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12th International Drug Resistance Workshop10–14 June 2003, Cabo del Sol, Los Cabos, Mexico |
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Plenary Abstract Abstract 1, Page S1 |
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| 1 | MECHANISMS OF HIV-1 DIVERSITY Antiviral Therapy 2003;8:S1 B Korber The rate of base substitution is extraordinarily high, and modelling the evolution of these changes enables phylogenetic reconstructions of HIV viruses. But HIV has other mechanisms of variation that can result in immune evasion including recombination, shifting glycosylation patterns, insertions and deletions, and action at a distance through conformational change.  Download Session 1 PDF: Abstracts 1 to 27
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Session 1: Resistance to New Antiretroviral Agents Abstract 2 thru 27, Pages S1 to S30 |
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| 2 | ELVUCITABINE: POTENT ANTIVIRAL ACTIVITY DEMONSTRATED IN MULTI-DRUGRESISTANT HIV INFECTION Antiviral Therapy 2003;8:S5 LM Dunkle1, JC Gathe2, DE Pedevillano1, HG Robison1, WG Rice1, JC Pottage Jr1 and the ACH-006 Study Team ELV demonstrated potent anti-HIV activity in patients with multidrug-resistant HIV, comparable or superior to other potential 'salvage' therapies, with a convenient single daily oral dose. Doses of 50 and 100 mg/day were similarly potent; the safety profile of 50 mg daily was more desirable than 100 mg. Further study with doses up to 50 mg daily is warranted to identify the optimum dose for long-term clinical development of ELV in this population with limited treatment options. Download Session 1 PDF: Abstracts 1 to 27
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| 3 | ANTIVIRAL ACTIVITY OF SPD754 AGAINST CLINICAL ISOLATES OF HIV-1 RESISTANT TO OTHER NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITORS Antiviral Therapy 2003;8:S6 RC Bethell1, N Parkin2 and Y Lie2 The presence of up to five mutations at codons 41, 67, 70, 210, 215 and 219 of RT confers no more than a twofold reduction in median sensitivity to SPD754. Mutation at codon 184 of RT is associated with a 1.8-fold reduction in sensitivity to SPD754. Download Session 1 PDF: Abstracts 1 to 27
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| 4 | SYNTHESIS AND ANTI-HIV ACTIVITY OF ENANTIOMERICALLY PURE D-FDOC Antiviral Therapy 2003;8:S7 S Mao1, M Bouygues1, DC Liotta1, RF Schinazi2, C Welch3, M Biba3, and J Chilenski3 Herein, we describe a synthetic approach that employs a tandem kinetic resolution/chiral salt crystallization protocol for preparing the D-enantiomer of FDOC in high enantiopurity. In addition, we report conditions that allow for the racemization and recycling of the unwanted butyrate ester of the L-enantiomer of FDOC. Download Session 1 PDF: Abstracts 1 to 27
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| 5 | IN VITRO INDUCTION OF HIV VARIANTS WITH REDUCED SUSCEPTIBILITY TO ELVUCITABINE (ACH-126,443, β-L-FD4C) Antiviral Therapy 2003;8:S8 J Fabrycki, Y Zhao, J Wearne, Y Sun, A. Agarwal, M Deshpande,WG Rice and M Huang An in vitro resistance induction study was performed with elvucitabine. The resulting variant with reduced susceptibility carried mutations at amino acid 184 (M to I) and 237 (D to E). The D237E mutation has not been described previously and its role in the generation of resistance variant is under investigation. The double mutation conferred moderate resistance to elvucitabine (approximately 10-fold shift in EC50). A computational model is proposed to explain the phenomenon. Download Session 1 PDF: Abstracts 1 to 27
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| 6 | ANTIVIRAL ACTIVITY OF THE NUCLEOSIDE REVERSET FOLLOWING SINGLE ORAL DOSES IN HIV-1-INFECTED PATIENTS Antiviral Therapy 2003;8:S9 L Stuyver1, TR McBrayer1, RL Murphy1,2, D Schürmann3, I Kravec3, A Beard1, RF Schinazi4, A De La Rosa1 and MJ Otto1 RVT reduced the HIV-1 viral load after a single dose by a mean of 0.4 log10 for all doses tested. One subject infected with a mutant virus responded as well as subjects infected with wild-type virus. Download Session 1 PDF: Abstracts 1 to 27
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| 7 | CHARACTERIZATION OF BASELINE AND TREATMENT-EMERGENT RESISTANCE MUTATIONS FOLLOWING 1 YEAR OF THERAPY ON AN ENTIRELY ONCE A DAY REGIMEN INCLUDING EMTRICITABINE Antiviral Therapy 2003;8:S10 K Borroto-Esoda, J Waters, JB Quinn, A Shaw, J Hinkle and F Rousseau for the FTC-301 Study Team These results demonstrate that a regimen containing once daily FTC was statistically superior to twice-daily d4T, in a background of oncedaily ddI plus EFV, with a significantly lower rate of VF with fewer mutations, even after adjusting for the prevalence of baseline mutations. Download Session 1 PDF: Abstracts 1 to 27
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| 8 | ANTIVIRAL ACTIVITY OF TMC125, A POTENT NEXT-GENERATION NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI), AGAINST >5000 RECOMBINANT CLINICAL ISOLATES EXHIBITING A WIDE RANGE OF NNRTI RESISTANCE Antiviral Therapy 2003;8:S11 J Vingerhoets1, H Van Marck1, J Veldeman2, M Peeters1, P McKenna2, R Pauwels1 and M-P de Béthune1 TMC125 is a potent next-generation NNRTI, with activity against most of recently circulating strains of HIV, including samples that are resistant to all marketed NNRTIs. The antiviral activity against class-associated NNRTI resistance together with the increased genetic barrier to development of resistance, are unique features of TMC125. Download Session 1 PDF: Abstracts 1 to 27
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| 9 | CHARACTERIZATION OF RESISTANCE BEFORE AND AFTER SHORT-TERM THERAPY WITH TMC125 IN PATIENTS WITH DOCUMENTED NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR RESISTANCE Antiviral Therapy 2003;8:S12 J Vingerhoets1, M Peeters1, H Azijn1, C Jordens2, P McKenna2, L Bacheler1, G Van ’t Klooster1, R Pauwels1 and M-P de Bethune1 TMC125 is effective in suppressing resistant HIV strains from patients failing on an NNRTI-containing regimen and with phenotypic evidence of resistance. No evidence has been found that TMC125 selected for increased resistance during 7 days of treatment. By overcoming class-associated NNRTI resistance, TMC125 is considered to be a next-generation NNRTI. Download Session 1 PDF: Abstracts 1 to 27
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| 10 | THE IDENTIFICATION OF ACTIVE SITE MUTATIONS THAT CONFER RESISTANCE TO STRUCTURALLY DIVERSE INHIBITORS OF HIV-1 INTEGRASE STRAND TRANSFER SUPPORTS A GENERAL MECHANISM OF PHOSPHOTRANSFERASE INHIBITION Antiviral Therapy 2003;8:S13 DJ Hazuda and the MRL HIV-1 Drug Discovery Team These analyses demonstrate it is possible to identify integrase inhibitors with distinct resistance profiles, however there appears to be a significant potential for cross resistance between many such compounds (such as, S-1360 and L-870810) despite their apparent differences in structure. Localization of the critical determinants for resistance to the integrase active site is consistent with biochemical studies that demonstrate these inhibitors function by sequestering the active site metals in integrase and the observation that similar compounds have been identified which inhibit mechanistically- related metal-dependent phosphotransferases such as HIV-1 RNase H. Download Session 1 PDF: Abstracts 1 to 27
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| 11 | MAPPICINE INHIBITORS OF HIV-1 REVERSE TRANSCRIPTASE-ASSOCIATED RIBONUCLEASE H Antiviral Therapy 2003;8:S14 MM Hossain1, W Zhang2, D Curran3 and MA Parniak1 The good antiviral activity in the absence of significant cytotoxicity suggest that mappicine analogues may represent an interesting new class of antiretroviral agents, those targeting RT-associated RNase H. Structural variants of mappicines are readily prepared by combinatorial methods, and it is therefore expected that improvements in antiviral potency may be attained. Download Session 1 PDF: Abstracts 1 to 27
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| 12 | CHARACTERIZATION OF THE IMPACT OF GENOTYPE, PHENOTYPE, AND INHIBITORY QUOTIENT ON ANTIVIRAL ACTIVITY OF TIPRANAVIR IN HIGHLY TREATMENT-EXPERIENCED PATIENTS Antiviral Therapy 2003;8:S15 S McCallister1, V Kohlbrenner1, K Squires2, A Lazzarin3, P Kumar4, E DeJesus5, J Nadler6, J Gallant7, S Walmsley8, P Yeni9, J Leith1, C Dohnanyi1, D Hall1, JP Sabo1, TR MacGregor1, W Verbiest10, P McKenna10 and D Mayers1 This analysis has determined that a good response to TPV is maintained in the presence of <3 UPAMs, IC50 <twofold WT, and IQ >50. Importantly, over two-thirds of patients, even in this HTE population, met these criteria. Considering that most HIV-1 isolates remain fully susceptible to TPV until a large number of protease gene mutations (>15) are present, this high IQ suggests that TPV/r will provide an important option for the majority of HTE HIV-1-positive patients. Download Session 1 PDF: Abstracts 1 to 27
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| 13 | CHARACTERIZATION OF TREATMENT-EMERGENT RESISTANCE MUTATIONS IN TWO PHASE II STUDIES OF TIPRANAVIR Antiviral Therapy 2003;8:S16 D Hall, S McCallister, D Neubacher, M Kraft and DL Mayers Analysis of HIV-1 viral isolates from patients enrolled in studies of treatment-experienced patients has identified several mutations that emerged during TPV/r treatment of patients with a mean of approximately 10 baseline protease gene mutations. The most frequent mutations seen in this study at codons 33, 82 and 84 are UPAMs located in the protease active site. The presence of ≥2 of these mutations, therefore, appears to require the accumulation of 16–20 other protease mutations, and may have important implications for the fitness of TPV-resistant HIV- 1. Few patients in these studies accumulated >2 UPAMs. Download Session 1 PDF: Abstracts 1 to 27
