Susceptibility to protease inhibitors in HIV-2 primary isolates from patients failing antiretroviral therapy

Antiretroviral Treatment of HIV-2 Infection: Available Drugs, Resistance Pathways, and Promising New Compounds

Currently, it is estimated that 1-2 million people worldwide are infected with HIV-2, accounting for 3-5% of the global burden of HIV. The course of HIV-2 infection is longer compared to HIV-1 infection, but without effective antiretroviral therapy (ART), a substantial proportion of infected patients will progress to AIDS and die. Antiretroviral drugs in clinical use were designed for HIV-1 and, unfortunately, some do not work as well, or do not work at all, for HIV-2. This is the case for non-nucleoside reverse transcriptase inhibitors (NNRTIs), the fusion inhibitor enfuvirtide (T-20), most protease inhibitors (PIs), the attachment inhibitor fostemsavir and most broadly neutralizing antibodies. Integrase inhibitors work well against HIV-2 and are included in first-line therapeutic regimens for HIV-2-infected patients. However, rapid emergence of drug resistance and cross-resistance within each drug class dramatically reduces second-line treatment options. New drugs are needed to treat infection with drug-resistant isolates. Here, we review the therapeutic armamentarium available to treat HIV-2-infected patients, as well as promising drugs in development. We also review HIV-2 drug resistance mutations and resistance pathways that develop in HIV-2-infected patients under treatment.

Management of HIV-2 resistance to antiretroviral therapy in a HIV-1/HIV-2/HBV co-infected patient

Background

The current standard of care is to start antiretroviral therapy in all patients diagnosed with HIV-1, as for HIV-2 current DHHS guideline suggests ART for HIV-2 as soon as diagnosis is established, although this practice is not universal, for instance, in Portugal there are specific criteria to start treatment.

Case presentation

We present a case of a man, chronically infected with HIV-1, HIV-2 and hepatitis B virus who developed resistance to HIV-2 while maintaining HIV-1 under control. 6 years after starting antiretroviral therapy he had his first virologic failure. We performed HIV-2 resistance tests that revealed high-grade resistance to all nucleoside reverse-transcriptase inhibitors except tenofovir and to all protease inhibitors except darunavir. After a decade of permanent poor adherence to therapy he developed resistance to both tenofovir and darunavir. We put together a new regiment with tenofovir alafenamide + emtricitabine + dolutegravir + maraviroc and nowadays he is with undetectable HIV-1 and HIV-2 viral loads.

Conclusions

This shows the importance of having access to HIV-2 viral load determination and HIV-2 resistance testing.

Expanded Spectrum of Antiretroviral-Selected Mutations in Human Immunodeficiency Virus Type 2

BACKGROUND

HIV-1 and HIV-2 differ in their antiretroviral (ARV) susceptibilities and drug resistance mutations (DRMs).

METHODS

We analyzed published HIV-2 pol sequences to identify HIV-2 treatment-selected mutations (TSMs). Mutation prevalences were determined by HIV-2 group and ARV status. Nonpolymorphic mutations were those in <1% of ARV-naive persons. TSMs were those associated with ARV therapy after multiple comparisons adjustment.

RESULTS

We analyzed protease (PR) sequences from 483 PR inhibitor (PI)-naive and 232 PI-treated persons; RT sequences from 333 nucleoside RT inhibitor (NRTI)-naive and 252 NRTI-treated persons; and integrase (IN) sequences from 236 IN inhibitor (INSTI)-naive and 60 INSTI-treated persons. In PR, 12 nonpolymorphic TSMs occurred in ≥11 persons: V33I, K45R, V47A, I50V, I54M, T56V, V62A, A73G, I82F, I84V, F85L, L90M. In RT, 9 nonpolymorphic TSMs occurred in ≥10 persons: K40R, A62V, K70R, Y115F, Q151M, M184VI, S215Y. In IN, 11 nonpolymorphic TSMs occurred in ≥4 persons: Q91R, E92AQ, T97A, G140S, Y143G, Q148R, A153G, N155H, H156R, R231 5-amino acid insertions. Nine of 32 nonpolymorphic TSMs were previously unreported.

CONCLUSIONS

This meta-analysis confirmed the ARV association of previously reported HIV-2 DRMs and identified novel TSMs. Genotypic and phenotypic studies of HIV-2 TSMs will improve approaches to predicting HIV-2 ARV susceptibility and treating HIV-2-infected persons.

Structural Impacts of Drug-Resistance Mutations Appearing in HIV-2 Protease

The use of antiretroviral drugs is accompanied by the emergence of HIV-2 resistances. Thus, it is important to elucidate the mechanisms of resistance to antiretroviral drugs. Here, we propose a structural analysis of 31 drug-resistant mutants of HIV-2 protease (PR2) that is an important target against HIV-2 infection. First, we modeled the structures of each mutant. We then located structural shifts putatively induced by mutations. Finally, we compared wild-type and mutant inhibitor-binding pockets and interfaces to explore the impacts of these induced structural deformations on these two regions. Our results showed that one mutation could induce large structural rearrangements in side-chain and backbone atoms of mutated residue, in its vicinity or further. Structural deformations observed in side-chain atoms are frequent and of greater magnitude, that confirms that to fight drug resistance, interactions with backbone atoms should be favored. We showed that these observed structural deformations modify the conformation, volume, and hydrophobicity of the binding pocket and the composition and size of the PR2 interface. These results suggest that resistance mutations could alter ligand binding by modifying pocket properties and PR2 stability by impacting its interface. Our results reinforce the understanding of the effects of mutations that occurred in PR2 and the different mechanisms of PR2 resistance.

The recent application of 3D-QSAR and docking studies to novel HIV-protease inhibitor drug discovery

INTRODUCTION

Despite the availability of FDA approved inhibitors of HIV protease, numerous efforts are still ongoing to achieve 'near-perfect' drugs devoid of characteristic adverse side effects, toxicities, and mutational resistance. While experimental methods have been plagued with huge consumption of time and resources, there has been an incessant shift towards the use of computational simulations in HIV protease inhibitor drug discovery.

AREAS COVERED

Herein, the authors review the numerous applications of 3D-QSAR modeling methods over recent years relative to the design of new HIV protease inhibitors from a series of experimentally derived compounds. Also, the augmentative contributions of molecular docking are discussed.

EXPERT OPINION

Efforts to optimize 3D QSAR and molecular docking for HIV-1 drug discovery are ongoing, which could further incorporate inhibitor motions at the active site using molecular dynamics parameters. Also, highly predictive machine learning algorithms such as random forest, K-means, decision trees, linear regression, hierarchical clustering, and Bayesian classifiers could be employed.

Impacts of drug resistance mutations on the structural asymmetry of the HIV-2 protease

Background

Drug resistance is a severe problem in HIV treatment. HIV protease is a common target for the design of new drugs for treating HIV infection. Previous studies have shown that the crystallographic structures of the HIV-2 protease (PR2) in bound and unbound forms exhibit structural asymmetry that is important for ligand recognition and binding. Here, we investigated the effects of resistance mutations on the structural asymmetry of PR2. Due to the lack of structural data on PR2 mutants, the 3D structures of 30 PR2 mutants of interest have been modeled using an in silico protocol. Structural asymmetry analysis was carried out with an in-house structural-alphabet-based approach.

Results

The systematic comparison of the asymmetry of the wild-type structure and a large number of mutants highlighted crucial residues for PR2 structure and function. In addition, our results revealed structural changes induced by PR2 flexibility or resistance mutations. The analysis of the highlighted structural changes showed that some mutations alter protein stability or inhibitor binding.

