title: Loss of the protease dimerization inhibition activity of tipranavir (TPV) and its association with the acquisition of resistance to TPV by HIV-1.
abstract: Tipranavir (TPV), a protease inhibitor (PI) inhibiting the enzymatic activity and dimerization of HIV-1 protease, exerts potent activity against multi-PI-resistant HIV-1 isolates. When a mixture of 11 multi-PI-resistant (but TPV-sensitive) clinical isolates (HIV(11MIX)), which included HIV(B) and HIV(C), was selected against TPV, HIV(11MIX) rapidly (by 10 passages [HIV(11MIX)(P10)]) acquired high-level TPV resistance and replicated at high concentrations of TPV. HIV(11MIX)(P10) contained various amino acid substitutions, including I54V and V82T. The intermolecular FRET-based HIV-1 expression assay revealed that TPV's dimerization inhibition activity against cloned HIV(B) (cHIV(B)) was substantially compromised. The introduction of I54V/V82T into wild-type cHIV(NL4-3) (cHIV(NL4-3(I54V/V82T))) did not block TPV's dimerization inhibition or confer TPV resistance. However, the introduction of I54V/V82T into cHIV(B) (cHIV(B)(I54V/V82T)) compromised TPV's dimerization inhibition and cHIV(B)(I54V/V82T) proved to be significantly TPV resistant. L24M was responsible for TPV resistance with the cHIV(C) genetic background. The introduction of L24M into cHIV(NL4-3) (cHIV(NL4-3(L24M))) interfered with TPV's dimerization inhibition, while L24M increased HIV-1's susceptibility to TPV with the HIV(NL4-3) genetic background. When selected with TPV, cHIV(NL4-3(I54V/V82T)) most readily developed TPV resistance and acquired E34D, which compromised TPV's dimerization inhibition with the HIV(NL4-3) genetic background. The present data demonstrate that certain amino acid substitutions compromise TPV's dimerization inhibition and confer TPV resistance, although the loss of TPV's dimerization inhibition is not always associated with significantly increased TPV resistance. The findings that TPV's dimerization inhibition is compromised with one or two amino acid substitutions may explain at least in part why the genetic barrier of TPV against HIV-1's development of TPV resistance is relatively low compared to that of darunavir.
authors.affiliation: Department of Infectious Diseases, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Aoki
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Danish
authors.forename: Hiromi
authors.initials: H
authors.lastname: Aoki-Ogata
authors.forename: Masayuki
authors.initials: M
authors.lastname: Amano
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ide
authors.forename: Debananda
authors.initials: D
authors.lastname: Das
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Koh
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Mitsuya
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D019281:Dimerization; D024882:Drug Resistance, Viral; D016333:HIV Protease / Q000737:chemistry*; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011725:Pyridines / Q000494:pharmacology*; D011753:Pyrones / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D013449:Sulfonamides
chemical_list: D017931:DNA Primers; D017320:HIV Protease Inhibitors; D011725:Pyridines; D011753:Pyrones; D013449:Sulfonamides; D016333:HIV Protease; C107201:tipranavir