Showing papers on "Integrase published in 2017"
TL;DR: While the selection of resistance substitutions in response to RAL and EVG bears high similarity in patients as compared to laboratory studies, there is less concurrence regarding the “second-generation” drugs of this class, highlighting the unpredictability of HIV resistance to these inhibitors, which is of concern as CAB and BIC proceed in their clinical development.
Abstract: Integrase strand transfer inhibitors (INSTIs) are the newest class of antiretroviral drugs to be approved for treatment and act by inhibiting the essential HIV protein integrase from inserting the viral DNA genome into the host cell’s chromatin. Three drugs of this class are currently approved for use in HIV-positive individuals: raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG), while cabotegravir (CAB) and bictegravir (BIC) are currently in clinical trials. RAL and EVG have been successful in clinical settings but have relatively low genetic barriers to resistance. Furthermore, they share a high degree of cross-resistance, which necessitated the development of so-called second-generation drugs of this class (DTG, CAB, and BIC) that could retain activity against these resistant variants. In vitro selection experiments have been instrumental to the clinical development of INSTIs, however they cannot completely recapitulate the situation in an HIV-positive individual. This review summarizes and compares all the currently available information as it pertains to both in vitro and in vivo selections with all five INSTIs, and the measured fold-changes in resistance of resistant variants in in vitro assays. While the selection of resistance substitutions in response to RAL and EVG bears high similarity in patients as compared to laboratory studies, there is less concurrence regarding the “second-generation” drugs of this class. This highlights the unpredictability of HIV resistance to these inhibitors, which is of concern as CAB and BIC proceed in their clinical development.
134 citations
TL;DR: In this article, crystal structures of Cas1-Cas2 bound to both donor and target DNA in intermediate and product integration complexes, as well as a cryo-electron microscopy structure of the full CRISPR locus integration complex, including the accessory protein IHF (integration host factor).
Abstract: CRISPR-Cas systems depend on the Cas1-Cas2 integrase to capture and integrate short foreign DNA fragments into the CRISPR locus, enabling adaptation to new viruses. We present crystal structures of Cas1-Cas2 bound to both donor and target DNA in intermediate and product integration complexes, as well as a cryo-electron microscopy structure of the full CRISPR locus integration complex, including the accessory protein IHF (integration host factor). The structures show unexpectedly that indirect sequence recognition dictates integration site selection by favoring deformation of the repeat and the flanking sequences. IHF binding bends the DNA sharply, bringing an upstream recognition motif into contact with Cas1 to increase both the specificity and efficiency of integration. These results explain how the Cas1-Cas2 CRISPR integrase recognizes a sequence-dependent DNA structure to ensure site-selective CRISPR array expansion during the initial step of bacterial adaptive immunity.
113 citations
TL;DR: Cryo–electron microscopy reveals how lentiviral DNA and the viral integrase assemble to promote retroviral integration into host cell DNA and explains how HIV-1 IN, which self-associates into higher-order multimers, can form a functional intasome.
Abstract: Retroviral integrase (IN) functions within the intasome nucleoprotein complex to catalyze insertion of viral DNA into cellular chromatin. Using cryo–electron microscopy, we now visualize the functional maedi-visna lentivirus intasome at 4.9 angstrom resolution. The intasome comprises a homo-hexadecamer of IN with a tetramer-of-tetramers architecture featuring eight structurally distinct types of IN protomers supporting two catalytically competent subunits. The conserved intasomal core, previously observed in simpler retroviral systems, is formed between two IN tetramers, with a pair of C-terminal domains from flanking tetramers completing the synaptic interface. Our results explain how HIV-1 IN, which self-associates into higher-order multimers, can form a functional intasome, reconcile the bulk of early HIV-1 IN biochemical and structural data, and provide a lentiviral platform for design of HIV-1 IN inhibitors.