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| 14 | CHARACTERIZATION OF HIV-1 SHOWING DECREASED SUSCEPTIBILITY TO TIPRANAVIR AND THEIR INHIBITION BY TIPRANAVIR-CONTAINING DRUG MIXTURES Antiviral Therapy 2003;8:S17 L Doyon, S Tremblay, E Wardrop, R Maurice, D Thibeault, J Archambault and MG Cordingley Resistance to TPV involves multiple mutations in the protease gene and leads to a reduced sensitivity to most other PIs and to a decreased replication capacity of viruses. TPV, however, maintains mostly additive effects on TPV-resistant or wild-type virus when used in combination with the protease inhibitors APV and LPV. Download Session 1 PDF: Abstracts 1 to 27
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| 15 | TMC114, A POTENT NEXT-GENERATION PROTEASE INHIBITOR: CHARACTERIZATION OF ANTIVIRAL ACTIVITY IN MULTIPLE PROTEASE INHIBITOR-EXPERIENCED PATIENTS PARTICIPATING IN A PHASE IIA STUDY Antiviral Therapy 2003;8:S18 S De Meyer1, M Peeters1, C Jordens2, P McKenna2, R van der Geest1, R Pauwels1 and M-P de Bethune1 This study demonstrates the potent antiviral activity of TMC114, a next-generation PI, in multiple PI-experienced patients over 14 days. No mutation patterns influencing the response to treatment with TMC114 could be detected in this study. Download Session 1 PDF: Abstracts 1 to 27
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| 16 | TMC114 BINDS WITHIN THE SUBSTRATE ENVELOPE OF HIV-1 PROTEASE, WHICH COULD ACCOUNT FOR ITS EFFICACY AGAINST MULTI-PROTEASE INHIBITOR-RESISTANT VIRUS Antiviral Therapy 2003;8:S19 N King1, M Prabu-Jeyabalan1, P Wigerinck2, M-P de Béthune2 and CA Schiffer1 Many drug-resistant variants of HIV protease evolve to maintain substrate recognition while compromising inhibitor binding, especially when the inhibitors extend beyond the substrate envelope. The fact that TMC114 fits well within the substrate envelope, associated with its tight binding to the enzyme, therefore, could account for why TMC114 remains active against most multi-PI-resistant variants. Hence, a mutation that affects TMC114 binding will likely cause a dramatic change in the ability of HIV-1 protease to recognize its substrates. This may also explain why selection of TMC114-resistant virus in vitro has proven difficult, as this might require changes beyond the protease gene, most probably in the cleavage sites. These results support our previous hypothesis that inhibitors that fit within the substrate envelope of HIV-1 protease may be more effective and less susceptible to drug resistance mutations. Download Session 1 PDF: Abstracts 1 to 27
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| 17 | ANTIVIRAL ACTIVITY OF TMC114, A POTENT NEXT-GENERATION PROTEASE INHIBITOR, AGAINST >4000 RECENT RECOMBINANT CLINICAL ISOLATES EXHIBITING A WIDE RANGE OF (PROTEASE INHIBITOR) RESISTANCE PROFILES Antiviral Therapy 2003;8:S20 S De Meyer1, H Van Marck1, J Veldeman2, P McKenna2, R Pauwels1 and M-P de Béthune1 TMC114 is a potent, next-generation PI with activity against a wide range of PI-resistant recombinant clinical isolates. This activity, defined by a median fold change of <4, extended to isolates resistant to all currently-approved PIs and also to isolates carrying up to four primary PI mutations. Download Session 1 PDF: Abstracts 1 to 27
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| 18 | IN VITRO CROSS RESISTANCE PROFILE OF RO033-4649 AGAINST A PANEL OF MULTIPLY-SUBSTITUTED PROTEASE INHIBITOR-RESISTANT VIRUSES: ROLE OF COMMON PROTEASE RESISTANCE MUTATIONS Antiviral Therapy 2003;8:S21 G Heilek-Snyder1, A Kohli1, N Cammack1 and N Parkin2 (1) An average of 14 mutations are required before RO033-4649 demonstrates a loss of susceptibility greater than 20-fold. (2) In a background of multiple (10–18) resistance mutations and polymorphisms, clinical samples carrying G73C, S or T show reduced susceptibility to RO033-4649. (3) In a background of seven pre-existing resistance mutations, V32I and I54V arose under drug pressure, confirming the requirement of multiple mutations to confer reduced susceptibility to RO033-4649. Download Session 1 PDF: Abstracts 1 to 27
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| 19 | HIV CLINICAL ISOLATES CONTAINING MUTATIONS REPRESENTATIVE OF THOSE SELECTED AFTER FIRST-LINE FAILURE WITH UNBOOSTED GW433908 REMAIN SENSITIVE TO OTHER PROTEASE INHIBITORS Antiviral Therapy 2003;8:S22 L Ross1, N Parkin2, C Chappey2, M Tisdale3 and R Elston3 Clinical isolates with mutational patterns similar to those selected by unboosted 908 remain sensitive to most other PIs, suggesting that viruses present after treatment failure of an unboosted 908 regimen will respond to second-line PI-containing therapy. Download Session 1 PDF: Abstracts 1 to 27
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| 20 | ANTIVIRAL ACTIVITY OF P-1946, A NOVEL ANTI-HIV PROTEASE INHIBITOR Antiviral Therapy 2003;8:S23 G Sévigny1, B Tian1, A Dubois1, B Stranix1, G Sauvé4, C Petropoulos2, Y Lie2, N Hellmann2, B Conway3 and J Yelle1 P-1946 is an amino acid derivative typical of a new family of PIs. Its antiviral activity profile makes it a good lead compound for the development of new potent agents that would offer therapeutic alternatives for individuals carrying isolates resistant to current PIs. Download Session 1 PDF: Abstracts 1 to 27
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| 21 | BASELINE AND ON-TREATMENT GP41 GENOTYPE AND SUSCEPTIBILITY TO ENFUVIRTIDE (ENF) AND T-1249 IN A 10-DAY STUDY OF T-1249 IN PATIENTS FAILING AN ENF-CONTAINING REGIMEN (T1249-102) Antiviral Therapy 2003;8:S24 GD Miralles1, T Melby1, R DeMasi1, Y Zhang1, R Spence1, N Cammack2, TJ Matthews1 and M Greenberg1 T-1249 retains antiviral activity in most patients experiencing viral replication in the presence of isolates with reduced susceptibility to ENF and/or changes in the target region of ENF. Treatment emergent amino acid substitutions in gp41 and reduced susceptibility to T-1249 were identified in some patients. Download Session 1 PDF: Abstracts 1 to 27
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| 22 | DETERMINANTS OF SUSCEPTIBILITY TO ENFUVIRTIDE MAP TO GP41 IN ENFUVIRTIDE-NAÏVE HIV-1 Antiviral Therapy 2003;8:S25 SA Stanfield-Oakley1, J Jeffrey1, CB McDanal1, S Mosier1, L Talton1, L Jin1, P Sista1, N Cammack2, TJ Matthews1 and ML Greenberg1, Previous studies have demonstrated that the HR1 region of the HIV-1 gp41 is the target for ENF. In addition, results from Phase III clinical studies of ENF have shown that this same region is the primary locus for development of ENF resistance. Our current results suggest that gp41 also contains the major determinants for baseline sensitivity to ENF of clade B FI-naïve virus. Download Session 1 PDF: Abstracts 1 to 27
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| 23 | SENSITIVITY OF ENV-GENE RECOMBINANT VIRUSES DERIVED FROM ANTIRETROVIRAL DRUG-SENSITIVE AND -RESISTANT HIV-1 CLINICAL ISOLATES TO THE NOVEL CCR5 ANTAGONIST, UK-427,857 Antiviral Therapy 2003;8:S26 M Westby1, C Napier1, R Mansfield1, D Collins1, W Huang2, N Hellmann2, Y Lie2 and M Perros1 These data provide further evidence that UK-427,857 is a potent antiviral compound with broad activity against recombinant viruses derived from a large number of clinically-relevant isolates and diverse clades. The compound inhibited CCR5-mediated infection of Env-recombinant viruses derived from antiretroviral drug-resistant R5 clinical isolates, suggesting that viruses selected in vivo during HIV drug treatment retain sensitivity to UK-427,857. The study supports the continued development of this compound for the treatment of HIV-infected individuals. Download Session 1 PDF: Abstracts 1 to 27
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| 24 | ADS-J1, A NON-PEPTIDIC LOW MOLECULAR WEIGHT HIV FUSION INHIBITOR TARGETING GP41, WITH NO CROSS-DRUG RESISTANCE WITH PEPTIDIC HIV FUSION INHIBITORS T-20 AND C-34, AND HIV BINDING INHIBITORS Antiviral Therapy 2003;8:S27 M Armand-Ugón1, A Gutiérrez1, S Jiang2, B Clotet1 and JA Esté1 If the activity of polyanionic compounds on HIV binding is ‘bypassed’ by selection of resistance, compounds such as ADS-J1 may exclusively act on gp41-dependent fusion. Our results support the hypothesis that ADS-J1 binds to a hydrophobic cavity region within gp41 for preventing fusion-active gp41 core formation. ADS-J1 may serve as a lead low molecular weight compound to develop new anti-HIV agents. Download Session 1 PDF: Abstracts 1 to 27
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| 25 | HUMAN β-DEFENSINS INHIBIT HIV-1 REPLICATION IN VITRO Antiviral Therapy 2003;8:S28 ME Quiñones-Mateu1,2, MM Lederman2, Z Feng2, B Chakraborty1, J Weber1, HR Rangel1, ML Marotta1, M Mirza1, B Jiang2, P Kiser1, K Medvik2 and A Weinberg2 This study shows for the first time that (i) HIV-1 induces hBD expression in human oral epithelial cells; and (ii) hBDs block HIV-1 replication via a direct interaction with virions and through modulation of the CXCR4 co-receptor. These properties may be exploited as new strategies for mucosal protection against HIV-1 transmission. Download Session 1 PDF: Abstracts 1 to 27
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| 26 | IN VITRO RESISTANCE DEVELOPMENT OF HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 TOWARDS MANNOSE-SPECIFIC PLANT LECTINS Antiviral Therapy 2003;8:S29 K Van Laethem1,2, Y Schrooten1,2, S Hatse1, K Vermeire1, E De Clercq1, W Peumans3, E Van Damme4, D Schols1, A-M Vandamme1,2 and J Balzarini1 Resistance development of HIV-1 against the mannose-specific plant lectins GNA and HHA is associated with a unique spectrum of resistance mutations in the gp120 envelope gene, which has not been previously observed with any of the other known viral entry inhibitors. Download Session 1 PDF: Abstracts 1 to 27
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| 27 | VIRAL RESISTANCE AGAINST A CANDIDATE HIV MICROBICIDE Antiviral Therapy 2003;8:S30 Z Ambrose1, CJ Miller2, L Compton2, SH Hughes1, JD Lifson3 and VN KewalRamani1 Should BCD continue to prevent SIV transmission and not perturb mucosal tissues in this model, its current approved use in humans suggests it would be an important candidate for use as an anti-HIV microbicide. Nonetheless, the possibility of drug resistance against microbicides should be carefully evaluated before such drugs are administered to humans. Systemic antiviral therapy to manage HIV infection indicates that combinatorial approaches have significant benefits over monotherapy. Thus, we are also evaluating new models in which to examine the efficacy of BCD in combination with other potential microbicides. Download Session 1 PDF: Abstracts 1 to 27
