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Updated: May 6, 2026
Purification of High Yield Extracellular Vesicle Preparations Away from Virus
Published on: September 12, 2019
Cell Infectivity in relation to bovine leukemia virus gp51 and p24 in bovine milk exosomes
Tetsuya Yamada1, Hiroaki Shigemura, Naotaka Ishiguro
1Department of Veterinary Medicine, Gifu University, Gifu, Japan.
Abstract:
Exosomes are small membranous microvesicles (40-100 nm in diameter) and are extracellularly released from a wide variety of cells. Exosomes contain microRNA, mRNA, and cellular proteins, which are delivered into recipient cells via these exosomes, and play a role in intercellular communication. In bovine leukemia virus (BLV) infection of cattle, although it is thought to be a minor route of infection, BLV can be transmitted to calves via milk. Here, we investigated the association between exosomes and BLV in bovine milk. BLV structural proteins, gp51 (Env) and p24 (Gag), were detected in bovine milk exosomes from BLV-infected cattle by Western blot analysis. In cells inoculated with these milk exosomes, BLV DNA was not detected during three serial passages by nested PCR. Purification of exosomes from persistently BLV-infected cells was achieved by immuno-magnetic separation using an antibody against exosomes coupled to magnetic beads. Consistently, BLV gp51 and p24 proteins were detected in purified exosomes. Moreover, reverse transcriptase activity was observed in purified exosomes, meaning that exosomes also contain viral enzyme. However, BLV DNA was not detected in serially passaged cells after inoculation of purified exosomes, indicating that exosomes carrying BLV proteins appeared to be not infectious. These results suggest that BLV proteins are released with milk exosomes and could be transferred into recipient cells of calves via milk exosomes as an alternative route not requiring virus infection. Moreover it is also possible that bovine milk exosomes play a role in clearance of BLV proteins from infected cells.
Insights
Bovine leukemia virus (BLV) proteins are found in milk exosomes from infected cattle. These exosomes transfer BLV proteins to recipient cells, suggesting a non-infectious transmission route for calves.
Area of Science:
- * Cell biology
- * Virology
- * Immunology
Background:
- * Exosomes are microvesicles involved in intercellular communication, carrying proteins and nucleic acids.
- * Bovine leukemia virus (BLV) can be transmitted to calves through milk, though this route is considered minor.
- * The role of exosomes in BLV transmission and pathogenesis remains largely unexplored.
Purpose of the Study:
- * To investigate the presence and role of exosomes in the context of BLV infection in cattle.
- * To determine if BLV proteins are associated with exosomes in bovine milk.
- * To assess the infectivity of BLV-associated exosomes.
Main Methods:
- * Western blot analysis to detect BLV proteins (gp51, p24) in milk exosomes.
- * Immuno-magnetic separation for exosome purification from infected cells.
- * Nested PCR to detect BLV DNA in cells after exosome inoculation.
- * Assay for reverse transcriptase activity in purified exosomes.
Main Results:
- * BLV structural proteins (gp51, p24) were detected in exosomes from BLV-infected cattle milk.
- * Purified exosomes from BLV-infected cells contained BLV proteins and reverse transcriptase activity.
- * Inoculation of cells with these exosomes did not lead to detectable BLV DNA, indicating lack of infectivity.
Conclusions:
- * Bovine milk exosomes carry BLV proteins, potentially serving as a non-infectious route for protein transfer to calves.
- * Exosomes may facilitate the transfer of BLV proteins, independent of infectious virus particles.
- * Bovine milk exosomes might play a role in clearing BLV proteins from infected cells.
