Hiv Integrase Mechanisms Of Resistance To Raltegravir, Elvitegravir, And Dolutegravir

ABSTRACT HIV INTEGRASE MECHANISMS OF RESISTANCE TO RALTEGRAVIR, ELVITEGRAVIR, AND DOLUTEGRAVIR by KYLA ROSS December 2015 Advisor: Dr. Ladislau Kovari Major: Biochemistry and Molecular Biology Degree: Master of Science HIV-1 integrase (HIV-1 IN or IN) is a multimeric enzyme that integrates the HIV-1 genome into the chromosomes of infected CD4+ T-cells. Currently there are three FDA approved HIV-1 IN strand transfer inhibitors (INSTIs) used in clinical practice: raltegravir (RAL), elvitegravir (ELV), and dolutegravir (DTG). The [Q148H], [Q148H, G140S], [Q148R], [Q148R, G140A] and [N155H, E92Q] mutations decrease IN susceptibility to RAL and ELV and may result in therapeutic failure. As an indicator of protein flexibility, the root mean square deviation (RMSD) of each HIV-1 IN residue in the last 5 ns of a 40 ns molecular dynamics simulation was calculated for HIV-1 IN catalytic core domain as an apoprotein and in complex with RAL, ELV, and DTG to study how the mutations affect HIV-1 IN flexibility. In addition, we studied the relationship between HIV-1 IN flexibility and resistance. We found that the mutants reduced overall HIV-1 IN flexibility relative to the WT IN apoprotein. We also observed that the catalytic 140s loop in the HIV-1 IN-INSTI complexes were more flexible in mutants that displayed higher reported EC50 FC (fold change) values. To further investigate the mutations effect on the more complexed full length HIV-1 IN structure, we used molecular dynamics simulations to study the impact of the mutants on binary (IN-viral DNA complex) and ternary (IN-viral DNA- INSTI) IN flexibility. RMSD analyses revealed that that the mutants have a rigid structure relative to the WT IN. Furthermore, mutant IN showed transient changes in the secondary structure of the 140s loop compared to the WT. In addition to these reduced flexibility and structural changes, resistance mutations alter the binding mode of RAL, ELV, and DTG to IN and viral DNA. This study is the first to identify a structural basis of IN mechanism of resistance to INSTIs that develops under treatment pressure in HIV-1 IN

Novel bimodular DNA aptamers with guanosine quadruplexes inhibit phylogenetically diverse HIV-1 reverse transcriptases

DNA aptamers RT5, RT6 and RT47 form a group of related sequences that inhibit HIV-1 reverse transcriptase (RT). The essential inhibitory structure is identified here as bimodular, with a 5′ stem–loop module physically connected to a 3′-guanosine quadruplex module. The stem–loop tolerates considerable sequence plasticity. Connections between the guanosine triplets in the quadruplex could be simplified to a single nucleotide or a nonnucleic acid linker, such as hexaethylene glycol. All 12 quadruplex guanosines are required in an aptamer retaining most of the original loop sequence from RT6; only 11 are required for aptamer R1T (single T residue in intra-quadruplex loops). Circular dichroism (CD) spectroscopy gave ellipticity minima and maxima at 240 nm and 264 nm, indicating a parallel arrangement of the quadruplex strands. The simplified aptamers displayed increased overall stability. An aptamer carrying the original intra-quadruplex loops from RT6 inhibited RT in K+ buffers but not in Na+ buffers and displayed significant CD spectral broadening in Na+ buffers, while R1T inhibited RT in both buffers and displayed less broadening in Na+ buffers. The bimodular ssDNA aptamers inhibited RT from diverse primate lentiviruses with low nM IC50 values. These data provide insight into the requirements for broad-spectrum RT inhibition by nucleic acid aptamers

