Protease Resistance Mutations Research Articles

Effectiveness of Ritonavir-Boosted Protease Inhibitor Monotherapy in Clinical Practice Even with Previous Virological Failures to Protease Inhibitor-Based Regimens.

Background and ObjectiveSignificant controversy still exists about ritonavir-boosted protease inhibitor monotherapy (mtPI/rtv) as a simplification strategy that is used up to now to treat patients that have not experienced previous virological failure (VF) while on protease inhibitor (PI) -based regimens. We have evaluated the effectiveness of two mtPI/rtv regimens in an actual clinical practice setting, including patients that had experienced previous VF with PI-based regimens.MethodsThis retrospective study analyzed 1060 HIV-infected patients with undetectable viremia that were switched to lopinavir/ritonavir or darunavir/ritonavir monotherapy. In cases in which the patient had previously experienced VF while on a PI-based regimen, the lack of major HIV protease resistance mutations to lopinavir or darunavir, respectively, was mandatory. The primary endpoint of this study was the percentage of participants with virological suppression after 96 weeks according to intention-to-treat analysis (non-complete/missing = failure).ResultsA total of 1060 patients were analyzed, including 205 with previous VF while on PI-based regimens, 90 of whom were on complex therapies due to extensive resistance. The rates of treatment effectiveness (intention-to-treat analysis) and virological efficacy (on-treatment analysis) at week 96 were 79.3% (CI95, 76.8−81.8) and 91.5% (CI95, 89.6–93.4), respectively. No relationships were found between VF and earlier VF while on PI-based regimens, the presence of major or minor protease resistance mutations, the previous time on viral suppression, CD4+ T-cell nadir, and HCV-coinfection. Genotypic resistance tests were available in 49 out of the 74 patients with VFs and only four patients presented new major protease resistance mutations.ConclusionSwitching to mtPI/rtv achieves sustained virological control in most patients, even in those with previous VF on PI-based regimens as long as no major resistance mutations are present for the administered drug.

Contribution of Gag and Protease to HIV-1 Phenotypic Drug Resistance in Pediatric Patients Failing Protease Inhibitor-Based Therapy.

Protease inhibitors (PIs) are used as a first-line regimen in HIV-1-infected children. Here we investigated the phenotypic consequences of amino acid changes in Gag and protease on lopinavir (LPV) and ritonavir (RTV) susceptibility among pediatric patients failing PI therapy. The Gag-protease from isolates from 20 HIV-1 subtype C-infected pediatric patients failing an LPV and/or RTV-based regimen was phenotyped using a nonreplicativein vitroassay. Changes in sensitivity to LPV and RTV relative to that of the matched baseline (pretherapy) sample were calculated. Gag and protease amino acid substitutions associated with PI failure were created in a reference clone by site-directed mutagenesis and assessed. Predicted phenotypes were determined using the Stanford drug resistance algorithm. Phenotypic resistance or reduced susceptibility to RTV and/or LPV was observed in isolates from 10 (50%) patients, all of whom had been treated with RTV. In most cases, this was associated with protease resistance mutations, but substitutions at Gag cleavage and noncleavage sites were also detected. Gag amino acid substitutions were also found in isolates from three patients with reduced drug susceptibilities who had wild-type protease. Site-directed mutagenesis confirmed that some amino acid changes in Gag contributed to PI resistance but only in the presence of major protease resistance-associated substitutions. The isolates from all patients who received LPV exclusively were phenotypically susceptible. Baseline isolates from the 20 patients showed a large (47-fold) range in the 50% effective concentration of LPV, which accounted for most of the discordance seen between the experimentally determined and the predicted phenotypes. Overall, the inclusion of thegaggene and the use of matched baseline samples provided a more comprehensive assessment of the effect of PI-induced amino acid changes on PI resistance. The lack of phenotypic resistance to LPV supports the continued use of this drug in pediatric patients.

