AN EVOLUTIONARILY CONSERVED SPLICE GENERATES A SECRETED ENV-BET FUSION PROTEIN DURING HUMAN FOAMY VIRUS-INFECTION

Foamy viruses (spumaretroviruses) represent a retroviral genus which e xhibits unusual features relating it to pararetroviruses. Previously, we reported the existence of a protein species harboring Env, Eel, and Bet epitopes in human foamy virus (HFV)-infected cells (M. L. Giron, F. Retain, M. C. Debons-Guillemin, M. Canivet, J. Peries, and R. Emano il-Ravier, J. Virol, 67:3596-3600, 1993). Here, we identify this prote in as a 160-kDa Env-Bet fusion glycoprotein (gp160) translated from an mRNA species harboring a highly conserved splice site which deletes t he membrane anchor domain of En, and fuses the env open reading frame with that of bel1/bet. While gp160 and Bet proteins were both secreted into the supernatant, only Bet was taken up by recipient cells, Since Bet plays a key role in the snitch from lytic to chronic infection, s ecretion of Bet and gp160, together with cellular uptake of Bet, could be highly relevant for both immune response and development of HFV in fection in vivo.