Conclusions

This work consists of a structural analysis of the impact of a large number of PR2 resistant mutants based on modeled structures. It suggests three possible resistance mechanisms of PR2, in which structural changes induced by resistance mutations lead to modifications in the dimerization interface, ligand recognition or inhibitor binding.

[HIV-2 infection in Senegal: virological failures and resistance to antiretroviral drugs (ARVs)]

Introduction

Le VIH-2, endémique en Afrique de l'Ouest, est naturellement résistant aux inhibiteurs non nucléosidiques de la rétro transcriptase (INNRTI), ce qui rend difficile la prise en charge dans les pays en développement. L’objectif ici était de déterminer la prévalence de l'échec virologique au 12^éme et 24^éme mois (M12 et M24) de traitement antirétroviral de première ligne chez les patients infectés par le VIH-2 et d'en décrire les résistances génotypiques associées.

Méthodes

Il s'agit d'une étude descriptive longitudinale et prospective, durant la période de novembre 2005 à juin 2017. L'échec virologique a été défini comme toute charge virale supérieure à 50 copies/ml après 6 mois de traitement ARV à deux reprises. La recherche de mutations de résistance a été réalisée dans les régions codantes de la protéase et de la transcriptase inverse.

Résultats

Au total 110 patients ont été colligés, d'âge médian de 46 ans (Extrêmes 18-67) avec un ratio F/H de 2,54. À l'inclusion, la charge virale était détectable dans 44% des cas avec une médiane de 935cp/ml (Extrêmes 17-144038). Le schéma antirétroviral associait 2 INTI à 1IP dans 94% des cas. La durée médiane de suivi était estimée à 1200 jours (Extrêmes 1-3840). 94 puis 76 patients ont respectivement complété leur bilan à M12 et M24. Au suivi M24, 39 patients étaient en échec virologique soit une prévalence de 39% estimée à 33% à M12 et 11% à M24. 45% des patients avaient des résistances aux inhibiteurs nucléosidiques de la transcriptase inverse (INTI), 41% des résistances aux IP et 30% des multi résistances aux INTI et IP.

Conclusion

Il est impératif de rendre accessible les nouvelles classes thérapeutiques pour le traitement de sauvetage des patients infectés par le VIH-2 dans les pays à ressources limitées.

Characterizing the structural variability of HIV-2 protease upon the binding of diverse ligands using a structural alphabet approach

The HIV-2 protease (PR2) is an important target for designing new drugs against the HIV-2 infection. In this study, we explored the structural backbone variability of all available PR2 structures complexed with various inhibitors using a structural alphabet approach. 77% of PR2 positions are structurally variable, meaning they exhibit different local conformations in PR2 structures. This variability was observed all along the structure, particularly in the elbow and flap regions. A part of these backbone changes observed between the 18 PR2 is induced by intrinsic flexibility, and ligand binding putatively induces others occurring in the binding pocket. These latter changes could be important for PR2 adaptation to diverse ligands and are accompanied by changes outside the binding pocket. In addition, the study of the link between structural variability of the pocket and PR2-ligand interactions allowed us to localize pocket regions important for ligand binding and catalytic function, regions important for ligand recognition that adjust their backbone in response to ligand binding and regions important for the pocket opening and closing that have large intrinsic flexibility. Finally, we suggested that differences in ligand effectiveness for PR2 could be partially explained by different backbone deformations induced by these ligands. To conclude, this study is the first characterization of the PR2 structural variability considering ligand diversity. It provides information about the recognition of PR2 to various ligands and its mechanisms to adapt its local conformation to bound ligands that could help understand the resistance of PR2 to its inhibitors, a major antiretroviral class. Communicated by Ramaswamy H. Sarma.

Characterization of HIV-2 Protease Structure by Studying Its Asymmetry at the Different Levels of Protein Description

HIV-2 protease (PR2) is a homodimer, which is an important target in the treatment of the HIV-2 infection. In this study, we developed an in silico protocol to analyze and characterize the asymmetry of the unbound PR2 structure using three levels of protein description by comparing the conformation, accessibility, and flexibility of each residue in the two PR2 chains. Our results showed that 65% of PR2 residues have at least one of the three studied asymmetries (structural, accessibility, or flexibility) with 10 positions presenting the three asymmetries in the same time. In addition, we noted that structural and flexibility asymmetries are linked indicating that the structural asymmetry of some positions result from their large flexibility. By comparing the structural asymmetry of the crystallographic and energetically minimized structures of the unbound PR2, we confirmed that the structural asymmetry of unbound PR2 is an intrinsic property of this protein with an important role for the PR2 deformation upon ligand binding. This analysis also allowed locating asymmetries corresponding to crystallization artefacts. This study provides insight that will help to better understand the structural deformations of PR2 and to identify key positions for ligand binding.

In Vitro Antiviral Activity of Cabotegravir against HIV-2

We examined the antiviral activity of the integrase inhibitor (INI) cabotegravir against HIV-2 isolates from INI-naive individuals. HIV-2 was sensitive to cabotegravir in single-cycle and spreading-infection assays, with 50% effective concentrations (EC₅₀s) in the low to subnanomolar range; comparable results were obtained for HIV-1 in both assay formats. Our findings suggest that cabotegravir should be evaluated in clinical trials as a potential option for antiretroviral therapy and preexposure prophylaxis in HIV-2-prevalent settings.

Exploration of the effect of sequence variations located inside the binding pocket of HIV-1 and HIV-2 proteases

HIV-2 protease (PR2) is naturally resistant to most FDA (Food and Drug Administration)-approved HIV-1 protease inhibitors (PIs), a major antiretroviral class. In this study, we compared the PR1 and PR2 binding pockets extracted from structures complexed with 12 ligands. The comparison of PR1 and PR2 pocket properties showed that bound PR2 pockets were more hydrophobic with more oxygen atoms and fewer nitrogen atoms than PR1 pockets. The structural comparison of PR1 and PR2 pockets highlighted structural changes induced by their sequence variations and that were consistent with these property changes. Specifically, substitutions at residues 31, 46, and 82 induced structural changes in their main-chain atoms that could affect PI binding in PR2. In addition, the modelling of PR1 mutant structures containing V32I and L76M substitutions revealed a cooperative mechanism leading to structural deformation of flap-residue 45 that could modify PR2 flexibility. Our results suggest that substitutions in the PR1 and PR2 pockets can modify PI binding and flap flexibility, which could underlie PR2 resistance against PIs. These results provide new insights concerning the structural changes induced by PR1 and PR2 pocket variation changes, improving the understanding of the atomic mechanism of PR2 resistance to PIs.

Analysis of the HIV-2 protease's adaptation to various ligands: characterization of backbone asymmetry using a structural alphabet

The HIV-2 protease (PR2) is a homodimer of 99 residues with asymmetric assembly and binding various ligands. We propose an exhaustive study of the local structural asymmetry between the two monomers of all available PR2 structures complexed with various inhibitors using a structural alphabet approach. On average, PR2 exhibits asymmetry in 31% of its positions-i.e., exhibiting different backbone local conformations in the two monomers. This asymmetry was observed all along its structure, particularly in the elbow and flap regions. We first differentiated structural asymmetry conserved in most PR2 structures from the one specific to some PR2. Then, we explored the origin of the detected asymmetry in PR2. We localized asymmetry that could be induced by PR2's flexibility, allowing transition from the semi-open to closed conformations and the asymmetry potentially induced by ligand binding. This latter could be important for the PR2's adaptation to diverse ligands. Our results highlighted some differences between asymmetry of PR2 bound to darunavir and amprenavir that could explain their differences of affinity. This knowledge is critical for a better description of PR2's recognition and adaptation to various ligands and for a better understanding of the resistance of PR2 to most PR2 inhibitors, a major antiretroviral class.

