Jörg-Peter Kleim

Changes in human immunodeficiency virus type 1 Gag at positions L449 and P453 are linked to I50V protease mutants in vivo and cause reduction of sensitivity to amprenavir and improved viral fitness in vitro.

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Gag protease cleavage sites (CS) undergo sequence changes during the development of resistance to several protease inhibitors (PIs). We have analyzed the association of sequence variation at the p7/p1 and p1/p6 CS in conjunction with amprenavir (APV)-specific protease mutations following PI combination therapy with APV. Querying a central resistance data repository resulted in the detection of significant associations (P < 0.001) between the presence of APV protease signature mutations and Gag L449F (p1/p6 LP1′F) and P453L (p1/p6 PP5′L) CS changes. In population-based sequence analyses the I50V mutant was invariably linked to either L449F or P453L. Clonal analysis revealed that both CS mutations were never present in the same genome. Sequential plasma samples from one patient revealed a transition from I50V M46L P453L viruses at early time points to I50V M46I L449F viruses in later samples. Various combinations of the protease and Gag mutations were introduced into the HXB2 laboratory strain of HIV-1. In both single- and multiple-cycle assay systems and in the context of I50V, the L449F and P453L changes consistently increased the 50% inhibitory concentration of APV, while the CS changes alone had no measurable effect on inhibitor sensitivity. The decreased in vitro fitness of the I50V mutant was only partially improved by addition of either CS change (I50V M46I L449F mutant replicative capacity ≈ 16% of that of wild-type virus). Western blot analysis of Pr55 Gag precursor cleavage products from infected-cell cultures indicated accumulation of uncleaved Gag p1-p6 in all I50V viruses without coexisting CS changes. Purified I50V protease catalyzed cleavage of decapeptides incorporating the L449F or P453L change 10-fold and 22-fold more efficiently than cleavage of the wild-type substrate, respectively. HIV-1 protease CS changes are selected during PI therapy and can have effects on both viral fitness and phenotypic resistance to PIs.

Absence of zidovudine resistance in antiretroviral-naive patients following zidovudine/lamivudine/protease inhibitor combination therapy: virological evaluation of the AVANTI 2 and AVANTI 3 studies.

ObjectivesTo assess the role of resistance mutations in subjects experiencing virological failure on zidovudine (ZDV) and lamivudine (3TC) combined with a protease inhibitor (PI) to those failing on ZDV/3TC alone. Design and methodsSamples were obtained from previously antiretroviral therapy-naive subjects enrolled into two studies, AVANTI 2 and AVANTI 3. Subjects were randomized to receive either: ZDV/3TC or ZDV/3TC plus indinavir (IDV) for 52 weeks (AVANTI 2), and ZDV/3TC or ZDV/3TC and nelfinavir (NFV) for 28 weeks (AVANTI 3). Emergence of viral resistance mutations was monitored by population sequencing and phenotypic resistance was determined by the recombinant virus assay. ResultsGenotypic data were obtained for subjects with plasma HIV-1 RNAu2004>u2004400 copies/ml. In AVANTI 2, ZDV mutations were detected in 27% of ZDV/3TC-treated patients at week 52, but were absent in subjects treated with ZDV/3TC/IDV. No subjects from either arm of AVANTI 3 developed ZDV resistance mutations at week 28. The M184V mutation developed in most ZDV/3TC-treated subjects from both studies. The presence of M184V was, however, associated with significantly lower plasma viral RNA levels when compared with values obtained before initiation of treatment. There was a high frequency (4 of 11) of the protease L10F substitution in ZDV/3TC/IDV-treated patients that was associated with virological failure but did not result in phenotypic resistance to any of the PIs tested. ConclusionsZDV mutations were not detected in ZDV/3TC/PI-treated patients and they developed slowly in those treated with ZDV/3TC. Few protease mutations known to confer phenotypic PI resistance developed in the ZDV/3TC/PI arms of either study. The low prevalence of ZDV and PI mutations is encouraging regarding the future treatment options of these patients.

Mutations in the non-nucleoside binding-pocket interfere with the multi-nucleoside resistance phenotype.

