The Molecular Characterization of Bovine Leukaemia Virus Isolates from Eastern Europe and Siberia and Its Impact on Phylogeny

Marzena Rola-Łuszczak,Anton Gerilovych,Jacek Kuźmak,Bhudipa Choudhury,Aneta Pluta,Maxim Petropavlovskiy,Irina Donnik,Monika Olech,Irina Vinogradova

doi:10.1371/journal.pone.0058705

Abstract

Recent studies have shown that bovine leukemia virus (BLV) sequences can be classified into seven distinct genotypes based on full gp51 sequence. This classification was based on available sequence data that mainly represented the BLV population that is circulating in cattle from the US and South America. In order to aid with a global perspective inclusion of data from Eastern Europe is required. In this study we examined 44 BLV isolates from different geographical regions of Poland, Belarus, Ukraine, and Russia. Phylogenetic analysis based on a 444bp fragment of env gene revealed that most of isolates belonged to genotypes 4 and 7. Furthermore, we confirmed the existence of a new genotype, genotype 8, which was highly supported by phylogenetic computations. A significant number of amino acid substitutions were found in the sequences of the studied Eastern European isolates, of which 71% have not been described previously. The substitutions encompassed mainly the C-part of the CD4+ epitope, zinc binding peptide region, CD8+ T cell epitope, and overlapping linear epitope E. These observations highlight the use of sequence data to both elucidate phylogenetic relationships and the potential effect on serological detection of geographically diverse isolates.

Highlights

Bovine leukaemia virus (BLV) belongs to the genus Deltaretrovirus of the Retroviridae family and it is etiologic agent for enzootic bovine leucosis (EBL) [1,2]
Phylogenetic analysis clearly showed the existence of three separated subgroups within G7, whether the tree topologies were derived from NJ or Bayesian methods
The existence of distinct subgroups within G7 fully corresponded to the geographical origin of the BLV isolates, since each particular subgroup contained isolates from one country only

Summary

Introduction

Bovine leukaemia virus (BLV) belongs to the genus Deltaretrovirus of the Retroviridae family and it is etiologic agent for enzootic bovine leucosis (EBL) [1,2]. An analysis focusing on genetic variations of gp sequence demonstrated significant sequence conservation of BLV isolates from multiple geographical locations [10,11] These observations are in agreement with those previously made by Mamoun et al [12] and Beier et al [13] who demonstrated only small differences, mainly point mutations, within seven and twenty two geographically different strains respectively. These mutations conferred some differences in restriction enzyme sites allowing the classification of BLV isolates into three [14] and six [15] genotypes by RFLP analysis. Fechner et al [14] reported the association between some BLV variants and the failure of antibody detection in infected cattle; Licursi et al [15] and Asfaw et al [17], did not observe a relationship between particular genotypes and the serological status of infected animals

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