Clinical Outcomes of Virologically-Suppressed Patients with Pre-existing HIV-1 Drug Resistance Mutations Switching to Rilpivirine/Emtricitabine/Tenofovir Disoproxil Fumarate in the SPIRIT Study

Objectives: Antiretroviral regimen switching may be considered for HIV-1-infected, virologically-suppressed patients to enable treatment simplification or improve tolerability, but should be guided by knowledge of pre-existing drug resistance. The current study examined the impact of pre-existing drug resistance mutations on virologic outcomes among virologically-suppressed patients switching to Rilpivirine (RPV)/emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF).Methods: SPIRIT was a phase 3b study evaluating the safety and efficacy of switching to RPV/FTC/TDF in virologically-suppressed HIV-1-infected patients. Pre-existing drug resistance at baseline was determined by proviral DNA genotyping for 51 RPV/FTC/TDF-treated patients with known mutations by historical RNA genotype and matched controls and compared with clinical outcome at Week 48.Results: Drug resistance mutations in protease or reverse transcriptase were detected in 62.7% of patients by historical RNA genotype and in 68.6% by proviral DNA genotyping at baseline. Proviral DNA sequencing detected 89% of occurrences of NRTI and NNRTI resistance-associated mutations reported by historical genotype. Mutations potentially affecting RPV activity, including E138A/G/K/Q, Y181C, and H221Y, were detected in isolates from 11 patients by one or both assays. None of the patients with single mutants had virologic failure through Week 48. One patient with pre-existing Y181Y/C and M184I by proviral DNA genotyping experienced virologic failure. Nineteen patients with K103N present by historical genotype were confirmed by proviral DNA sequencing and 18/19 remained virologically-suppressed.Discussion: Virologic success rates were high among virologically-suppressed patients with pre-existing NRTI and NNRTI resistance-associated mutations who switched to RPV/FTC/TDF in the SPIRIT study. While plasma RNA genotyping remains preferred, proviral DNA genotyping may provide additional value in virologically-suppressed patients for whom historical resistance data are unavailable.

Elucidation of the Molecular Mechanism Driving Duplication of the HIV-1 PTAP Late Domain.

HIV-1 uses cellular machinery to bud from infected cells. This cellular machinery is comprised of several multiprotein complexes known as endosomal sorting complexes required for transport (ESCRTs). A conserved late domain motif, Pro-Thr-Ala-Pro (PTAP), located in the p6 region of Gag (p6(Gag)), plays a central role in ESCRT recruitment to the site of virus budding. Previous studies have demonstrated that PTAP duplications are selected in HIV-1-infected patients during antiretroviral therapy; however, the consequences of these duplications for HIV-1 biology and drug resistance are unclear. To address these questions, we constructed viruses carrying a patient-derived PTAP duplication with and without drug resistance mutations in the viral protease. We evaluated the effect of the PTAP duplication on viral release efficiency, viral infectivity, replication capacity, drug susceptibility, and Gag processing. In the presence of protease inhibitors, we observed that the PTAP duplication in p6(Gag) significantly increased the infectivity and replication capacity of the virus compared to those of viruses bearing only resistance mutations in protease. Our biochemical analysis showed that the PTAP duplication, in combination with mutations in protease, enhances processing between the nucleocapsid and p6 domains of Gag, resulting in more complete Gag cleavage in the presence of protease inhibitors. These results demonstrate that duplication of the PTAP motif in p6(Gag) confers a selective advantage in viral replication by increasing Gag processing efficiency in the context of protease inhibitor treatment, thereby enhancing the drug resistance of the virus. These findings highlight the interconnected role of PTAP duplications and protease mutations in the development of resistance to antiretroviral therapy. Resistance to current drug therapy limits treatment options in many HIV-1-infected patients. Duplications in a Pro-Thr-Ala-Pro (PTAP) motif in the p6 domain of Gag are frequently observed in viruses derived from patients on protease inhibitor (PI) therapy. However, the reason that these duplications arise and their consequences for virus replication remain to be established. In this study, we examined the effect of PTAP duplication on PI resistance in the context of wild-type protease or protease bearing PI resistance mutations. We observe that PTAP duplication markedly enhances resistance to a panel of PIs. Biochemical analysis reveals that the PTAP duplication reverses a Gag processing defect imposed by the PI resistance mutations in the context of PI treatment. The results provide a long-sought explanation for why PTAP duplications arise in PI-treated patients.

