Important note: Information in this article was accurate in 1994. The state of the art may have changed since the publication date.
Bovine leukemia virus: regulation of viral gene expression during pathogenesis (Meeting abstract).
International Association for Comparative Research on Leukemia and Related Diseases, 16th Symposium. July 11-16, 1993, Montreal, Quebec, Canada, A43, 1993.. Unique Identifier : AIDSLINE ICDB/94698643 Radke K; Dept. of Avian Sciences, Univ. of California, Davis, CA 95616
Abstract:
A hallmark of infection by bovine leukemia virus (BLV) and its relative, human T-cell leukemia virus (HTLV), is that the virus is virtually silent, while infected lymphocytes circulate through peripheral blood. Infection may also be latent in most infected lymphocytes within lymphoid tissues. Nevertheless, some cells express viral genes and produce virus that in turn infects new host cells, increasing the population of cells at risk for tumorigenesis. We have used peripheral blood mononuclear cells (PBMCs) from sheep experimentally infected with BLV to investigate virus expression from initial infection through the development of clonal malignancies. Even during the first months of infection, when the prevalence of BLV-infected cells and the host's immunological response change markedly, only rare circulating PBMCs can be found by in situ hybridization to contain BLV RNA. However, as many as 1% of PBMCs transcribe BLV after being cultured for a few hours. Beginning about 2 months after infection, very few PBMCs transcribe BLV under the same conditions, suggesting that infected cells more readily express BLV in the early months of a new infection. Numbers of infected PBMCs gradually increase with time, as does the ease with which they express BLV. After 4 to 5 years, between 0.5 and 10% of PBMCs express BLV in culture, enabling detection of polyadenylated transcripts by Northern analysis. BLV transcription is activated as early as 30 min after PBMCs are cultured. Expression is characterized by early and late stages, confirming models of HTLV and BLV expression. In early expression, doubly-spliced 2-kb transcripts containing tax/rex sequences are cytoplasmic, while larger viral transcripts are confined to the nucleus. The rapid transition to late stage expression in which all transcripts are cytoplasmic begins as early as 1 hr in culture. This transition requires the synthesis of new proteins, including the viral Rex protein that acts as a switch between early and late expression.
Keywords: Animal Cattle Gene Expression Regulation, Leukemic/*GENETICS Gene Products, rex/GENETICS Gene Products, tax/GENETICS Leukemia Virus, Bovine/*GENETICS Leukemia, Experimental/*GENETICS/MICROBIOLOGY Leukocytes, Mononuclear/MICROBIOLOGY Transcription, Genetic ABSTRACT 940830
M9480799
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Important note: Information in this article was accurate in 1994. The state of the art may have changed since the publication date.
