from virulent NDV (with RRQKRF motif)-infected chickens. These sera also showed reactivity to peptides bearing other virulence motifs ((112)KRQKRF(117), (112)RRQRRF(117) and (112)RRRKRF(117)) but not an avirulence motif ((112)GRQGRL(117)) by ELISA. The synthetic bearing RRQKRF motif reacted with 60% to 91% of sera taken from surviving chickens on ND outbreak farms but not with sera from vaccinated birds, even though most of the sera had antibody to NDV due to vaccination. This indicates that the virulence motif has the potential to differentiate virulent NDV infected birds from vaccinated birds.

Development of Competitive ELISA for Detection of Avian Metapneumovirus Antibodies in Chicken

Avian metapneumovirus (aMPV) causes an acute and highly contagious upper respiratory tract infection in turkeys and chickens. In this study, a competitive ELISA (C-ELISA) was developed for the detection of antibodies to aMPV in chicken sera and/or their egg yolks. This assay is based on the competitive binding of monoclonal antibody with serum antibodies to recombinant aMPV N protein expressed by a recombinant baculovirus. The C-ELISA showed specificity and sensitivity of 100% and 98.0%, respectively, when compared to the virus neutralization test. In specific pathogen-free chickens experimentally infected with aMPV SC1509 strain, the C-ELISA started to detect antibodies to aMPV as early as 5 days post infection from birds infected with aMPV, while a commercial ELISA kit detected first 10 days post infection. The C-ELISA was similar or superior to a commercial ELISA kit when serum and egg yolk samples collected from chickens on six outbreak farms were tested for diagnosis. The C-ELISA developed in the present work provides a short turnaround time and can be a useful diagnostic and screening tool for aMPV infection in the field.

Evaluation of a competitive ELISA for antibody detection against avian influenza virus

Active serologic surveillance is necessary to control the spread of the avian influenza virus (AIV). In this study, we evaluated a commercially-available cELISA in terms of its ability to detect AIV antibodies in the sera of 3,358 animals from twelve species. cELISA detected antibodies against reference H1- through H15-subtype AIV strains without cross reactivity. Furthermore, the cELISA was able to detect antibodies produced following a challenge of the AIV H9N2 subtype in chickens, or following vaccination of the AIV H9 or H5 subtypes in chickens, ducks and geese. Next, we tested the sensitivity and specificity of the cELISA with sera from twelve different animal species, and compared these results with those obtained by the hemagglutination-inhibition (HI) test, the "gold standard" in AIV sera surveillance, a second commercially-available cELISA (IZS ELISA), or the agar gel precipitation (AGP) test. Compared with the HI test, the sensitivities and specificities of cELISA were 95% and 96% in chicken, 86% and 88% in duck, 97% and 100% in turkey, 100% and 87% in goose, and 91% and 97% in swine, respectively. The sensitivities and specificities of the cELISA in this study were higher than those of IZS ELISA for the duck, turkey, goose, and grey partridge sera samples. The results of AGP test against duck and turkey sera also showed significant correlation with the results of cELISA (R-value >0.9). In terms of flock sensitivity, the cELISA correlated better with the HI test than with commercially-available indirect ELISAs, with 100% flock sensitivity.

Pathogenicity and antigenicity of a new variant of Korean nephropathogenic infectious bronchitis virus

Despite the existence of an active vaccination program, recently emerged strains of nephropathogenic infectious bronchitis virus (IBV) in Korea have caused significant economic losses in the poultry industry. In this study, we assessed the pathogenic and antigenic characteristics of a K-IIb type field strain of IBV that emerged in Korea since 2003, such as Kr/Q43/06. Specific pathogen free 1-week-old chickens exhibited severe respiratory symptoms (dyspnea) and nephropathogenic lesions (swollen kidneys with nephritis and urate deposits) following challenge with the recent IBV field strain. The antigenic relatedness (R value), based on a calculated virus neutralization index, of the K-IIb type field strain and K-IIa type strain KM91 (isolated in 1991) was 30%, which indicated that the recent strain, Kr/Q43/06, is a new variant that is antigenically distinct from strain KM91. This report is the first to document the emergence of a new antigenic variant of nephropathogenic IBV in chicken from Korea.

