Partial reverse transcripts in virions from human immunodeficiency and murine leukemia viruses

Reverse transcription of the retroviral genome is thought to start after virions enter target cells. Purified preparations of human immunodeficiency virus were found to contain virus-specific DNA, detectable by polymerase chain reaction amplification. This DNA resulted from reverse transcription in newly assembled virus particles and not from contamination by cellular DNA, because virions contained a striking excess of early versus late transcripts and because the accumulation of these products was sensitive to 3'-azido-3'-deoxythymidine (zidovudine) treatment of producer cells. A similar observation was made with murine amphotropic retrovirus particles. It is therefore likely that all retroviruses contain partial reverse transcripts.