90 citations
TL;DR: This review summarizes and compares the pharmacokinetics and pharmacodynamics of the INSTIs, and describes specific pharmacokinetic considerations for special patient conditions: hepatic impairment, renal dysfunction, pregnancy and co-infections.
Abstract: Dolutegravir (DTG), elvitegravir (EVG) and raltegravir (RAL) are members of the latest class of antiretrovirals (ARVs) that have become available to treat human immunodeficiency virus (HIV) infection: integrase strand transfer inhibitors (INSTIs). INSTIs are potent inhibitors of the HIV integrase enzyme, with protein binding–adjusted concentration inhibiting viral replication by 90/95 % [IC90/95] values in the low nanogram per millilitre range, and they retain antiviral activity against strains of HIV with acquired resistance to other classes of ARVs. Each of the INSTIs has unique pharmacokinetic/pharmacodynamic properties, influencing its role in clinical use in specific subsets of patients. RAL and DTG have minimal drug–drug interaction profiles, as their metabolism has minimal cytochrome P450 (CYP) involvement. Conversely, EVG metabolism occurs primarily via CYP3A4 and requires pharmacokinetic boosting to achieve systemic exposures amenable to once-daily dosing. EVG and DTG have the added benefit of availability of fixed-dose combination tablets, allowing for convenient and simplified ARV regimens. RAL is the only INSTI to be listed as a preferred agent in the current US perinatal treatment guidelines. All three INSTIs are recommended regimens for treatment-naive individuals in the US adult and adolescent HIV treatment guidelines. This review summarizes and compares the pharmacokinetics and pharmacodynamics of the INSTIs, and describes specific pharmacokinetic considerations for special patient conditions: hepatic impairment, renal dysfunction, pregnancy and co-infections.
85 citations
TL;DR: A virus is reported for the first time, a virus with selected mutations outside the HIV-1 integrase gene that confer resistance to all integrase inhibitors currently used to treat patients, such as raltegravIR, elvitegravir, and dolutegravirs.
Abstract: Resistance to the integrase strand transfer inhibitors raltegravir and elvitegravir is often due to well-identified mutations in the integrase gene. However, the situation is less clear for patients who fail dolutegravir treatment. Furthermore, most in vitro experiments to select resistance to dolutegravir have resulted in few mutations of the integrase gene. We performed an in vitro dolutegravir resistance selection experiment by using a breakthrough method. First, MT4 cells were infected with human immunodeficiency virus type 1 (HIV-1) Lai. After integration into the host cell genome, cells were washed to remove unbound virus and 500 nM dolutegravir was added to the cell medium. This high concentration of the drug was maintained throughout selection. At day 80, we detected a virus highly resistant to dolutegravir, raltegravir, and elvitegravir that remained susceptible to zidovudine. Sequencing of the virus showed no mutations in the integrase gene but highlighted the emergence of five mutations, all located in the nef region, of which four were clustered in the 3' polypurine tract (PPT). Mutations selected in vitro by dolutegravir, located outside the integrase gene, can confer a high level of resistance to all integrase inhibitors. Thus, HIV-1 can use an alternative mechanism to develop resistance to integrase inhibitors by selecting mutations in the 3' PPT region. Further studies are required to determine to what extent these mutations may explain virological failure during integrase inhibitor therapy.IMPORTANCE Integrase strand transfer inhibitors (INSTIs) are increasingly used both as first-line drugs and in rescue therapy because of their low toxicity and high efficacy in both treatment-naive and treatment-experienced patients. Until now, resistance mutations selected by INSTI exposure have either been described in patients or selected in vitro and involve the integrase gene. Most mutations selected by raltegravir, elvitegravir, or dolutegravir exposure are located inside the catalytic site of the integrase gene, but mutations outside the catalytic site of the integrase gene have also been selected with dolutegravir. Following in vitro selection with dolutegravir, we report, for the first time, a virus with selected mutations outside the HIV-1 integrase gene that confer resistance to all integrase inhibitors currently used to treat patients, such as raltegravir, elvitegravir, and dolutegravir. Our observation may explain why some viruses responsible for virological failure in patients treated with dolutegravir did not show mutations in the integrase gene.
