CD4 expressing human 293 cells as a tool for studies in HIV-1 replication: the efficiency of translational frameshifting is not altered by HIV-1 infection.

An adherent human cell line (293) was made susceptible for HIV-1 infection by transfer of a CD4 expression plasmid. These cells could be infected with HIV-1 and produced infectious virus up to a titer of 10(6) TCID50/ml releasing p24 protein up to 1 micrograms/ml. Since they can be efficiently transfected with reporter genes, these cells are a suitable model system to monitor biochemical events during productive infection of HIV-1 and can be used for antiviral drugs. Translational frameshifting determines the balance of the structural Gag versus the catalytic Pol proteins which is probably crucial for correct virus assembly. We have genetically engineered CD4 expressing 293 cells with a sensitive in vivo reporter system to monitor the extent of frameshifting in HIV-1-infected versus uninfected cells. During the time course of productive HIV-1 infection the low efficiency of ribosomal frameshifting is not altered.