Sang-Geon Yeo

Complete genomic characterization of a European type 1 porcine reproductive and respiratory syndrome virus isolate in Korea.

Porcine reproductive and respiratory syndrome virus (PRRSV) isolates belonging to the European genotype 1 have recently emerged in South Korea, suggesting potential problems for disease control. In the present study, we attempted to determine the complete nucleotide sequence of the first Korean type 1 PRRSV isolate, designated KNU-07. The full-length genome of KNU-07 was found to be 15,038 nucleotides in length, which was 60 nucleotides shorter than the type 1 prototype strain Lelystad due to a notable 60-bp deletion within the nonstructural protein 2 (NSP2). The KNU-07 genome was shown to consist of a 221-nucleotide (nt) 5′ untranslated region (UTR), a 14,703-nt protein-coding region, and a 114-nt 3′ UTR, followed by a 42-73-bp poly(A) tail. A nucleotide sequence comparison of the KNU-07 genome with 20 complete PRRSV genomes revealed a 10.5–13.3% and 39.5–40.3% divergence from type 1 and type 2 strains, respectively, at the genome level, indicating a high similarity to the virus strains commonly identified as the European genotype. In order to investigate genetic variation and to understand the molecular evolution of the type 1 isolate in Korea, extensive phylogenetic analyses were performed using the ORF5 and ORF7 nucleotide sequences of published type 1 PRRSV isolates. The data further indicated that the newly emerging type 1 isolate KNU-07 belongs to the recently proposed pan-European subtype 1. Taken together, the results of this study describe the genomic characterization of the type 1 PRRSV isolated in South Korea, suggesting a recent introduction of the virus typical for this genotype that has commonly appeared worldwide.

Loop-mediated isothermal amplification assay for the rapid and visual detection of novel porcine circovirus 3

A loop-mediated isothermal amplification (LAMP) assay using hydroxynaphthol blue was developed for the rapid and visual detection of the capsid gene of porcine circovirus 3 (PCV3). The amplification could be completed in 40 min at 62°C, and the results could be visually detected by the naked eye. The assay specifically amplified PCV3 DNA and not other porcine viral nucleic acids. The limit of detection of the assay was 50 PCV3 DNA copies, which was comparable to that of the real-time polymerase chain reaction (qPCR) and lower than that of conventional PCR. In the clinical evaluation, the PCV3 detection rate of the LAMP assay was higher than that of PCR and agreed 100% with that of qPCR. These results indicate that the LAMP assay will be a valuable tool for the rapid, sensitive, and specific detection of PCV3 in clinical samples.

Prevalence of Trichinella spp. antibodies in wild boars (Sus scrofa) and domestic pigs in Korea.

Trichinellosis is a parasitic zoonosis that is of importance to public health; human trichinellosis usually occurs when improperly cooked pork or wild animal meat is consumed. The purpose of this study was to determine the nationwide seroprevalence of Trichinella infection in wild boar and domestic pig populations in Korea. Using ELISA, we detected no seropositivity among the serum samples of 2350 domestic pigs collected in 2013, indicating that the domestic cycles of Trichinella spp. have disappeared from the domestic pig population in Korea. In contrast, approximately 13% of the 434 wild boars hunted in 2013 were seropositive. Furthermore, the seroprevalence of six of the seven provinces was between 6.7% and 18.3%, indicating that Trichinella infection occurred in the wild boar population throughout the country. The results of this study suggest that Trichinella circulates in the wild boar population and could be transmitted from infected wild boars to other wildlife, domestic pigs, and humans in Korea. Therefore, we recommend continued surveillance of Trichinella infection prevalence in wild animals and an appropriate strategy to prevent human infection in Korea.