How does curcumin work with poor bioavailability? Clues from experimental and theoretical studies

Curcumin is a natural product with multiple biological activities and numerous potential therapeutic applications. However, its poor systemic bioavailability fails to explain the potent pharmacological effects and hinders its clinical application. Using experimental and theoretical approaches, we compared curcumin and its degradation products for its biological activities against Alzheimer's disease (AD), including the superoxide anion radical (O2(.-))-scavenging activity, Aβ fibrils (fAβ) formation-inhibiting activity, and enzymatic inhibition activity. We showed that compared to the parent compound curcumin, the degradation products mixture possessed higher O2(.-)-scavenging activity and stronger inhibition against fAβ formation. The docking simulations revealed that the bioactive degradation products should make important contribution to the experimentally observed enzymatic inhibition activities of curcumin. Given that curcumin is readily degraded under physiological condition, our findings strongly suggested that the degradation products should make important contribution to the diverse biological activities of curcumin. Our novel findings not only provide novel insights into the complex pharmacology of curcumin due to its poor bioavailability, but also open new avenues for developing therapeutic applications of this natural product.

Inhibition Profiling of Retroviral Protease Inhibitors Using an HIV-2 Modular System

Retroviral protease inhibitors (PIs) are fundamental pillars in the treatment of HIV infection and acquired immunodeficiency syndrome (AIDS). Currently used PIs are designed against HIV-1, and their effect on HIV-2 is understudied. Using a modular HIV-2 protease cassette system, inhibition profiling assays were carried out for protease inhibitors both in enzymatic and cell culture assays. Moreover, the treatment-associated resistance mutations (I54M, L90M) were introduced into the modular system, and comparative inhibition assays were performed to determine their effect on the susceptibility of the protease. Our results indicate that darunavir, saquinavir, indinavir and lopinavir were very effective HIV-2 protease inhibitors, while tipranavir, nelfinavir and amprenavir showed a decreased efficacy. I54M, L90M double mutation resulted in a significant reduction in the susceptibility to most of the inhibitors with the exception of tipranavir. To our knowledge, this modular system constitutes a novel approach in the field of HIV-2 protease characterization and susceptibility testing.

Four Amino Acid Changes in HIV-2 Protease Confer Class-Wide Sensitivity to Protease Inhibitors

Protease is essential for retroviral replication, and protease inhibitors (PI) are important for treating HIV infection. HIV-2 exhibits intrinsic resistance to most FDA-approved HIV-1 PI, retaining clinically useful susceptibility only to lopinavir, darunavir, and saquinavir. The mechanisms for this resistance are unclear; although HIV-1 and HIV-2 proteases share just 38 to 49% sequence identity, all critical structural features of proteases are conserved. Structural studies have implicated four amino acids in the ligand-binding pocket (positions 32, 47, 76, and 82). We constructed HIV-2ROD9 molecular clones encoding the corresponding wild-type HIV-1 amino acids (I32V, V47I, M76L, and I82V) either individually or together (clone PRΔ4) and compared the phenotypic sensitivities (50% effective concentration [EC50]) of mutant and wild-type viruses to nine FDA-approved PI. Single amino acid replacements I32V, V47I, and M76L increased the susceptibility of HIV-2 to multiple PI, but no single change conferred class-wide sensitivity. In contrast, clone PRΔ4 showed PI susceptibility equivalent to or greater than that of HIV-1 for all PI. We also compared crystallographic structures of wild-type HIV-1 and HIV-2 proteases complexed with amprenavir and darunavir to models of the PRΔ4 enzyme. These models suggest that the amprenavir sensitivity of PRΔ4 is attributable to stabilizing enzyme-inhibitor interactions in the P2 and P2' pockets of the protease dimer. Together, our results show that the combination of four amino acid changes in HIV-2 protease confer a pattern of PI susceptibility comparable to that of HIV-1, providing a structural rationale for intrinsic HIV-2 PI resistance and resolving long-standing questions regarding the determinants of differential PI susceptibility in HIV-1 and HIV-2.

IMPORTANCE

Proteases are essential for retroviral replication, and HIV-1 and HIV-2 proteases share a great deal of structural similarity. However, only three of nine FDA-approved HIV-1 protease inhibitors (PI) are active against HIV-2. The underlying reasons for intrinsic PI resistance in HIV-2 are not known. We examined the contributions of four amino acids in the ligand-binding pocket of the enzyme that differ between HIV-1 and HIV-2 by constructing HIV-2 clones encoding the corresponding HIV-1 amino acids and testing the PI susceptibilities of the resulting viruses. We found that the HIV-2 clone containing all four changes (PRΔ4) was as susceptible as HIV-1 to all nine PI. We also modeled the PRΔ4 enzyme structure and compared it to existing crystallographic structures of HIV-1 and HIV-2 proteases complexed with amprenavir and darunavir. Our findings demonstrate that four positions in the ligand-binding cleft of protease are the primary cause of HIV-2 PI resistance.

A modular system to evaluate the efficacy of protease inhibitors against HIV-2

The human immunodeficiency virus (HIV) protease is a homodimeric aspartyl protease that is crucial for the viral life-cycle, cleaving proviral polyproteins, hence creating mature protein components that are required for the formation of an infectious virus. With diagnostic measures and clinically used protease inhibitors focusing on HIV-1, due to its higher virulence and prevalence, studies of the efficacy of those inhibitors on HIV-2 protease remain widely lacking. Utilizing a wild-type HIV-2 vector backbone and cloning techniques we have developed a cassette system where the efficacy of clinically used protease inhibitors can be studied for various serotypes of HIV-2 protease both in enzymatic and cell culture assays. In our experiments, optimization of the expression protocol led to a relatively stable enzyme, for cell culture assays, the efficiency of transfection and transduction capability of the modified vector was tested and was not found to differ from that of the wild-type, moreover, a 2^nd generation protease inhibitor was used to demonstrate the usefulness of the system. The combination of assays performed with our cassette system is expected to provide an accurate measure of the efficacy of currently used; as well as experimental protease inhibitors on HIV-2.

Revealing origin of decrease in potency of darunavir and amprenavir against HIV-2 relative to HIV-1 protease by molecular dynamics simulations

Clinical inhibitors Darunavir (DRV) and Amprenavir (APV) are less effective on HIV-2 protease (PR2) than on HIV-1 protease (PR1). To identify molecular basis associated with the lower inhibition, molecular dynamics (MD) simulations and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculations were performed to investigate the effectiveness of the PR1 inhibitors DRV and APV against PR1/PR2. The rank of predicted binding free energies agrees with the experimental determined one. Moreover, our results show that two inhibitors bind less strongly to PR2 than to PR1, again in agreement with the experimental findings. The decrease in binding free energies for PR2 relative to PR1 is found to arise from the reduction of the van der Waals interactions induced by the structural adjustment of the triple mutant V32I, I47V and V82I. This result is further supported by the difference between the van der Waals interactions of inhibitors with each residue in PR2 and in PR1. The results from the principle component analysis suggest that inhibitor binding tends to make the flaps of PR2 close and the one of PR1 open. We expect that this study can theoretically provide significant guidance and dynamics information for the design of potent dual inhibitors targeting PR1/PR2.

