Regulation of porcine endogenous retrovirus by dual LTR1+2 (Long Terminal Region) miRNA in primary porcine kidney cells

Porcine endogenous retroviruses (PERVs) integrate into germline DNA as proviral genome that enables vertical transmission from parents to their offspring. The provirus usually survives as part of the host genome rather than as an infectious agent, but may become pathogenic if it crosses species barriers. Therefore, replication-competent PERV should be controlled through selective breeding or knockout technologies. Two microRNAs (miRNAs), dual LTR1 and LTR2, were selected to inhibit the expression of PERV in primary porcine kidney cells. The inhibition efficiency of the miRNAs was compared based on their inhibition of different PERV regions, specifically long terminal repeats (LTRs), gag, pol, and env. Gene expression was quantified using real-time polymerase chain reaction and the C-type reverse transcriptase (RT) activity was determined. The messenger RNA (mRNA) expression of the PERV LTR and env regions was determined in HeLa cells co-cultured with primary porcine kidney cells. The mRNA expression of the LTR, gag, pol, and env regions of PERV was dramatically inhibited by dual miRNA from 24 to 144 h after transfection, with the highest inhibition observed for the LTR and pol regions at 120 h. Additionally, the RT activity of PERV in the co-culture experiment of porcine and human cells was reduced by 84.4% at the sixth passage. The dual LTR 1+2 miRNA efficiently silences PERV in primary porcine kidney cells.

Guideline on safety evaluation of cell-based medicinal products for animal use

With the increased use of cell therapy in the veterinary sector, there is a growing demand for the development of cell-based medicinal products and the determination of their safety. Currently, the Korean Animal and Plant Quarantine Agency has established a guideline for evaluating the safety of cell-based medicinal products for animal use. The guideline includes items related to definition, classification, management, manufacturing procedure and quality control (standard and test method), stability testing, toxicity testing, pharmacological testing, and performance of clinical trials. In addition, testing protocols related to safety assessment of animal cell-based products such as chromosome karyotyping, tumorigenicity testing, confirmatory testing of biodistribution and kinetics, and target animal safety testing are described in detail. Moreover, because cell-based medicinal products are novel therapies, deviations from traditional designs may be justified in order to obtain relevant safety information on the treatment. Additionally, this guideline can be amended on the basis of new scientific findings.

Duplex nested reverse transcriptase polymerase chain reaction for simultaneous detection of type 2 porcine reproductive and respiratory syndrome virus and porcine circovirus type 2 from tissue samples

There are high levels of co-incidence of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2) in porcine tissue. This study established a duplex nested reverse transcriptase polymerase chain reaction (RT-PCR) method that targets the genomic RNA of type 2 PRRSV and the mRNA of PCV2 in infected tissues. The method amplified discriminative bands of 347 bp and 265 bp specific for type 2 PRRSV and PCV2, respectively. The limits of detection of the duplex nested RT-PCR were 10(1.5) TCID₅₀/mL for type 2 PRRSV and 10² infected cells/mL for PCV2. The kappa statistic, which measures agreement between methods, was 0.867, indicating a good level of agreement. This RNA-based duplex RT-PCR approach can be another way to detect type 2 PRRSV and PCV2 simultaneously and with improved convenience.

Genetic Characteristics and Immunogenicity of Pandemic H1N1 Influenza Virus Isolate from Pig in Korea

A pandemic influenza A (H1N1) virus strain was isolated from a pig farm in Korea in December 2009. The strain was propagated in and isolated from both the Madin-Darby canine kidney cell line and embryonated eggs. The partial and complete sequences of the strain were identical to those of A/California/04/2009, with >99% sequence similarity in the HA, NA, M, NS, NP, PA, PB1, and PB2 genes. The isolated strain was inactivated and used to prepare a swine influenza vaccine. This trial vaccine, containing the new isolate that has high sequence similarity with the pandemic influenza A (H1N1) virus, resulted in seroconversion in Guinea pigs and piglets. This strain could therefore be a potential vaccine candidate for swine influenza control in commercial farms.

