Bovine leukemia virus encoded blv-miR-b4-3p microRNA is associated with reduced expression of anti-oncogenic gene in vivo

The BLV-miRNAs pathway of BLV inhibits the expression of Lactoferrin, Lactoperoxidase, Alpha-lactalbumin and Beta-lactoglobulin proteins

Bovine leukemia virus (BLV) is a widespread virus that decreases milk production and quality in dairy cows. As crucial components of BLV, BLV-encoded microRNAs (BLV-miRNAs) affect BLV replication and may impact the synthesis of Lactoferrin (LTF), Lactoperoxidase (LPO), Alpha-lactalbumin (alpha-LA), and Beta-lactoglobulin (beta-LG). In this study, we investigated the targeting relationship between BLV-miRNAs and LTF, LPO, alpha-LA, and beta-LG in cow's milk. Additionally, we investigated the possible mechanisms by which BLV reduces milk quality. The results showed that cow's milk had significantly lower levels of LTF, LPO, and alpha-LA proteins in BLV-positive cows than in BLV-negative cows. BLV-△miRNAs (miRNA-deleted BLV) enhanced the reduction of LPO, alpha-LA, and beta-LG protein levels caused by BLV infection. Multiple BLV-miRNAs have binding sites with LTF and LPO mRNA; however, only BLV-miR-B1-5 P has a targeting relationship with LPO mRNA. The results revealed that BLV-miR-B1-5 P inhibits LPO protein expression by targeting LPO mRNA. However, BLV does not directly regulate the expression of LTF, alpha-LA, or beta-LG proteins through BLV-miRNAs.

The Global Epidemiology of Bovine Leukemia Virus: Current Trends and Future Implications

Bovine leukemia virus (BLV) is a retrovirus that causes enzootic bovine leucosis (EBL), which is the most significant neoplastic disease in cattle. Although EBL has been successfully eradicated in most European countries, infections continue to rise in Argentina, Brazil, Canada, Japan, and the United States. BLV imposes a substantial economic burden on the cattle industry, particularly in dairy farming, as it leads to a decline in animal production performance and increases the risk of disease. Moreover, trade restrictions on diseased animals and products between countries and regions further exacerbate the problem. Recent studies have also identified fragments of BLV nucleic acid in human breast cancer tissues, raising concerns for public health. Due to the absence of an effective vaccine, controlling the disease is challenging. Therefore, it is crucial to accurately detect and diagnose BLV at an early stage to control its spread and minimize economic losses. This review provides a comprehensive examination of BLV, encompassing its genomic structure, epidemiology, modes of transmission, clinical symptoms, detection methods, hazards, and control strategies. The aim is to provide strategic information for future BLV research.

A complex network of transcription factors and epigenetic regulators involved in bovine leukemia virus transcriptional regulation

Bovine Leukemia Virus (BLV) is the etiological agent of enzootic bovine leukosis, a disease characterized by the neoplastic proliferation of B cells in cattle. While most European countries have introduced efficient eradication programs, BLV is still present worldwide and no treatment is available. A major feature of BLV infection is the viral latency, which enables the escape from the host immune system, the maintenance of a persistent infection and ultimately the tumoral development. BLV latency is a multifactorial phenomenon resulting in the silencing of viral genes due to genetic and epigenetic repressions of the viral promoter located in the 5' Long Terminal Repeat (5'LTR). However, viral miRNAs and antisense transcripts are expressed from two different proviral regions, respectively the miRNA cluster and the 3'LTR. These latter transcripts are expressed despite the viral latency affecting the 5'LTR and are increasingly considered to take part in tumoral development. In the present review, we provide a summary of the experimental evidence that has enabled to characterize the molecular mechanisms regulating each of the three BLV transcriptional units, either through cis-regulatory elements or through epigenetic modifications. Additionally, we describe the recently identified BLV miRNAs and antisense transcripts and their implications in BLV-induced tumorigenesis. Finally, we discuss the relevance of BLV as an experimental model for the closely related human T-lymphotropic virus HTLV-1.