Sequencing and phylogenetic analysis of the gp51 gene from Korean bovine leukemia virus isolates

Abstract

BackgroundBovine Leukemia virus (BLV) infection of cattle has been reported in Korea for more than three decades. However, to date, there have been few studies regarding Korean BLV since 1980s. Thus, the purpose of this study is to perform a diagnosis and molecular characterization of BLV strains circulating in Korea and to estimate genetic diversity of different genotypes of BLV.MethodTo investigate the distribution of BLV variants in the world and assess the evolutionary history of Korean BLV isolates, a comprehensive molecular analysis of the BLV env gp51 gene was conducted using recent worldwide BLV isolates. The isolates included 50 samples obtained from two cattle farms in southeastern Korea in 2014.ResultsSequence and phylogenetic analyses of partial 444-nt fragment sequences and complete gp51 sequences of BLV revealed eight distinct genotypes of BLV showing geographic distribution of the world. Most Korean BLV isolates were found to belong to genotype 1 which is a major genotype prevailed throughout the world, and only four isolates from one farm were classified as genotype 3 related to the US and Japan isolates. Analysis of amino acids of Korean BLV isolates showed several sequence substitutions in the leader peptide, conformational epitope, and neutralizing domain regions. The observations suggest the possibility of affecting on viral infectivity and formation.ConclusionKorean BLV isolates showed the close relationship to genotype 1 and 3. Further study to identify the diversity of BLV circulating in Korea is necessary with samples collected nationwide because this study is the first report of BLV genotype 3 being in circulation in Korea.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-015-0286-4) contains supplementary material, which is available to authorized users.

Molecular Characterization of Bovine Leukaemia Virus (BLV) Strains Reveals Existence of Genotype 6 in Cattle in India with evidence of a new subgenotype

“…We first analysed the partial gp51 (444 bp) and then full‐length gp51 (903 bp) sequences of 10 Indian BLV strains and other geographical diverse BLV strains representing all the 10 genotypes reported so far. Due to the high conservation of the BLV env gp51 gene among geographical diverse strains, phylogenetic analysis of partial (444 bp) or full‐length (903 bp) gp51 sequences has most often been used for genotyping of BLV strains (Fechner et al., ; Felmer et al., ; Hemmatzadeh, ; Lee et al., , ; Polat, Ohno et al., ; Polat, Takeshima et al., ; Rodriguez et al., ; Rola‐Luszczak et al., ). Phylogenetic analyses of 444 bp gp51 were carried out, as a large number of BLV sequences from diverse geographical regions worldwide corresponding to this region are available and have been used for BLV genetic typing and only partial gp51 sequences are available for BLV genotype 6 strains from Peru, Bolivia and Philippines (Polat, Ohno et al., ; Polat, Takeshima et al., ).…”

“…Genotype 6 strains of BLV have so far been reported from Argentina (Rodriguez et al., ), Brazil (Camargos et al., ), Peru, Paraguay and Bolivia (Polat, Takeshima et al., ) in South America and from Philippines (Polat et al., ) and Thailand (Lee et al., ) in Asia. Although correlation between BLV genotype and geographical location has been demonstrated, prevalence of more than one genotype at a particular location has also been reported (Camargos et al., ; Lee et al., , ; Polat, Takeshima et al., ; Rola‐Luszczak et al., ). Genotype 1 has a worldwide distribution including United States, South American countries, Asian countries and Australia, while genotype 2 has been found in Japan and South America.…”

“…BLV env gene encodes the envelope (Env) protein complex which is composed of gp51 surface glycoprotein (SU) subunits anchored to virions by gp30 transmembrane (TM) protein subunits (Wallin, Ekström, & Garoff, ). As the env gp51 plays an important role in the viral life cycle, such as cell entry (Johnston & Radke, ) and production of virus neutralizing antibodies (Mamoun et al., ), this gene has been widely used for molecular characterization and genotyping of BLV strains (Felmer, Munoz, Zuniga, & Recabal, ; Hemmatzadeh et al., Rodriguez, Golemba, Campos, Trono, & Jones, ; Rola‐Luszczak et al., ; Lee et al., , ; Polat, Ohno et al., ; Polat, Takeshima et al., ).…”

Development and evaluation of an immunochromatographic assay using a gp51 monoclonal antibody for the detection of antibodies against the bovine leukemia virus

“…KP201460) [20] that had been extracted from the peripheral blood mononuclear cells of BLV-infected cattle collected in Korea in April 2014. The N-terminal portion of the gp51 protein was expressed as a 6× histidine-tagged recombinant protein using the pET-21a(+) plasmid (Novagen, USA) and E. coli strain BL21 (Yeastern Biotech, Taiwan) according to the manufacturer's protocols.…”

“…In recent studies, the prevalence of EBL in dairy cattle has been determined to be greater than 50% [317]. The most recent Korean BLV isolates characterized were classified as BLV genotypes 1 and 3 [20]. …”