Experimental infection of chickens, ducks and quails with the highly pathogenic H5N1 avian influenza virus

Highly pathogenic avian influenza viruses (HPAIV) of the H5N1 subtype have spread since 2003 in poultry and wild birds in Asia, Europe and Africa. In Korea, the highly pathogenic H5N1 avian influenza outbreaks took place in 2003/2004, 2006/2007 and 2008. As the 2006/2007 isolates differ phylogenetically from the 2003/2004 isolates, we assessed the clinical responses of chickens, ducks and quails to intranasal inoculation of the 2006/2007 index case virus, A/chicken/Korea/IS/06. All the chickens and quails died on 3 days and 3-6 days post-inoculation (DPI), respectively, whilst the ducks only showed signs of mild depression. The uninoculated chickens and quails placed soon after with the inoculated flock died on 5.3 and 7.5 DPI, respectively. Both oropharyngeal and cloacal swabs were taken for all three species during various time intervals after inoculation. It was found that oropharyngeal swabs showed higher viral titers than in cloacal swabs applicable to all three avian species. The chickens and quails shed the virus until they died (up to 3 to 6 days after inoculation, respectively) whilst the ducks shed the virus on 2-4 DPI. The postmortem tissues collected from the chickens and quails on day 3 and days 4-5 and from clinically normal ducks that were euthanized on day 4 contained the virus. However, the ducks had significantly lower viral titers than the chickens or quails. Thus, the three avian species varied significantly in their clinical signs, mortality, tissue virus titers, and duration of virus shedding. Our observations suggest that duck and quail farms should be monitored particularly closely for the presence of HPAIV so that further virus transmission to other avian or mammalian hosts can be prevented.

Isolation and Characterization of Avian Metapneumovirus from Broiler Breeder Chickens in Korea

Avian metapneumovirus (AMPV) is an emerging pathogen causing respiratory and reproductive illness in poultry worldwide. To demonstrate the presence of AMPV in domestic chickens in Korea, we attempted to isolate AMPV from affected chickens. A cytopathic agent was isolated using chicken tracheal ring culture from dead chickens from a broiler breeder farm with reduced egg production in Korea. This agent, termed SC1509 strain, subsequently passed in Vero cells with distinct cytopathic effects. The SC1509 strain was confirmed as avian metapneumovirus (AMPV) using both RT-PCR test and monoclonal antibody-based immunofluorescence assay. Sequence analysis based on the G glycoprotein revealed that the SC1509 strain had 22.5 to 96.0% nucleotide sequence identity and 11.1 to 92.7% predicted amino acid sequence identity with previously published AMPV strains, particularly with the highest sequence homology (95.8 to 96% for nucleotides and 92.2 to 92.7% for amino acids) to European strains belonging to genotype B. The SC1509 strain was phylogenetically clustered with genotype B viruses, confirming that the SC1509 strain belongs to genotype B. This is the first report of genotype B avian metapneumovirus from chickens in Korea.

Characterization of Lentogenic Newcastle Disease Virus Isolated in Jeju, Korea during 2007~2008 Surveillance

To expand the epidemiological understanding of Newcastle disease in Jeju Province, Korea, active surveillance was extensively performed through a virological examination for poultry farms and wild birds in Jeju Province during 2007~2008. Samples (swabs or fresh feces) were collected from a total of 6,485 birds including 6,405 domestic birds (chickens, ducks, pheasants, geese, quails, turkeys, and ostriches) and 80 wild birds. A total of 24 hemagglutinating agents were isolated from domestic birds on fourteen farms including five Korean native chicken, one layer chicken, two broiler chicken, four duck and two pheasant farms. The hemagglutinating agents were all identified as lentogenic NDV based on the reverse transcriptase polymerase chain reaction, sequence analysis of amino acids on the F cleavage site and mean death time in chicken embryos. The F gene-based phylogenetic analysis revealed that the NDV isolates were classified into genotypes 1 or 2 of class II. These lentogenic viruses were closely related to NDV vaccine strains used in Jeju Province. Active surveillance conducted for Newcastle disease indicates no scientific evidence of virulent NDV infection in chickens in Jeju Province, Korea since 2005.

An inactivated vaccine to control the current H9N2 low pathogenic avian influenza in Korea

