• Korean Journal of Veterinary Service
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• v.37 no.1
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• pp.1-9
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• 2014

Although it has been generally accepted that porcine reproductive and respiratory syndrome virus (PRRSV) induces weak and delayed protective immunity after infection, it is unclear that the same immunological features can be applicable to all PRRS viruses because huge genetic variation exists even among the same genotypes of PRRSV (Type 1 and 2). In the current study, two genetically distinct type 2 PRRSV strains (VR-2332 and JA142) which showed approximately 90% nucleotide homology based on ORF5 sequences were characterized by both in vitro and in vivo assessments to determine the immunological features of the viruses. For in vitro assessment, porcine alveolar macrophages (PAM) were infected with the viruses at $10^{-3}$ multiplicity of infection (MOI) and then supernatants and cells were collected separately at 36 hrs post infection to determine the relative expression levels of IL-$1{\alpha}$, IL-12, TNF-${\alpha}$ and INF-${\alpha}/{\beta}$ by quantitative RT-PCR. In addition, five PRRSV-free pigs were inoculated with either of JA142 or VR2332 for in vivo assessment. Serum samples were collected every week until 6 weeks post challenge. The serum samples were analyzed for the levels of viremia, PRRSV nucleocapsid-specific antibody and virus neutralizing antibody. Based on those assessments, the two viruses showed different patterns of cytokine expression in PAM and immune responses in pigs after infection. These results indicate that genetically distinct PRRSV strains have different immunological features, which might be criteria for virus classification and selection of candidate virus strains for vaccine development in the future.

• Korean Journal of Veterinary Research
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• v.43 no.3
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• pp.463-469
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• 2003

Eight nursery to grower pigs exhibiting weight loss and sudden death were diagnosed as postweaning multisystemic wasting syndrome (PMWS) based on the results of gross findings, histopathology, immunohistochemistry, fluorescent antibody test, virus isolation, PCR, serology, and electron microscopy. Groosly, the pigs had a rough hair coats and were severely emaciated. And moot lymph nodes were pale and enlarged. Lungs were not fully collapsed and exhibited 10 to 40% pale red cranioventral consolidation. Histopathologically, typical lymphohistiocytic interstitial to bronchointerstitial pneumonia, chronic lymphadenitis, severe lymphoid depletion, and basophilic intracytoplasmic inclusions were noted in the most lymphoid tissues. Porcine circovirus panicles were observed in the inguinal lymph node of the pigs by electron microscopy. Porcine circovirus type 2 (PCV2) antigens or viral DNAs were detected in the lesions of all pigs using immunohistochemistry or PCR. Two PCV2 were isolated from a homogenate of pooled lung and lymph node in 2 of the 5 pigs. Additionally, antigens of porcine reproductive and respiratory syndrome virus (PRRSV) and Hemophilus (H.) parasuis were also detected by immunofluorescent antibody test. Serologically, 55% of randomly selected sows and fattening pigs was serum antibody positive to PCV2 by an indirect fluorescent antibody (IFA) test and approximately 18 % of animals in the herd were serologically pooitive by the ELISA kit for PRRSV. To our knowledge, this is the first report of PMWS co-infected with PCV-2, PRRS, and H. parasuis in Korea.

• Korean Journal of Veterinary Research
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• v.37 no.4
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• pp.793-807
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• 1997

We tried to develop detection system of porcine reproductive and respiratory syndrome virus(PRRSV) by in situ hybridization(ISH) in the piglets experimentally infected with KPRRS-2, the Korean isolate(12 piglets) or Mn-1b, the American isolate(4 piglets), and in the natural infection suspected 6 piglets. Twelve 30-days-old piglets(two pigs per each inoculated group) were inoculated by nasal instillation of KPRRS-2 virus(total dose $10^{4.5}TCID_{50}$), Six piglets(one pig per each group) were induced contact infection with inoculated piglets, during the experiment, and two piglets were used as control. Inoculated or contacted piglets were euthanized at 1, 3, 5, 7, 14 and 21 days postinoculation(DPI). The respiratory signs such as coughing and nasal discharge were observed on day 3 DPI, and ear cyanosis were on day 5 DPI, including contacted piglets. Through the necropsy, purple discolorization of dorsal part of lung, and hypertrophy of local lymph nodes were observed. The histopathological lesions of lung were interstitial pneumonia characterized by type 2 pneumocyte hyperplasia. We prepared the probe for ISH by RNA isolation from KPRRS-2, RT-PCR, and biotin labeling. We performed the ISH within only 1~2 hours using $Microprobe^{TM}$ capillary action system. As the results, the strong red specific positive signals, means PRRSV distribution, was mainly observed in the cytoplasm of alveolar macrophages. And also signals were detected in some type 2 pneumocytes and bronchiolar epithelium of lung, myocardium, liver, kidney, tonsil, spleen, gastrointestinal mucosa, testis and lymph nodes.