Comparison of the antigenic relationship between Japanese encephalitis virus genotypes 1 and 3

PURPOSE: The Japanese encephalitis virus (JEV) genotype circulating in Korea has changed from G3 to G1. Therefore, the purpose of this study was to compare the antigenic relationship between the two genotypes by using antibody tests. MATERIALS AND METHODS: Blood samples from 42 sows and 216 horses were collected, and their seroprevalence was monitored using the hemagglutination inhibition and virus neutralization tests. Antisera against JEV G1 and G3 were isolated and prepared from guinea pigs. The cross-reactivity of these two viruses was then compared using the neutralizing antibody test. RESULTS: We found that there was a difference in the seropositive ratios of JEV G1 and G3. However, the difference was dependent on the antibody test used. There was also an observed difference in the antigenicity between the two genotypes, as ascertained using the neutralizing antibody test. CONCLUSION: There is an evident difference in JEV antigenicity between the genotypes G1 and G3. Therefore, we propose monitoring of the seroprevalence of JEV, and reevaluating the antigenicity of the current vaccine by using the relevant tests.

Increased humoral antibody response of foot-and-mouth disease virus vaccine in growing pigs pre-treated with poly-γ-glutamic acid

This study was conducted to determine if humoral antibody response of foot-and-mouth disease (FMD) vaccine improved in 8-week-old growing pigs born to well-vaccinated sows pre-treated with 60 mg of poly-γ-glutamic acid (γ-PGA) three days before vaccination. Antibody against FMD virus serotype O was measured 0, 2, 4 and 6 weeks post-vaccination, using a PrioCHECK FMDV type O ELISA kit. The results showed that positive antibody reactions against FMDV serotype O antigen among a component of the vaccine significantly increased in response to pre-injection with γ-PGA.

GC/MS analysis of high-performance liquid chromatography fractions from Sophora flavescens and Torilis japonica extracts and their in vitro anti-neosporal effects on Neospora caninum

We analyzed alcoholic extracts of herbs possessing anti-neosporal activity against Neospora (N.) caninum. To identify the chemical components of Sophora (S.) flavescens and Torilis (T.) japonica associated with anti-neosporal activity, specific fractions were isolated by high-performance liquid chromatography (HPLC). In vitro activity of the fractions against N. caninum was then assessed. Gas chromatography/mass spectrometry (GC/MS) was used to identify and quantify specific anti-neosporal molecules in the herbal extracts. Almost all HPLC fractions of S. flavescens and T. japonica had higher levels of anti-neosporal activity compared to the not treated control. Active constituents of the extracts were sophoridane, furosardonin A, and tetraisopropylidene-cyclobutane in S. flavescens; 5,17-beta-dihydroxy-de-A-estra-5,7,9,14-tetraene, furanodiene, and 9,12-octadecadienoic acid (Z,Z)-(CAS,1) in T. japonica.

Quantification and genotyping of PCV2 DNA in the tissues of PCV2-infected conventional pigs with different clinical signs / 대한수의학회지

This study was focused on the genotyping and quantification of Porcine circovirus type 2 (PCV2) in thirty PCV2-positive pigs with different clinical symptoms (PCV2-infected without wasting, PCV2-infected with wasting, PCV2-infected with wasting and lymphoid depletion). The quantity of PCV2 DNA in diverse tissues was significantly differed among these groups. (One-way ANOVA test, p < 0.001) Interestingly, PCV2-DNA load in tissues of PCV2-infected pigs without wasting and PCV2-infected pigs with wasting and lymphoid depletion were not significantly differed (p = 0.38), while they were all significantly higher when compared with PCV2-infected pigs with wasting-only. PCV2 DNA quantity in tissues was significantly higher in PCV2a and 2b co-infected pigs compared to the PCV2b only-infected pigs (Wilcoxon test, p = 0.039). The PCV2a and 2b co-infected pigs had increased wasting and lymphoid depletion rate but it was not statistically significant. Therefore, this cross-sectional study suggested that PCV2 DNA load in tissues was diverse by clinical and histological findings. Furthermore, co-infection of PCV2a and 2b affected to the PCV2 DNA load in tissues with increased rate of wasting and lymphoid depletion.