The H9N2 subtype low pathogenic avian influenza is one of the most prevalent avian diseases worldwide, and was first documented in 1996 in Korea. This disease caused serious economic loss in Korea's poultry industry. In order to develop an oil-based inactivated vaccine, a virus that had been isolated in 2001 (A/chicken/Korea/01310/ 2001) was selected based on its pathogenic, antigenic, and genetic properties. However, in animal experiments, the efficacy of the vaccine was found to be very low without concentration of the antigen (2(7) to 2(10) hemagglutinin unit). In order to overcome the low productivity, we passaged the vaccine candidate virus to chicken eggs. After the 20th passage, the virus was approximately ten times more productive compared with the parent virus. For the most part, the passaged virus maintained the hemagglutinin cleavage site amino acid motif (PATSGR/GLF) and had only three amino acid changes (T133N, V216G, E439D, H3 numbering) in the hemagglutinin molecule, as well as 18 amino acid deletions (55-72) and one amino acid change (E54D) in the NA stalk region. The amino acid changes did not significantly affect the antigenicity of the vaccine virus when tested by hemagglutination inhibition assay. Though not complete, the vaccine produced after the 20th passage of the virus (01310 CE20) showed good protection against a homologous and recent Korean isolate (A/chicken/Korea/Q30/2004) in specific pathogen- free chickens. The vaccine developed in this study would be helpful for controlling the H9N2 LPAI in Korea.

Molecular characterization and genogrouping of VP1 of aquatic birnavirus GC1 isolated from rockfish Sebastes schlegeli in Korea

The cDNA nucleotide sequence of genome segment B encoding the VP1 protein was determined for the aquatic birnavirus GC1 isolated from the rockfish Sebastes schlegeli in Korea. The VP1 protein of GC1 contains a 2,538 bp open reading frame, which encodes a protein comprising 846 amino acid residues that has a predicted MW of 94 kDa. The sequence contains 6 potential Asn-X-Ser/Thr motifs. Eight potential Ser phosphorylation sites and 1 potential Tyr phophorylation site were also identified. GC1 contains the Leu-Lys-Asn (LKN) motif instead of the typical Gly-Asp- Asp (GDD) motif found in other aquatic birnaviruses. We also identified the GLPYIGKT motif, the putative GTPbinding site at amino acid position 248. In total, the VP1 regions of 22 birnavirus strains were compared for analyzing the genetic relationship among the family Birnaviridae. Based on the deduced amino acid sequences, GC1 was observed to be more closely related to the infectious pancreatic necrosis virus (IPNV) from the USA, Japan, and Korea than the IPNV from Europe. Further, aquatic birnaviruses containing GC1 and IPNV have genogroups that are distinct from those in the genus Avibirnaviruses and Entomo-birnaviruses. The birnavirusstrains were clustered into 5 genogroups based on their amino acid sequences. The marine aquatic birnaviruses (MABVs) containing GC1 were included in the MABV genogroup; the IPNV strains isolated from Korea, Japan, and the USA were included in genogroup 1 and the IPNV strains isolated primarily from Europe were included in genogroup 2. Avibirnaviruses and entomobirnaviruses were included in genogroup 3 and 4, respectively.

Protective efficacy of commercial inactivated Newcastle disease virus vaccines in chickens against a recent Korean epizootic strain

Despite the intensive vaccination policy that has been put in place to control Newcastle disease virus (NDV), the recent emergence of NDV genotype VII strains in Korea has led to significant economic losses in the poultry industry. We ssessed the ability of inactivated, oil-emulsion vaccines derived from La Sota or Ulster 2C NDV strains to protect chickens from challenge with Kr-005/00, which is a recently isolated Korean epizootic genotype VII strain. Six-week-old SPF chickens were vaccinated once and challenged three weeks later via the eye drop/intranasal route. All vaccinated birds were fully protected from disease, regardless of the vaccine strains used. All vaccinated and challenged groups showed significant sero-conversion 14 days after challenge. However, some vaccinated birds, despite being protected from disease, shed the challenge virus from their oro-pharynx and cloaca, albeit at significantly lower titers than the unvaccinated challenged control birds. The virological, serological, and epidemiological significance of our observations with regard to NDV disease eradication is discussed.

Detection of Infectious Bursal Disease Virus by Double Antibody Sandwich ELISA

Infectious bursal disease virus (IBDV) is responsible for a highly contagious disease of poultry causing severe immunosuppression in chickens. A double antibody sandwich ELISA (DAS-ELISA) was developed to detect IBDV from clinical samples. Two kinds of anti-IBDV antibodies, monoclonal antibody R63 and chicken anti-IBDV sera, were used for DAS-ELISA. Detection limit of IBDV by DAS-ELISA was approximately 10(2.7) EID(50)/ml. The DAS-ELISA detected IBDV from most (13/14) of vaccine products including mild, intermediate and intermediate-plus types. The DAS-ELISA also detected IBDV from all (19/19) of field Korean isolates including very virulent and intermediate-plus phenotypes. Our results indicate that the DAS-ELISA would provide useful diagnostic tool to detect IBDV from clinical samples as well as rapid quantitative detection of IBDV.

