Detection and characterization of infectious DNA intermediates of a primary foamy virus

DNA from human T-lymphoid (Molt-4) and hamster kidney (BHK-21) cells infected with the T-lymphotropic simian foamy virus LK-3 was shown to be infectious, when assayed by transfection of BHK-21 cells. The proviral genome was further characterized by blot hybridization to a specific cDNA probe, which had been prepared by reverse transcription in vitro using viral RNA and RNA-dependent DNA polymerase present in cytoplasmic extracts of infected BHK-21 cells. This probe hybridized to a DNA species of 14 kbp in extracts from LK-3-infected diploid human fibroblasts, Molt-4 and BHK-21 cells, whereas no hybridization occurred with DNA from the respective uninfected controls. No integrated proviral DNA could be demonstrated, and the 14 kbp DNA was shown not to represent circular DNA. The patterns of restriction endonuclease and S1 nuclease fragments indicated a unique configuration of linear double-stranded DNA containing a single-stranded section separating two subunits one of which may be sufficient to transmit LK-3 by transfection with DNA.