The L33F darunavir resistance mutation acts as a molecular anchor reducing the flexibility of the HIV-1 protease 30s and 80s loops

HIV-1 protease (PR) is a 99 amino acid protein responsible for proteolytic processing of the viral polyprotein – an essential step in the HIV-1 life cycle. Drug resistance mutations in PR that are selected during antiretroviral therapy lead to reduced efficacy of protease inhibitors (PI) including darunavir (DRV). To identify the structural mechanisms associated with the DRV resistance mutation L33F, we performed X-ray crystallographic studies with a multi-drug resistant HIV-1 protease isolate that contains the L33F mutation (MDR769 L33F). In contrast to other PR L33F DRV complexes, the structure of MDR769 L33F complexed with DRV reported here displays the protease flaps in an open conformation. The L33F mutation increases noncovalent interactions in the hydrophobic pocket of the PR compared to the wild-type (WT) structure. As a result, L33F appears to act as a molecular anchor, reducing the flexibility of the 30s loop (residues 29–35) and the 80s loop (residues 79–84). Molecular anchoring of the 30s and 80s loops leaves an open S1/S1′ subsite and distorts the conserved hydrogen-bonding network of DRV. These findings are consistent with previous reports despite structural differences with regards to flap conformation.

Genetic Changes in HIV-1 Gag-Protease Associated with Protease Inhibitor-Based Therapy Failure in Pediatric Patients.

Studies have shown a low frequency of HIV-1 protease drug resistance mutations in patients failing protease inhibitor (PI)-based therapy. Recent studies have identified mutations in Gag as an alternate pathway for PI drug resistance in subtype B viruses. We therefore genotyped the Gag and protease genes from 20 HIV-1 subtype C-infected pediatric patients failing a PI-based regimen. Major protease resistance mutations (M46I, I54V, and V82A) were identified in eight (40%) patients, as well as Gag cleavage site (CS) mutations (at codons 373, 374, 378, 428, 431, 449, 451, and 453) in nine (45%) patients. Four of these Gag CS mutations occurred in the absence of major protease mutations at PI failure. In addition, amino acid changes were noted at Gag non-CS with some predicted to be under HLA/KIR immune-mediated pressure and/or drug selection pressure. Changes in Gag during PI failure therefore warrant further investigation of the Gag gene and its role in PI failure in HIV-1 subtype C infection.

Deep sequencing of protease inhibitor resistant HIV patient isolates reveals patterns of correlated mutations in Gag and protease.

While the role of drug resistance mutations in HIV protease has been studied comprehensively, mutations in its substrate, Gag, have not been extensively cataloged. Using deep sequencing, we analyzed a unique collection of longitudinal viral samples from 93 patients who have been treated with therapies containing protease inhibitors (PIs). Due to the high sequence coverage within each sample, the frequencies of mutations at individual positions were calculated with high precision. We used this information to characterize the variability in the Gag polyprotein and its effects on PI-therapy outcomes. To examine covariation of mutations between two different sites using deep sequencing data, we developed an approach to estimate the tight bounds on the two-site bivariate probabilities in each viral sample, and the mutual information between pairs of positions based on all the bounds. Utilizing the new methodology we found that mutations in the matrix and p6 proteins contribute to continued therapy failure and have a major role in the network of strongly correlated mutations in the Gag polyprotein, as well as between Gag and protease. Although covariation is not direct evidence of structural propensities, we found the strongest correlations between residues on capsid and matrix of the same Gag protein were often due to structural proximity. This suggests that some of the strongest inter-protein Gag correlations are the result of structural proximity. Moreover, the strong covariation between residues in matrix and capsid at the N-terminus with p1 and p6 at the C-terminus is consistent with residue-residue contacts between these proteins at some point in the viral life cycle.