Detection of Antibodies to Infectious Bursal Disease Virus (IBDV) by Agar Gel Immunodiffusion using Recombinant VP2 Protein

Infectious bursal disease virus (IBDV) causes a highly contagious and immunosuppressive disease of chicken. Agar gel immunodiffusion using IBDV antigen extracted from bursa of Fabricius of infected chicken has been used officially for diagnosis of IBDV in Korea. In this study, in order to replace the IBDV whole virus antigen with non-infectious antigen, recombinant VP2 protein (rVP2) of IBDV was produced using recombinant baculovirus expression system. Purified baculovirus-expressed rVP2 was used as an antigen in an agar gel immunodiffusion (AGID). rVP2 antigen precipitated specifically IBDV antibodies. AGID using rVP2 antigen detected anti-IBDV antibodies from 6 dpi to 28 dpi (termination of the experiment) when specific pathogen free chickens were experimentally infected with IBDV 52/70 strain. This was consistent with result by AGID using IBDV antigen, virus neutralization test (VNT) and a commercial ELISA kit (except for one serum). The sensitivity of rVP2 was the same with that of IBDV antigen when field sera (n=324) were tested by AGID. However, AGID using rVP2 antigen detected maternal antibodies from broiler chickens (n=20) on a broiler farm up to 15 days old, although the detection rate of the AGID was relatively low compared to a commercial ELISA kit. Our results indicate that IBDV whole virus antigen from IBDV infected chickens would be replaced with recombinant VP2 protein as an antigen for AGID.

Heterosporis anguillarum infections in farm cultured eels (Anguilla japonica) in Korea

Ten eels (Anguilla japonica) from a fish farm in Korea were examined and diagnosed with a Heterosporis infection. The gross lesions on the trunk were uneven and the concave parts were pasty. Histopathologically, lyses of the trunk muscles, degenerative muscle fibers and the scattered spores were observed. The sporophorocyst (SPC) contained several spores with a variety of shapes. Some SPC were disrupted and the spores in the SPC were scattered in the muscle tissues. Macrophages existed near the scattered spores. Electron microscopy revealed special structures such as sporophorocyst containing various developmental parasitic stages such as meronts, sporonts, sporophorous vesicles and spores.

Development and evaluation of indirect ELISA for the detection of antibodies against Japanese encephalitis virus in swine

The Japanese encephalitis virus (JEV) is one of causative agents of reproductive failure in pregnant sows. An indirect enzyme-linked immunosorbent assay (I-ELISA) was examined for its potential use in the rapid monitoring of the JEV, and the results were compared with those from the hemagglutination inhibition (HI) and serum neutralization (SN) tests. The comparative analysis showed that the results of I-ELISA showed a significant correlation with the conventional HI (r = 0.867) and SN tests (r = 0.804), respectively. When the I-ELISA results were compared with the traditional diagnostic assays, the sensitivity of the I-ELISA was 94.3% with the HI test and 93.7% with the SN test, respectively. The specificity was found to be 81.4% and 80.0% with the HI and SN tests, respectively. To determine the applicability of I-ELISA in the field, the serum samples from 720 pigs were collected from 4 regions in Korea between July and August 2004. The results indicated that 21.7% of screened pigs were seropositive for the JEV. The seropositive rates of JEV in the 4 provinces were 12.6% in Gyeonggi, 45.0% in Gyeongnam, 16.7% in Jeonbuk, and 12.2% in Jeju. The I-ELISA methodology developed in this study was shown to have considerable sensitivity and specificity through a comparison with HI and the SN tests. Therefore, it might be one of convenient methods for screening a large number of samples in various fields.

Immunogenicity of baculovirus expressed recombinant proteins of Japanese encephalitis virus in mice

Genes encoding for the premembrane and envelope (prME), envelope (E) and nonstructural protein (NS1) of Japanese encephalitis virus (JEV) were cloned. Each protein was expressed in baculovirus expression system. Of the three proteins expressed in baculovirus system, only prME had hemagglutination activity. The prME (72 and 54 kDa), E (54 kDa) and NS1 (46 kDa) proteins could be detected by Western blotting in the recombinant virus infected cells. Immunogenicity of the recombinant proteins obtained from infected Spodoptera frugiperda (Sf-9) cells was examined in mice. The 3 week-old ICR mice immunized intraperitoneally with three recombinant proteins three times were challenged with a lethal JEV. A survival rate was increased from about 7.7% in unimmunized mice to 92.3% in E + prME and only E groups. The complete protection was shown in prME and live vaccine inoculated groups, respectively. We also measured neutralizing antibody and three immunoglobulin subtypes of IgG1, IgG2a and IgG2b in the sera of mice before and after challenge. Titers of IgG1 antibodies were approximately two to three times higher than that of IgG2b antibodies in all the immunized groups as compared to the control group. However, IgG2a antibody level somewhat increased after challenge, indicating T-helper type 1 (Th1) cell response. The results of this study can provide useful information for developing efficacious subunit vaccine against JEV.