Epidemiological characteristics of pulmonary pneumocystosis and concurrent infections in pigs in Jeju Island, Korea

Epidemiological characteristics of swine pulmonary Pneumocystis (P.) carinii and concurrent infections were surveyed on Jeju Island, Korea, within a designated period in 172 pigs submitted from 54 farms to the Department of Veterinary Medicine, Jeju National University. The submitted cases were evaluated by histopathology, immunohistochemistry, PCR/RT-PCR, and bacteriology. P. carinii infection was confirmed in 39 (22.7%) of the 172 pigs. Histopathologically, the lungs had moderate to severe lymphohistioctyic interstitial pneumonia with variable numbers of fungal organisms within lesions. Furthermore, porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV-2) co-infection was a common phenomenon (12.8%, 20.5%, and 48.7% were positive for PRRS, PCV-2, or both, respectively, as determined by PCR/RT-PCR). Infection was much more concentrated during winter (December to March) and 53.8% of the infected pigs were 7- to 8-weeks old. In addition, three pigs showed co-infection with bacteria such as Pasteurella multocida and Streptococcus suis. The results of the present study suggest that the secondary P. carinii infection is common following primary viral infection in swine in Korea. They further suggest that co-infection of P. carinii might be enhanced by the virulence of primary pathogens or might have synergistic effects in the pigs with chronic wasting diseases.

Identification of two cytopathogenic agents, Mycoplasma hyorhinis and mammalian orthoreovirus 3 based on modified particle associated nucleic acids PCR / 대한수의학회지

Swine diseases could be caused by unrecognized or minor pathogens. In this study, two unknown cytopathogenic agents were isolated from swine, through cell culture. In order to identify these two cytopathogenic agent (designated CP129 and #2045-7), a particle associated nucleic acids PCR (PAN-PCR) from previous paper was used with simple modification. The cloning procedure was more specified in this study by adding cell control system. According to the modified PAN-PCR, two and four agents-specific DNA sequences were obtained from CP129 and #2045-7, respectively, and they were identified as Mycoplasma (M.) hyorhinis and Mammalian orthoreovirus by nucleotide BLAST. Since M. hyorhinis (CP129) was filterable and non-visible by microscope, this unusual virus-like nature of M. hyorhinis (CP129) was discussed. Especially, the reovirus (#2045-7) was a serotype 3 and a triple reassortant among three serotypes of reoviruses. It was grouped with recently reported reoviruses from disease cases (swine, human and feline), based on the genetic analysis of L1 and S1 partial sequences. In conclusion, two unknown cytopathogenic agents were successfully identified using modified PAN-PCR with cell control system and they were characterized in this study.

Simultaneous detection and subtyping of porcine endogenous retroviruses proviral DNA using the dual priming oligonucleotide system

The purpose of this study was to develop a multiplex PCR that can detect porcine endogenous retrovirus (PERV) proviral genes (pol, envA, envB, envC) and porcine mitochondrial DNA, using a dual priming oligonucleotide (DPO) system. The primer specifically detected the PERV proviral genes pol, envA, envB, envC, and porcine mitochondrial DNA only in samples of pig origin. The sensitivity of the primer was demonstrated by simultaneous amplification of all 5 target genes in as little as 10 pg of pig DNA containing PERV proviral genes and mitochondrial DNA. The multiplex PCR, when applied to field samples, simultaneously and successfully amplified PERV proviral genes from liver, blood and hair root samples. Thus, the multiplex PCR developed in the current study using DPO-based primers is a rapid, sensitive and specific assay for the detection and subtyping of PERV proviral genes.