68 citations
TL;DR: There is potential hope that the use of dolutegravir in first line therapy could actually form part of the long-sought goal of attainment of a functional cure for HIV disease, where non-nucleoside reverse transcriptase inhibitors continue to be a mainstay of initial therapy.
57 citations
TL;DR: Antiretroviral drugs which had been developed for the treatment of human immunodeficiency virus-1 (HIV-1) infections have been tested in vitro for their efficacy in inhibiting PERV replication and inhibitor of the viral reverse transcriptase was azidothymidine.
Abstract: Porcine endogenous retroviruses (PERVs) are integrated in the genome of all pigs; they are released as infectious particles, and under certain conditions they can infect human cells. Therefore, they represent a risk when pigs are used as sources of cells, tissues, or organs for xenotransplantation. Xenotransplantation is under development due to the increasing shortage of human transplants. Whereas most porcine microorganisms which may be able to induce a disease (zoonosis) in the transplant recipient can be eliminated, this is not possible in the case of PERVs. Antiretroviral drugs which had been developed for the treatment of human immunodeficiency virus-1 (HIV-1) infections have been tested in vitro for their efficacy in inhibiting PERV replication. Inhibitors of the viral reverse transcriptase and of the integrase have been found effective. The most effective inhibitor of the reverse transcriptase was azidothymidine (AZT); the integrase inhibitors were the most potent inhibitors of PERV. Although in the past PERV transmission has not been observed after experimental or clinical xenotransplantation of pig cells or organs, and although PERVs may one day be inactivated in pigs by genome editing using CRISPR/Cas, knowing which antiretroviral drugs can effectively restrict PERV infection will still be important.
41 citations
TL;DR: The design, synthesis and biological evaluation of a novel N-hydroxy thienopyrimidine-2,3-dione chemotype (11) which potently and selectively inhibited RNase H with considerable potency against HIV-1 in cell culture is reported.
39 citations
TL;DR: Two alternative architectures of integrase tetramers are described, highlighting both evolutionary and structural constraints that result in the different integrase-DNA stoichiometries across Retroviridae.
38 citations
TL;DR: A practicable six-step synthetic pathway has been developed to access a library of novel 3-[(N-cycloalkylbenzamido)methyl]-2-quinolones using Morita-Baylis-Hillman methodology and reveals selective inhibition of HIV-1 IN.
37 citations
TL;DR: The current knowledge of serine integrase structure and mechanism is summarized, then key factors that affect the performance of these phage recombination systems are outlined.
TL;DR: The equal or higher potency in non-B subtypes of DTG, CAB and BIC compared with RAL and EVG confirms their suitability for use in countries dominated by non-A subtypes, and the high prevalence of major accessory mutations, especially E157Q, requires long-term follow-up studies.
