• The Journal of Korean Society of Virology
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• v.27 no.2
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• pp.217-225
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• 1997

PCR amplication using the primers for gag, pol and env genes in BLV (bovine leukemia virus) proviral DNA and syncytium assay were carried out for the Korean native goats experimentally infected with bovine leukemia virus to investigate pathogenesis of BLV in the goats, and to establish a model animal for BLV infection. The oligonucleotide primers used in PCR revealed very high specificity. The minimal amount of FLK-BLV cellular chromosomal DNA to detect the integrated BLV proviral DNA was 10 ng. The peripheral blood lymphocytes from the goat infected with BLV were examined at regular intervals by PCR amplification and syncytium assay. Pol or gag genes were detected in none of three infected goats at the 1st week post-infection (p.i.). At the 4th week p.i., one of three goats showed the amplified gag gene. Thereafter detection rates for the genes were increased, indicating that the BLV proviral genes were integrated in all of the lymphocytes from three goats, at the 16th weeks p.i., when it was evident in syncytium assay that the lymphocytes from all of three goats were infested with infective BLV. Investigating the tissues from the necropsied goats at the 8th month p.i., the amplified BLV proviral genes and infective BLV were detected in all of the peripheral lymphocytes from three infected-goats. Among various tissues examined, the amplified BLV proviral genes were observed in spleen and superficial cervical, mandibular and retropharyngeal lymph nodes, and the infective BLV, in superficial cervical and mandibular lymph nodes. It was assumed that the Korean native goat was quite susceptible to BLV infection, indicating that the goat could be a good model animal for BLV.

• Biomedical Science Letters
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• v.5 no.1
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• pp.101-107
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• 1999

Bovine immunodeficiency virus (BIV) which was grouped into the Lentivirinae of family Retroviridae, was known to be causing many immunodeficiency syndromes among cows. The BIV was studied worldwide during last several years for its importance in cattle industries but nothing was reported in Korea until now Thus we initially tried to study the existence of BIV in cattle around the Daegu·Kyungpook area by PCR related molecular techniques. As a prerequisite investigation for detecting Korean-type BIV, we had focused our aim into BLV infected cows because the BLV infected cows tend to show BIV infection with 5％ ranges. Hence we randomly sampled fresh bloods from 248 cows and bulls near the Daegu·Kyungpook area and collected peripheral blood monocytes (PBMC) from the sample bloods. After extracting genomic DNA from the PBMC, we subjected it to PCR and Soluthern blot analysis for BIV/BLV detection. Overall, 66.9% (81/121) of the cow PBMC samples turned out to be BLV positive by PCR and the result was reconfirmed by Southern blot analysis. The value was two times higher than the previously reported results of BLV infection in Korea. The significant difference was mainly due to 1) applying highly specific methods for BLV detection such as PCR 2) that BLV was continuously spreaded in the Daegu Kyungpook area without any notice during last ten years. We also tested the BLV positive samples with the same techniques for BIV detection. And we found some BIV positives among the lot 3C samples by PCR, which had showed 100% BLV positive.

• Biomedical Science Letters
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• v.10 no.1
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• pp.55-63
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• 2004

Bovine leukemia virus (BLV) is a causative agent for lymphoma disease in cattle including cows worldwide. BLV shares similar virion structure and characteristics with other retroviruses. The pol gene of the BLV genome produced reverse transcriptase (RT) and integrase (IN) for important roles for BLV genome integration into host cell chromosomes that is known to be coded in the 3' side of the BLV pol gene (one third portion). In this study, we have sequenced 978 bp in the 3' side of the BLV pol gene from BLV 10C3 in order to determine the BLV IN region of it. And we compared it to the nucleotide sequences of an Australian BLV isolate. As a result, nucleotide sequences of the IN region of the Korean-type BLV pol gene were mutated at a rate of 3.7%. We can confirm that the typical mutations are such as Arg (AGG) $\rightarrow$ Lys (AAG), Thr (ACG) $\rightarrow$ Met (ATG), Ile (ATT) $\rightarrow$ Val (GTT), Asn (ACC) $\rightarrow$ His (CAC), Phe (TTT) $\rightarrow$ Leu (TTG) and Asn (ACC) $\rightarrow$ Asp (GAC). From the analysis of the sequencing data, we were able to determine the zinc-finger-like "HHCC" motif in the amino terminus of BLV IN, that was H-$X_3$-H-$X_{25}-C-X_2$-C. It was also found the DD35E motif in the IN catalytic domain as D-$X_{56}$-D-$X_{35}$-E. It fits very well to the consensus sequences of retroviral IN as well as HHCC motif.

