Aneta Pluta
National Veterinary Research Institute, Poland
Title: Naturally occurring mutations within LTR region impair transcription activity of bovine leukemia virus
Biography
Biography: Aneta Pluta
Abstract
Bovine leukemia virus (BLV) is a deltaretrovirus infecting bovine B cells and causing enzootic bovine leucosis. Repression of viral expression is a major strategy developed by retroviruses to escape from the host immune response. BLV transcription appears to be regulated by several elements (TxRE, NF-κB, GRE, PU.1/Spi-B, USF, DAS and IRF) located mainly in the U3 region of the Long Terminal Repeats (LTR). The aim of the study was to analyse the mutations in the LTR region of the BLV and determine the associations between these mutations and transcriptional activity of BLV. Samples were collected from animals represented the cases of the so-called newly emerging infections, noted in herds already having freedom from BLV infection. At first, LTR sequences obtained from one hundred BLV isolates were analyzed for their genetic variability. The variants characterized by the most significant mutations were selected and used for in vitro transcription study. The reporter vectors plasmid containing the luciferase gene under control of the promoter sequence of particular BLV variant and the expression plasmid containing sequence encoded the Tax protein were constructed. Both plasmids were used for co-transfection of HeLa cells and the level of expression of the reporter gene were measured. Remarkably, transcriptional activity of LTR region of BLV variants having mutation at positions T169G in GRE site and A74G in TRE2 element decreased twice, as compared to wild type virus. These features warrant further exploration as they could be related to proviral load and distinctive down regulation of BLV transcription and its replication.