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Session 2: Mechanisms of HIV Drug Resistance Abstracts 28 thru 55, Pages S33 to S60 |
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| 28 | MECHANISMS INVOLVED IN ZIDOVUDINE HYPERSUSCEPTIBILITY IN THE PRESENCE OF FOSCARNET RESISTANCE-CONFERRING MUTATIONS Antiviral Therapy 2003;8:S33 B Marchand and M Götte Enzymes containing PFA resistance conferring mutations alter the precise positioning of RT on its nucleic acid substrate. Such displacement diminishes the unblocking of ZDV-terminated primer strands. The high concentrations of dNTPs that are required to force translocation also helps to explain the diminished rates of DNA synthesis. These parameters may directly correlate with ZDV resensitization effects and diminished viral replication fitness associated with viruses that contain the E89K mutation. Download Session 2 PDF: Abstracts 28 to 55
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| 29 | HIV-1 REVERSE TRANSCRIPTASE MUTATIONS THAT SUPPRESS ZIDOVUDINE RESISTANCE ALSO INCREASE IN VITRO SUSCEPTIBILITY TO TENOFOVIR, BUT NOT STAVUDINE Antiviral Therapy 2003;8:S34 NT Parkin, C Chappey, CJ Petropoulos and N Hellmann M184I/V increases susceptibility to zidovudine, tenofovir and stavudine. Other suppressive mutations in RT affect tenofovir and zidovudine, but not stavudine. Susceptibility to stavudine decreased in the presence of L74I/V and Y181I/C/V. Additive effects were observed when suppressive mutations were present together. Combined mutations were capable of re-sensitizing tenofovir (FC<1.4) and zidovudine (FC<2.5) in the presence of multiple thymidine analogue mutations. Since genotype interpretation algorithms do not account for the effects of most suppressive mutations, these observations provide an explanation for phenotype/genotype discordance for zidovudine and tenofovir. Download Session 2 PDF: Abstracts 28 to 55
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| 30 | THE Δ67 COMPLEX OF MUTATIONS ENHANCES THE ABILITY OF HIV-1 REVERSE TRANSCRIPTASE TO EXCISE ZIDOVUDINE, STAVUDINE AND PMPA FROM BLOCKED PRIMERS Antiviral Therapy 2003;8:S35 PL Boyer1, T Imamichi2, SG Sarafianos3, E Arnold3 and SH Hughes1 It would appear that PMPA is relatively susceptible to excision by RTs that carry the classical AZT resistance mutations. PMPA excision is enhanced by RTs carrying the mutations in the Δ67 complex. The ability of RT carrying the Δ67 complex mutations to efficiently excise AZT at low ATP concentrations might provide an advantage for the virus in quiescent cells, where ATP levels are expected to be low. The data suggest that one or more of the Δ67, T69G, L74I or K103N mutations contribute to the ability of the mutant RT to excise AZT at low ATP concentrations. Download Session 2 PDF: Abstracts 28 to 55
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| 31 | THE 3′-AZIDO GROUP IS NOT THE PRIMARY STRUCTURAL DETERMINANT FOR THE EXCISION PHENOTYPE CORRELATED WITH HIV-1 RESISTANCE TO AZT Antiviral Therapy 2003;8:S36 N Sluis-Cremer1, D Koontz1, D Arion1, U Parikh1, R Schinazi2, J Mellors1 and MA Parniak1 AZT resistance mutations do not confer significant cross resistance of RT or virus to other nucleosides having a 3′-azido group. Furthermore, the presence of a 3′-azido group on the 3′-terminal nucleotide of the primer does not enhance phosphorolytic excision by AZT-resistant RT in vitro, suggesting that other structural factors must play a role in defining the specificity of the excision phenotype arising from mutations correlated with AZT-resistance. Download Session 2 PDF: Abstracts 28 to 55
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| 32 | EVOLUTION OF AMINO ACID 215 IN HIV-1 REVERSE TRANSCRIPTASE IN RESPONSE TO INTERMITTENT DRUG SELECTION Antiviral Therapy 2003;8:S37 C Chappey1, T Wrin1, S Deeks2 and CJ Petropoulos1 T215 revertants are common in HIV-1 patients. T215Y and F revert preferably to 215- codons that are one nucleotide different (Y215S/D/C, F215S/V). The relationship between the variant at the first time point and at the second time point supports the model that the RC of the various variants determines their relative presence in the archived virus pool and their subsequent emergence in the absence of selective pressure. Download Session 2 PDF: Abstracts 28 to 55
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| 33 | MOLECULAR MECHANISMS OF RESISTANCE TO TENOFOVIR BY HIV-1 REVERSE TRANSCRIPTASE CONTAINING A DI-SERINE INSERTION AFTER RESIDUE 69 AND MULTIPLE THYMIDINE ANALOGUEASSOCIATED MUTATIONS Antiviral Therapy 2003;8:S38 KL White1, JM Chen1, NA Margot1, T Wrin2, CJ Petropoulos2, LK Naeger1, S Swaminathan1 and MD Miller1 Increased ATP-mediated excision of incorporated tenofovir without efficient inhibition by the next nucleotide appears to be the primary mechanism of tenofovir resistance for HIV-1 RT with T69 insertion mutations and multiple TAMs. Decreased binding/incorporation of tenofovir also makes a minor contribution to tenofovir resistance. The same TAMs without the insertion mutation showed detectable, but lower levels of excision and greater inhibition by the next nucleotide. Increased flexibility of the β3-β4 loop by the insertion mutation may be the basis for the high-level and broad NRTI cross resistance caused by the T69 insertion mutations. Download Session 2 PDF: Abstracts 28 to 55
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| 34 | DRUG RESISTANCE AND VIRAL FITNESS AT THE MOLECULAR LEVEL: THE CASE OF TENOFOVIR Antiviral Therapy 2003;8:S39 J Deval1, KL White2, MD Miller2, J Courcambeck3, B Selmi1, J Boretto1 and B Canard1 Our data describe at the molecular level both how a resistant virus is unable to resist to two drugs simultaneously, and for the first time, how viral fitness of a resistant virus is directly linked to its decreased ability to use natural nucleotide substrates. All together, these data predict a benefit for the combination of tenofovir DF with 3TC, as well as open new avenues in how to drive resistant virus to reduced viral fitness. Download Session 2 PDF: Abstracts 28 to 55
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| 35 | MOLECULAR MECHANISM FOR THE MUTUAL EXCLUSION OF K65R AND L74V SUBSTITUTIONS IN HIV-1 REVERSE TRANSCRIPTASE-MEDIATED DIDEOXYNUCLEOSIDE RESISTANCE Antiviral Therapy 2003;8:S40 J Deval1, J-M Navarro2, B Selmi1, J Courcambeck3, J Boretto1, P Halfon3, J Sire2 and B Canard1 These results explain why the two mutations K65R and L74V do not combine in the clinic, and give a mechanism for a decreased viral fitness at the molecular level. This study gives rational support to the benefit in combining mutations that impair viral replication. Download Session 2 PDF: Abstracts 28 to 55
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| 36 | MECHANISM OF ANTI-HIV ACTIVITY OF DIOXOLANE NUCLEOSIDES AGAINST LAMIVUDINE-RESISTANT HIV-1 REVERSE TRANSCRIPTASE-MOLECULAR MODELLING APPROACH Antiviral Therapy 2003;8:S41 YH Chong1, RF Schinazi2 and CK Chu1 The molecular modeling studies show that the dioxolane moiety of D-dioxolane nucleosides enables the nucleoside triphosphate to strongly bind to the active site of 3TC-resistant mutant reverse transcriptase without steric hindrance with Val184. It is noteworthy that, depending upon the attached heterocyclic moiety, the binding modes of each dioxolane nucleoside triphosphate is different. This work would lead to the discovery of additional dioxolane with improved activity against 184V mutants (supported by NIH AI32351,AI25899 and Veterans Affairs). Download Session 2 PDF: Abstracts 28 to 55
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| 37 | PREVALENCE AND QUANTITATIVE PHENOTYPIC RESISTANCE PATTERNS OF SPECIFIC NUCLEOSIDE ANALOGUE MUTATION COMBINATIONS AND OF MUTATIONS 44 AND 118 IN REVERSE TRANSCRIPTASE IN A LARGE DATASET OF RECENT HIV-1 CLINICAL ISOLATES Antiviral Therapy 2003;8:S42 M Van Houtte1, P Lecocq1 and L Bacheler2 Associations among mutations causing resistance to NRTIs vary, as do levels of NRTI resistance associated with specific NAM combinations. The predominance of isolates belonging to the 41-210-215 pathway with higher levels of NRTI resistance may influence response to NRTI-containing therapy in treatment-experienced patients. Download Session 2 PDF: Abstracts 28 to 55
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| 38 | REMOVAL OF CHAIN-TERMINATING NUCLEOSIDE ANALOGUES BY HIV-1 REVERSE TRANSCRIPTASE UTILIZING INTRACELLULAR SUBSTRATES Antiviral Therapy 2003;8:S43 AJ Smith, PR Meyer, D Asthana, MR Ashman and WA Scott The main substrate acceptors recovered from cells were ATP, PPi and GTP. In the presence of cell extract, mutant HIV-1 RT can transfer ddAMP from the DNA primer terminus to one of these acceptor metabolites, generating Ap4ddA (ATP), ddATP (PPi) or Gp4ddA (GTP). For unstimulated T cells, monocytes and MDMs, ATP was the predominant substrate acceptor utilized for ddAMP removal. Upon activation of T cells, PPi levels increased three- to eightfold and became the predominant acceptor substrate for the removal reaction. In light of previous results from our laboratory and others that the nucleotidedependent excision reaction but not the PPi-dependent excision reaction is enhanced in RT containing the AZT-resistance mutations, the in vivo selection of AZT-resistance mutations requires further explanation. It is possible that selection occurs specifically in a cell subpopulation or a subcellular compartment containing low levels of PPi. Download Session 2 PDF: Abstracts 28 to 55
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| 39 | COLINEARITY OF REVERSE TRANSCRIPTASE INHIBITOR RESISTANCE MUTATIONS DETECTED BY POPULATION-BASED SEQUENCING Antiviral Therapy 2003;8:S44 MJ Gonzales, B Johnston, KM Dupnik, RW Shafer In this study multi-RTI-resistant isolates obtained from heavily treated patients generally consisted of viruses containing either all or nearly all of the mutations detected by population-based sequencing. This suggests that most RTI-resistance mutations are colinear. The potential benefit of mega-HAART in this population is likely to derive from the decreased replication that is often found in viruses containing multiple RTI-resistance mutations rather than from the effects of different drugs acting on different virus sub-populations. Download Session 2 PDF: Abstracts 28 to 55