• Applied Microscopy
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• v.35 no.1
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• pp.23-30
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• 2005

Many studies have been performed on the bovine leukemia virus (BLV) since bovine leukosis had been reported in 1968 in Korea. However, there was no report on the ultrastructural examination of BLV. An attempt to detect C-type viral particles in the cultured peripheral blood lymphocytes of Holstein-Friesian dairy cattle, was made to determine whether in vitro viral expression might be used as a reliable method to identify the cow which is likely to transmit BLV. In transmission electron microscopic (TEM) examination, the virus particles were found predominantly outside of the lymphocytes even though a few particles were also observed within the membrane bound cytoplasmic vacuoles. All of them were C-type particles consisting of a central, electron-dense core separated by a clear area from a limiting envelope with a unit membrane structure. Virus particles were easily detected in the lymphocyte which was cultured with medium supplemented with either T-lymphocyte mitogen (conconavalin A) or B-lymphocyte mitogen (lipopolysaccharide). Identical viral particles, although fewer, were also consistently present in the lymphocytes cultured with medium which was containing foetal bovine serum (FBS) only and which was containing neither FBS or mitogen. By contrast, no virus particle was detected in extensive examination of lymphocytes before culture. In conclusion, the BLV cultivation and detection methods established in this study could be used as a tool to identify and eliminate the cattle which can transmit the BLV.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.6
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• pp.879-883
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• 2005

The integral relationship between the occurrence of lymphocyte nuclear pockets (LNPs) and BLV-infection was examined in Holstein-Friesian dairy cattle in Korea. Transmission electron microscope (TEM) was used to detect LNP in peripheral blood lymphocytes. Morphologically, the membranes of LNP were composed of two layers of double nuclear membrane. The full thickness of LNP membranes including inner and outer nuclear membrane was 60 to 70 nm. LNP prevalence was different according to the bovine leukemia virus (BLV) infection status; in BLV-seropositive cattle, LNP prevalence was 48.4% and in BLV-seronegative cattle prevalence was 5.9%. Moreover, even in seropositive animals, leukemic group was the highest at 70% positive among the groups, followed by suspect group (42.4%) and aleukemic group (23.1%). Consequently, the numbers of LNP were increased in proportion to increase of the numbers of leukocytes among BLV-seropositive cattle. The numbers of LNP per lymphocyte were increased in BLVseropositive cattle compared with seronegative cattle. The mean numbers of LNP per 100-lymphocytes were 0.35, 0.77, 1.64 and 4.7 in BLV-seronegative, BLV-seropositive aleukemic, suspect and leukemic groups, respectively. Thus, it is reasonable that LNP test can be used as the one of the diagnostic criteria of BLV infection.

• The Journal of Korean Society of Virology
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• v.30 no.2
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• pp.131-139
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• 2000

Bovine leukemia virus (BLV) is an etiological agent of chronic diseases in cows worldwide. The BLV is one of retroviruses that contain a multi-functional enzyme, reverse transcriptase produced from the pol gene in its genome. We have sequenced some regions in the pol gene of BLV proviruses found in the Southern province of Korea from samples that turned out to be BL V positives by a PCR analysis. On the 5' side of the BLV pol gene (polymerase region), it was found that there were four leucines located at every 7 amino acids. They can form a leucine zipper motif that was not same as the pol gene of Japanese BLV isolate. The sequencing result of the proviral pol gene in Korean-type BLV also revealed some mutations leading to amino acid changes such as $CCT(Pro){\to}CTC(Leu)$, $AAT(Asn){\to}AAA(Lys)$, and non-sensible variations i.e., $TCT(Ser){\to}TCC(Ser)$, $ATT(Ile){\to}ATC(I1e)$ and $ACG(Thr){\to}ACA(Thr)$. On the 3' side of the pol gene (integrase region), some nucleotide sequences were mutated and led to amino acid changes. Among them, a mutation, $GAA(Glu){\to}GAC(Asp)$ occurred in many Korean-type BLV proviruses was very interesting because the amino acid was regarded as one of the most conserved amino acids in the retroviral integrase. It was also notable that the mutation on any leucine residue did not occur, in spite of its frequent appearance.