Genetic analysis of ORF5 of recent Korean porcine reproductive and respiratory syndrome viruses (PRRSVs) in viremic sera collected from MLV-vaccinating or non-vaccinating farms

The 23 open reading frame (ORF) 5 sequences of Korean type II porcine reproductive and respiratory syndrome virus (PRRSV) were collected from viremic sera from the (modified live vaccine) MLV-vaccinating and non-vaccinating farms from 2007 to 2008. The samples were phylogenetically analyzed with previous ORF5 sequences, including type I Korean PRRSV, and previously reported or collected sequences from 1997 to 2008. A MN184-like subgroup of type II Korean PRRSV was newly identified in the viremic sera collected from 2007 to 2008. And of the type I PRRSVs, one subgroup had 87.2~88.9% similarity with the Lelystad virus, showing a close relationship with the 27~2003 strain of Spain. The maximum parsimony tree of type II PRRSV from 1997 to 2008 showed that they had evolved to four lineages, subgroups 1, 2, 3 and 4. Most of the recently collected type II PRRSVs belonged to subgroup 4 (48%). The region of three B-cell epitopes and two T-cell epitopes of ORF5 amino acids sequences was considerably different from the MLV in subgroups 3 and 4. In conclusion, the existence of type I PRRSV, which was genetically different from Lelystad virus (Prototype of type I PRRSV), and heterologous type II PRRSVs of viremic pigs detected even in the MLV-vaccinating farms indicated the need for new vaccine approaches for the control of PRRSV in Korea.

Porcine abortion outbreak associated with Toxoplasma gondii in Jeju Island, Korea

This report deals with the acute onset of an abortion outbreak and high sow mortality in one pig herd consisted of 1,200 pigs and 120 sows on Jeju Island, Korea. Affected pregnant sows showed clinical signs, including high fever, gradual anorexia, vomiting, depression, recumbency, prostration, abortion, and a few deaths. Four dead sows, five aborted fetuses from the same litter, and 17 sera collected from sows infected or normal were submitted to the Pathology Division of the National Veterinary Research and Quarantine Service for diagnostic investigation. Grossly, hepatomegaly and splenomegaly were observed in sows. Multiple necrotic foci were scattered in the lungs, liver, spleen, and lymph nodes. Microscopically, multifocal necrotizing lesions and protozoan tachyzoites were present in the lesions. Tachyzoites of Toxoplasma (T.) gondii were detected immunohistochemically. Latex agglutination showed that the sera of 7 of 17 (41.2%) sows were positive for antibody to T. gondii. The disease outbreak in this herd was diagnosed as epizootic toxoplasmosis. To our knowledge, this is the first report of porcine toxoplasmosis with a high abortion rate and sow mortality in Korea.

Comparison of the age-related porcine endogenous retrovirus (PERV) expression using duplex RT-PCR

Porcine endogenous retroviruses (PERVs) are members of family Retroviridae, genus Gamma retrovirus, and transmitted by both horizontally and vertically like other endogenous retroviruses (ERVs). PERV was initially described in the 1970s having inserted its gene in the host genome of different pig breeds, and three classes, PERV-A, PERV-B, and PERV-C are known. The therapeutic use of living cells, tissues, and organs from animals called xenotransplantation might relieve the limited supply of allografts in the treatment of organ dysfunction. Because of ethical considerations, compatible organ sizes, and physiology, the pig has been regarded as an alternative source for xenotransplantation. Sensitive duplex reverse transcription-polymerase chain reaction protocols for simultaneously detecting PERV gag mRNA and porcine glyceraldehydes 3-phosphate dehydrogenase mRNA in one tube was established. To compare the age-related PERV expression patterns of the lung, liver, spleen, kidney, heart, and pancreas in commercial pigs, 20 pigs from four age groups (5 heads each in 10 days-, 40 days-, 70 days-, and 110 days-old, respectively) were used in this study. The expression patterns of PERV were statistically different among age groups in lung, liver, and kidney (ANOVA, p<0.05). These data may support in the selection of appropriate donor pigs expressing low levels of PERV mRNA.

