Semen-Derived Exosomes Mediate Immune Escape and Transmission of Reticuloendotheliosis Virus

Reticuloendotheliosis virus (REV) causes immune-suppression disease in poultry, leading to a significant economic burden worldwide. Recent evidence demonstrated that the REV can enter the semen and then induce artificial insemination, but how the virus gets into semen was little known. Accumulating studies indicated that exosomes serve as vehicles for virus transmission, but the role of exosomes in viral shedding through the semen remains unclear. In this study, exosomes purified from the REV-positive semen were shown with reverse transcription-PCR and mass spectrometry to contain viral genomic RNA and viral proteins, which could also establish productive infections both in vivo and in vitro and escape from the REV-specific neutralizing antibodies. More importantly, compared with the infection caused by free virions, the exosome is more efficient for the virus to ensure effective infection and replication, which can also help the REV compromise the efficacy of the host immune response. In summary, this study demonstrated that semen-derived exosomes can medicate the transmission and immune escape of REV, implicating a novel mechanism for REV entering the semen and leading to vertical transmission.

Reticuloendotheliosis in breeder turkeys

Reticuloendotheliosis virus (REV) was isolated at 21 weeks from a flock of breeder turkeys with lymphoid neoplasms. Except for about 2% mortality due to tumors mainly between 20 and 30 weeks of age, the livability and egg production of the flock were normal. Egg transmission as a source of infection seemed unlikely, because no REV antibodies or production problems were observed in two sister flocks (hatchmates) and in three progeny flocks, and because eggs obtained from the breeder flock at 45 weeks lacked REV group-specific antigen and produced poults negative for REV infection. The virus isolate, designated REV strain 339, produced an acute neoplastic disease when inoculated into young chickens.