Kui bioloog kohtab keemikut: HIV-1 inhibiitorite otsingul

Väitekirja elektrooniline versioon ei sisalda publikatsioone.HIV-1 on pandeemiline viirus ning nakatatud inimeste arv maailmas suureneb pidevalt. Vaktsiin selle vastu puudub, kuid nakatatud patsientide raviks on kliinilise kasutuse loa saanud ligi 30 erinevat ühendit. Erinevatesse klassidesse kuuluvate inhibiitorite kombineeritud kasutamine (ART) on kujunenud HIV-ga nakatunud patsientide ravimise aluseks. ART ravi kõige olulisemaks puuduseks on ravimite toksilised kõrvaltoimed ning uute resistentsete viiruse tüvede teke. Antud väitekirja põhieesmärgiks oli leida efektiivseid mittetoksilisi ühendeid, mis suruvad maha HIV-1 replikatsiooni (nii metsik-tüüpi viiruse kui ka resistentsete tüvede oma) keskendudes eelkõige pöördtranskriptaasi inhibiitoritele. Kolm gruppi keemilisi ühendeid testiti antiretroviirus-vastase toime suhtes: atsüklilised tümidiini nukleosiidi analoogid, bimorfoliinid ja nende derivaadid ning sahariidhüdrasoonid. Samuti tõestati eksperimentaalselt eelneva in silico skriiningu käigus saadud tulemusi. Käesoleva töö tulemusena töötati välja meetod HIV-1 inhibiitorite skriinimiseks ViraPower lentiviiruse ekspressioonisüsteemi (Invitrogen) põhjal. Meetod on kiire, lihtne, usaldusväärne ning on kõlblik kasutamiseks väljaspool kõrgenenud ohutustasemega laborit (BSL3). Kõige tugevam toime meie laboris uuritud ühenditest oli mitte-nukleosiidsel pöördtranskriptaasi inhibiitoril (NNRTI), mis omas tuntud ravimi Nevirapiiniga sarnast aktiivsust, kuid oli kahjuks mitteaktiivne viiruse resistentsete vormide vastu. Antud ühend leiti ratsionaalse ravimidisaini strateegiat kasutades. Antud töö tulemused võimaldasid täiustada olemasolevat in silico skriiningu meetodit, mis võimaldab tulevikus kavandada uusi ning efektiivsemaid HIV-1 inhibiitoreid.HIV-1 is a pandemic virus and the numbers of infected people are constantly increasing all over the world. There is no vaccine available, but about 30 compounds have been approved by FDA for the treatment of HIV-infected patients. ART (antiretroviral therapy) consists of a combination of at least 3 inhibitors with different mechanism of action. The main drawback of such treatment is side effects of the drugs and the appearance of new resistant forms of the virus. The aim of this work was to find non-toxic compounds which can effectively suppress HIV-1 replication (both wild-type and resistant forms of the virus). We focused our efforts mostly on the discovery of novel reverse transcriptase inhibitors. Three groups of compounds were tested for their antiretroviral activity (acyclic thymine nucleoside analogues, bimorpholines and their derivatives, and saccharide hydrazones); also we experimentally verified the results of the previous in silico screening. As a result of this work, we developed an assay for HIV-1 inhibitors′ screening. This assay is based on ViraPower Lentiviral Expression System (Invitrogen) and is simple, fast, reliable and can be used outside BSL3 facilities. The most potent compound, found by us so far, acts as a non-nucleoside reverse transcriptase inhibitor (NNRTI) and has activity comparable to the activity of a known NNRTI nevirapine, but is unfortunately inactive against the resistant forms of the virus. This compound was found using ration drug design strategy. Most importantly, the results of this work allowed us to improve the existing in silico screening method, which could result in more potent HIV-1 inhibitors in the future

The Impact of HIV-1 Drug Escape on the Global Treatment Landscape

The rising prevalence of HIV drug resistance (HIVDR) could threaten gains made in combating the HIV epidemic and compromise the 90-90-90 target proposed by United Nations Programme on HIV/AIDS (UNAIDS) to have achieved virological suppression in 90% of all persons receiving antiretroviral therapy (ART) by the year 2020. HIVDR has implications for the persistence of HIV, the selection of current and future ART drug regimens, and strategies of vaccine and cure development. Focusing on drug classes that are in clinical use, this Review critically summarizes what is known about the mechanisms the virus utilizes to escape drug control. Armed with this knowledge, strategies to limit the expansion of HIVDR are proposed

Computational studies of mutations associated to resistance in HIV-1 macromolecular targets and implications in rational design of novel antiviral agents