Discriminatory capacity between HIV-1 and HIV-2 of the new rapid confirmation assay Geenius

The currently used HIV confirmatory assays, Western blot and line immunoassay, are costly, complex and time-consuming. There is a need for cheaper, simpler and faster assays for use in high- and low-resource settings. Furthermore, it is necessary to differentiate between HIV-1 and HIV-2 infection due to differences in disease progression, monitoring and treatment options. Because the new Geenius HIV 1/2 Confirmatory Assay (Bio-Rad) has a European Community (CE) label, this study focused on its differentiation capacity using serum/plasma specimens from established HIV-1, HIV-2 and HIV untypable infections from the AIDS Reference Laboratory (ARL) of the Institute of Tropical Medicine (ITM) in Belgium. The results were compared with ARL's standard algorithm for diagnosis of HIV-infection and the new interpretation criteria for discrimination of the INNO-LIA HIVI/II Score, Fujirebio, Ghent, Belgium (LIA). The study showed a performance comparable to that of the reference LIA, with an overall sensitivity of 99.3% and specificity of 98%. Differentiation capacity was much better for the Geenius assay, with 93.8% of samples identified correctly as HIV-1 or HIV-2. When the new interpretation criteria for the LIA were used, the differentiation capacity of LIA increased to 98.5%. The results show that the Geenius assay is a reliable and fast alternative for the confirmation and differentiation of HIV-1 and HIV-2 infection in resource-rich and poor settings.

Reference panel of cloned HIV-2 plasmid DNA for nucleic acid assay development, evaluation, and quality monitoring

BACKGROUND

Currently, no FDA-approved HIV-2 nucleic acid assay is commercially available in the United States, although several laboratories have developed in-house assays to confirm HIV-2 infections. A major limitation in the development of novel HIV-2 diagnostic assays is the lack of reference materials that can be used to evaluate, optimize, and monitor assay performance.

STUDY DESIGN

Eleven viral stocks of HIV-2 isolates from various West African countries, including the Ivory Coast, Senegal, and Guinea-Bissau, were used to clone the entire LTR and pol regions from each virus.

RESULTS

We successfully cloned, sequenced, and group classified 22 HIV-2 DNA plasmids including 11 full length LTR (∼849 bp) and 11 pol (∼2995 bp) sequences. There were eight HIV-2 group A and three group B in both the LTR and pol regions.

CONCLUSIONS

This reference panel provides a robust, quantifiable, renewable, and non-infectious set of reagents that can be used for the development and evaluation of new HIV-2 molecular diagnostic assays and quality assurance and quality control reagents for use in the clinical laboratories.

HIV-2 integrase polymorphisms and longitudinal genotypic analysis of HIV-2 infected patients failing a raltegravir-containing regimen

To characterize the HIV-2 integrase gene polymorphisms and the pathways to resistance of HIV-2 patients failing a raltegravir-containing regimen, we studied 63 integrase strand transfer inhibitors (INSTI)-naïve patients, and 10 heavily pretreated patients exhibiting virological failure while receiving a salvage raltegravir-containing regimen. All patients were infected by HIV-2 group A. 61.4% of the integrase residues were conserved, including the catalytic motif residues. No INSTI-major resistance mutations were detected in the virus population from naïve patients, but two amino acids that are secondary resistance mutations to INSTIs in HIV-1 were observed. The 10 raltegravir-experienced patients exhibited resistance mutations via three main genetic pathways: N155H, Q148R, and eventually E92Q - T97A. The 155 pathway was preferentially used (7/10 patients). Other mutations associated to raltegravir resistance in HIV-1 were also observed in our HIV-2 population (V151I and D232N), along with several novel mutations previously unreported. Data retrieved from this study should help build a more robust HIV-2-specific algorithm for the genotypic interpretation of raltegravir resistance, and contribute to improve the clinical monitoring of HIV-2-infected patients.

Antiretroviral therapy and drug resistance in human immunodeficiency virus type 2 infection

One to two million people worldwide are infected with the human immunodeficiency virus type 2 (HIV-2), with highest prevalences in West African countries, but also present in Western Europe, Asia and North America. Compared to HIV-1, HIV-2 infection undergoes a longer asymptomatic phase and progresses to AIDS more slowly. In addition, HIV-2 shows lower transmission rates, probably due to its lower viremia in infected individuals. There is limited experience in the treatment of HIV-2 infection and several antiretroviral drugs used to fight HIV-1 are not effective against HIV-2. Effective drugs against HIV-2 include nucleoside analogue reverse transcriptase (RT) inhibitors (e.g. zidovudine, tenofovir, lamivudine, emtricitabine, abacavir, stavudine and didanosine), protease inhibitors (saquinavir, lopinavir and darunavir), and integrase inhibitors (raltegravir, elvitegravir and dolutegravir). Maraviroc, a CCR5 antagonist blocking coreceptor binding during HIV entry, is active in vitro against CCR5-tropic HIV-2 but more studies are needed to validate its use in therapeutic treatments against HIV-2 infection. HIV-2 strains are naturally resistant to a few antiretroviral drugs developed to suppress HIV-1 propagation such as nonnucleoside RT inhibitors, several protease inhibitors and the fusion inhibitor enfuvirtide. Resistance selection in HIV-2 appears to be faster than in HIV-1. In this scenario, the development of novel drugs specific for HIV-2 is an important priority. In this review, we discuss current anti-HIV-2 therapies and mutational pathways leading to drug resistance.

[Consensus Statement by GeSIDA/National AIDS Plan Secretariat on antiretroviral treatment in adults infected by the human immunodeficiency virus (Updated January 2013)]

OBJECTIVE

This consensus document is an update of combined antiretroviral therapy (cART) guidelines for HIV-1 infected adult patients.

METHODS

To formulate these recommendations a panel composed of members of the GeSIDA/National AIDS Plan Secretariat (Grupo de Estudio de Sida and the Secretaría del Plan Nacional sobre el Sida) reviewed the efficacy and safety advances in clinical trials, cohort and pharmacokinetic studies published in medical journals (PubMed and Embase) or presented in medical scientific meetings. The strength of the recommendations and the evidence which support them are based on a modification of the criteria of Infectious Diseases Society of America.

RESULTS

cART is recommended in patients with symptoms of HIV infection, in pregnant women, in serodiscordant couples with high risk of transmission, in hepatitisB co-infection requiring treatment, and in HIV nephropathy. cART is recommended in asymptomatic patients if CD4 is <500cells/μl. If CD4 are >500cells/μl cART should be considered in the case of chronic hepatitisC, cirrhosis, high cardiovascular risk, plasma viral load >100.000 copies/ml, proportion of CD4 cells <14%, neurocognitive deficits, and in people aged >55years. The objective of cART is to achieve an undetectable viral load. The first cART should include 2 reverse transcriptase inhibitors (RTI) nucleoside analogs and a third drug (a non-analog RTI, a ritonavir boosted protease inhibitor, or an integrase inhibitor). The panel has consensually selected some drug combinations, for the first cART and specific criteria for cART in acute HIV infection, in tuberculosis and other HIV related opportunistic infections, for the women and in pregnancy, in hepatitisB or C co-infection, in HIV-2 infection, and in post-exposure prophylaxis.

CONCLUSIONS

These new guidelines update previous recommendations related to first cART (when to begin and what drugs should be used), how to monitor, and what to do in case of viral failure or adverse drug reactions. cART specific criteria in comorbid patients and special situations are similarly updated.