ObjectivesTo investigate the genotypic and phenotypic effects of in vitro resistance selection with lamivudine and/or the second generation non-nucleoside reverse transcriptase inhibitor (NNRTI) quinoxaline HBY097 using HIV-1 isolates carrying the multi-nucleoside resistance pattern linked to the Q151M mutation. MethodsVirus strains were selected in C8166 cells in the presence of increasing concentrations of lamivudine or HBY097. In parallel control experiments, the virus was cultured in C8166 cells in the absence of drugs. The entire reverse transcriptase encoding region was amplified using polymerase chain reaction and was subsequently sequenced. Antiviral activities of drugs were evaluated in C8166 cells. ResultsHigh-level resistant viruses were selected rapidly in the presence of lamivudine and quinoxaline (less than 10 passages). The multi-nucleoside resistance mutations were stable during in vitro resistance selection. Lamivudine elicited the acquisition of the M184I mutation. Phenotypic resistance to all nucleoside-analog reverse transcriptase inhibitors (NRTIs) was increased when M184I was added to the multi-nucleoside resistance background in the absence of NNRTI-resistance mutations. In most cases of HBY097 resistance selection, at least two mutations associated with NNRTI resistance resulted in high-level NNRTI resistance. The NNRTI resistance-related mutations partially reversed the phenotypic resistance to most NRTIs, except to abacavir. The addition of the M184I mutation to the NNRTI-multi-nucleoside resistance set abolished this antagonizing effect for didanosine, zalcitabine and lamivudine, but further potentiated the phenotypic reversal for zidovudine and stavudine. ConclusionChanges in the non-nucleoside binding pocket must affect the conformation of residues at the dNTP binding site, and can result in a partial phenotypic reversal of the multi-nucleoside resistance phenotype.

Antiviral Activity of the Human Immunodeficiency Virus Type 1—Specific Nonnucleoside Reverse Transcriptase Inhibitor HBY 097 Alone and in Combination with Zidovudine in a Phase II Study

The safety and antiviral activity of the second-generation nonnucleoside inhibitor HBY 097 was investigated in asymptomatic or mildly symptomatic human immunodeficiency virus (HIV)-1-infected patients in a randomized, double-blinded, dose-escalation study. Mean maximum virus load decreases ranged from -1.31 log10 copies/mL of plasma at week 1 in the group receiving HBY 097 monotherapy (250 mg three times daily) to -2.19 log10 copies/mL at week 4 in the group receiving zidovudine plus HBY 097 (750 mg three times daily). After 12 weeks, these patients had viral RNA copy numbers 1.05 log10 below baseline. Genotypic analysis of resistance development revealed reverse transcriptase K103N variants in most patients, which was associated with less durable efficacy of HBY 097 treatment. Fewer patients receiving combination therapy with high-dose HBY 097 developed the K103N variant (P<.01). HBY 097 caused pronounced acute suppression of HIV-1 replication both in combination with zidovudine and alone. Therefore, sustained antiviral activity can be expected from multiple combination therapy regimens including a quinoxaline derivative.

Zidovudine-Resistant Human Immunodeficiency Virus Type 1 Strains Subcultured in the Presence of Both Lamivudine and Quinoxaline HBY 097 Retain Marked Sensitivity to HBY 097 but Not to Lamivudine

Replication of zidovudine-resistant human immunodeficiency virus type 1 (HIV-1) strains (containing the 41 Met-->Leu and 215 Thr-->Tyr mutations in reverse transcriptase [RT]) was inhibited to a significantly greater extent by the combination of lamivudine and quinoxaline HBY 097 than by either drug alone or even fully suppressed by concomitant HBY 097 and lamivudine administration at relatively low concentrations. The virus recovered after exposure to the drug combinations individually had acquired the 103 Lys-->Arg, 138 Glu-->Lys, 184 Met-->Ile, and 189 Val-->Ile mutations in the genetic zidovudine-resistance background of zidovudine-resistant HIV-1. These mutants retained marked sensitivity to HBY 097. The genotypic zidovudine-resistance mutations were maintained in the mutant virus RT genomes, and the viruses also remained phenotypically resistant to zidovudine. Given the exquisite potency of the combination of lamivudine and HBY 097 in suppressing viral replication, this combination should be further pursued in clinical trials examining treatment of HIV-1-infected persons.