FIG 2 .

Emergence of the V32I substitution during the selection of highly DRV-resistant HIV-1 variants but not in HIV^WT and HIV^L33F. (A) Amino acid sequences deduced from the nucleotide sequence of the protease-encoding region (direct sequencing) were determined using proviral DNA. In the selection with DRV, proviral DNA was extracted at week 50 for HIV^WT and HIV^L33F, at week 36 for HIV^V32I, at weeks 7, 24, and 36 for HIV^I54M, at weeks 8, 17 and 29 for HIV^I84V, at week 22 for HIV^V32I/I54M, at week 26 for HIV^L33F/I84V, and at week 17 for HIV^{V32I/L33F/I54M/I84V}. (B) Absence of the V32I substitution in two infectious clones, rHIV^WT and rHIV^L33F, which were selected with DRV over 50 weeks. Two clones, rHIV^WT and rHIV^L33F, selected with DRV over 50 weeks (generating HIV^WT-WK50 and HIV^L33F-WK50, respectively), apparently failed to develop DRV resistance as shown in Fig. 1. To confirm the absence of V32I, HIV^WT-WK50 and HIV^L33F-WK50 were further cloned (20 clones), and each clone generated was sequenced. Note that the V32I substitution did not emerge in either of the virus populations. The consensus sequence of pNL4-3 is illustrated at the top of panels A and B as a reference. Amino acids that are identical to those in the consensus sequence at individual amino acid positions are indicated by dots. The fractions of the virus which each clone is presumed to have originated from over the total number of clones examined are shown to the right of the sequences.