Al fine di identificare nuovi farmaci anti-HIV capaci di superare i problemi legati alla resistenza, è stato condotto uno studio teorico combinando l’analisi strutturale sui modelli cristallografici della trascrittasi inversa (RT), i dati clinici relativi ai residui conservati dell’RT ed un’innovativa metodica computazionale basata sulle mappe di GRID. Tale analisi ha permesso di riprodurre i risultati clinici e di evidenziare le conseguenze delle mutazioni nella fase di ricognizione. Inoltre l’approccio computazionale ha portato all’identificazione di un modello farmacoforico utile per la progettazione di nuovi inibitori dell’RT. E’ stato riscontrato che la presenza del polimorfismo I135T nei pazienti NNRTI-naïve correlasse in modo significativo con la mutazione K103N nei casi di fallimento agli NNRTI, suggerendo così che la sostituzione I135T rappresenti un punto cruciale per l’evoluzione della resistenza agli NNRTI. Le simulazioni di dinamica molecolare (MD) hanno mostrato che la mutazione I135T contribuisce alla stabilizzazione della chiusura della tasca di legame degli NNRTI indotta dalla K103N in seguito alla riduzione della distanza ed all’aumento del numero di legami idrogeno tra l’Asn103 e la Tyr188. Inoltre è stata valutata l’influenza di due mutazioni associate a resistenza, L33F e L76V, presenti a livello della proteasi (PR) di HIV-1 rispetto alla ricognizione molecolare del Lopinavir (LPV) e dell’Atazanavir (ATV). L’analisi delle energie di interazione ottenute in seguito alla MD ha rivelato che la mutazione L33F determina una riduzione delle interazioni tra il ligando ed il recettore, dell’affinità di legame e della stabilità del dimero per entrambi gli inibitori della PR. In presenza della mutazione L76V, il LPV ha mostrato una minore affinità di legame ed un ridotto network di legami idrogeno, mentre i complessi con l’ATV hanno rivelato una migliore affinità, un effetto stabilizzante a livello dell’interfaccia del dimero e più efficaci interazioni ligando-recettore, in accordo con i dati di ipersuscettibilità. Al fine di valutare la stabilità del 6-helix bundle, sono state studiate le proprietà conformazionali della glicoproteina gp41 in presenza delle mutazioni associate a resistenza all’enfuvirtide V38A ed N140I. Le simulazioni di MD hanno mostrato che la copresenza delle mutazioni V38A+N140I è in grado di abolire l’interazione stabilita tra i residui 38 e 145, che risulta fondamentale per la stabilizzazione del 6-helix bundle.In order to discover novel selective anti-HIV resistance-evading drugs, a theoretical study was carried out combining structural analysis of RT crystallographic models, clinical data about RT conserved residues and an innovative computational method based on GRID maps. Such analysis allowed to reproduce clinical results and to highlight the consequences of the mutations in the recognition step. Moreover the computational approach generated a pharmacophore model useful for the design of novel RT inhibitors. The presence of the I135T polymorphism in NNRTI-naive patients significantly correlated with the appearance of K103N in cases of NNRTI failure, suggesting that I135T may represent a crucial determinant of NNRTI resistance evolution. Molecular Dynamics simulations (MD) showed that I135T can contribute to the stabilization of the K103N-induced closure of the NNRTI binding pocket by reducing the distance and increasing the number of hydrogen bonds between 103N and 188Y. In addition the influence of two drug resistance-associated mutations, L33F and L76V, of HIV-1 PR has been evaluated with respect to lopinavir (LPV) and atazanavir (ATV) molecular recognition. The evaluation of the interaction energies after the MD revealed that L33F substitution is related to reduced host/guest interactions, decreased affinity and to a dimer destabilizing effect for both PR inhibitors. In presence of L76V mutation, LPV showed a lowered binding affinity and a reduced hydrogen bonding network, while ATV complexes revealed a more productive binding affinity, increased host/guest interactions and dimer stabilizing effects, in agreement with hyper susceptibility data. With the aim to estimate the stability of its 6-helix bundle, the gp41 conformational properties were investigated in presence of V38A and N140I, known enfuvirtide resistance-associated mutations. MD showed that the co-presence of V38A+N140I abolished the interaction between residue 38 and 145 important for the 6-helix-bundle stabilization

An Unusual Helix Turn Helix Motif in the Catalytic Core of HIV-1 Integrase Binds Viral DNA and LEDGF

Background: Integrase (IN) of the type 1 human immunodeficiency virus (HIV-1) catalyzes the integration of viral DNA into host cellular DNA. We identified a bi-helix motif (residues 149–186) in the crystal structure of the catalytic core (CC) of the IN-Phe185Lys variant that consists of the a 4 and a 5 helices connected by a 3 to 5-residue turn. The motif is embedded in a large array of interactions that stabilize the monomer and the dimer. Principal Findings: We describe the conformational and binding properties of the corresponding synthetic peptide. This displays features of the protein motif structure thanks to the mutual intramolecular interactions of the a4 and a5 helices that maintain the fold. The main properties are the binding to: 1- the processing-attachment site at the LTR (long terminal repeat) ends of virus DNA with a Kd (dissociation constant) in the sub-micromolar range; 2- the whole IN enzyme; and 3- the IN binding domain (IBD) but not the IBD-Asp366Asn variant of LEDGF (lens epidermal derived growth factor) lacking the essential Asp366 residue. In our motif, in contrast to the conventional HTH (helix-turn-helix), it is the N terminal helix (a 4) which has the role of DNA recognition helix, while the C terminal helix (a 5) would rather contribute to the motif stabilization by interactions with the a4 helix. Conclusion: The motif, termed HTHi (i, for inverted) emerges as a central piece of the IN structure and function. It coul