Uracil-DNA glycosylase-treated reverse transcription loop-mediated isothermal amplification for rapid detection of avian influenza virus preventing carry-over contamination

Here, we describe a uracil-DNA glycosylase (UNG)-treated reverse transcription loop-mediated isothermal amplification (uRT-LAMP) for the visual detection of all subtypes of avian influenza A virus (AIV). The uRT-LAMP assay can prevent unwanted amplification by carryover contamination of the previously amplified DNA, although the detection limit of the uRT-LAMP assay is 10-fold lower than that of the RT-LAMP without a UNG treatment. To the best of our knowledge, this is the first successful application of deoxyuridine triphosphate/UNG strategy in RT-LAMP for AIV detection, and the assay can be applied for the rapid, and reliable diagnosis of AIVs, even in contaminated samples.

Evaluation of single nucleotide polymorphisms of pvmdr1 and microsatellite genotype in Plasmodium vivax isolates from Republic of Korea military personnel

AbstractBackgroundChloroquine has been administered to the soldiers of the Republic of Korea as prophylaxis against vivax malaria. Recent increase in the number of chloroquine-resistant parasites has raised concern over the chemoprophylaxis and treatment of vivax malaria.MethodsTo monitor the development of chloroquine-resistant parasites in the Republic of Korea, analyses of single nucleotide polymorphisms (SNPs) of pvmdr1 and microsatellite markers were performed using samples collected from 55 South Korean soldiers infected with Plasmodium vivax.ResultsFour SNPs, F1076L, T529, E1233, and S1358, were identified. Among these, S1358 was detected for the first time in Korea. The microsatellite-based study revealed higher genetic diversity in samples collected in 2012 than in 2011.ConclusionsTaken together, the results indicate that P. vivax with a newly identified SNP of pvmdr1 has been introduced into the Korean P. vivax population. Therefore, continuous monitoring for chloroquine-resistant parasites is required for controlling vivax malaria in the Republic of Korea.

An improved reverse transcription loop-mediated isothermal amplification assay for sensitive and specific detection of serotype O foot-and-mouth disease virus

A sensitive and specific swarm primer-based reverse transcription loop-mediated isothermal amplification (sRT-LAMP) assay for the detection of serotype O foot-and-mouth disease virus (FMDV) was developed and evaluated. The assay specifically amplified the VP3 gene of serotype O FMDV, but did not amplify the VP3 gene of other serotype FMDVs or any other viruses. The limit of detection of the assay was 102 TCID50/mL or 103 RNA copies/μL, which is 100 times lower than that of the RT-LAMP assay without swarm primers. The new assay is 10 times more sensitive than reverse transcription-polymerase chain reaction (RT-PCR) and is comparable to the sensitivity of real time RT-PCR (qRT-PCR). Evaluation of the assay using different serotypes of FMDV strains showed 100% agreement with the RT-PCR results. The previously reported serotype O FMDV-specific RT-LAMP assay did not detect 20 out of 22 strains of serotype O FMDVs, probably due to multiple mismatches between the primer and template sequences, showing that it is not suitable for detecting the serotype O FMDVs circulating in Pool 1 region countries, including Korea. In contrast, the developed sRT-LAMP assay with improved primers can rapidly and accurately diagnose serotype O FMDVs circulating in Pool 1 region countries and will be a useful alternative to RT-PCR and qRT-PCR.

Detection and genetic characterization of porcine circovirus 3 from aborted fetuses and pigs with respiratory disease in Korea

A novel porcine circovirus 3 (PCV3) was first detected in pigs showing porcine dermatitis and nephropathy syndrome, reproductive failure, and multisystemic inflammation in the USA. Herein, we report on PCV3 as a potential etiological agent of clinical signs, reproductive failure and respiratory distress on Korean pig farms, based on in situ hybridization, pathological, and molecular findings. Confirmation of the presence of PCV3 may increase co-infection with other causative agents of disease in Korean pig herds, indicating the need for further systemic investigation of pathogenicity and of multiple infections with PCV2 genotypes and bacteria, and the development of an effective PCV3 vaccine.