FIGURE 7.

Trans-dominant effect of very low amounts of specific intermediate cleavage products. 293T cells were co-transfected with a mixture of pNLC4-3 wild-type and the pNLC4-3 variants carrying mutations at specific PR cleavage sites (see scheme in Fig. 1B). At 44 hours post transfection, supernatants and cells were harvested for analysis. A, fraction of the respective incompletely processed forms relative to total Gag was determined by quantitative immunoblot using the indicated polyclonal antisera. The figure shows immunoblots of tissue culture supernatants from cells transfected with mixtures containing between 0 and 100% of the respective mutated plasmid, as indicated above the lanes. Positions of molecular mass standards are indicated at the left (in kDa). Infectivity of virus preparations was determined by single-round infection of TZM-bl cells (B) and TCID₅₀ titration on C8166 cells (C), respectively. Infectivities per ng of CA were normalized to the value for the wild-type control and plotted against the fraction of total Gag represented by the indicated incompletely processed Gag derivative used for titration. Note that relative titers in C are plotted on a logarithmic scale, and infectivities on TZM-bl cells (B) are plotted on a linear scale.