RESISTANCE OF HIV TYPE-1 TO PROTEINASE-INHIBITOR RO-31-8959

During replication of human inmunodeficiency virus type 1 (HIV-1), pro teolytic cleavage of Gag and Gag-Pol precursor proteins into different functional protein submits is catalyzed by the viral proteinase, and this enzyme is the target of the antiviral proteinase inhibitor, Ro 31 -8959, We investigated in vitro which HIV mutants with reduced sensiti vity to Ro 31-8959 emerged during proteinase inhibition treatment; fro m three different HIV-1 strains, comparable progeny virus resistant to proteinase inhibitor were found, whereas the same experimental protoc ol detected no resistant HIV-2 mutants, Molecular analysis of the muta tions underlying resistance revealed a multistep mechanism in which an amino acid exchange at position 48 of the proteinase from glycine to valine seemed to play an initial role, This amino acid exchange was co mmon to all resistant isolates, and in all experiments preceded furthe r exchanges at position 90 (leucine to methionine) and/or at position 54 (isoleucine to valine), For wild-type strains the 90% inhibitory co ncentrations of Ro 31-8959 were close to 20 nM, whereas HIV-1 mutants with all 3 amino acid exchanges had more than 50-fold increased 90% in hibitory concentrations (above 1000 nM), The primary event (Gly-48 to valine) occurs at the hinge of the flaps of the proteinase, thus hampe ring entry of the inhibitor to the active center and suggesting steric hindrance, Detailed knowledge of this stereotypic process could open inhibitor design, thus preventing conceivable escape of resistant viru s on proteinase inhibitor action.