Transmitted drug resistance in French HIV-2-infected patients

We report the first transmitted drug resistance survey study in HIV-2-infected patients living in France. The prevalence of transmitted drug resistance was 5.0% (95% confidence interval, 0.1-9.9) with mutations detected only in protease, not in reverse transcriptase. In this series, 10% of patients displayed X4/dual-mixed viruses. These findings classified the rate of transmitted drug resistance in the HIV-2 French Cohort as low prevalence.

Complex patterns of protease inhibitor resistance among antiretroviral treatment-experienced HIV-2 patients from Senegal: implications for second-line therapy

Protease inhibitor (PI)-based antiretroviral therapy (ART) can effectively suppress HIV-2 plasma load and increase CD4 counts; however, not all PIs are equally active against HIV-2, and few data exist to support second-line therapy decisions. To identify therapeutic options for HIV-2 patients failing ART, we evaluated the frequency of PI resistance-associated amino acid changes in HIV-2 sequences from a cohort of 43 Senegalese individuals receiving unboosted indinavir (n = 18 subjects)-, lopinavir/ritonavir (n = 4)-, or indinavir and then lopinavir/ritonavir (n = 21)-containing ART. Common protease substitutions included V10I, V47A, I54M, V71I, I82F, I84V, L90M, and L99F, and most patients harbored viruses containing multiple changes. Based on genotypic data, we constructed a panel of 15 site-directed mutants of HIV-2ROD9 containing single- or multiple-treatment-associated amino acid changes in the protease-encoding region of pol. We then quantified the susceptibilities of the mutants to the HIV-2 "active" PIs saquinavir, lopinavir, and darunavir using a single-cycle assay. Relative to wild-type HIV-2, the V47A mutant was resistant to lopinavir (6.3-fold increase in the mean 50% effective concentration [EC50]), the I54M variant was resistant to darunavir and lopinavir (6.2- and 2.7-fold increases, respectively), and the L90M mutant was resistant to saquinavir (3.6-fold increase). In addition, the triple mutant that included I54M plus I84V plus L90M was resistant to all three PIs (31-, 10-, and 3.8-fold increases in the mean EC50 for darunavir, saquinavir, and lopinavir, respectively). Taken together, our data demonstrate that PI-treated HIV-2 patients frequently harbor viruses that exhibit complex patterns of PI cross-resistance. These findings suggest that sequential PI-based regimens for HIV-2 treatment may be ineffective.

HIV-2EU: supporting standardized HIV-2 drug resistance interpretation in Europe

Considering human immunodeficiency virus type 2 (HIV-2) phenotypic data and experience from HIV type 1 and from the follow-up of HIV-2-infected patients, a panel of European experts voted on a rule set for interpretation of mutations in HIV-2 protease, reverse transcriptase, and integrase and an automated tool for HIV-2 drug resistance analyses freely available on the Internet (http://www.hiv-grade.de).

Impact of gag genetic determinants on virological outcome to boosted lopinavir-containing regimen in HIV-2-infected patients

OBJECTIVE

This study investigated the impact on virological outcome of the gag cleavage sites and the protease-coding region mutations in protease inhibitor-naive and protease inhibitor-experienced patients infected with HIV-2 receiving lopinavir (LPV) containing regimen.

METHODS

Baseline gag and protease-coding region were sequenced in 46 HIV-2 group A-infected patients receiving lopinavir. Virological response was defined as plasma viral load less than 100 copies/ml at month 3. Associations between virological response and frequencies of mutations in gag [matrix/capsid (CA), CA/p2, p2/nucleocapsid (NC), NC/p1, p1/p6] and gag-pol (NC/p6) cleavage site and protease-coding region, with respect to the HIV-2ROD strain, were tested using Fisher's exact test.

RESULTS

Virological response occurred in 14 of 17 (82%) protease inhibitor-naive and 17 of 29 (59%) protease inhibitor-experienced patients. Virological failure was associated with higher baseline viral load (median: 6765 versus 1098 copies/ml, P = 0.02). More protease-coding region mutations were observed in protease inhibitor-experienced compared with protease inhibitor-naive patients (median: 8 versus 5, P = 0.003). In protease inhibitor-naive patients, T435A (NC/p6), V447M (p1/p6), and Y14H (protease-coding region) were associated with virological failure (P = 0.011, P = 0.033, P = 0.022, respectively). T435A and V447M were associated with Y14H (P = 0.018, P = 0.039, respectively). In protease inhibitor-experienced patients, D427E (NC/p1) was associated with virological response (P = 0.014). A430V (NC/p1) and I82F (protease-coding region) were associated with virological failure (P = 0.046, P = 0.050, respectively). Mutations at position 430 were associated with a higher number of mutations in protease-coding region (median: 10 versus 7, P = 0.008).

CONCLUSION

We have demonstrated, for the first time, an association between gag, gag-pol cleavage site and protease-coding region mutations, with distinct profiles between protease inhibitor-naive and protease inhibitor-experienced patients. These mutations might impact the virological outcome of HIV-2-infected patients receiving LPV-containing regimen.

[Consensus document of Gesida and Spanish Secretariat for the National Plan on AIDS (SPNS) regarding combined antiretroviral treatment in adults infected by the human immunodeficiency virus (January 2012)]

This consensus document has been prepared by a panel consisting of members of the AIDS Study Group (Gesida) and the Spanish Secretariat for the National Plan on AIDS (SPNS) after reviewing the efficacy and safety results of clinical trials, cohort and pharmacokinetic studies published in medical journals, or presented in medical scientific meetings. Gesida has prepared an objective and structured method to prioritise combined antiretroviral treatment (cART) in naïve patients. Recommendations strength (A, B, C) and the evidence which supports them (I, II, III) are based on a modification of the Infectious Diseases Society of America criteria. The current antiretroviral treatment (ART) of choice for chronic HIV infection is the combination of three drugs. ART is recommended in patients with symptomatic HIV infection, in pregnancy, in serodiscordant couples with high transmission risk, hepatitis B fulfilling treatment criteria, and HIV nephropathy. Guidelines on ART treatment in patients with concurrent diagnosis of HIV infection and an opportunistic type C infection are included. In asymptomatic patients ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts <350 cells/μL; 2) when CD4 counts are between 350 and 500 cells/μL, therapy will be recommended and only delayed if patient is reluctant to take it, the CD4 are stabilised, and the plasma viral load is low; 3) therapy could be deferred when CD4 counts are above 500 cells/μL, but should be considered in cases of cirrhosis, chronic hepatitis C, high cardiovascular risk, plasma viral load >10(5) copies/mL, proportion of CD4 cells <14%, and in people aged >55 years. ART should include 2 reverse transcriptase inhibitors nucleoside analogues and a third drug (non-analogue reverse transcriptase inhibitor, ritonavir boosted protease inhibitor or integrase inhibitor). The panel has consensually selected and given priority to using the Gesida score for some drug combinations, some of them co-formulated. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures, but an undetectable viral load may be possible nowadays. Adverse events are a fading problem of ART. Guidelines in acute HIV infection, in women, in pregnancy, and to prevent mother-to-child transmission and pre- and post-exposition prophylaxis are commented upon. Management of hepatitis B or C co-infection, other co-morbidities, and the characteristics of ART in HIV-2 infection are included.