Abstract: OBJECTIVE To determine the antiretroviral activity of the integrase strand transfer inhibitors (INSTIs), raltegravir (RAL), elvitegravir (EVG), dolutegravir (DTG), cabotegravir (CAB) and bictegravir (BIC), against different subtypes as well as primary and acquired drug resistance mutations (DRMs) in a patient-cohort infected with diverse subtypes. DESIGN Biochemical and virological drug sensitivity analyses using patient-derived HIV type 1 (HIV-1) genes and cross-sectional/longitudinal clinical study. METHODS Assays for 50% inhibition of 3'-end processing (IC50-3EP), strand transfer (IC50-ST) and drug sensitivity for five INSTIs were done using patient-derived integrase or gag-pol genes from subtypes A1, B, C, 01_AE and 02_AG. Integrase from INSTI-naive (n = 270) and experienced (n = 96) patients were sequenced. RESULTS RAL had higher IC50-ST than the other INSTIs for all subtypes. EVG had higher IC50-ST for HIV 1 subtype C (P < 0.05) and 02_AG (P < 0.05) than HIV 1 subtype B (HIV-1B). DTG showed lower IC50-ST in HIV 1 subtype C than HIV-1B (P = 0.003). In CAB , the non-B subtypes showed lower IC50-ST (P < 0.05) than HIV-1B. In BIC, lower IC50-ST in 01_AE (P = 0.017) and 02_AG (P = 0.045) than HIV-1B. In drug sensitivity assay, inhibiting virus replication by 50% for DTG [median (IQR) 2.14 (1.3-2.56)], CAB [1.68 (1.34-2.55)] and BIC [1.07 (0.22-2.53)] were lower than RAL and EVG. One patient had a primary DRMs (0.3%, 1/270), but 17 (6.3%) had one major accessory DRM, of which 12 were E157Q. CONCLUSION The equal or higher potency in non-B subtypes of DTG, CAB and BIC compared with RAL and EVG confirms their suitability for use in countries dominated by non-B subtypes. Any impact of the high prevalence of major accessory mutations, especially E157Q, requires long-term follow-up studies.
TL;DR: Although signature InSTI substitutions were not detected, polymorphisms and substitutions conferring low-level resistance to ralteg Gravir and elvitegravir were frequently found in a baseline genotypic test.
Abstract: OBJECTIVES The most recent guidelines suggest using integrase strand-transfer inhibitors (InSTIs) as the preferred antiretroviral regimens for naive HIV-infected individuals. However, resistance to InSTIs is not monitored in many centres at baseline. This study aimed to evaluate the prevalence of InSTI resistance substitutions in newly diagnosed patients with acute/recent HIV infection. METHODS Genotypic drug resistance tests were performed in all consecutive patients prospectively enrolled with a documented infection of <6 months, from 12 May 2015 to 12 May 2016. Sequences were obtained by high-throughput sequencing. RESULTS Five out of 36 consecutive patients (13.89%, 95% CI = 4.67-29.5) with acute/recent HIV infection were detected to have strains carrying InSTI polymorphisms or substitutions conferring low-level resistance to raltegravir and elvitegravir. Four patients had the 157Q polymorphism and one patient had the Q95K substitution. All cases were MSM patients infected with subtype B strains. Viral loads ranged from 2.92 to 6.95 log10 copies/mL. In all cases, the mutational viral load was high. Three patients initiated dolutegravir-based regimens and became undetectable at first viral load control. There were no major viral or epidemiological differences when compared with patients without InSTI substitutions. CONCLUSIONS Although signature InSTI substitutions (such as Y143R/C, N155H or Q148K/R/H) were not detected, polymorphisms and substitutions conferring low-level resistance to raltegravir and elvitegravir were frequently found in a baseline genotypic test. All cases were infected with subtype B, the most frequent in Europe. In the context of primary HIV infection, virological response should be carefully monitored to evaluate the impact of these InSTI polymorphisms and substitutions.
TL;DR: BIC possesses an excellent resistance profile in regard to HIV and SIV and could be useful in nonhuman primate models of HIV infection.
