CHARACTERIZATION OF A NOVEL BABOON VIRUS CLOSELY RESEMBLING HUMAN T-CELL LEUKEMIA-VIRUS

We report the isolation of a virus from a baboon imported from Kenya a nd the analysis of the nucleotide sequence of the env gene. Comparison of the complete nucleotide sequence of the env gene of different HTLV -1 strains and the baboon T-cell leukemia virus (designated BTLV) indi cated similarities ranging from 92.5 to 97.4%. In contrast, only 89.1% similarity was observed between the BTLV env sequence and that of sim ian T-cell leukemia virus (PtM3). The sequences corresponding to the g lycosylation sites, endoproteolytic processing site, and major immunol ogical determinants were strictly conserved between BTLV and HTLV-1. T o characterize the expressed protein we used a vaccinia expression sys tem, which indicated that a protein of 62 kDa is encoded by the envelo pe gene. The protein acquired mostly high mannose modifications and wa s localized predominantly in the endoplasmic reticulum. A fraction of the protein was expressed at the cell surface, where it could induce m embrane fusion of target cells. The existence of HTLV-1-like viruses i n baboons indicates the potential risk of transmission of such virus f rom these nonhuman primates to humans, thus highlighting the need for specific screening for such viruses during xenotransplantation. (C) 19 96 Academic Press, Inc.