No correspondence between resistance mutations in the HCV-NS3 protease at baseline and early telaprevir-based triple therapy

Direct-acting antiviral (DAA)-based therapy is the new standard treatment for chronic hepatitis C virus (HCV) infection. However, protease inhibitor (PI)-resistant viral variants have been often described. This study aimed to examine HCV-NS3 protease variants at baseline and at 4weeks under triple therapy. To this end, we analyzed the presence of variants in HCV-NS3 protease region from peripheral blood samples of 16 patients infected with HCV-1 at baseline and at 4weeks of combined therapy with telaprevir, pegylated interferon, and ribavirin, using next-generation sequencing. Several variants with synonymous and non-synonymous amino acid substitutions were detected at both time points. Variants detected at low frequency corresponded to 74% (HCV-1a) and 35% (HCV-1b) of non-synonymous substitutions. We found nine PI-resistance-associated variants (V36A, T54S, V55I, Q80K, Q80R, V107I, I132V, D168E, M175L) in HCV-NS3 of 10 patients. There was no correspondence of resistance-associated variant profile between baseline and at 4weeks. Moreover, these resistance variants at baseline and short-term treatment are not good predictors of outcome under triple therapy. Our study also shows a large number of others minor and major non-synonymous variants in HCV-NS3 early in telaprevir-based therapy that can be important for further drug resistance association studies with newly developed PI agents.

Appearance of drug resistance-associated mutations in human immunodeficiency virus type 1 protease and reverse transcriptase derived from drug-treated Indonesian patients.

Although HIV-1 drug resistance is a major obstacle in Indonesia, information on drug resistance is limited. In this study, the viral subtype and appearance of drug resistance mutations in the HIV-1 protease (PR) and reverse transcriptase (RT) genes were determined among drug-treated, HIV-1-infected patients in Surabaya. HIV-1 patients who received antiretroviral therapy (ART) more than 2 years were randomly recruited regardless of the viral load or ART failure. Fifty-eight HIV-1 PR genes and 53 RT genes were sequenced. CRF01_AE viruses were identified as the predominant strain. Major drug resistance mutations were not detected in the PR genes. In contrast, 37.7% (20/53) of the participants had one or more major drug resistance mutations in the RT genes, predominantly M184V (28.3%), K103N (11.3%), and thymidine analogue mutations (TAMs) (20.8%). The high prevalence of drug resistance mutations in RT genes indicated the necessity of monitoring the effectiveness of ART in Indonesia.

Viral escape in the CNS with multidrug-resistant HIV-1.

IntroductionHIV-1 viral escape in the cerebrospinal fluid (CSF) despite viral suppression in plasma is rare [1,2]. We describe the case of a 50-year-old HIV-1 infected patient who was diagnosed with HIV-1 in 1995. Antiretroviral therapy (ART) was started in 1998 with a CD4 T cell count of 71 cells/ìL and HIV-viremia of 46,000 copies/mL. ART with zidovudine (AZT), lamivudine (3TC) and efavirenz achieved full viral suppression. After the patient had interrupted ART for two years, treatment was re-introduced with tenofovir (TDF), emtricitabin (FTC) and ritonavir boosted atazanavir (ATVr). This regimen suppressed HIV-1 in plasma for nine years and CD4 cells stabilized around 600 cells/ìL. Since July 2013, the patient complained about severe gait ataxia and decreased concentration.Materials and MethodsAdditionally to a neurological examination, two lumbar punctures, a cerebral MRI and a neuropsycological test were performed. HIV-1 viral load in plasma and in CSF was quantified using Cobas TaqMan HIV-1 version 2.0 (Cobas Ampliprep, Roche diagnostic, Basel, Switzerland) with a detection limit of 20 copies/mL. Drug resistance mutations in HIV-1 reverse transcriptase and protease were evaluated using bulk sequencing.ResultsThe CSF in January 2014 showed a pleocytosis with 75 cells/ìL (100% mononuclear) and 1,184 HIV-1 RNA copies/mL, while HIV-1 in plasma was below 20 copies/mL. The resistance testing of the CSF-HIV-1 RNA showed two NRTI resistance-associated mutations (M184V and K65R) and one NNRTI resistance-associated mutation (K103N). The cerebral MRI showed increased signal on T2-weighted images in the subcortical and periventricular white matter, in the basal ganglia and thalamus. Four months after ART intensification with AZT, 3TC, boosted darunavir and raltegravir, the pleocytosis in CSF cell count normalized to 1 cell/ìL and HIV viral load was suppressed. The neurological symptoms improved; however, equilibrium disturbances and impaired memory persisted. The neuro-psychological evaluation confirmed neurocognitive impairments in executive functions, attention, working and nonverbal memory, speed of information processing, visuospatial abilities and motor skills.ConclusionsHIV-1 infected patients with neurological complaints prompt further investigations of the CSF including measurement of HIV viral load and genotypic resistance testing since isolated replication of HIV with drug resistant variants can rarely occur despite viral suppression in plasma. Optimizing ART by using drugs with improved CNS penetration may achieve viral suppression in CSF with improvement of neurological symptoms.