• Korean Journal of Veterinary Service
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• v.41 no.4
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• pp.263-269
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• 2018

Developing drugs targeting respiratory pathogen is essential to control respiratory diseases. Many experiments have been performed under in vivo situation. However, in vivo experiments have economical and ethical issues. The objective of this study was to determine the possibility of developing an ex vivo lung culture system with possible application for respiratory infection studies. After isolating lungs from naïve pigs, agarose-inflated lung tissues were prepared and sliced manually. These sliced lung tissues were then subsequently placed on 24-well plates. Eight different combinations of media were used to determine the optimum ex vivo lung culture condition. In addition, lung tissues were infected with porcine reproductive and respiratory syndrome (PRRS) virus at a titer of $1{\times}10^4\;TCID_{50}/mL$. Virus growth was confirmed by titration in MARC-145 cells at 2, 4, 6 days post infection (dpi). We found that ex vivo lung culture in physiological environment was not media specific based on histopathology and cytotoxicity. However, under virus-infected condition, thickened alveolar walls in the lung tissues and stable virus titers at 2, 4, 6 dpi were shown in F12K medium suggesting that it was useful for tissue maintenance and virus infection using PRRS virus infected lung tissues. The present study shows the possibility of using porcine ex vivo lung model for respiratory infection studies.

• Korean Journal of Veterinary Service
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• v.27 no.3
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• pp.273-280
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• 2004

The studies were performed for the PRRS antigen and antibody detection from breeding farms, artificial insemination(AI) center and growing farms in Jeonbuk province. 1. Specific PRRS primers were successfully amplified ORF6 617bp and ORF7 448 bp on agarose gel. 2. RT-PCR method has been establish by commercial kit and the thermal cycler program consisted of 30 cycles: $95^{\circ}C$ for 30 sec, $45^{\circ}C$ for 30 sec, and $72^{\circ}C$ for 45 sec. 3. The results of PRRS antibody test by ELISA method in AI centers were $6.6\%,\;53.3\%$ and breeding farms $65\%,\;65\%\;and\;38.7\%$, respectively. The serological positive of the antibody in gilt higher than sow. 4. The sero-positive of the PRRS antibody showed average $21\%$ in domestic farms, $56.2\%$ in breeding farms, and $29.9\%$ in AI center.

• International Journal of Industrial Entomology and Biomaterials
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• v.32 no.2
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• pp.90-97
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• 2016

The major structural proteins of porcine reproductive and respiratory syndrome virus (PRRSV) are derived from ORFs 4, 5, and 6. They have been considered very important to arouse the humoral and cellular immune responses against PRRSV infection and proposed to be the excellent candidate proteins in the design of PRRS bioengineering vaccine. However, the PRRSV structural proteins are produced in low levels in the infected cells because it forms insoluble protein and possesses several transmembrane regions. To overcome this problem, we fused the ORF4, ORF5, and ORF6 with SUMO (small ubiquitin-related modifier). The resulting fusion protein SUMO-ORF4, -ORF5, and -ORF6 were highly expressed in Bm5 cells. The level of protein expression using the Bombyx mori larvae was higher than that using Bm5 cells. In addition, fusion to SUMOstar, which is not processed by native SUMO proteases, significantly enhanced protein expression levels compared to SUMO fusion. This study demonstrated that SUMO or SUMOstar, when fused with PRRSV structural proteins, was able to promote its soluble expression. This may be a better method to produce PRRSV structural proteins for vaccine development.

• Korean Journal of Veterinary Service
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• v.30 no.3
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• pp.305-312
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• 2007

The present studies was to seroepidemiological investigation with the related pneumonia due to a combination of both viral and bacterial agents. In selected herd in Jeonbuk-Iksan area of swine farms in 2006. The seroprevalence of antibody titers of PRRS, PCV-2 and mycoplasmal pneumonia were 87.2%, 69.8% and 47.4%, respectively. High seroprevalence of antibody in sow indicate that the infected sow major source of the diseases, and play an important role in circulation between production stage.

• Journal of Veterinary Clinics
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• v.34 no.2
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• pp.140-145
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• 2017