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| 40 | IDENTIFICATION OF THE MINIMAL CONSERVED STRUCTURE OF THE HIV REVERSE TRANSCRIPTASE UNDER THE PRESENCE AND ABSENCE OF DRUG PRESSURE Antiviral Therapy 2003;8:S45 F Ceccherini-Silberstein1, M Santoro1, V Svicher1, F Forbici2, C Gori2, R Esnouf3, M Ciccozzi4, M Ruiz Alvarez4, R D'Arrigo2, MC Bellocchi2, C Balotta5, A Bertoli2, S Giannella2, A Cenci1, MP Trotta2, J Balzarini6, A d'Arminio Monforte5, A Antinori2 and CF Perno1,2 Even in drug-treated patients, HIV-1 RT requires the preservation of at least two-thirds of aa (some with still unknown function), and of large areas of its tertiary structure in order to maintain a stable and functional structure. Future HIV RT inhibitors may be designed to target with these invariant domains. Download Session 2 PDF: Abstracts 28 to 55
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| 41 | IDENTIFICATION OF A CLINICAL REVERSE TRANSCRIPTASE BACKBONE THAT IMPROVES REPLICATION OF A NONNUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR-RESISTANT MUTANT BY INCREASING THE RATE OF POLYMERIZATION Antiviral Therapy 2003;8:S46 R Domaoal, C Dykes, R Bambara and LM Demeter A clinical RT backbone that partially compensates for the replication defect of P236L also improves its reduced turnover rate (kss) during polymerization. We postulate that this significantly contributes to the ability of this clinical RT sequence to compensate for P236L’s replication defect. These studies demonstrate that pre-steady state kinetics can identify the underlying biochemical mechanisms leading to modulation of drug resistance mutations by clinical RT backbones. In addition, these studies indicate that the polymerization abnormalities identified for P236L/NL4-3 RT contribute significantly to the reduction in replication efficiency conferred by this mutant in cell culture. We believe these abnormalities account for the infrequent occurrence of this mutant during delavirdine therapy, despite its high level of drug resistance, and that such studies can be used to better understand resistance patterns during clinical failure of other non-nucleoside RT inhibitors. Download Session 2 PDF: Abstracts 28 to 55
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| 42 | NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR HYPERSUSCEPTIBILITY CAN BE DEMONSTRATED IN MULTICYCLE PHENOTYPE ASSAYS AND IN INHIBITION ASSAYS OF PURIFIED HIV-1 REVERSE TRANSCRIPTASES Antiviral Therapy 2003;8:S47 NS Shulman, J Delgado, MA Winters, E Johnston, DA Katzenstein, RW Shafer, T Merigan NNRTI HS is not an assay-dependent phenomenon, but exists in multicycle replication and cell-free assays as well as single-cycle phenotypic assays. As would be expected by the location of the NNRTI binding pocket, NNRTI HS is determined by the active p66 RT subunit. Download Session 2 PDF: Abstracts 28 to 55
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| 43 | GENETIC CORRELATES OF PHENOTYPIC HYPERSUSCEPTIBILITY TO EFAVIRENZ AMONG 446 BASELINE ISOLATES FROM FIVE ACTG STUDIES Antiviral Therapy 2003;8:S48 NS Shulman1, RJ Bosch2, JW Mellors3, MA Albrecht4, and DA Katzenstein1 for the DACS 217 study team Univariate and CART analyses of 446 genotype/phenotype pairs identified key mutations in RT associated with EFV HS. Mutation at codon 215 (Y>F) is most discriminatory but other mutations contribute to the HS phenotype including 67N, 208Y and 210W. In addition, polymorphisms in the NNRTIbinding region (K103R and V179I) appear to be associated with EFV HS. These results can be used to identify the biochemical and structural basis for EFV HS and to predict its presence in clinical samples. Download Session 2 PDF: Abstracts 28 to 55
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| 44 | RARE 1 AND 2 AMINO ACID INSERTIONS IN THE NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR (NNRTI) BINDING POCKET OF HIV-1 REVERSE TRANSCRIPTASE AFFECT NNRTI SUSCEPTIBILITY Antiviral Therapy 2003;8:S49 MA Winters1, RM Kagan2, PNR Heseltine2, L Kovari3 and TC Merigan1 HIV strains possessing 1 or 2 amino acid inserts in the NNRTI binding pocket can be found in patients failing antiretroviral therapy and contribute to reduced susceptibility to NNRTI. The presence of these insertions appears to be dependent on other mutations and/or polymorphisms in the RT gene. The inserts affect molecular interactions between the NNRTI binding pocket and NNRTI. Further monitoring of treated patients will determine if these insertions are a new, emerging mechanism of resistance. Download Session 2 PDF: Abstracts 28 to 55
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| 45 | CRYSTAL STRUCTURE OF A MULTIDRUG-RESISTANT HIV-1 PROTEASE CLINICAL ISOLATE REVEALS AN EXPANDED ACTIVE SITE CAVITY AND REPRESENTS A NOVEL TARGET FOR THE DESIGN OF PROTEASE INHIBITORS Antiviral Therapy 2003;8:S50 LC Kovari1, JF Vickrey1, BC Logsdon1, G Proteasa1, Z Wawrzak2, MA Winters3 and TC Merigan3 The crystal structure of an HIV-1 protease MDR clinical isolate reveals an expanded active site cavity and provides a structural basis for protease inhibitor resistance. The crystal structure of the complex represents a novel binding mode where the peptide binds only to one side of the active site cavity and the ‘flaps’ of the protease stay wide open. This crystal structure will provide structural insight to develop a new class of inhibitors against the ‘open’ form of the HIV-1 protease. All the licensed inhibitors were designed based on the structure of the ‘closed’ form of the HIV-1 protease. Download Session 2 PDF: Abstracts 28 to 55
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| 46 | STRUCTURAL CORRELATES OF BROAD-SPECTRUM ACTIVITY FOR A RESISTANCE-REPELLENT HIV PROTEASE INHIBITOR Antiviral Therapy 2003;8:S51 AM Silva, SV Gulnik, B Yu, M Eissenstat, JW Erickson Our analysis has led to the discovery of a conserved substructure of the active site of HIV PR that is important for the broad-spectrum activity of rrPIs. The mode of binding of UIC-94003 and APV are rigidly conserved in both the wild-type and mutant enzymes, but APV lacks key interactions with the conserved substructure. In SQV, critical interactions with the wild-type enzyme are lost due to mutations. Mutations involved in drug resistance not only affect the interactions between inhibitor and enzyme, but also can alter intrinsic properties of the enzyme, such as active site solvation and dimer stability. Our analysis reveals that structural flexibility of PIs is not a necessary factor in their ability to exhibit broad-spectrum activity. Download Session 2 PDF: Abstracts 28 to 55
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| 47 | CO-EVOLUTION OF THE NUCLEOCAPSID-P1 CLEAVAGE SITE WITH THE V82A MUTATION IN HIV-1 PROTEASE PRESERVES SUBSTRATE RECOGNITION Antiviral Therapy 2003;8:S52 M Prabu-Jeyabalan1, N King1, E Nalivaika1, R Swanstrom2 and CA Schiffer1 The NC-p1 substrate peptide appears to have an unusual fit in the active site cavity of HIV-1 protease compared with the substrate peptides whose complexes have been solved which may account for the its slow cleavage rate. The backbone is rearranged and the P1′-Phe is in an unusual conformation contacting V82. This is most likely due to the P2- Ala that is unable to fill the S2 pocket of the active site effectively. When the drug-resistant V82A mutation occurs, this likely further destabilizes the complex as the P1′-Phe contact is lost. P2-Val compensates for this protease mutation, as has been reflected in previously measured kinetics, by filling the S2 pocket and stabilizing the substrate’s conformation in the active site. Download Session 2 PDF: Abstracts 28 to 55
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| 48 | PRELIMINARY CHARACTERIZATION OF A NEWLY DESCRIBED PROTEASE SUBSTRATE CLEFT MUTATION AT POSITION 23 Antiviral Therapy 2003;8:S53 E Johnson, MA Winters, K Vyas, TC Merigan and RW Shafer L23I is a rare substrate cleft mutation that occurs in about 1% of patients receiving multiple PIs. By itself, L23I appears to be associated with nelfinavir resistance and decreased replication capacity. In combination with other mutations, L23I appears to be associated with multi-PI resistance and increased replication capacity. Download Session 2 PDF: Abstracts 28 to 55
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| 49 | EMERGENCE OF A NOVEL LOPINAVIR RESISTANCE MUTATION AT CODON 47 CORRELATES WITH ARV UTILIZATION Antiviral Therapy 2003;8:S54 RM Kagan1, M Shenderovich2, K Ramnarayan2 and PNR Heseltine1 We have identified a second pathway to high-level LPV resistance that does not result from cross resistance to other PIs. Increased usage of LPV correlates with increased frequencies of the I47V mutation leading to the stepwise emergence of the LPV-resistant I47A variant. Surveillance of emerging resistance in large clinical databases may be facilitated by structural phenotypic methods that enable rapid computational determinations of the significance of newly identified mutational patterns. Download Session 2 PDF: Abstracts 28 to 55
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| 50 | PARAMETERS DRIVING THE SELECTION OF NELFINAVIR-RESISTANT HIV-1 VARIANTS Antiviral Therapy 2003;8:S55 V Perrin and F Mammano Different biological properties account for the replicative advantage of D30N and L90M mutants in the presence of nelfinavir. The higher prevalence of D30N mutation in patients receiving nelfinavir reflects the higher level of resistance that can be attained by viruses engaged in the D30N pathway. In addition, restoration of infectivity of D30N-L90M double mutant by a common polymorphism reinforces the notion that the genetic context of the virus may substantially influence the impact of resistance mutations. Download Session 2 PDF: Abstracts 28 to 55