Drug resistance is rarely the cause or consequence of long-term persistent low-level viraemia in HIV-1-infected patients on ART.

The introduction of highly sensitive HIV-1 viral load assays with a lower quantification limit of 20 copies/ml uncovered that in a number of patients on ART, the viral load systematically fluctuates around or slightly above the detection limit of the assays. This study aimed to analyse the presence or occurrence of drug resistance mutations in HIV-1-infected patients during long-term persistent low-level viraemia (PLLV) under ART. A retrospective study was carried out in which baseline and on-therapy presence of drug resistance mutations in the HIV-1 protease and reverse transcriptase genes were analysed in patients with PLLV between 20 and 250 copies/ml. For all available plasma samples collected during PLLV, resistance analysis was attempted with an ultrasensitive amplification and sequencing protocol. Resistance analysis was successful for 154 samples collected longitudinally from 23 patients over a median period of 4.7 years (IQR 3.3-5.7). Twenty of these patients were on a boosted protease inhibitor (PI)-based regimen (87%). Single drug resistance mutations were detected in isolated samples of 4 patients, 2 of the 3 patients who initiated a non-nucleoside reverse transcriptase inhibitor-based regimen and 2 of the 20 on a PI-based regimen. Only one of the detected mutations decreased susceptibility to the therapy regimen taken at the time of sample collection. Drug resistance mutations were not found in the three patients who developed virological failure (viral load >250 copies/ml) during the study. Long episodes of PLLV in patients on boosted PI-based regimens rarely result in the selection of new drug-resistant variants.

Assessment of Second-Line Antiretroviral Regimens for HIV Therapy in Africa

BackgroundThe efficacy and toxic effects of nucleoside reverse-transcriptase inhibitors (NRTIs) are uncertain when these agents are used with a protease inhibitor in second-line therapy for human immunodeficiency virus (HIV) infection in resource-limited settings. Removing the NRTIs or replacing them with raltegravir may provide a benefit.MethodsIn this open-label trial in sub-Saharan Africa, we randomly assigned 1277 adults and adolescents with HIV infection and first-line treatment failure to receive a ritonavir-boosted protease inhibitor (lopinavir–ritonavir) plus clinician-selected NRTIs (NRTI group, 426 patients), a protease inhibitor plus raltegravir in a superiority comparison (raltegravir group, 433 patients), or protease-inhibitor monotherapy after 12 weeks of induction therapy with raltegravir in a noninferiority comparison (monotherapy group, 418 patients). The primary composite end point, good HIV disease control, was defined as survival with no new World Health Organization stage 4 events, a CD4+ count of more than 250 cells per cubic millimeter, and a viral load of less than 10,000 copies per milliliter or 10,000 copies or more with no protease resistance mutations at week 96 and was analyzed with the use of imputation of data (≤4%).ResultsGood HIV disease control was achieved in 60% of the patients (mean, 255 patients) in the NRTI group, 64% of the patients (mean, 277) in the raltegravir group (P=0.21 for the comparison with the NRTI group; superiority of raltegravir not shown), and 55% of the patients (mean, 232) in the monotherapy group (noninferiority of monotherapy not shown, based on a 10-percentage-point margin). There was no significant difference in rates of grade 3 or 4 adverse events among the three groups (P=0.82). The viral load was less than 400 copies per milliliter in 86% of patients in the NRTI group, 86% in the raltegravir group (P=0.97), and 61% in the monotherapy group (P<0.001).ConclusionsWhen given with a protease inhibitor in second-line therapy, NRTIs retained substantial virologic activity without evidence of increased toxicity, and there was no advantage to replacing them with raltegravir. Virologic control was inferior with protease-inhibitor monotherapy. (Funded by European and Developing Countries Clinical Trials Partnership and others; EARNEST Current Controlled Trials number, ISRCTN37737787, and ClinicalTrials.gov number, NCT00988039.)