• Korean Journal of Agricultural Science
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• v.38 no.2
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• pp.249-255
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• 2011

This study was performed to investigate the characterization of infectious BLV env gene isolated form Korean Holstein Cattle and to determine its incoming origin. Gp51 region of BLV env gene known as having important role in immunological function was characterized using PCR-RFLP sequencing and phylogenetic analysis. BLV env gene was grouped into PCR-RFLP patterns with three restriction endonucleases including Pvu II, BamHI and Hae III, and we identified two new RFLP patterns from nucleotide sequences of each group. Phylogenetic analysis showed that 80% of the Korean Holstein was included in the USA and Japanese group. These results here can provide a valuable information about the character of the BLV env gene and research on infection route of BLV.

• Korean Journal of Veterinary Research
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• v.26 no.1
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• pp.61-68
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• 1986

This paper described the distribution and transmissibility of BLV(bovine leukemia virus), the relationship between antibodies against BLV and lymphocyte count in 313 dairy cattle from 36 herds, the clinical signs and hematological findings of 2 lymphosarcomatous cattle in the northern area of Kyungpook. Eighty three (26.5%) of 313 cattle from 36 herds were positive for BLV antibodies and 19 (52.8%) of 36 herds were infected with BLV by the immunodiffusion test with BLV-gp antigen. The rate of BLV infection in cattle varied from 9.5 to 87.5% in 19 positive herds, it was higher in herds pastured during summer and included lymphosarcomatous onset than the other and also higher with the age. Eight (88.9%) out of 9 cattle which showed persistent lymphocytosis by the hematological test were positive for BLV antibodies. After 5 to 14 months, 13 (31.0%) of 42 cattle being negative for BLV antibodies in the positive herds converted into positive. Two lymphosarcomatous cattle were identified to be EBL (enzootic bovine leukemia) by the clinical sign, hematological examination and serological test.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.45-50
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• 2011

This study was conducted to investigate the farm situation about bovine leukemia virus(BLV) infection that greatly influence productivity in dairy cattle and compare the accuracy of diagnosis for BLV infection between PCR and ELISA techniques. Blood samples of 193 heads from 5 herds in Chungnam and Chungbuk area were used to analyze BLV gene and serum, and the results were obtained as follows. The amplified BLV gene in dairy cattle by PCR technique resulted in 226 bp, 596 bp and 434 bp, respectively, for gag, pol and env, which were well amplified. The infection rates of BLV virus diagnosed by PCR and ELISA techniques ranged from 80.55 to 100% and from 22.22 to 86.95%, respectively, and the infection rates among 5 herds were significantly different in both methods (P<0.05). Further, the average infection rates of 5 herds were 87.05 and 63.21%, respectively, for PCR and ELISA techniques. Kappa statistics for examining consistency of diagnosis by PCR and ELISA techniques showed 0.246, which represents low consistency. Consequently, PCR based BLV technique was considered as a corrective measure for diagnosis of BLV infection in Holstein dairy cattle.

• Korean Journal of Agricultural Science
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• v.27 no.2
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• pp.101-106
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• 2000

A total of 181 Holstein and 73 Korean cattle were used to investigate the association of bovine leukemia virus (BLV) resistance stains with major economic traits. The frequencies of BLV resistance strain with 91bp PCR products were 60.0% and 40.0% in Holsten and Korean cattle, respectively. The association of BLV resistance and susceptibility strains with 305-d milk and 305-d milk fat yields were not significant(P>0.05) in Holstein cattle. Body weights at birth, 6-mon, and 120-mon of age were not significantly associated with the BLV resistance and susceptibility strains of Holstein and Korean cattle. It could be concluded that the alleletypers of BLV resistance were not associated with major economic traits in Holstein and Korean cattle.