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| 51 | I84A AND I84C MUTATIONS IN PROTEASE CONFER HIGH-LEVEL RESISTANCE TO PROTEASE INHIBITORS AND IMPAIR REPLICATION CAPACITY Antiviral Therapy 2003;8:S56 H Mo1, N Parkin2, KD Stewart, L Lu1, T Dekhtyar1, D Kempf1 and A Molla1 In general, I84V mutants without other major mutations display relatively modest resistance to PIs. Increased resistance is accomplished by addition of other major mutations (common pathway) or (less commonly) by selection of I84C or I84A. Molecular modelling provides useful insight into the mechanism of resistance mutations on drug susceptibility and replicative capacity. Download Session 2 PDF: Abstracts 28 to 55
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| 52 | THE HIV-1 PROTEASE MUTATION K55R IS ASSOCIATED WITH THE PRESENCE OF THE M46I/L MUTATION Antiviral Therapy 2003;8:S57 E Morgan1, D Pillay2, P Cane1, JP Kleim3, M Tisdale3, M Maguire3, S Macmanus3, P Yates3 and R Elston3 Analysis of the associations between non-consensus substitutions across all 99 protease amino acids identified additional associations not previously described including K55R being associated with either M46I or L, or V82A/S/T or I54V. K55R was only rarely detected in PI-naïve subjects suggesting that this mutation could represent an accessory resistance mutation. Download Session 2 PDF: Abstracts 28 to 55
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| 53 | NUCLEIC ACID DIFFERENCES BETWEEN HIV-1 NON-B AND B REVERSE TRANSCRIPTASE AND PROTEASE SEQUENCES AT DRUG RESISTANCE POSITIONS Antiviral Therapy 2003;8:S58 R Kantor1, AP Carvalho2, B Wynhoven3, MA Soares4, P Cane5, J Clarke6, J Snoeck7, C Pillay8, S Sirivichayakul9, K Ariyoshi10, A Holguin11, H Rudich12, R Rodrigues13, MB Bouzas14, P Cahn14, LF Brigido13, Z Grossman12, V Soriano11, W Sugiura10, P Phanuphak9, L Morris8, A-M Vandamme7, J Weber6, D Pillay5, A Tanuri4, PR Harrigan3, R Camacho2, JM Schapiro1, RW Shafer1 and D Katzenstein1 There are characteristic, subtype-specific baseline synonymous NA differences at RT and protease drug resistance positions, which rarely result in different non-synonymous substitutions with drug therapy. However, as described by Brenner et al., V106M uniquely predominates in sequences from subtype C-infected persons after efavirenz, and to a lesser extent, as shown here, after nevirapine exposure. The predominant use of GTG/valine and a G to A transition select ATG/methionine at V106 preferentially in subtype C. This may be a consequence of G to A hypermutation, seen also at other RT valine drug resistance positions. This unique codon use may contribute to a lower threshold for NNRTI resistance in subtype C. Download Session 2 PDF: Abstracts 28 to 55
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| 54 | SEARCH FOR POLYMORPHIC SITES IN R5 TROPIC HIV-1 ENV AND ENFUVIRTIDE DRUG SUSCEPTIBILITY IN BASELINE ISOLATES FROM TORO 1 AND TORO 2 Antiviral Therapy 2003;8:S59 C Su1, G Heilek-Snyder1, D Fenger1, P Ravindran1, K Tsai1, N Cammack1, P Sista2 and S Chiu1 Statistical analyses have revealed an association between polymorphic sites in HIV Env and baseline variability of ENF susceptibility in HIV-1 R5 tropic recombinants. Cluster analysis of gp41 viral sequences identified combinations of polymorphisms that were associated with higher ENF susceptibility in the 12 non-B R5 recombinants and a regression tree model illustrated amino acid interactions associated with ENF susceptibility. The significance of these associations is under study. Download Session 2 PDF: Abstracts 28 to 55
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| 55 | SUBGROUP ANALYSIS OF BASELINE SUSCEPTIBILITY AND EARLY VIROLOGICAL RESPONSE TO ENFUVIRTIDE IN THE COMBINED TORO STUDIES Antiviral Therapy 2003;8:S60 P Sista1, T Melby1, ML Greenberg1, R DeMasi1, D Kuritzkes2, M Nelson3, C Petropoulos4, M Salgo5, N Cammack6 and TJ Matthews1 No significant association between BL susceptibility to ENF and early virological response in patients with the lowest GSS was observed, suggesting that other factors may be influencing virological response. The inverse correlation seen between BL GSS and reduced susceptibility to ENF at VF suggests that the antiviral activity of ENF is preserved when combined with additional active agents in the optimized background. Download Session 2 PDF: Abstracts 28 to 55
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Session 3: HIV Pathogenesis, Fitness and Resistance Abstracts 56 thru 84, Pages S63 to S91 |
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| 56 | VIRUS CHARACTERISTICS PREDICT VIRAEMIA CONTROL AFTER CESSATION OF ANTIRETROVIRAL THERAPY Antiviral Therapy 2003;8:S63 H Günthard1, B Joos1, H Kuster1, M Fischer1, C Leemann1, J Böni3, A Oxenius4, C Fagard2, B Hirschel2, J Wong5, R Phillips6, S Bonhoeffer4, R Weber1, A Trkola1 and the Swiss HIV Cohort Study Viral characteristics such as in vitro replication capacity and infectivity predicted control of plasma viraemia after last cessation of therapy in patients undergoing STI. Low pretreatment env diversity in patients controlling viraemia after STI suggests that those viral characteristics were not influenced by STI but were already present years ago before any therapy was started. SSITT-baseline neutralizing activity but not HIV-specific CTL- or T-help responses were associated with control of viraemia. Download Session 3 PDF: Abstracts 56 to 84
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| 57 | DISTINCT PATTERNS OF THE VIROLOGICAL AND IMMUNOLOGICAL RESPONSE TO ANTIRETROVIRAL THERAPY INTERPRETED IN TERMS OF THE DYNAMICS OF IMMUNE ACTIVATION AND HIV TRANSMISSION Antiviral Therapy 2003;8:S64 Z Grossman1, Z Grossman2, PW Hunt3 and SG Deeks3 Consistent with mixing, we previously observed that resistance mutations did develop in patients with intermittent viraemia episodes, who showed limited evidence of generalized T cell activation but had large numbers of HIV-specific T cells. Importantly, PAT predicts that in the absence of rapid spreading and mixing, wild-type HIV and resistant variants can coexist, actively replicating in relative isolation Download Session 3 PDF: Abstracts 56 to 84
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| 58 | BOTH STABLE AND DECAYING HIV PLASMA VIRAL LOADS ARE OBSERVED IN SUBJECTS WITH SUSTAINED SUPPRESSION OF VIRAEMIA <50 COPIES/ML AND ARE UNINFLUENCED BY INFLUENZA VACCINATION Antiviral Therapy 2003;8:S65 EP Coakley1, A Tiro1, A Wurcel2, R D′Aquila3 and DR Stone2 A quantifiable viraemia was observed in 61% of subjects with apparent sustained suppression of the viral load below the limit of detection by current assays. Transient viraemic episodes may be markers of such ongoing viraemia irrespective of the duration of time <50 copies/ml. Conversely, among those with no documented blips lower viral loads are correlated with longer periods of time <50 copies/ml, suggesting that total body viral burden may be decreasing in those lacking blips. Despite prior reports of transient viraemia after influenza vaccination in those with stable viraemic suppression we did not observe any short-term change in viral load below 50 copies in this population. Download Session 3 PDF: Abstracts 56 to 84
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| 59 | HIV DNA AS A PREDICTOR OF RESIDUAL VIRAEMIA IN PATIENTS TREATED WITH TENOFOVIR+LAMIVUDINE+EFAVIRENZ OR STAVUDINE+LAMIVUDINE+EFAVIRENZ Antiviral Therapy 2003;8:S66 DV Havlir1, M Strain2, MD Miller3, C Ignacio2, B Lu3 and J Wong2 for 903 Study Team Lower baseline proviral HIV DNA levels and randomization to the TDF arm were associated with lower levels of residual viraemia, independent of baseline HIV RNA levels. In this exploratory analysis, lower levels of residual viraemia in the TDF arm suggests greater antiviral potency of this regimen as compared to the d4T regimen. Higher proviral HIV DNA at baseline may either directly contribute to residual viraemia through subsequent activation of the latent reservoir, or alternatively, the proviral HIV DNA level may be a surrogate for host factors that sustain residual HIV infection during therapy. Download Session 3 PDF: Abstracts 56 to 84
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| 60 | STABLE, PERSISTENT VIRAEMIA IN PATIENTS WITH PLASMA HIV-1 RNA SUPPRESSED TO LESS THAN 75 COPIES/ML ON POTENT ANTIRETROVIRAL THERAPY Antiviral Therapy 2003;8:S67 A Wiegand1, F Maldarelli1, S Palmer1, M Polis2, J Falloon3, J Mican3, R Davey3, D Rock3, S Liu3, A Planta3, J Shen3, R Burke3, JA Metcalf3, J Mellors4 and J Coffin1 Most patients on antiretroviral therapy with plasma HIV-1 RNA suppressed to less than 75 copies/ml have stable persistent viraemia of 0.3–41 copies RNA/ml, as measured by our single copy assay. Viraemia plateaued within 4–15 months of initiating antiretroviral therapy. Additional studies are in progress to assess the relationship between regimen potency and the level of persistent viraemia. Download Session 3 PDF: Abstracts 56 to 84
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| 61 | CCR5 CELL SURFACE DENSITY AND HIV-1 ENVELOPE SEQUENCES GOVERN ANTIRETROVIRAL POTENCY OF CCR5 ANTAGONISTS Antiviral Therapy 2003;8:S68 MD Miller1, JE Lineberger1, G Dornadula1, RC Danzeisen1, CR Blau1, RM Danovich1, MA Miller2, PE Finke3, BD Oates3, CG Caldwell3, P Chen3, LC Meurer3, SG Mills3, MS Springer4, CJ Petropoulos5, J Whitcomb5, W Huang5, S Fransen5, AJ Simon1 and DJ Hazuda1 The apparent antiviral potency of CCR5 antagonists can be affected significantly by at least two factors, CCR5 surface density and envelope glycoprotein sequence. These factors are both likely to be physiologically relevant: CCR5 expression levels have been reported to vary widely among different subjects and on different primary cells, and extensive diversity in envelope sequences is present in populations of HIV-infected people. Taken together, these observations raise the possibility that clinical responses to CCR5-directed antiretroviral agents might be highly variable. Download Session 3 PDF: Abstracts 56 to 84
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| 62 | POPULATION GENETICS IN HIV-1 SUPER-INFECTION Antiviral Therapy 2003;8:S69 S Palmer1, M Kearney1, V Boltz1, F Maldarelli1, G Achaz3, J Mellors2, E Daar4 and J Coffin1 Our results indicate that this patient was initially infected with a multidrug-resistant virus, and was subsequently super-infected with a wild-type virus, which dominated the replicating virus population, leaving only a very small proportion of resistant virus (0.1% or less). Longitudinal samples showed the diversification of the wild-type super-infecting virus from a monomorphic population to a more heterogeneous one by 1–1.5 years after infection. The diversification of the super-infecting wild-type virus occurred slowly by de novo mutation rather than recombination with the initially infecting virus. Download Session 3 PDF: Abstracts 56 to 84