The goal of this study was to investigate risk factors associated with porcine reproductive and respiratory syndrome (PRRS) in pig farms in the Republic of Korea using logistic regression and a multilevel model. A cross-sectional study was applied to 305 pig farms with a questionnaire-based interview by veterinarians between March 2014 and February 2015. The questionnaire comprised eight categories: proximity to neighbors, disinfection, visitors, vehicles, insecticides, wild animals, gilts, and feeding. In total, 61 questions in eight categories related to pig farm biosecurity were investigated. Farms were classified as PRRS stable or unstable based on the results of an antibody test and PCR. For univariate analysis, keeping production records with computers (OR = 0.283, 95% CI = 0.056 - 1.425), accredited farm with no use of antibiotics (OR = 0.412, 95% CI = 0.134 - 1.269), reviewing health record of semen prior to purchasing (OR = 0.492, 95% CI = 0.152 - 1.589), complete isolation of runt pigs (OR = 0.264, 95% CI = 0.084 - 0.829), compulsory registering for visitors (OR = 0.424, 95% CI = 0.111 - 1.612), keeping records of insecticide history (OR = 0.406, 95% CI = 0.089 - 1.846), routine on-farm monitoring by veterinarians (OR = 0.314, 95% CI = 0.069 - 1.423), and use of on-farm checklist for biosecurity monitoring (OR = 0.313, 95% CI = 0.063 - 1.553) were found to decrease the probability of PRRS infection. Multivariate and multilevel analysis revealed only two factors, complete isolation of runt pigs (OR = 0.165, 95% CI = 0.045 - 0.602 and OR = 0.208, 95% CI = 0.055 - 0.782) and compulsory registering for visitors (OR = 0.106, 95% CI = 0.017 - 0.655 and OR = 0.119, 95% CI = 0.017 - 0.809) were found to decrease the probability of PRRS infection. The intracluster correlation coefficient of a province for multilevel model was 0.05. The results of this study might facilitate biosecurity measures for individual farms to reduce the probability of PRRS infection.

• Journal of Veterinary Clinics
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• v.33 no.2
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• pp.102-106
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• 2016

More than 20 years after the first report of porcine reproductive and respiratory syndrome virus (PRRSV) in Korea, the disease is still having major impact on domestic pig health and relevant industries. Although ELISA tests are commonly used by veterinarians to guide herd management, data on diagnostic performance of the test in field settings are very limited. The objective of this study was to evaluate two commercially available PRRSV ELISA (IDEXX PRRS X3 ELISA and Bionote PRRSV ELISA 4.0) to detect antibodies against PRRSV on serum samples. To this end, a total of 1,108 sera were recruited from 35 swine farms located in Gyeonggi province and tested at the Gyeonggi Province Veterinary Service Center. All tests were performed according to the manufacturer's instructions, by laboratory technicians who routinely perform PRRS testing on blood samples. Samples were collected from two sources of swine populations with different PRRS prevalence; 60 samples (5.4%) were originated from breeding farms and the remaining 1,048 samples (94.6%) were from farrow-to-finish farms. We applied Bayesian latent class model (LCM) for two-tests in the two-population when the accuracy of the gold standard is not available. The model estimated that Bionote ELISA was a bit more specific but slightly less sensitive. The estimated sensitivity and specificity of the IDEXX ELISA were 99.8% (95% CI 98.1-100%) and 86.4% (95% CI 81.4-96.5%), respectively. Sensitivity, specificity, positive predictive value and negative predictive value for Bionote kit were 98.7% (95% CI 92.8-100%), 89.8% (95% CI 86.2-93.1%), 93.8% (95% CI 91.5-96.0%), and 97.8% (95% CI 87.1-100%), respectively. Based on the Bayesian 95% credible intervals, the sensitivity and specificity of the two ELISAs were not significantly different each other when assuming that two kits were imperfect, indicating that two kits performed equally well in terms of sensitivity and specificity in our filed setting.

• Korean Journal of Veterinary Research
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• v.38 no.1
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• pp.77-83
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• 1998

돼지 생식기호흡기증후군(porcine reproductive and respiratory syndrome, PRRS) 바이러스가 웅돈에 감염되었을 경우에는 정충의 기형 등 정액의 질 저하와 더불어 정액에 바이러스가 함유되어 있어 종부시 모돈에 바이러스를 전파하는 것으로 알려져 있다. 감염된 웅돈의 정액으로 인공수정을 실시할 경우 농장의 모돈 전체에 순식간에 바이러스를 전파하여 막대한 피해를 유발할 가능성이 높다. 따라서 감염웅돈을 신속히 검색하여 격리함으로써 피해를 사전에 방지해야 하며, 이를 위해서 웅돈의 감염여부를 신속히 확진하는 진단법의 개발이 필요한 실정이다. PRRS의 진단을 위해서는 바이러스학적인 진단법으로는 바이러스 분리동정, 혈청학적인 방법으로 바이러스 분리동정이 필수적이나 검사시간이 많이 소요되고, 분리동정 자체가 까다로운 단점이 있다. 본 연구에서는 웅돈의 정액내에서 PRRSV 바이러스에 대한 유전자를 RT-PCR법으로 증폭하는 방법을 개발하였으며, 진단의 민감도를 높이기 위하여 Nested PCR법으로 재확인 할 경우, 바이러스의 역가가 $1TCID_{50}$만 함유되어 있어도 진단이 가능한 조건을 확립하였다. 이 방법을 이용할 경우 웅돈의 정액시료에 대한 PRRS 바이러스 감염여부를 신속, 정확하게 검색하여 감염웅돈을 통한 PRRS바이러스의 전파를 미리 차단할 수 있으므로 PRRS방제에 효과적으로 이용될 것으로 사료된다.