MULTIPLE MUTATIONS IN THE HUMAN-IMMUNODEFICIENCY-VIRUS PROTEASE GENE ARE RESPONSIBLE FOR DECREASED SUSCEPTIBILITY TO PROTEASE INHIBITORS

The protease (PR) of the human immunodeficiency virus (HIV) is essenti al for replication of the virus, and accordingly has become an attract ive target for the development of an antiretroviral drug, We have prev iously reported that passage of HIV-1 in the presence of increasing co ncentrations of the C-2 symmetrical, linear diol P9941 resulted in the isolation of virus with a valine-to-alanine change at position 82 (V8 2A) of the PR, and reduced sensitivity to certain PR inhibitors, In th is study, we passaged four different variants of HIV-1 in increasing c oncentrations of XM323, and isolated variants with reduced sensitivity to inhibitors of PR, Twenty-three passages of HIV-1 (RF) in the prese nce of XM323 resulted in a variant that exhibited an approximately 100 -fold reduction in susceptibility to XM323 and that contained V82F and 184V changes, When two other viruses, HIV-1(RF41D2) and HIV-1(RF41E4) , previously derived from HIV-1 (RF) by passage in the presence of P99 41, were passaged in the presence of XM323, variants with V82A/L97V an d M46/V82A/L97V changes, respectively, were obtained, The M46L/V82A/L9 7V variant showed a 6-fold reduction in sensitivity to XM323, whereas the susceptibility of the V82A/L97V mutant remained unchanged, Sevente en passages of a clinical isolate of HIV-1, HIV-1 (Pat.E), in the pres ence of XM323 produced a V82F/L97V mutant with an approximately 9-fold reduction in sensitivity to XM323.