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| 63 | CO- AND SUPER-INFECTION: PERSISTENT REPLICATION OF BOTH HIV-1 STRAINS? Antiviral Therapy 2003;8:S70 L Perrin1, S Yerly1, M Monnat2, A Telenti3, A Cavassini3, P Burgisser4 and the Swiss HIV Cohort Study In co-infected patients both HIV-1 subtypes persist during the follow-up, whereas in superinfected patients, despite massive immune activation associated with the ARS at the time of super-infection, only the second strain was detectable in plasma. Download Session 3 PDF: Abstracts 56 to 84
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| 64 | HIV VIRAL SEX: INBREEDING, RECOMBINATION, DRUG RESISTANCE AND CLINICAL OUTCOME Antiviral Therapy 2003;8:S71 C Fraser and RM Anderson Recombination acts on the prevalence of multipoint-resistant mutants in two opposing directions, by re-assorting lesser resistant genotypes to increase resistance, and by re-assorting multipointresistant mutants with lesser resistant genotypes to reduce resistance. The kinetics of this balance are such that fitness differences are smoothed, boosting the frequency of resistance mutations with high fitness costs, but suppressing the frequency of mutants with compensatory fitness gains. This revised calculation, including recombination, makes firmer the prediction that all one, two and three but not higher point mutants are present in untreated drug-naïve patients. We predict that treatment regimens that can suppress all strains with three or fewer point mutations should, if adhered to, not fail due to emergent resistance. Download Session 3 PDF: Abstracts 56 to 84
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| 65 | HIV-1 GENETICS OF INTERMITTENT LOW-LEVEL VIRAEMIA Antiviral Therapy 2003;8:S72 NH Tobin1, Y Wang1, GH Learn1, JL McKernan1, GM Ellis1, KM Mohan1, SE Holte1, DM Pawluk1, AJ Melvin1, PL Lewis2, LM Heath1, IA Beck1, WE Naugler1, JI Mullins1 and LM Frenkel1 These genetic studies of HIV-1 suggest three phenomena lead to LLV during effective HAART: 1) viral expression from long-lived proliferating HIV-1-infected cells, without evidence of full cycles of viral replication; 2) viral replication, including the selection of new drug-resistant mutants; and 3) detection of nonamplifiable virus, possibly due to false-positive tests. Distinguishing between these processes may be clinically important. Additionally, this study documents clonal expression of virus in LLV, supporting proliferation of latently infected cells. Download Session 3 PDF: Abstracts 56 to 84
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| 66 | LIMITED GENOTYPIC AND PHENOTYPIC EVOLUTION AFTER INTERRUPTION OF A SINGLE THERAPEUTIC DRUG CLASS IN PATIENTS WITH MULTIDRUG-RESISTANT HIV Antiviral Therapy 2003;8:S73 SG Deeks, EE Paxinos, T Wrin, R Hoh, F Aweeka, JN Martin, CJ Petropoulos and RM Grant Interrupting PI therapy in patients with multidrug-resistant HIV is associated with stable viremia and persistent levels of PI resistance. Several mechanisms may have accounted for the failure of PI resistance to wane. First, the close proximity of RT and protease makes genetic recombination unlikely. Second, viral evolution in presence of PI therapy is associated with the accumulation of compensatory mutations that increase viral fitness. Back mutations may require remodelling within these regions and an early decrease in relative fitness; this fitness ‘valley’ prevents reversion. Third, archived RTI-resistant and PI-susceptible virus likely contains fewer RTI-associated mutations than more recent variants. Thus, the archived virus may be relatively more susceptible to RTIs. Collectively, these data suggest that decreases in replication capacity associated with PI resistance will persist in the absence of the inhibitor. Download Session 3 PDF: Abstracts 56 to 84
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| 67 | CLONAL ANALYSIS OF HIV-1 VARIANTS IN PROVIRAL DNA DURING TREATMENT INTERRUPTION IN PATIENTS WITH MULTIPLE THERAPY FAILURES Antiviral Therapy 2003;8:S74 S Boucher1, P Recordon-Pinson1, D Neau2, J-M Ragnaud2, M Faure1, H Fleury1 and B Masquelier1 In patients with multiple virological failure having a TI before a salvage therapy, archiving of pre-interruption resistance mutations in proviral DNA can be responsible for virological failure after treatment resumption. Download Session 3 PDF: Abstracts 56 to 84
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| 68 | VAGINAL HIV-1 SHOWS DISTINCT DRUG RESISTANCE MUTATION PATTERNS COMPARED TO PLASMA HIV-1 AND REMAIN M-TROPIC DESPITE ADVANCED DISEASE Antiviral Therapy 2003;8:S75 G Tirado, GR Jove and Y Yamamura This cross-sectional study suggests that local selective forces allow distinct viral lineages to emerge and evolve independently in the plasma and the vaginal compartment. Delayed clearance of drug resistance mutants was observed in vaginal compartment and these viruses remained M-tropic despite presence of T cell tropism in plasma and advanced HIV-1 disease thus suggesting the vaginal tract could serve as reservoir for M-tropic drug resistant mutants and perhaps contribute to the transmission of drug resistance. Download Session 3 PDF: Abstracts 56 to 84
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| 69 | EFFECTS OF FAILING ANTIRETROVIRAL THERAPY ON THE COMPOSITION OF HIV-1 IN CSF AND BLOOD Antiviral Therapy 2003;8:S76 JK Wong1,2, S Letendre1,3, MC Strain1, S Pillai1, TM Russell1, CC Ignacio1, HF Gunthard4, DD Richman1,2, I Grant1,3, JA McCutchan1,3 and R Ellis1,3 Among patients not on ART, the majority of patients demonstrated distinct viral populations in CSF. The composition of three codons within V3 was 80% predictive of the anatomic source of virus and suggests that these positions may be important for virus selection in the CNS. ART and the emergence of drug resistance was accompanied by co-mingling of CSF and plasma sequences. If, as is suspected, HIV env plays a central role in neurotropism and neurovirulence, selection of drug resistance during failing ART may have biological consequences beyond those predicted by virological failure alone. Download Session 3 PDF: Abstracts 56 to 84
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| 70 | IMMUNE-MEDIATED SUPPRESSION OF VIRULENT SIMIAN IMMUNODEFICIENCY VIRUS INDUCED BY TENOFOVIR TREATMENT Antiviral Therapy 2003;8:S77 KKA Van Rompay1, R Singh1, C Wingfield2, DL Sodora3, JR Lawson1, B Pahar1, KA Reimann4, ML Marthas1 and N Bischofberger5 In the absence of CD8 lymphocytes, K65R viral mutants are highly replication-competent despite concomitant tenofovir treatment. This suggests that suppression of replication of K65R SIV mutants is under relatively little direct control of tenofovir, but is mediated mainly by CD8-mediated immune responses. Continued tenofovir treatment is required to maintain optimal suppression of viraemia. Our results help to explain the absence of viral rebound that has been described in tenofovir-treated humans who developed K65R HIV-1 mutants. Download Session 3 PDF: Abstracts 56 to 84
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| 71 | A POTENTIAL ROLE FOR CD63 IN CCR5-MEDIATED HIV-1 INFECTION OF MACROPHAGES Antiviral Therapy 2003;8:S78 JJ von Lindern1, D Rojo1, K Grovit-Ferbas2, C Cheng Deng1, MR Ferguson1, JM Decker3, A Singh4, RG Collman4 and WA O’Brien1 It is likely that tetraspan membrane glycoprotein CD63 is involved in HIV infection of macrophages with R5 viruses, either through associations with CCR5 or at a post-fusion step of virus entry. A potential mechanism of action is CD63-mediated stabilization of membrane protein organization important for Mø infection. Further studies may reveal suitable therapeutic targets. Download Session 3 PDF: Abstracts 56 to 84
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| 72 | MECHANISMS UNDERLYING A SUSTAINED CD4 T CELL RECOVERY DESPITE THE EMERGENCE OF RESISTANCE IN ANTIRETROVIRAL-EXPERIENCED PATIENTS ON PROLONGED ENFUVIRTIDE TREATMENT Antiviral Therapy 2003;8:S79 E Poveda1, B Rodes1, JM Benito1, MA Munoz-Fernandez2, M Lopez1, J Gonzalez-Lahoz and V Soriano1 A single mutation within HR1 (aa 36–45) results in virological failure to ENF. Individuals on ENF may experience CD4 T cell rises despite virological failure due to a redistribution of CD4 T cells, hypothetically driven by low levels of T cell activation. Furthermore, selection of R5 viruses by ENF may result in a lower HIV deleterious effect on thymic function. Download Session 3 PDF: Abstracts 56 to 84
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| 73 | WIDE VARIATION IN PRO/POL REPLICATION CAPACITY IN RECENTLY TRANSMITTED HIV-1 IS CONFERRED IN PART BY PROTEASE INHIBITOR RESISTANCE MUTATIONS Antiviral Therapy 2003;8:S80 JD Barbour1,2, T Wrin3, FM Hecht2, NS Hellmann3, CJ Petropoulos3, MR Segal2 and RM Grant1,2 Resistance mutations accounted for a small fraction of the variation in RC in this population of newly infected patients (although the assay uses patient-derived pro/pol gene segments in an isogenic background). Genetic interactions, and mutations not associated with drug resistance, may also contribute to variations in RC. Low RC was associated most strongly with PI resistance. Impaired transmissibility of PIresistant viruses could explain the relative scarcity of PI resistance among recently infected persons. Download Session 3 PDF: Abstracts 56 to 84
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| 74 | MODULATION OF REPLICATION CAPACITY IN DRUG SENSITIVE CLADE B HIV-1 BY PROTEASE AND THE C-TERMINAL END OF GAG Antiviral Therapy 2003;8:S81 M Bates, C Chappey, S Bates and N Parkin Univariate analyses of a database of WT viruses demonstrates that selected mutations in gag and in Pr are associated with high or low RC values. Multivariate analyses utilizing larger datasets may provide additional insights. Download Session 3 PDF: Abstracts 56 to 84