TaqMan reverse transcription polymerase chain reaction for the detection of Japanese encephalitis virus

One step TaqMan reverse transcription polymerase chain reaction (RT-PCR) using TaqMan probe was developed for detection of Japanese encephalitis virus (JEV). Real-time RT-PCR was optimized to quantify JEV using the detection system (Rotor Gene 2000 detector) and dual-labeled fluorogenic probes. The gene specific labeled fluorogenic probe for the 3' non-translated region (3' NTR) was used to detect JEV. When the specificity of the assay using specific JEV primers was evaluated by testing three different JEV strains, other swine viruses and bovine viral diarrhea virus, no cross-reactions were detected with non-JE reference viruses. A single tube TaqMan assay was shown to be 10-fold more sensitive than the conventional two-step RT-PCR method. Detection limits of two step and real-time RT-PCR for JEV were 112 TCID50 /ml and 11.2 TCID50 /ml, respectively. Quantification of JEV was accomplished by a standard curve plotting cycle threshold values (Ct ) versus infectivity titer. Real-time RT-PCR assay using single tube method could be used as a sensitive diagnostic test, and supplied the results in real time for detection and quantification of JEV. We could detect JEV RNA genome in plasma samples of pigs inoculated with KV1899 strain at 2 days post inoculation, but couldn't in 41 fetus samples. This assay was sensitive, specific, rapid and quantitative for the detection of JEV from laboratory and field samples.

Molecular characterization of full-length genome of Japanese encephalitis virus (KV1899) isolated from pigs in Korea

We have determined the complete nucleotide and deduced amino acid sequences of the Japanese encephalitis virus (JEV) strain KV1899, isolated from a fattening pig in Korea. In comparison with 22 fully sequenced JEV genomes currently available, we found that the 10,963-nucleotide RNA genome of KV1899 has a 13-nucelotide deletion in the 3' non-translated variable region and 53 unique nucleotide sequences including 3' non-translated region (NTR). Its single open reading frame has a total of 28 amino acid substitutions. Comparison of the KV1899 genomic sequence with those of the 21 fully sequenced JEV strains in published databases showed nucleotide homology ranging from 97.4% (Ishikawa strain) to 87.0% (CH2195 strain). Amino acid homology with KV1899 strain ranged from 96.4% (K94P05) to 91.0% (GP78). The KV1899 showed the highest nucleotide homology with Ishikawa strain and the highest amino acid homology with K94P05. We performed an extensive E gene based phylogenetic analysis on a selection of 41 JEV isolates available from the GenBank. Compared with Anyang strain, isolated from a pig in 1969, that is current live vaccine strain for swine in Korea, the homology of nucleotide sequence in envelope gene was only 87.1%. The prM gene of the isolate was closely related with those of Ishikawa and K94P05 strains, which were grouped into genotype I of JEV.

Biophysical characterization of Japanese encephalitis virus (KV1899) isolated from pigs in Korea

A virus strain, showing cytopathic effect in Vero cell, was isolated from plasma of a fattening pig in Gyeonggi province, Korea in October 1999. The evaluation of physicochemical/biological properties of the isolate showed that the virus, KV1899, inoculated suckling mouse showed paralysis and died within 7 days post-inoculation, the mouse brain suspension had hemagglutinating activity with goose RBC. Pathogenicity of isolate was carried out by intracranial and intraperitoneal inoculation of 3-4 weeks mice. The mice inoculated with isolate showed 10 4.5 LD50/ 0.03 ml and 10 3.0 LD50/0.5 ml according to the inoculation route. The isolate was identified as RNA and enveloped virus using IUDR and chloroform sensitivity test. The virus particles within the infected Vero cell were measured to be 40-50 nm in size by electron microscopy. The isolate was further characterized by immuno-fluorescence assay using Japanese encephalitis virus (JEV) specific monoclonal antibodies. Reverse transcription polymerase chain reaction (RT-PCR) revealed the presence of JE specific conserved sequences in this isolate. The artificially inoculated pigs had HI titer of 320 to 2,560 against JEV at 14 to 42 days post inoculation. We confirmed this isolate as Japanese encephalitis virus. It was the second isolation of JEV in pigs in Korea.