Abstract: Animal models are essential to study novel antiretroviral drugs, resistance-associated mutations (RAMs), and treatment strategies. Bictegravir (BIC) is a novel potent integrase strand transfer inhibitor (INSTI) that has shown promising results against HIV-1 infection in vitro and in vivo and against clinical isolates with resistance against INSTIs. BIC has a higher genetic barrier to the development of resistance than two clinically approved INSTIs, termed raltegravir and elvitegravir. Another clinically approved INSTI, dolutegravir (DTG) also possesses a high genetic barrier to resistance, while a fourth compound, termed cabotegravir (CAB), is currently in late phases of clinical development. Here we report the susceptibilities of simian immunodeficiency virus (SIV) and HIV-1 integrase (IN) mutants containing various RAMs to BIC, CAB, and DTG. BIC potently inhibited SIV and HIV-1 in single cycle infection with 50% effective concentrations (EC50s) in the low nM range. In single cycle SIV infections, none of the E92Q, T97A, Y143R, or N155H substitutions had a significant effect on susceptibility to BIC (≤4-fold increase in EC50), whereas G118R and R263K conferred ∼14-fold and ∼6-fold increases in EC50, respectively. In both single and multiple rounds of HIV-1 infections, BIC remained active against the Y143R, N155H, R263K, R263K/M50I, and R263K/E138K mutants (≤4-fold increase in EC50). In multiple rounds of infection, the G140S/Q148H combination of substitutions decreased HIV-1 susceptibility to BIC 4.8-fold compared to 16.8- and 7.4-fold for CAB and DTG, respectively. BIC possesses an excellent resistance profile in regard to HIV and SIV and could be useful in nonhuman primate models of HIV infection.
TL;DR: This work shows that the viral RNA genome and IN from ALLINI-treated virions are prematurely degraded in target cells, whereas reverse transcriptase remains active and stably associated within the capsid lattice.
Abstract: Recent evidence indicates that inhibition of HIV-1 integrase (IN) binding to the viral RNA genome by allosteric integrase inhibitors (ALLINIs) or through mutations within IN yields aberrant particles in which the viral ribonucleoprotein complexes (vRNPs) are eccentrically localized outside the capsid lattice. These particles are noninfectious and are blocked at an early reverse transcription stage in target cells. However, the basis of this reverse transcription defect is unknown. Here, we show that the viral RNA genome and IN from ALLINI-treated virions are prematurely degraded in target cells, whereas reverse transcriptase remains active and stably associated with the capsid lattice. The aberrantly shaped cores in ALLINI-treated particles can efficiently saturate and be degraded by a restricting TRIM5 protein, indicating that they are still composed of capsid proteins arranged in a hexagonal lattice. Notably, the fates of viral core components follow a similar pattern in cells infected with eccentric particles generated by mutations within IN that inhibit its binding to the viral RNA genome. We propose that IN-RNA interactions allow packaging of both the viral RNA genome and IN within the protective capsid lattice to ensure subsequent reverse transcription and productive infection in target cells. Conversely, disruption of these interactions by ALLINIs or mutations in IN leads to premature degradation of both the viral RNA genome and IN, as well as the spatial separation of reverse transcriptase from the viral genome during early steps of infection.IMPORTANCE Recent evidence indicates that HIV-1 integrase (IN) plays a key role during particle maturation by binding to the viral RNA genome. Inhibition of IN-RNA interactions yields aberrant particles with the viral ribonucleoprotein complexes (vRNPs) eccentrically localized outside the conical capsid lattice. Although these particles contain all of the components necessary for reverse transcription, they are blocked at an early reverse transcription stage in target cells. To explain the basis of this defect, we tracked the fates of multiple viral components in infected cells. Here, we show that the viral RNA genome and IN in eccentric particles are prematurely degraded, whereas reverse transcriptase remains active and stably associated within the capsid lattice. We propose that IN-RNA interactions ensure the packaging of both vRNPs and IN within the protective capsid cores to facilitate subsequent reverse transcription and productive infection in target cells.
TL;DR: The current findings support and extend the substrate envelope concept that broadly effective INSTIs can be designed by filling the envelope defined by the DNA substrates by identifying novel substituents at the 6-position that are highly effective.
Abstract: Integrase mutations can reduce the effectiveness of the first-generation FDA-approved integrase strand transfer inhibitors (INSTIs), raltegravir (RAL) and elvitegravir (EVG). The second-generation agent, dolutegravir (DTG), has enjoyed considerable clinical success; however, resistance-causing mutations that diminish the efficacy of DTG have appeared. Our current findings support and extend the substrate envelope concept that broadly effective INSTIs can be designed by filling the envelope defined by the DNA substrates. Previously, we explored 1-hydroxy-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamides as an INSTI scaffold, making a limited set of derivatives, and concluded that broadly effective INSTIs can be developed using this scaffold. Herein, we report an extended investigation of 6-substituents as well the first examples of 7-substituted analogues of this scaffold. While 7-substituents are not well-tolerated, we have identified novel substituents at the 6-position that are highly effective, with t...
