Figure 2. Vpx delivered to macrophages by SIV_WT infection removes a block to subsequent infection by SIV_Δvpx.

(A) Macrophages were initially infected (1° infection) with envelope deleted SIV variants harboring intact or defective Vpx genes. The nature of the envelope deletion is shown in the lower panel. Those cells were then super-infected (2° infection) with SIV_WT or SIV_Δvpx variants harboring intact envelope genes. cDNA products resulting from the super infection were then specifically amplified using envelope-specific primers. (B) Similar experiment was performed using SIV_WT or SIV_Δvpx for 1° infection and SIV_WT or SIV_Δvpx GFP variants for 2° infection. Number of GFP-positive cells was determined 24 hr post 2° infection (error bars are s.d., n = 3).