Persistent production of an integrase-deleted HIV-1 variant with no resistance mutation and wild-type proviral DNA in a treated patient

An HIV-1-infected patient with suppressed viremia for several years, in whom a variant carrying a deleted integrase (IN) gene, without reverse transcriptase (RT) or protease (PR) resistance mutations, emerged in the plasma and persisted is described.

HIV-1 Protease-Substrate Coevolution in Nelfinavir Resistance

Resistance to various human immunodeficiency virus type 1 (HIV-1) protease inhibitors (PIs) challenges the effectiveness of therapies in treating HIV-1-infected individuals and AIDS patients. The virus accumulates mutations within the protease (PR) that render the PIs less potent. Occasionally, Gag sequences also coevolve with mutations at PR cleavage sites contributing to drug resistance. In this study, we investigated the structural basis of coevolution of the p1-p6 cleavage site with the nelfinavir (NFV) resistance D30N/N88D protease mutations by determining crystal structures of wild-type and NFV-resistant HIV-1 protease in complex with p1-p6 substrate peptide variants with L449F and/or S451N. Alterations of residue 30's interaction with the substrate are compensated by the coevolving L449F and S451N cleavage site mutations. This interdependency in the PR-p1-p6 interactions enhances intermolecular contacts and reinforces the overall fit of the substrate within the substrate envelope, likely enabling coevolution to sustain substrate recognition and cleavage in the presence of PR resistance mutations. Resistance to human immunodeficiency virus type 1 (HIV-1) protease inhibitors challenges the effectiveness of therapies in treating HIV-1-infected individuals and AIDS patients. Mutations in HIV-1 protease selected under the pressure of protease inhibitors render the inhibitors less potent. Occasionally, Gag sequences also mutate and coevolve with protease, contributing to maintenance of viral fitness and to drug resistance. In this study, we investigated the structural basis of coevolution at the Gag p1-p6 cleavage site with the nelfinavir (NFV) resistance D30N/N88D protease mutations. Our structural analysis reveals the interdependency of protease-substrate interactions and how coevolution may restore substrate recognition and cleavage in the presence of protease drug resistance mutations.

Contribution of Gag and protease to variation in susceptibility to protease inhibitors between different strains of subtype B human immunodeficiency virus type 1

Recent reports have shown that human immunodeficiency virus type 1 (HIV-1) Gag can directly affect susceptibility to protease inhibitors (PIs) in the absence of known resistance mutations in protease. Inclusion of co-evolved Gag alongside protease in phenotypic drug susceptibility assays can alter PI susceptibility in comparison with protease with a WT Gag. Using a single-replication-cycle assay encompassing full-length Gag together with protease we demonstrated significant variation in PI susceptibility between a number of PI-naïve subtype B viruses. Six publicly available subtype B molecular clones, namely HXB2, NL4-3, SF2, YU2, JRFL and 89.6, displayed up to nine-fold reduced PI susceptibility in comparison with the assay reference strain. For two molecular clones, YU2 and JRFL, Gag contributed solely to the observed reduction in susceptibility, with the N-terminal region of Gag contributing significantly. Gag and protease from treatment-naïve, patient-derived viruses also demonstrated significant variation in susceptibility, with up to a 17-fold reduction to atazanavir in comparison with the assay reference strain. In contrast to the molecular clones, protease was the main determinant of the reduced susceptibility. Common polymorphisms in protease, including I13V, L63P and A71T, were shown to contribute to this reduction in PI susceptibility, in the absence of major resistance mutations. This study demonstrated significant variation in PI susceptibility of treatment-naïve patient viruses, and provided further evidence of the independent role of Gag, the protease substrate and in particular the N-terminus of Gag in PI susceptibility. It also highlighted the importance of considering co-evolved Gag and protease when assessing PI susceptibility.