Seroprevalence of low pathogenic avian influenza (H9N2) and associated risk factors in the Gyeonggi-do of Korea during 2005-2006

Between November 2005 and March 2006, a total of 253 poultry flocks in the Gyeonggi-do of Korea were examined for seroprevalence against avian influenza (AI) using a hemagglutination inhibition (HI) test and an agar gel precipitation test. No low pathogenic avian influenza (LPAI) virus was isolated from 47 seropositive flocks that lacked clinical signs during sampling. The unadjusted percentage of seroprevalence rates of layer and broiler flocks were not significantly different, i.e., 26% (25/96) and 23% (22/97), respectively. The HI titer of the layers (mean = 89) was higher than the broilers (mean = 36; p < 0.001). A cross-sectional study was conducted for the seroprevalence of LPAI in the layers. Of 7 risk factors, farms employing one or more workers had a higher seropositive prevalence as compared to farms without hired employees (adjusted prevalence OR = 11.5, p = 0.031). Layer flocks older than 400 d had higher seropositivity than flocks younger than 300 d (OR = 4.9, p = 0.017). The farmers recognized at least one of the clinical signs in seropositive flocks, such as decreased egg production, respiratory syndromes, and increased mortality (OR = 2.3, p = 0.082). In a matched case-control study, 20 pairs of case and control flocks matched for type of flock, hired employees, age, and flock size were compared. Frequent cleansing with disinfectants was associated with a decreased risk of seropositivity (OR = 0.2, p = 0.022). Although there was a low statistical association, using a foot disinfectant when entering the building led to a decreased rate of seropositivity (OR = 0.3, p = 0.105).

Establishment of Rapid Detection Methods for Bovine Viral Diarrhea Virus(Pestivirus) in Attenuated Animal Viral Vaccines by RT-PCR and Nested PCR

Bovine viral diarrhea virus (BVDV) of the genus Pestivirus is known as a common contaminant of cell culture-derived vaccines. Hog cholera virus (HCV), which is also of the genus Pestivirus and an important livestock disease in Korea, is recognized as a potential contaminant of vaccines produced in porcine cells. However, it is difficult for the National Biological Assays of korea to adequately detect contamination of these agents in biological products. For these reasons, we established rapid and sensitive methods for the detection of BVDV and HCV contamination in cell cultures and veterinary biologicals by using RT-PCR and nested PCR assays. We designed a Pestivirus primer amplifying 152 bp to detect both BVDV and HCV and a common primer amplifying 237 bp to detect only BVDV. Also, for the differentiation between BVDV type 1 and type 2, nested PCR was conducted using the amplified 237 bp PCR product, to amplify 179 bp in BVDV type 2 genome. The sensitivity of the PCR using common primer for the detection of BVDV was 400 TCID50/ml. All 6 strains of Korean BVDV isolates, 5 vaccines strains and the standard strain NADL could be detected. No reactions were observed when testing 5 types of viruses infecting pigs (HCV, TGEV, PEDV, JEV, PRRSV), 4 types infecting cattle (Akabane virus, BEFV, BCV, BRV) and 4 types infecting cats (FIP, FPL, FCV, FVR). Using this RT-PCR assay, commercial vaccines were tested and, 55 lots from 12 vaccine companies, were negative for BVDV contaminations. Same results were obtained by the immunoflourescence assay. The newly developed PCR or RT-PCR assays can be used as rapid, reliable, sensitive, and simple methods for the detection of BVDV (Pestivirus) in cell cultures, master seeds, and live viral vaccines.

Comparison of an enzyme-linked immunosorbent assay with serum neutralization test for serodiagnosis of porcine epidemic diarrhea virus infection

An indirect porcine epidemic diarrhea (PED) virus (PEDV) enzyme-linked immunosorbent assay (ELISA) was compared with the serum neutralization (SN) test by testing 46 samples from experimentally infected sows, 73 samples from naive sows, and 1, 024 field sow samples from 48 commercial swine farms of undefined PED status. The SN test and the ELISA were performed using PEDV, KPEDV-9 strain. Viral proteins as a coating antigen of PEDV ELISA were extracted from the cytoplasm of PEDV-infected Vero cells using a non-ionic detergent, Triton X-100, and a simple protocol of PEDV ELISA was followed. The presence of antibodies in these experimental samples was confirmed by SN and ELISA in which the sensitivity of the ELISA was 89.1%, and the corresponding specificity was 94.5%. On testing 1, 024 field samples, an overall agreement of 84.2% was generated between the SN and ELISA. This study demonstrates that the PEDV ELISA is a useful serodiagnostic screening test at herd level for detecting swine antibodies against PEDV.