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| 75 | DRUG-RESISTANT PHENOTYPE IS ASSOCIATED WITH DECREASED IN VIVO T-CELL ACTIVATION INDEPENDENT OF CHANGES IN VIRAL REPLICATION AMONG PATIENTS DISCONTINUING ANTIRETROVIRAL THERAPY Antiviral Therapy 2003;8:S82 PW Hunt1, JN Martin1, E Sinclair1, TB Neilands1, RM Grant1, NS Hellmann2 and SG Deeks1 The observed reduction in T-cell activation among patients with MDR viraemia is mediated through both partial viral suppression and a change in the viral phenotype, though we cannot exclude an independent drug-effect on T-cell activation. These data suggest that suppression of viraemia below a pre-therapy baseline and the maintenance of a drug-resistant phenotype are necessary to preserve the immunological benefit of therapy. Moreover, these data provide the most direct in vivo evidence that the drugresistant variant is less capable of causing generalized T-cell activation. Download Session 3 PDF: Abstracts 56 to 84
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| 76 | EFFECTS OF AMINO ACID AND SYNONYMOUS POLYMORPHISMS IN HIV-1 PROTEASE ON VIRAL FITNESS Antiviral Therapy 2003;8:S83 SDW Frost1, SL Kosakovsky Pond2, Z Grossman3, E Daar4, J Condra5, DD Richman1, SJ Little1 and AJ Leigh Brown6 Amino acid targets of CTL selection are expected to vary between human populations that are genetically distinct due to differences in HLA allele frequencies. We find evidence of both: 1) populationspecific; and 2) subtype-specific selection. 1) is most likely to be HLA-associated, while 2) could be both HLA-associated and influenced by other factors, such as subtype-specific differences in RNA folding. The large difference among codons in synonymous variation suggests some of these changes are not selectively neutral and that selection may act at the RNA as well as the protein level in the pol gene. Download Session 3 PDF: Abstracts 56 to 84
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| 77 | INFLUENCE OF GAG AND POL REGIONS ON REPLICATION EFFICIENCY OF A MULTIDRUG-RESISTANT HIV-1 VARIANT: A SYSTEMATIC ASSESSMENT Antiviral Therapy 2003;8:S84 V Simon1, N Padte1, I Driver1, NC Wang1, M DiMascio2 and M Markowitz1 These results suggest that relevant compensatory changes occur both within and outside the drug resistance conferring regions, and that the interplay of these MDR regions results in optimal replication efficiency as demonstrated by MDR2gag/pol/vif. Furthermore, the replacement of MDR2 gag and PR genes by wild-type sequences results in a loss of replication capacity providing a possible explanation for the observed genetic stability and persistence of some drug-resistant isolates in vivo Download Session 3 PDF: Abstracts 56 to 84
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| 78 | RAPID FLUX IN NON-NUCLEOSIDE REVERSE TRANSCRIPTASE INHIBITOR RESISTANCE MUTATIONS AMONG SUBTYPE C HIV-1-INFECTED WOMEN AFTER SINGLE DOSE NEVIRAPINE Antiviral Therapy 2003;8:S85 R Kantor, E Lee, E Johnston, P Mateta, L Zijenah, Y Maldonado and D Katzenstein for the HPTN 023 Study Team Samples obtained within 2 weeks of SD NVP demonstrated a high frequency of NNRTI resistance mutations. Dual mutations, observed in some samples may be mixtures of competing single mutants. There is evidence for rapid reversion to WT of plasma RT by 8 and 24 weeks. Although Y181C predominates in early samples, K103N is retained as the predominant mutation detected at 8 weeks. Sequencing multiple clones from sequential timepoints will be useful for quantification and linkage of mutations. The change over time in the proportion of specific mutations may serve as an indication of in vivo fitness relative to WT RT in subtype C HIV-1. Download Session 3 PDF: Abstracts 56 to 84
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| 79 | HIV-1 VARIANTS WITH DIVERSE NEVIRAPINE RESISTANCE MUTATIONS EMERGE RAPIDLY AFTER SINGLE-DOSE NEVIRAPINE: HIVNET 012 Antiviral Therapy 2003;8:S86 SH Eshleman1, D Jones1, L Guay1, P Musoke2, F Mmiro2 and JB Jackson1 Cloning and characterization of individual HIV-1 variants reveals rapid selection of diverse subpopulations of HIV-1 after single-dose NVP. Some variants contained more than one NVPR mutation and many contained NVPR mutations that were not detected by population sequencing. Detection of variants with NVPR mutations only 7 days after single-dose NVP suggests that those variants were present at low levels prior to NVP administration. Further studies of NVPR in women and infants receiving single-dose NVP may help optimize use of NVP for prevention of MTCT. Download Session 3 PDF: Abstracts 56 to 84
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| 80 | PERSISTENCE OF MULTIDRUG-RESISTANT HIV-1 WITHOUT ANY ANTIRETROVIRAL TREATMENT 2 YEARS AFTER SEXUAL TRANSMISSION Antiviral Therapy 2003;8:S87 C Delaugerre1, L Morand-Joubert2, ML Chaix3, O Picard2, AG Marcelin1, V Schneider4, A Krivine5, A Compagnucci6, C Katlama1, PM Girard2 and V Calvez1 In the source patients, only MDR viruses were detected and therefore transmitted. In the index patients, an expansion of predominant MDR quasispecies and the ‘archival’ of all resistance mutations were observed. These results explain the persistence of mutations and suggest the high difficulty to return to a wild-type viral population sensitive to an antiretroviral treatment. The treatment of index patients is limited and the major risk is the transmission of these MDR viruses. Download Session 3 PDF: Abstracts 56 to 84
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| 81 | IMPACT OF TRANSMISSION OF DRUG-RESISTANT HIV VIRUSES ON VIRAL LOAD, CD4 COUNTS AND CD4 DECLINE IN RECENT SEROCONVERTERS Antiviral Therapy 2003;8:S88 C de Mendoza1, M Ortiz2, S Pérez-Hoyos3, A Corral1, A García-Saínz2, J del Amo4, J del Romero5, V Soriano1, C Rodríguez5 and the Study Group of Seroconverters of Madrid Transmission of drug-resistant HIV viruses does not seem to affect initial CD4 cell counts nor viral load values in recent HIV seroconverters. Moreover, no effect is seen on CD4 decline overtime along 3 years follow-up in the absence of antiretroviral therapy. Download Session 3 PDF: Abstracts 56 to 84
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| 82 | TRANSMITTED HIV-1 CARRYING D67N OR K219Q EVOLVE RAPIDLY TO ZIDOVUDINE RESISTANCE IN VITRO AND SHOW A HIGH REPLICATIVE FITNESS IN THE PRESENCE OF ZIDOVUDINE Antiviral Therapy 2003;8:S89 JG García-Lerma1, H MacInnes1, D Bennett2, H Weinstock2 and W Heneine1 Our findings demonstrate that transmitted HIV-1 strains with D67N and/or K219Q/E are phenotypically different from WT viruses. Download Session 3 PDF: Abstracts 56 to 84
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| 83 | MALE GENITAL TRACT COMPARTMENTALIZATION AND TRANSMISSION OF 215L REVERTANT Antiviral Therapy 2003;8:S90 DM Smith, KK Koelsch, JK Wong, GK Hightower, CI Ignacio, DD Richman and SJ Little These investigations show compartmentalization of 215 revertants in the male genital tract. This may be explained by the isolation of a founding virus or the selection of such variants in the genital tract. Since antiretrovirals differentially penetrate the blood and male genital compartments, it may facilitate the production and/or selective retention of revertants. This has significant public health implications, as these revertants represent highly fit viruses that can become resistant to ZDV more readily than wild-type virus. Download Session 3 PDF: Abstracts 56 to 84
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| 84 | ANALYSIS OF VIRION MORPHOLOGY AND ASSEMBLY PROCESS IN PROTEASE INHIBITOR-RESISTANT HIV-1 Antiviral Therapy 2003;8:S91 L Myint, M Matsuda, T Chiba, H Yan, J Kakizawa, A Okano, M Hamatake, M Nishizawa and W Sugiura Immature virion morphologies and intracellular budding were observed in PI-resistant viruses with impaired gag processing. Our results suggest aberrant interaction between virus proteins and host factors in PI-resistant viruses. Download Session 3 PDF: Abstracts 56 to 84
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Session 4: New Resistance Technologies and Interpretations Abstracts 85 thru 113, Pages S95 to S123 |
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| 85 | THE IMPACT OF MINOR POPULATIONS OF WILD-TYPE hiv ON THE REPLICATION CAPACITY AND PHENOTYPE OF MUTANT VARIANTS IN A SINGLE-CYCLE HIV RESISTANCE ASSAY Antiviral Therapy 2003;8:S95 H Mo, L Lu, D Kempf and A Molla Due to the unique co-transfection step inherent to single-cycle HIV resistance assays, even relatively small amounts of WT virus within a viral population can significantly impact the apparent RC and phenotype of mutant strains. The RC and susceptibility of plasma isolates from patients who are off therapy or not adherent to treatment, in which WT virus may expand to significant levels, should be interpreted with caution. Download Session 4 PDF: Abstracts 56 to 113
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| 86 | COMPARISON OF SINGLE-GENOME SEQUENCING WITH STANDARD GENOTYPE ANALYSIS FOR DETECTION OF HIV-1 DRUG RESISTANCE MUTATIONS Antiviral Therapy 2003;8:S96 M Kearney1, S Palmer1, F Maldarelli1, C Bixby4, H Bazmi4, D Rock2, J Falloon3, R Davey3, R Dewar2, J Metcalf2, J Mellors4 and J Coffin1 These results illustrate the inadequacy of composite genotype analysis for detecting drug resistance mutations present in less than 35% of the plasma virus population. Mutations present in <10% of the virus population were almost never detected and those present in 10–35% were inconsistently detected. In addition to its greater sensitivity, SGS permits detection of linked mutations that confer high-level drug resistance. Such linkage cannot be detected in composite genotypes. Download Session 4 PDF: Abstracts 56 to 113
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| 87 | DRUG-RESISTANT MUTANTS OF HIV-1 PERSIST AT HIGHER CONCENTRATIONS IN PERIPHERAL BLOOD MONONUCLEAR CELLS COMPARED TO PLASMA AND ARE DETECTED AT A HIGHER RATE BY OLA COMPARED TO CONSENSUS SEQUENCING Antiviral Therapy 2003;8:S97 GM Ellis1, M Mahalanabis1, IA Beck1, G Pepper2, A Wright2, S Hamilton2, S Holte3, WE Naugler1, DM Pawluk1, C-C Li1 and LM Frenkel1,2 These data indicate that concentrations of drug-resistant mutants were greater in PBMCs than in plasma after changes in ART, and that the OLA was more sensitive than consensus sequencing in detecting low levels of select drug-resistant mutants. Download Session 4 PDF: Abstracts 56 to 113