TL;DR: A series of N′-acylhydrazone ligands with groups able to chelate the Mg(II) hard Lewis acid ions in the active sites of both the enzymes, resulting in dual inhibitors with micromolar and even nanomolar activities.
Abstract: Human immunodeficiency virus type 1 (HIV-1) infection, still represent a serious global health emergency. The chronic toxicity derived from the current anti-retroviral therapy limits the prolonged use of several antiretroviral agents, continuously requiring the discovery of new antiviral agents with innovative strategies of action. In particular, the development of single molecules targeting two proteins (dual inhibitors) is one of the current main goals in drug discovery. In this contest, metal-chelating molecules have been extensively explored as potential inhibitors of viral metal-dependent enzymes, resulting in some important classes of antiviral agents. Inhibition of HIV Integrase (IN) is, in this sense, paradigmatic. HIV-1 IN and Reverse Transcriptase-associated Ribonuclease H (RNase H) active sites show structural homologies, with the presence of two Mg(II) cofactors, hence it seems possible to inhibit both enzymes by means of chelating ligands with analogous structural features. Here we present a series of N’-acylhydrazone ligands with groups able to chelate the Mg(II) hard Lewis acid ions in the active sites of both the enzymes, resulting in dual inhibitors with micromolar and even nanomolar activities. The most interesting identified N’-acylhydrazone analog, compound 18, shows dual RNase H-IN inhibition and it is also able to inhibit viral replication in cell-based antiviral assays in the low micromolar range. Computational modeling studies were also conducted to explore the binding attitudes of some model ligands within the active site of both the enzymes.
TL;DR: Results reveal an unanticipated role of IN for polyprotein proteolytic processing during virion morphogenesis and solve the X-ray structure of the drug-resistant catalytic core domain protein, which provides means for rational development of second-generation MINIs.
TL;DR: The case of a 44-year-old male with a history of hemophilia A who developed diabetes mellitus four months after switching from abacavir, lamivudine, and efavirenz to abacvir, Lamivudines, and raltegravir is reported.
Abstract: Integrase strand transfer inhibitors (INSTIs) have become integral antiretroviral therapy (ART) agents for treating HIV infection. We report the case of a 44-year-old male with a history of hemophilia A who developed diabetes mellitus four months after switching from abacavir, lamivudine, and efavirenz to abacavir, lamivudine, and raltegravir. Hemoglobin A1C normalized without further need for exogenous insulin after raltegravir was switched back to efavirenz. In this case report, we will review a possible mechanism for INSTI-induced hyperglycemia and/or diabetes mellitus.
TL;DR: DTG has the potential to effectively suppress the viral load within the first four weeks of treatment and thus reduces infectiousness and side effects such as low mood, anxiety and sleep disturbance were high, with 8% of patients discontinuing treatment.
Abstract: Dolutegravir (DTG) is the third HIV integrase inhibitor (INI) available for prescription in Belfast since July 2014. It has shown high virological efficacy in both treatment-naive and -experienced ...
TL;DR: The potential usefulness of PCR based detection of prophage integrase genes as a rapid indicator of genome diversity in S. enterica is demonstrated.