Critical differences in HIV-1 and HIV-2 protease specificity for clinical inhibitors

Clinical inhibitor amprenavir (APV) is less effective on HIV-2 protease (PR₂) than on HIV-1 protease (PR₁). We solved the crystal structure of PR₂ with APV at 1.5 Å resolution to identify structural changes associated with the lowered inhibition. Furthermore, we analyzed the PR₁ mutant (PR(1M) ) with substitutions V32I, I47V, and V82I that mimic the inhibitor binding site of PR₂. PR(1M) more closely resembled PR₂ than PR₁ in catalytic efficiency on four substrate peptides and inhibition by APV, whereas few differences were seen for two other substrates and inhibition by saquinavir (SQV) and darunavir (DRV). High resolution crystal structures of PR(1M) with APV, DRV, and SQV were compared with available PR₁ and PR₂ complexes. Val/Ile32 and Ile/Val47 showed compensating interactions with SQV in PR(1M) and PR₁, however, Ile82 interacted with a second SQV bound in an extension of the active site cavity of PR(1M). Residues 32 and 82 maintained similar interactions with DRV and APV in all the enzymes, whereas Val47 and Ile47 had opposing effects in the two subunits. Significantly diminished interactions were seen for the aniline of APV bound in PR₁ (M) and PR₂ relative to the strong hydrogen bonds observed in PR₁, consistent with 15- and 19-fold weaker inhibition, respectively. Overall, PR(1M) partially replicates the specificity of PR₂ and gives insight into drug resistant mutations at residues 32, 47, and 82. Moreover, this analysis provides a structural explanation for the weaker antiviral effects of APV on HIV-2.

G140S/Q148R and N155H mutations render HIV-2 Integrase resistant to raltegravir whereas Y143C does not

BACKGROUND

HIV-2 is endemic in West Africa and has spread throughout Europe. However, the alternatives for HIV-2-infected patients are more limited than for HIV-1. Raltegravir, an integrase inhibitor, is active against wild-type HIV-2, with a susceptibility to this drug similar to that of HIV-1, and is therefore a promising option for use in the treatment of HIV-2-infected patients. Recent studies have shown that HIV-2 resistance to raltegravir involves one of three resistance mutations, N155H, Q148R/H and Y143C, previously identified as resistance determinants in the HIV-1 integrase coding sequence. The resistance of HIV-1 IN has been confirmed in vitro for mutated enzymes harboring these mutations, but no such confirmation has yet been obtained for HIV-2.

RESULTS

The integrase coding sequence was amplified from plasma samples collected from ten patients infected with HIV-2 viruses, of whom three RAL-naïve and seven on RAL-based treatment at the time of virological failure. The genomes of the resistant strains were cloned and three patterns involving N155H, G140S/Q148R or Y143C mutations were identified. Study of the susceptibility of integrases, either amplified from clinical isolates or obtained by mutagenesis demonstrated that mutations at positions 155 and 148 render the integrase resistant to RAL. The G140S mutation conferred little resistance, but compensated for the catalytic defect due to the Q148R mutation. Conversely, Y143C alone did not confer resistance to RAL unless E92Q is also present. Furthermore, the introduction of the Y143C mutation into the N155H resistant background decreased the resistance level of enzymes containing the N155H mutation.

CONCLUSION

This study confirms that HIV-2 resistance to RAL is due to the N155H, G140S/Q148R or E92Q/Y143C mutations. The N155H and G140S/Q148R mutations make similar contributions to resistance in both HIV-1 and HIV-2, but Y143C is not sufficient to account for the resistance of HIV-2 genomes harboring this mutation. For Y143C to confer resistance in vitro, it must be accompanied by E92Q, which therefore plays a more important role in the HIV-2 context than in the HIV-1 context. Finally, the Y143C mutation counteracts the resistance conferred by the N155H mutation, probably accounting for the lack of detection of these mutations together in a single genome.

Ritonavir-boosted protease inhibitors in HIV therapy

The advent of combination antiretroviral therapy has led to significant improvement in the care of HIV-infected patients. Originally designed as a protease inhibitor (PI), ritonavir is currently exclusively used as a pharmacokinetic enhancer of other protease inhibitors, predominantly due to ritonavir's potent inhibition of the cytochrome P450 3A4 isoenzyme. Ritonavir-boosting of PIs decrease pill burden and frequency of dosing. Boosted PIs are recommended for first-line therapy in treatment and play a key role in the management of treatment-experienced patients. Potential problems associated with PIs include metabolic abnormalities (e.g. dyslipidemia), increased cardiovascular risk, and drug interactions.

Drug resistance mutations in patients infected with HIV-2 living in Spain

BACKGROUND

In contrast with HIV-1, information about drug resistance in HIV-2 is scarce and mainly derived from small series of patients failing antiretroviral therapy.

METHODS

The spectrum of changes in the reverse transcriptase (RT), protease (PR) and integrase (INT) genes was examined in HIV-2 individuals enrolled in the HIV-2 Spanish register.

RESULTS

From a total of 236 HIV-2-infected individuals registered in Spain from 1989 to June 2010, 53 PR, 44 RT and 8 INT sequences were obtained. Low plasma viraemia precluded collection of this information from most of the remaining cases. No major mutations associated with drug resistance in HIV-1 were recognized in 29 PR, 20 RT and 5 INT sequences from antiretroviral-naive HIV-2 individuals, although natural polymorphisms with potential effects on susceptibility to PR inhibitors were recognized at 10 positions (L10V/I, V32I, M36I, M46I, I47V, Q58E, A71V/I, G73A, V82I and L89I/V) and for nucleoside reverse transcriptase inhibitors at three positions (T69N, V75I and K219E). In 24 antiretroviral-experienced patients with virological failure the most frequent major RT resistance mutations were M184V (58%), Q151M (33%) and K65R (21%), which are rarely seen thymidine analogue mutations. In PR the most frequent major changes were V47A (17%), I54M (17%), I82F (13%), L90M (29%) and L99F (29%). Two of the three patients who failed on raltegravir had N155H in the INT region.

CONCLUSIONS

Drug resistance mutations in HIV-2 are selected at the same positions as in HIV-1, although with different frequency. Polymorphisms in the RT and PR associated with drug resistance in HIV-1 as compensatory changes are common in untreated HIV-2 subjects. These findings highlight the need for specific guidelines for interpreting genotypic resistance patterns in HIV-2 infection.

Antiretroviral Therapy for HIV-2 Infection: Recommendations for Management in Low-Resource Settings

HIV-2 contributes approximately a third to the prevalence of HIV in West Africa and is present in significant amounts in several low-income countries outside of West Africa with historical ties to Portugal. It complicates HIV diagnosis, requiring more expensive and technically demanding testing algorithms. Natural polymorphisms and patterns in the development of resistance to antiretrovirals are reviewed, along with their implications for antiretroviral therapy. Nonnucleoside reverse transcriptase inhibitors, crucial in standard first-line regimens for HIV-1 in many low-income settings, have no effect on HIV-2. Nucleoside analogues alone are not sufficiently potent enough to achieve durable virologic control. Some protease inhibitors, in particular those without ritonavir boosting, are not sufficiently effective against HIV-2. Following review of the available evidence and taking the structure and challenges of antiretroviral care in West Africa into consideration, the authors make recommendations and highlight the needs of special populations.

Polymorphisms of HIV-2 integrase and selection of resistance to raltegravir

BACKGROUND

Human Immunodeficiency Virus type 2 is naturally resistant to some antiretroviral drugs, restricting therapeutic options for patients infected with HIV-2. Regimens including integrase inhibitors (INI) seem to be effective, but little data on HIV-2 integrase (IN) polymorphisms and resistance pathways are available.