Effect of soluble porcine aminopeptidase N on antibody production against porcine epidemic diarrhea virus

A few members of coronavirus group I which includes porcine epidemic diarrhea virus (PEDV) use porcine aminopeptidase N (pAPN) as a cellular receptor. Cellular receptors play an important role in virus attachment and entry. However, the low permissiveness of PEDV to APN-expressing porcine cell lines has made it difficult to elucidate the role of pAPN in vitro. The purpose of this study was to prove whether the treatment of soluble pAPN could enhance the antibody production against PEDV in guinea pigs, rabbits and sows. The animals (20 guinea pigs, 8 rabbits and 20 sows) were divided into 4 groups. Group A was injected intramuscularly (IM) with soluble pAPN at one hour before intramuscular infection of PEDV on the same site, group B for IM simultaneous injection of pAPN and PEDV, and group C for IM injection of PEDV only. Group D served as a control of pAPN treatment or PEDV infection. Antibody production against PEDV was compared among groups at regular intervals. The results suggested that pAPN could enhance the antibody production against PEDV in guinea pigs and rabbits which are free of pAPN, however, the effect of pAPN treatment in sows was not clearly elucidated.

Identification of a putative cellular receptor 150 kDa polypeptide for porcine epidemic diarrhea virus in porcine enterocytes

Porcine epidemic diarrhea virus (PEDV) causes an acute enteritis in pigs of all ages, often fatality for neonates. PEDV occupies an intermediate position between two well characterized members of the coronavirus group I, human coronavirus (HCoV-229E)and transmissible gastroenteritis virus (TGEV) which uses aminopeptidase N (APN), a 150 kDa protein, as their receptors. However, the receptor of the PEDV has not been identified yet. A virus overlay protein binding assay (VOPBA) was used to identify PEDV binding protein in permissive cells. The binding ability of PEDV to porcine APN (pAPN) and the effects of pAPN on infectivity of PEDV in Vero cells were also investigated. VOPBA identified a 150 kDa protein, as a putative PEDV receptor in enterocytes and swine testicle (ST) cells. Further the PEDV binding to pAPN was blocked by anti-pAPN and pAPN enhanced PEDV infectivity in Vero cells. In conclusion, these results suggested that pAPN may act as a receptor of PEDV.

Host Immune Responses Against Hog Cholera Virus in Pigs Treated with an Ionized Alkali Mineral Complex

To determine the immune responses in pigs to hog cholera virus after treatment with an ionized alkali mineral complex (IAMC), 40 healthy pigs (28-32 days old) from a commercial swine farm were purchased and housed into 4 groups (n=10 each). All pigs were vaccinated intramuscularly (1 ml) with an attenuated live hog cholera virus (HCV, LOM strain) at 28-32 days old and challenged with a virulent hog cholera virus at 8 weeks after vaccination. Each group was treated with PowerFeelTM sprayed diet as 0.05% (w/w) in a final concentration (T-1, n=10), a diet mixed with SuperFeedTM as 3% (w/w) in a final concentration (T-2, n=10), or a diluted PowerFeelTM solution (1:500, v/v) as drinking water (T-3, n=10), respectively. A group (n=10) served as a non-treated control. Proportions of expressing CD2+ and CD8+ cells increased significantly (p<, 0.05) at 8-week post-application. Mean antibody titers of each group against HCV gradually increased to higher levels after vaccination and with challenge of the virulent virus. In conclusion, the IAMC-treated diets can be helpful for the improvement of growth in pigs with proper vaccination program, while the IAMC-treated diets have no effects on the clinical protection against hog cholera.