Potential Elucidation of a Novel CTL Epitope in HIV-1 Protease by the Protease Inhibitor Resistance Mutation L90M

The combination of host immune responses and use of antiretrovirals facilitate partial control of human immunodeficiency virus type 1 (HIV-1) infection and result in delayed progression to Acquired Immunodeficiency Syndrome (AIDS). Both treatment and host immunity impose selection pressures on the highly mutable HIV-1 genome resulting in antiretroviral resistance and immune escape. Researchers have shown that antiretroviral resistance mutations can shape cytotoxic T-lymphocyte immunity by altering the epitope repertoire of HIV infected cells. Here it was discovered that an important antiretroviral resistance mutation, L90M in HIV protease, occurs at lower frequencies in hosts that harbor the B*15, B*48 or A*32 human leukocyte antigen subtypes. A likely reason is the elucidation of novel epitopes by L90M. NetMHCPan predictions reveal increased affinity of the peptide spanning the HIV protease region, PR 89–97 and PR 90–99 to HLA-B*15/B*48 and HLA-A*32 respectively due to the L90M substitution. The higher affinity could increase the chance of the epitope being presented and recognized by Cytotoxic T-lymphocytes and perhaps provide additional immunological pressures in the presence of antiretroviral attenuating mutations. This evidence supports the notion that knowledge of HLA allotypes in HIV infected individuals could augment antiretroviral treatment by the elucidation of epitopes due to antiretroviral resistance mutations in HIV protease.

Resistance Mutations outside the Integrase Coding Region Have an Effect on Human Immunodeficiency Virus Replicative Fitness but Do Not Affect Its Susceptibility to Integrase Strand Transfer Inhibitors

Most studies describing phenotypic resistance to integrase strand transfer inhibitors have analyzed viruses carrying only patient-derived HIV-1 integrase genes (INT-recombinant viruses). However, to date, many of the patients on INSTI-based treatment regimes, such as raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG) are infected with multidrug-resistant HIV-1 strains. Here we analyzed the effect of drug resistance mutations in Gag (p2/NCp7/p1/p6), protease (PR), reverse transcriptase (RT), and integrase (IN) coding regions on susceptibility to INSTIs and viral replicative fitness using a novel HIV-1 phenotyping assay. Initial characterization based on site-directed mutant INSTI-resistant viruses confirmed the effect of a series of INSTI mutations on reduced susceptibility to EVG and RAL and viral replicative fitness (0.6% to 99% relative to the HIV-1NL4-3 control). Two sets of recombinant viruses containing a 3,428-bp gag-p2/NCp7/p1/p6/pol-PR/RT/IN (p2-INT) or a 1,088 bp integrase (INT) patient-derived fragment were constructed from plasma samples obtained from 27 virologic failure patients participating in a 48-week dose-ranging study of elvitegravir, GS-US-183-0105. A strong correlation was observed when susceptibility to EVG and RAL was assayed using p2-INT- vs. INT-recombinant viruses (Pearson coefficient correlation 0.869 and 0.918, P<0.0001 for EVG and RAL, respectively), demonstrating that mutations in the protease and RT have limited effect on susceptibility to these INSTIs. On the other hand, the replicative fitness of viruses harboring drug resistance mutations in PR, RT, and IN was generally impaired compared to viruses carrying only INSTI-resistance mutations. Thus, in the absence of drug pressure, drug resistance mutations in the PR and RT contribute to decrease the replicative fitness of the virus already impaired by mutations in the integrase. The use of recombinant viruses containing most or all HIV-1 regions targeted by antiretroviral drugs might be essential to understand the collective effect of epistatic interactions in multidrug-resistant viruses.