Structure Function Studies Of Hiv-1 Protease

HIV-1 is the causative agent of the devastating human disease Acquired Immunodeficiency Syndome (AIDS). While much progress has been made over the past two decades, HIV-1 remains a major global health concern. HIV-1 protease is 99-amino acid homodimer aspartyl protease that is essential to the life cycle of HIV. This has rendered it an attractive and very successful drug target. However, due to the high error rate of the HIV -1 reverse transcriptase, drug resistance mutations in the protease can develop very rapidly in some patients, rendering current protease inhibitors (one of the main classes of drug in common antiretroviral therapy) less effective or completely ineffective. In this thesis, we investigate the structural impact of a number of HIV-1 protease drug resistance mutations. These include L33F, which is selected for on darunavir treatment (one of the most prescirbed protease inhibitors), I47V, and V54I (which we identify as compensatory mutations involved in the tethering of the protease flaps and proper formation of the active site). A fuller understanding of the structural impact of these resistance mutations will hopefully facilitate the development of protease inhibitors that can overcome this common drug resistance

In vitro selection and characterisation of human immunodeficiency virus type-1 subtype C integrase strand transfer inhibitor resistant mutants

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy in Medicine Johannesburg 2015The currently approved integrase strand transfer inhibitors (INSTIs), raltegravir (RAL) and elvitegravir (EVG) effectively halt HIV-1 replication but their use is limited by their low genetic resistance barrier and cross resistance. For instance, integrase amino acids N155 and Q148 represent genetic pathways selected by both drugs and are associated with considerable cross resistance to both RAL and EVG. Dolutegravir (DTG) is a second generation drug manufactured to exhibit a more robust resistance profile than RAL and EVG, and retains activity against RAL and EVG resistant isolates. Most research on drug resistance patterns have been carried out with emphasis on HIV-1 subtype B and inadequately assessed in HIV-1 subtype C. Thus, the aim of this study was to establish the drug resistance mutation profiles of HIV-1 subtype C primary virus isolates that evolve/emerge under selective pressure of the INSTIs RAL, EVG and DTG, and evaluate their impact on strand transfer. In vitro selection experiments were carried out using six primary virus isolates (three wild-type, FV, and three reverse transcriptase drug resistant, MR, viruses) grown in peripheral blood mononuclear cells in the presence of increasing concentrations of RAL, EVG and DTG, and monitored to beyond virus break-through. Viral RNA was extracted from various time points and the pol region was RT-PCR amplified and sequenced using conventional Sanger-based sequencing and next generation sequencing (Illumina MiSeq). HIV-1 subtype C FV6 wild-type and mutant recombinant integrase (generated by site-directed mutagenesis) were expressed, purified and used in strand transfer assays and surface plasmon resonance (SPR) experiments to establish the binding affinities of IN-DNA. Wild-type FV primary viruses were successfully grown in the presence of increasing concentrations of RAL, EVG and DTG, up to 266 nM, 66 nM and 32 nM, respectively. Drug resistant MR viruses were successfully grown in the presence of increasing concentrations of RAL, EVG and DTG, up to 266 nM, 16 nM and 8 nM, respectively. Sequence analysis on both platforms revealed the presence of the previously described drug resistance mutations T66IK, E92Q, F121Y, Q148R, N155H and R263K in some viruses, and additionally H114L was detected. RAL was observed to select for substitutions Q148R and N155H/H114L in isolates FV6 and MR69, respectively. EVG selected F121Y, T66I/R263K, T66K and T66I in FV3, FV6, MR69, MR81, and MR89, respectively. DTG selected substitutions E92Q and M50I in FV3 and MR81, respectively. In silico data exhibited changes in hydrophilicity, hydrophobicity and side chain changes as well as changes in polarity, and all substitutions displayed acceptable minimisation energies and distances between the atoms. Seven IN mutants were expressed and purified, and thereafter tested for efficiency in strand transfer. All mutant FV6T66I, FV6E92Q, FV6H114L, FV6F121Y, FV6Q148R, FV6N155H and FV6R263K IN enzymes demonstrated an overall loss in strand transfer capacity of 37.1%, 21.5%, 66.1%, 63.2%, 60.2%, 30.5% and 3.4%, respectively. This is the first report on loss of strand transfer activity associated with H114L. The loss in strand transfer capacity in all the mutants was not reflected by their overall binding affinities to donor DNA, as determined by surface plasmon resonance, likely attributed to the role of different residues associated with DNA and drug binding in the IN quaternary structure. In conclusion, this is the first report describing IN drug selection experiments using primary HIV-1 subtype C isolates, and a detailed genotypic and biochemical characterisation of the associated mutations