FIG. 2.

Single-cycle infectivity of recombinant viruses carrying pretherapy (gray bars) or postresistance (blade bars) HIV protease sequences from patients treated with protease inhibitors. The single-cycle titer of each recombinant virus carrying the postresistance protease was measured by titration on P4 (HeLa-CD4 LTR-LacZ) cells and expressed as a percentage of the titer of the pretherapy virus from the same patient. Postresistance viruses from patients 202, 401, 402, and 506 are resistant to ritonavir; postresistance virus from patient 246 is resistant to saquinavir. Viral input was normalized according to the HIV-1 p24 antigen content of transfected HeLa cell supernatants. The results presented are the mean standard deviation for at least three separate titration experiments for three different transfections.