MATERIALS AND METHODS

The integrase coding sequence from 45 HIV-2-infected, INI-naïve, patients was sequenced and aligned against the ROD (group A) or EHO (group B) reference strains and polymorphic or conserved positions were analyzed.To select for raltegravir (RAL)-resistant variants in vitro, the ROD strain was cultured under increasing sub-optimal RAL concentrations for successive rounds. The phenotype of the selected variants was assessed using an MTT assay.

RESULTS

We describe integrase gene polymorphisms in HIV-2 clinical isolates from 45 patients. Sixty-seven percent of the integrase residues were conserved. The HHCC Zinc coordination motif, the catalytic triad DDE motif, and AA involved in IN-DNA binding and correct positioning were highly conserved and unchanged with respect to HIV-1 whereas the connecting residues of the N-terminal domain, the dimer interface and C-terminal LEDGF binding domain were highly conserved but differed from HIV-1. The N155 H INI resistance-associated mutation (RAM) was detected in the virus population from one ARV-treated, INI-naïve patient, and the 72I and 201I polymorphisms were detected in samples from 36 and 38 patients respectively. No other known INI RAM was detected.Under RAL selective pressure in vitro, a ROD variant carrying the Q91R+I175M mutations was selected. The Q91R and I175M mutations emerged simultaneously and conferred phenotypic resistance (13-fold increase in IC50). The Q91R+I175M combination was absent from all clinical isolates. Three-dimensional modeling indicated that residue 91 lies on the enzyme surface, at the entry of a pocket containing the DDE catalytic triad and that adding a positive charge (Gln to Arg) might compromise IN-RAL affinity.

CONCLUSIONS

HIV-2 polymorphisms from 45 INI-naïve patients are described. Conserved regions as well as frequencies of HIV-2 IN polymorphisms were comparable to HIV-1. Two new mutations (Q91R and I175M) that conferred high resistance to RAL were selected in vitro, which might affect therapeutic outcome.

[Current situation of human immunodeficiency virus type 2 and Human T lymphotropic virus in Spain]

The Spanish HIV-2 and HTLV Group was founded in 1989. Since then, a total of 144 cases of HTLV-1 and 717 cases of infection with HTLV-2 have been reported. Most patients infected with HTLV-1 are immigrants from Latin America and Sub-Saharan Africa. A total of 34 patients had developed diseases associated with HTLV-1: 21 tropical spastic paraparesis and 13 leukemias. The profile of patients infected with HTLV-2 is of males, native Spaniards, intravenous drug users and coinfected with HIV-1. The majority of transfusion centres in Spain have recently introduced anti-HTLV screening of blood donors, at the moment only among persons coming from HTLV-1 endemic areas. In 2009 a total of 30 new HIV-2 cases were reported, making a total of 216 so far. Most are male, originating from Sub-Saharan Africa.

Resistance and viral subtypes: how important are the differences and why do they occur?

PURPOSE OF REVIEW

The global HIV-1 pandemic has evolved to include 11 subtypes and 34 circulating recombinant forms. Our knowledge of HIV-1 response to antiretroviral drugs and emergent drug resistance has, however, been limited to subtype B infections circulating in Europe and North America, with little comparative information on non-B subtypes representing approximately 90% of worldwide epidemics. This review summarizes publications in the past year that highlight intersubtype differences influencing viral susceptibility to antiretroviral drugs and emergent drug resistance.

RECENT FINDINGS

Cumulative findings from clinical studies suggest that antiretroviral therapy will be of benefit in the overall treatment of non-B subtype infections, and result in drug-resistance profiles comparable to those observed for subtype B infections. Nevertheless, the 10-15% sequence diversity in the Pol region contributes to intersubtype differences in response to particular nucleoside and non-nucleoside analogues, as well as protease inhibitors. Distinct signature mutations and mutational pathways are identified for specific non-B subtypes. The implications of subtype on clinical outcome and interpretative algorithms are described.

SUMMARY

Understanding intersubtype differences in drug resistance is important in optimizing treatment strategies in resource-poor settings. Hopefully, this may assist in the design of prophylactic approaches to prevent HIV-1 horizontal and vertical HIV-1 transmission.

Emergence of multiclass drug-resistance in HIV-2 in antiretroviral-treated individuals in Senegal: implications for HIV-2 treatment in resouce-limited West Africa

BACKGROUND

The efficacy of various antiretroviral (ARV) therapy regimens for human immunodeficiency virus type 2 (HIV-2) infection remains unclear. HIV-2 is intrinsically resistant to the nonnucleoside reverse-transcriptase inhibitors and to enfuvirtide and may also be less susceptible than HIV-1 to some protease inhibitors (PIs). However, the mutations in HIV-2 that confer ARV resistance are not well characterized.

METHODS

Twenty-three patients were studied as part of an ongoing prospective longitudinal cohort study of ARV therapy for HIV-2 infection in Senegal. Patients were treated with nucleoside reverse-transcriptase inhibitor (NRTI)- and PI (indinavir)-based regimens. HIV-2 pol genes from these patients were genotyped, and the mutations predictive of resistance in HIV-2 were assessed. Correlates of ARV resistance were analyzed.

RESULTS

Multiclass drug-resistance mutations (NRTI and PI) were detected in strains in 30% of patients; 52% had evidence of resistance to at least 1 ARV class. The reverse-transcriptase mutations M184V and K65R, which confer high-level resistance to lamivudine and emtricitabine in HIV-2, were found in strains from 43% and 9% of patients, respectively. The Q151M mutation, which confers multinucleoside resistance in HIV-2, emerged in strains from 9% of patients. HIV-1-associated thymidine analogue mutations (M41L, D67N, K70R, L210W, and T215Y/F) were not observed, with the exception of K70R, which was present together with K65R and Q151M in a strain from 1 patient. Eight patients had HIV-2 with PI mutations associated with indinavir resistance, including K7R, I54M, V62A, I82F, L90M, L99F; 4 patients had strains with multiple PI resistance-associated mutations. The duration of ARV therapy was positively associated with the development of drug resistance (P = .02). Nine (82%) of 11 patients with HIV-2 with no [corrected] detectable ARV resistance had undetectable plasma HIV-2 RNA loads (<1.4 log(10) copies/mL), compared with 3 (25%) of 12 patients with HIV-2 with detectable ARV resistance (P = .009). Patients with ARV-resistant virus had higher plasma HIV-2 RNA loads, compared with those with non-ARV-resistant virus (median, 1.7 log(10) copies/mL [range, <1.4 to 2.6 log(10) copies/mL] vs. <1.4 log(10) copies/mL [range, <1.4 to 1.6 log(10) copies/mL]; P = .003).

CONCLUSIONS

HIV-2-infected individuals treated with ARV therapy in Senegal commonly have HIV-2 mutations consistent with multiclass drug resistance. Additional clinical studies are required to improve the efficacy of primary and salvage treatment regimens for treating HIV-2 infection.

Mutation N155H in HIV-2 integrase confers high phenotypic resistance to raltegravir and impairs replication capacity

BACKGROUND

Raltegravir has been shown to be active against wildtype HIV-2 with a phenotypic susceptibility similar to HIV-1. Due to the recent introduction of these novel inhibitors, information on the selection of resistance mutations and its phenotypic effect in this population is scarce.

OBJECTIVES

To explore in vitro the effect of raltegravir resistance in one individual with HIV-2 infection who failed raltegravir-HAART.