Resistance in Pediatric Patients Experiencing Virologic Failure With First-line and Second-line Antiretroviral Therapy

We examined HIV-1 resistance in children failing first-line and second-line antiretroviral therapy in South Africa, all with clade C virus. Those exposed to full-dose ritonavir had multiple protease resistance mutations. Nineteen percent had wild-type virus. Appropriate antiretroviral therapy sequencing in sub-Saharan African children is essential for prolong treatment options.

Dynamics of resistance mutations to NS3 protease inhibitors in a cohort of Brazilian patients chronically infected with hepatitis C virus (genotype 1) treated with pegylated interferon and ribavirin: a prospective longitudinal study

About sixty thousand new cases of Hepatitis C virus (HCV) infection are recorded in Brazil each year. These cases are currently treated with pegylated interferon (PEG-IFN) and ribavirin (RBV) with an overall success rate of 50%. New compounds for anti-HCV therapy targeted to the HCV NS3 protease are being developed and some already form the components of licensed therapies. Mapping NS3 protease resistance mutations to protease inhibitors or anti-viral drug candidates is important to direct anti-HCV drug treatment.MethodsSequence analysis of the HCV NS3 protease was conducted in a group of 68 chronically infected patients harboring the HCV genotype 1. The patients were sampled before, during and after a course of PEG-IFN-RBV treatment.ResultsResistance mutations to the protease inhibitors, Boceprevir and Telaprevir were identified in HCV isolated from three patients (4.4%); the viral sequences contained at least one of the following mutations: V36L, T54S and V55A. In one sustained virological responder, the T54S mutation appeared during the course of PEG-IFN and RBV therapy. In contrast, V36L and V55A mutations were identified in virus isolated from one relapsing patient before, during, and after treatment, whereas the T54S mutation was identified in virus isolated from one non-responding patient, before and during the treatment course.ConclusionsThe incidence and persistence of protease resistance mutations occurring in HCV from chronically infected patients in Brazil should be considered when using protease inhibitors to treat HCV disease. In addition, patients treated with the current therapy (PEG-IFN and RBV) that are relapsing or are non-responders should be considered candidates for protease inhibitor therapy.

Low Prevalence of Antiretroviral Resistance Among HIV Type 1-Positive Prisoners in the Southeast United States

Drug-resistant HIV complicates management of HIV infection. Although an estimated 14% of all HIV-positive persons pass through a prison or jail in the United States each year, little is known about the overall prevalence of antiretroviral (ARV) resistance in incarcerated persons. All genotypic sequence data on HIV-positive prisoners in the North Carolina (NC) Department of Corrections (DOC) were obtained from LabCorp. Screening for major resistance mutations in protease (PI) and reverse transcriptase (NRTI and NNRTI) was done using Genosure and the Stanford HIV Database. For subjects with multiple genotype reports, each mutation was counted only once and considered present on all subsequent genotypes. Between October 2006 and February 2010, the NC DOC incarcerated 1,911 HIV(+) individuals of whom 19.2% (n=367) had at least one genotype performed. The overall prevalence of a major resistance mutation was 28.3% (95% CI 23.7, 33.0). Among prisoners ever exposed to an ARV during incarceration (n=329) prevalence of a major resistance mutation was 29.8% (95% CI 24.9, 34.7); resistance by class was 20.4% (95% CI 16.0, 24.7) for NRTIs, 19.8% (95% CI 15.5, 24.1) for NNRTIs, and 8.8% (95% CI 5.8,11.9) for PIs. Single class drug resistance was most prevalent at 14.2% (10.2,17.7) followed by dual 12.5% (I8.9,16.0) and triple class 3.3% (1.4,5.3) resistance. The three most prevalent mutations were K103N 15.8% (12.0, 20.2), M184V 14.3% (10.7,18.5), and M41L 4.9% (2.8,7.8). In the NC DOC ARV resistance prevalence, dual and triple class drug resistance was moderate over the study period. Resistance to PIs was lower than NNRTIs and NRTIs, likely reflecting higher usage of these two classes or a lower barrier to resistance.