Morphologic changes in human immunodeficiency virus type 1 virions secondary to intravirion reverse transcription - Evidence indicating that reverse transcription may not take place within the intact viral core

Introduction: In the past, retroviral endogenous reverse transcription (ERT ) was considered an artificial process, secondary to permeabilization of th e viral envelope by detergents or amphipathic peptides. However, recently a re have demonstrated that ERT may occur in a variety of lentiviruses withou t detergent treatment and may lead ro increased infectivity of lentivirions in initially quiescent T lymphocytes and nonproliferating cells, such as m acrophages. As full-length reverse transcripts could be synthesized within lentiviral particles, it is worth evaluating the potential alterations in l entiviral morphology due to the stimulation of intravirion reverse transcri ption, Methods: Using quantitative DNA-polymerase chain reaction (PCR) and transmi ssion electron microscopy (TEM), we characterized critical alterations in h uman immunodeficiency virus type 1 (HTV-1) virions after stimulation of int ravirion reverse transcription. Results: Intravirion reverse transcription in HTV-1 virions was stimulated using deoxyribonucleoside triphosphates (dNTPs) and physiologic polyamines. Our studies indicated that HTV-1 virions, in which intravirion reverse tra nscription was stimulated, showed dissolution of the p24-shelled viral core and absence of the core-envelope linkage (CEL) region by TEM. These change s in the structure of the core correlate with the in vitro alterations in v irion infectivity on primary cells. Conclusions: Stimulation of intravirion HN-I reverse transcription leads to morphologic changes in the viral particles that suggest changes in the com pact viral core, which is consistent with active reverse transcription befo re infection of target cells. Further, via this unique approach, we suggest that intravirion or intracellular reverse transcription of HTV-1 is unlike ly to take place within intact viral cores made up of p24-containing outer shells. As such, these results suggest a new approach to further dissect th e intravirion or intracellular reverse transcription machinery of lentiviru ses.