Molecular Characterization of a Variant of Proviral Bovine Leukaemia Virus (BLV)

Abstract

Summary Southern‐blot hybridization and partial sequencing of the pol and env genes were used to characterize BLV‐integrated provirus of seropositive cattle from two dairy herds in northern Italy. Comparison of the data obtained with those of previously characterized BLV strains from other geographic areas (Australia, Belgium, Japan and USA) revealed the presence of a viral variant (BLV‐I2), which showed both conserved and unique features. Regarding the gp51 envelope glycoprotein, the BLV‐I2 variant showed: 1. A high extent of conservation, which included potential glycosylation sites and cysteine residues; 2. Three unique amino acid residues not present in any of the other BLV strains analysed; and 3. Some variability at the level of one (G) of the three (F, G and H) conformational epitopes, which is probably important in the process of infection. These results agree with the suggestion that the sequence variability of the gp51 glycoprotein preferentially involves structures whose change is thought to underlie the phenomenon of escape from immune surveillance.

Molecular characterization of the env gene from Brazilian field isolates of Bovine Leukemia Virus

“…The results suggest that these regions are important to maintain the biological activity of the gp51 and gp30 proteins, thus confirming previous reports [11,14,16,18,19,[30][31][32][33][34][35].…”

“…Of 1,545 sequenced nucleotides, 1,431 were conserved (92.6% of identity). The average substitution rate in relation to the AF257515 sequence was 3.5%, similar to the rates for env gene sequences from isolates from Australia, Belgium, France, Germany, Italy, Japan and USA (11,16,18,19,30). The highest variation between Brazilian sequences and the Argentinean sequence AF257515 was 5.3%.…”

“…However, these small alterations may affect infectivity and/or even pathogenicity of the BLV [13][14][15][16][17]. BLV variants were found in different geographic regions [18,19]. These can also be detected by restriction fragment length polymorphism (RFLP) [20,21].…”

Detection and molecular characterization of bovine leukemia virus in Philippine cattle

“…Analysis of BLV gp51 env gene sequences from different geographic regions has revealed the presence of different genetic groups that correlate with the geographic origin of the isolates [21][22][23][24][25][26][27][28][29]. Recent phylogenetic studies on the BLV env gene of strains isolated worldwide demonstrate that the virus can be classified into eight genotypes [27,30,31].…”

Genetic diversity of bovine leukemia virus worldwide

“…genotype -4, -7 and -8 in cattle samples from Russia and Ukraine (Rola-Luszzak et al 2013);genotype-8 in Croatia (Balic et al 2012); genotype-3 and -4 in France (Mamoun et al 1990);genotype-1 and -4 in Germany (Fechner et al 1997); and genotype-7 in Italy (Molteni et al 1996). A total of seven BLV genotypes have been identified in samples from Asia (G-1, -2, -3, -4, -6, -7 and -10): genotype -1, -2 and -3 in Japan (Licursi et al 2003;Zhao & Buehring 2007;Matsumura et al 2011;Inoue et al 2011); genotype -1 and -3 in Korea (Lim et al 2009;Lee et al 2015); genotype -1 and -6 in The Philippines (Polat et al 2015); genotype-1, -6…”