METHODS

A 20-year-old man with HIV-2 infection received a raltegravir-based HAART regimen. Drug resistance mutations were examined in the integrase gene by sequence analysis. Phenotypic analyses were performed in two HIV-2 isolates from the patient (wildtype isolate: SP-2p2-175 and mutant isolate: SP-2p2-189) and a laboratory reference strain (HIV-2 ROD). Susceptibility to raltegravir was assessed in a PBMC culture assay. Furthermore, a replicative capacity assay was performed.

RESULTS

After introduction of raltegravir, patient's HIV-2 viremia dropped 1 log but did not reach undetectability. Genotypic analysis at month 8 with raltegravir, revealed the development of N155H resistant mutation along with other changes in the HIV-2 integrase: V72I, I84V, A153G, N160K and S163S/G. These changes resulted in a 37-fold increase in phenotypic resistance to raltegravir. Wildtype HIV-2 integrase (SP-2p2-175) had an IC(50) of 21.5nM and HIV-2 mutant virus (SP-2p2-189) showed an IC(50) of 789nM. SP-2p2-189 virus presented also lower replicative capacity in the absence of raltegravir than wildtype.

CONCLUSION

A continued low HIV-2 viral load seems to be enough to select the N155H mutation, which despite significantly impairing viral replication, shows a level of resistance sufficient to give a selective advantage to the virus that maintains this pathway of resistance to raltegravir overtime.

Good response to lopinavir/ritonavir-containing antiretroviral regimens in antiretroviral-naive HIV-2-infected patients

In 29 antiretroviral-naive HIV-2-infected patients starting lopinavir/ritonavir-containing regimen, the median CD4 cell count change from baseline (142 cells/microl) was +71 cells/microl at week 24 and +132 cells/microl at week 96. Seventeen (59%) patients had a CD4 cell count increase of at least 50 cells/microl and undetectable HIV-2 RNA at week 24 and were considered as responders to treatment. This sustained elevation of CD4 cell count in the first 2 years of combination antiretroviral therapy shows the potential for lopinavir/ritonavir regimens as first-line therapy in HIV-2 infection.

Virological response to highly active antiretroviral therapy in patients infected with human immunodeficiency virus type 2 (HIV-2) and in patients dually infected with HIV-1 and HIV-2 in the Gambia and emergence of drug-resistant variants

Drug design, antiretroviral therapy (ART), and drug resistance studies have focused almost exclusively on human immunodeficiency virus type 1 (HIV-1), resulting in limited information for patients infected with HIV-2 and for those dually infected with HIV-1 and HIV-2. In this study, 20 patients, 12 infected with HIV-2 and 8 dually infected with HIV-1 and HIV-2, all treated with zidovudine (ZDV), lamivudine (3TC), and lopinavir-ritonavir (LPV/r), were followed up longitudinally for about 3 years. For 19/20 patients, viral loads were reduced to undetectable levels; the patient whose viral load remained detectable reported adverse effects associated with LPV/r that had caused him to stop taking all the drugs. HIV-2 strains containing mutations in both the protease and the reverse transcriptase gene that may confer drug resistance were observed in two patients with viral rebound, as early as 130 days (4.3 months) after the initiation of therapy. We conclude that the combination of ZDV, 3TC, and LPV/r is able to provide efficient and durable suppression of HIV-1 and HIV-2 for as long as 3 years in HIV-2-infected and dually infected patients. However, the emergence of HIV-1 and HIV-2 strains containing drug-resistant mutations can compromise the efficacy of this highly active ART.

[Viral resistance and genetic barrier of atazanavir]

Resistance to protease inhibitors (PI) is generally due to a mutation in the protease gene. Different changes have been described for each PI. The I 50L mutation is characteristic of resistance to atazanavir (ATV). It does not produce cross resistance to other PI; but it does increase susceptibility to all of them (hypersusceptibility). When PI are given concomitantly with low doses of ritonavir, the exposure to higher levels of PI requires that multiple resistance mutations have to be selected in the protease so that there is a significant loss of susceptibility. For the majority of PI/r, including ATV/r, >or=5 mutations in the protease are required to produce a compromise in the virological response. Despite having a moderate genetic barrier when not boosted with ritonavir, the prolonged half life of ATV minimises the risk of resistance in clinical practice.

Structural evidence for effectiveness of darunavir and two related antiviral inhibitors against HIV-2 protease

No drug has been targeted specifically for HIV-2 (human immunodeficiency virus type 2) infection despite its increasing prevalence worldwide. The antiviral HIV-1 (human immunodeficiency virus type 1) protease (PR) inhibitor darunavir and the chemically related GRL98065 and GRL06579A were designed with the same chemical scaffold and different substituents at P2 and P2' to optimize polar interactions for HIV-1 PR (PR1). These inhibitors are also effective antiviral agents for HIV-2-infected cells. Therefore, crystal structures of HIV-2 PR (PR2) complexes with the three inhibitors have been solved at 1.2-A resolution to analyze the molecular basis for their antiviral potency. Unusually, the crystals were grown in imidazole and zinc acetate buffer, which formed interactions with the PR2 and the inhibitors. Overall, the structures were very similar to the corresponding inhibitor complexes of PR1 with an RMSD of 1.1 A on main-chain atoms. Most hydrogen-bond and weaker C-H...O interactions with inhibitors were conserved in the PR2 and PR1 complexes, except for small changes in interactions with water or disordered side chains. Small differences were observed in the hydrophobic contacts for the darunavir complexes, in agreement with relative inhibition of the two PRs. These near-atomic-resolution crystal structures verify the inhibitor potency for PR1 and PR2 and will provide the basis for the development of antiviral inhibitors targeting PR2.

HIV-2 diagnosis and quantification in high-risk patients

Current diagnostic assays for HIV-1 do not always test for the presence of HIV-2 in the United States. We present the case of a patient from Cape Verde, who was admitted to our hospital with rapidly deteriorating neurological function and multiple white matter lesions on MRI likely secondary to progressive multifocal leukoencephalopathy (PML). Initially, the patient had a positive EIA for HIV, but a negative HIV-1 Western Blot and no viral load detected on a branched-DNA assay. A repeat viral load by reverse transcriptase methodology (RT-DNA) detected 121,000 copies and an HIV-2 Western Blot was positive. The case highlights an extremely rare presentation of HIV-2 with severe neurological disease. We discuss the different tests available for the diagnosis and monitoring of HIV-2 in the United States.

Screening and Management of HIV-2-Infected Individuals in Northern Italy

There is a lack of updated estimates of HIV-2 infection in Italy. Moreover, lack of standardized HIV-2 viral load (VL) and drug resistance tests challenges clinical practice. Among 2941 HIV-positive patients followed in our center (Brescia, Northern Italy), 220 (7.5%) were African at the beginning of the study period. We assessed a population of 151 HIV-Ab positive patients (141 of African origin), presenting for routine blood testing from January 2006 to May 2007. Those found infected with HIV-2 started an appropriate disease management with HIV-2 VL and genotypic drug resistance testing. Sixteen of 151 (10.6%) patients were positive for HIV-2. Of those 16 patients, 14 came from Africa. Among 7 experienced patients, 1 was responding to nelfinavir and 4 to lopinavir/ritonavir-containing regimens. Two patients were failing treatment: 1 patient was switched to a saquinavir/ritonavir-containing regimen and responded. The remaining patient switched to lamivudine + atazanavir + saquinavir + ritonavir did not respond, having had previous experience to multiple ineffective drugs, resulting in a very complex HIV-2 drug-resistance pattern. Accurate screening programs and integration of virological tools must be implemented urgently, given the high prevalence of HIV-2, particularly in immigrant patients.