Co-expression of Bovine leukemia virus and Bovine foamy virus-derived miRNAs in naturally infected cattle

MicroRNAs (miRNAs) derived from viruses play a central role in modulating the expression of both viral and host gene, facilitating immune evasion, viral persistence, and pathogenesis. Among the viruses that encode miRNAs and infect cattle such as Bovine leukemia virus (BLV), Bovine foamy virus (BFV), Bovine herpesvirus type 1 (BoHV-1), and Bovine herpesvirus type 5 (BoHV-5), BLV has gained increasing attention due to the critical role that BLV-miRNAs may play in inducing leukemia and lymphoma in infected animals. BLV is highly prevalent in the Americas and has a negatively affects dairy herds, primarily due to restrictions on the commercialization of dairy products from infected animals and a decrease in milk production.

Mixed infections involving BLV and BFV appear to be common in cattle. Considering the ability of foamy viruses to cross species barriers, preventing their presence within the food chain is essential. In this study, through small RNA sequencing, we identified the co-expression of seven BLV-derived miRNAs ( blv-miR-B1-3p , blv-miR-B2-5p , blv-miR-B2-3p , blv-miR-B3-5p , blv-miR-B3-3p , blv-miR-B4-3p, and blv-miR-B5-5p ) and three BFV-derived ( bfv-miR-BF1-5p , bfv-miR-BF1-3p , and bfv-miR-BF2-5p ) in naturally BLV-infected cattle, while no BoHV-1/5 miRNAs were detected. A differential expression analysis revealed seven bovine miRNAs ( bta-miR-375 , bta-miR-133a , bta-miR-677 , bta-miR-1, bta-miR-3613a , bta-miR-9-5p , and bta-miR-95 ) with altered expression levels (fold change > |1.5| and q-value < 0.05) between cows with a high BLV proviral load (PVL) and uninfected counterparts. A comprehensive functional analysis of protein-protein interaction networks for genes targeted by both viral and host-derived miRNAs highlighted key pathways implicated in tumorigenesis and the regulation of the immune response. Notably, bta-miR-375 , previously proposed as an early biomarker for the progression of enzootic bovine leukosis progression, exhibited differential expression in cows with elevated PVL, reinforcing its diagnostic potential. The functional interaction among miRNAs derived from BLV and BFV raises important concerns regarding their potential influence on disease severity and the increased dissemination of BFV. The findings derived from this study offer new perspectives for creating diagnostic and treatment approaches to manage viral persistence and tumor growth in cattle.