A novel approach for producing lentiviruses that are limited to a single cycle of infection.
We have devised a novel approach for producing simian immunodeficiency virus (SIV) strains and, potentially, human immunodeficiency virus type 1 (HIV-1) strains that are limited to a single cycle of infection. Unlike previous lentiviral vectors, our single-cycle SIV is capable of expressing eight of the nine viral gene products and infected cells release immature virus particles that are unable to complete subsequent rounds of infection. Single-cycle SIV (scSIV) was produced by using a two-plasmid system specifically designed to minimize the possibility of generating replication-competent virus by recombination or nucleotide reversion. One plasmid carried a full-length SIV genome with three nucleotide substitutions in the gag-pol frameshift site to inactivate Pol expression. To ensure inactivation of Pol and to prevent the recovery of wild-type virus by nucleotide reversion, deletions were also introduced into the viral pol gene. In order to provide Gag-Pol in trans, a Gag-Pol-complementing plasmid that included a single nucleotide insertion to permanently place gag and pol in the same reading frame was constructed. We also mutated the frameshift site of this Gag-Pol expression construct so that any recombinants between the two plasmids would remain defective for replication. Cotransfection of both plasmids into 293T cells resulted in the release of Gag-Pol-complemented virus that was capable of one round of infection and one round of viral gene expression but was unable to propagate a spreading infection. The infectivity of scSIV was limited by the amount of Gag-Pol provided in trans and was dependent on the incorporation of a functional integrase. Single-cycle SIV produced by this approach will be useful for addressing questions relating to viral dynamics and viral pathogenesis and for evaluation as an experimental AIDS vaccine in rhesus macaques.
New England Primate Research Center, Harvard Medical School, Southborough, Massachusetts, USA. dte@u.washington.edu.
David T
DT
Evans
Jennifer E
JE
Bricker
Ronald C
RC
Desrosiers
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D016368:Frameshift Mutation; D015685:Fusion Proteins, gag-pol / Q000502:physiology; D015751:Genes, pol; D016341:Genes, vif; D006801:Humans; D008253:Macaca mulatta; D008264:Macrophages / Q000821:virology; D008969:Molecular Sequence Data; D015302:Simian Immunodeficiency Virus / Q000502:physiology*; D013601:T-Lymphocytes / Q000821:virology; D014771:Virion / Q000502:physiology; D014779:Virus Replication
D015685:Fusion Proteins, gag-pol