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| 88 | SIMULTANEOUS ASSESSMENT OF ASSOCIATION BETWEEN TWO OR MORE HIV-1 DRUG SUSCEPTIBILITY PHENOTYPES AND GENOTYPE Antiviral Therapy 2003;8:S98 G DiRienzo Several groups of antiretroviral drugs are considered to be similar with respect to the genotype patterns associated with resistance, which may lead to the belief that available treatment options are limited for patients with such patterns; however, it may be the case that specific genotype patterns are in fact associated with sensitivity to one or more of these drugs in a given group. The methods used may accommodate a wide range of outcome variables, including virological and immunological response, and viral replication capacity. Download Session 4 PDF: Abstracts 56 to 113
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| 89 | USING GENE-CODE TECHNOLOGY TO DETECT EARLY EMERGING POPULATIONS OF DRUG-RESISTANT HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 Antiviral Therapy 2003;8:S99 MJ Moser1, PL Sharma2, V Nurpeisov2, RF Schinazi2 and JR Prudent1 To our knowledge, no other technology even approaches such a level of sensitive specificity. Additional development of GENE-CODE to include a larger number of HIV variants could lead to a simple-to-run and widely-used method for research and clinical diagnostics. Download Session 4 PDF: Abstracts 56 to 113
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| 90 | EVIDENCE FOR PREFERENTIAL GENOTYPING OF MINORITY HIV POPULATIONS DUE TO PRIMER MISMATCHING DURING PCR-BASED AMPLIFICATION Antiviral Therapy 2003;8:S100 K Morales-Lopetegi1, C Gutierrez2, N Izquierdo1, S Marfil1, B Clotet1, L Ruiz1 and J Martínez-Picado1 The extremely high variability of the HIV genome may result in a preferential annealing of the PCR-based amplification primers for virus variants present as minority populations in the sample. This observation might explain unexpected PRO or RT genotypes, as those being wild-type during viral breakthrough to antiviral therapy. Download Session 4 PDF: Abstracts 56 to 113
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| 91 | QUALITY CONTROL ASSESSMENT FOR HIV-1 GENOTYPIC ANTIRETROVIRAL TESTING (2002) Antiviral Therapy 2003;8:S101 F Brun-Vézinet1, B Masquelier2, J Izopet3, V Calvez4, ML Chaix5, A Ruffault6, C Tamalet7, S Yerly8, D Descamps1, D Costagliola9 and the ANRS Resistance Group The use of supernatants from co-cultivated viruses does not improve the definition of the consensus amino acid sequences as compared to the use of diluted plasma specimens. Quality control assessment for HIV drug resistance sequencing must include an HIV-negative control, specimens with low viral load, specimen in duplicate and samples with high number of resistance mutations. Download Session 4 PDF: Abstracts 56 to 113
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| 92 | UPDATED, BLINDED, MULTICENTRE COMPARISON OF THE SENSITIVITY OF DIFFERENT TECHNOLOGIES TO DETECT AND QUANTIFY A MINOR DRUG-RESISTANT HIV-1 VARIANT Antiviral Therapy 2003;8:S102 E Halvas1, G Aldrovandi2, JP Balfe3, I Beck4, V Boltz5, L Frenkel4, J Hazelwood2, V Johnson2, M Kearney5, A Kovacs6, D Kuritzkes7, K Metzner8, D Nissley5, M Nowicki6, R Ziermann9, Y Zhao10, C Jennings11, J Bremer11, D Brambilla12 and J Mellors1 Blind testing of a panel of plasmidderived virus mixtures showed that two of three ASRT assays and the Ty1 assay could detect and quantify the 103N variant at frequencies <1%. One of the ASRT assays could quantify as low as 0.1% and possibly 0.01%. A potential advantage of Ty1 assay over ASRT is that the mutant allele is cloned and its presence can be confirmed by DNA sequencing. The other methods evaluated had detection and quantification limits ranging from 2 to 10% mutant. FDA-approved bulk sequencing technologies (ViroSeq and TruGene) had detection and quantification limits of 5–10% for 103N. These findings indicate that several technologies are available to address the role of minor drug-resistant variant in failure of antiretroviral therapy. Download Session 4 PDF: Abstracts 56 to 113
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| 93 | DETECTION OF RARE DRUG-RESISTANT HIV-1 REVERSE TRANSCRIPTASE VARIANTS USING A SENSITIVE PHENOTYPIC ASSAY Antiviral Therapy 2003;8:S103 DV Nissley1,3, E Halvas2, D Garfinkel3, J Mellors2 and J Strathern3 The TyHRT system is a sensitive phenotypic assay that detects HIV-1 drug-resistant variants present at less than 1%. The system can be used to identify novel drug-resistant variants. The simplicity and sensitivity of this assay makes it possible to monitor the emergence of drug resistance in basic and clinical research environments. Download Session 4 PDF: Abstracts 56 to 113
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| 94 | EXAMINATION OF WIDE VARIATION IN REPLICATION CAPACITY OF WILD-TYPE HIV-1: ANALYSIS OF GENOTYPE–PHENOTYPE ASSOCIATION VIA TREE-STRUCTURED METHODS Antiviral Therapy 2003;8:S104 JD Barbour1,2, T Wrin3, SG Deeks2, FM Hecht2, NS Hellmann3, CJ Petropoulos3, RM Grant1,2 and MR Segal2 TSM are effective techniques for genotype–phenotype association problems where genotype is represented by amino acid sequence. Due to the potential for overfitting, use of cross-validation or test sample data for evaluation of predictive performance is crucial. Recently proposed methods for enhancing performance (bagging, random forests) showed only modest improvement in performance over standard TSM. We identified three RT sites, not previously associated with drug resistance, associated with variation in RC of wild-type virus. RT135, which sits behind the RT active site, may restrict rotation of the RT ‘thumb’ as the enzyme binds to, and extends its ligand. RT177 and RT178 sit on a loop containing two key RT catalytic residues, D185 and D186, which coordinate two Mg2+ cations required for RT function. Subtle changes in the positioning of these residues may alter RT activity, impacting on viral replication capacity. Download Session 4 PDF: Abstracts 56 to 113
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| 95 | REVERSE TRANSCRIPTION FITNESS ASSAY BY QUANTITATIVE DETERMINATION OF INTERMEDIATE HIV-1 REVERSE TRANSCRIPTION CDNA PRODUCTS IN PBMCS Antiviral Therapy 2003;8:S105 M Nijhuis, L de Graaf, D Eggink, J den Dunnen, C Boucher and R Schuurman This rapid real-time Taqman PCR approach to quantify the formation of HIV-1 cDNA intermediates during the natural reverse transcription process in primary cells can be used to determine differences in reverse transcription efficiency for drugresistant RT variants. Clear defects in the reverse transcription process were observed for the lamivudineresistant M184V, I and T variants, which is in concordance with results obtained from enzymatical and virological data. Download Session 4 PDF: Abstracts 56 to 113
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| 96 | QUANTITATIVE PREDICTION OF HIV DRUG SUSCEPTIBILITY FROM VIRAL GENOTYPE THROUGH LINEAR REGRESSION MODELLING Antiviral Therapy 2003;8:S106 H Van Marck1, T Van den Bulcke1, M Van Houtte2, P Lecocq2 and L Bacheler3 Linear regression modelling is a promising new technique for the analysis of drug resistance in HIV-1. It is an attractive tool for identifying primary and secondary resistance-associated mutations for new and existing drugs and for calculating the contribution of mutations and combinations of mutations to resistance. The power of the method is most fully exploited when applied to large datasets of matched genotype/phenotype results. Download Session 4 PDF: Abstracts 56 to 113
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| 97 | TREE MODELS FOR THE EVOLUTION OF DRUG RESISTANCE Antiviral Therapy 2003;8:S107 N Beerenwinkel1, R Kaiser2, J Rahnenführer1, M Däumer2, D Hoffmann3, J Selbig4 and T Lengauer1 The proposed tree models capture important features of viral evolution. They provide a probabilistic framework for the appearance of new mutations under drug pressure. The model class of trees is computationally feasible and readable by humans, yet considerably richer than that of linear paths. Moreover, the approach is not limited to monotherapies, but also allows for analysing sequences under selective pressure of a combination therapy. Download Session 4 PDF: Abstracts 56 to 113
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| 98 | PREDICTIVE VALUE OF DRUG RESISTANCE INTERPRETATION SYSTEMS AND THERAPEUTIC DRUG MONITORING FOR VIROLOGICAL THERAPY RESPONSE TO SALVAGE THERAPY Antiviral Therapy 2003;8:S108 H Walter1, M Helm2, R Ehret3, B Schmidt4, K Korn1, H Knechten3 and P Braun3 1) All IS were predictive for therapy response. However, differences could be found in particular for ANRS_AC11, that showed to be most predicitve. 2) Including of TDM was more predictive than resistance interpreted by IS alone, indicating that there is additional benefit by performing TDM, although the differences were not high. 3) The finding that a substantial part of the new therapy would be necessary to avoid an viral load increase could represent the remaining activity of the pretreatment. Therefore, the influence of the actual pretreatment needs further to be evaluated. Download Session 4 PDF: Abstracts 56 to 113
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| 99 | PREDICTING PHENOTYPE FROM GENOTYPE: A COMPARISON OF STATISTICAL METHODS Antiviral Therapy 2003;8:S109 AS Foulkes1, L Zhou1 and V DeGruttola2 All three approaches resulted in reasonably high sensitivity while in this data setting the ROC approach performed better than clustering and recursive partitioning in 10/10 of the cross-validated samples. On the other hand, the combination of clustering and recursive partitioning had a higher specificity than the ROC approach in all cases. In general, as sensitivity of a prediction rule increases, specificity decreases. For patient management, maximizing sensitivity, that is the probability of correctly classifying someone as resistant, may be particularly important, since optimizing the effectiveness of a new drug requires that it be combined with other active drugs. |