Abstract: Salmonella enterica is a bacterial species that is a major cause of illness in humans and food-producing animals. S. enterica exhibits considerable inter-serovar diversity, as evidenced by the large number of host adapted serovars that have been identified. The development of methods to assess genome diversity in S. enterica will help to further define the limits of diversity in this foodborne pathogen. Thus, we evaluated a PCR assay, which targets prophage integrase genes, as a rapid method to investigate S. enterica genome diversity. To evaluate the PCR prophage integrase assay, 49 isolates of S. enterica were selected, including 19 clinical isolates from clonal serovars (Enteritidis and Heidelberg) that commonly cause human illness, and 30 isolates from food-associated Salmonella serovars that rarely cause human illness. The number of integrase genes identified by the PCR assay was compared to the number of integrase genes within intact prophages identified by whole genome sequencing and phage finding program PHASTER. The PCR assay identified a total of 147 prophage integrase genes within the 49 S. enterica genomes (79 integrase genes in the food-associated Salmonella isolates, 50 integrase genes in S. Enteritidis, and 18 integrase genes in S. Heidelberg). In comparison, whole genome sequencing and PHASTER identified a total of 75 prophage integrase genes within 102 intact prophages in the 49 S. enterica genomes (44 integrase genes in the food-associated Salmonella isolates, 21 integrase genes in S. Enteritidis, and 9 integrase genes in S. Heidelberg). Collectively, both the PCR assay and PHASTER identified the presence of a large diversity of prophage integrase genes in the food-associated isolates compared to the clinical isolates, thus indicating a high degree of diversity in the food-associated isolates, and confirming the clonal nature of S. Enteritidis and S. Heidelberg. Moreover, PHASTER revealed a diversity of 29 different types of prophages and 23 different integrase genes within the food-associated isolates, but only identified 4 different phages and integrase genes within clonal isolates of S. Enteritidis and S. Heidelberg. These results demonstrate the potential usefulness of PCR based detection of prophage integrase genes as a rapid indicator of genome diversity in S. enterica.
TL;DR: It is shown that the palindromic consensus sequence is not present in individual integration sites of human T-cell lymphotropic virus type 1 (HTLV-1) and human immunodeficiency virustype 1 (HIV-1), but arises in the population average as a consequence of the existence of a non-palindroma nucleotide motif that occurs in approximately equal proportions on the plus strand and the minus strand of the host genome.
Abstract: Many DNA-binding factors, such as transcription factors, form oligomeric complexes with structural symmetry that bind to palindromic DNA sequences1. Palindromic consensus nucleotide sequences are also found at the genomic integration sites of retroviruses2-6 and other transposable elements7-9, and it has been suggested that this palindromic consensus arises as a consequence of the structural symmetry in the integrase complex2,3. However, we show here that the palindromic consensus sequence is not present in individual integration sites of human T-cell lymphotropic virus type 1 (HTLV-1) and human immunodeficiency virus type 1 (HIV-1), but arises in the population average as a consequence of the existence of a non-palindromic nucleotide motif that occurs in approximately equal proportions on the plus strand and the minus strand of the host genome. We develop a generally applicable algorithm to sort the individual integration site sequences into plus-strand and minus-strand subpopulations, and use this to identify the integration site nucleotide motifs of five retroviruses of different genera: HTLV-1, HIV-1, murine leukaemia virus (MLV), avian sarcoma leucosis virus (ASLV) and prototype foamy virus (PFV). The results reveal a non-palindromic motif that is shared between these retroviruses.
TL;DR: The synthesis and biochemical evaluation of a few C-5, C-6 or C-7 substituted HID subtypes as HIV RNase H inhibitors indicate that while some of these subtypes inhibited both theRNase H and polymerase (pol) functions of RT, potent and selective RNaseH inhibition was achieved with subtypes 8-9 as exemplified with compounds 8c and 9c.
TL;DR: The genome of a new Streptomyces phage, ϕ Joe, is presented, and the conditions for integration and excision of the ϕJoe genome are investigated, and a phage-encoded recombination directionality factor (RDF) was identified and its function was confirmed in vivo.
Abstract: Bacteriophages are the source of many valuable tools for molecular biology and genetic manipulation. In Streptomyces, most DNA cloning vectors are based on serine integrase site-specific DNA recombination systems derived from phage. Because of their efficiency and simplicity, serine integrases are also used for diverse synthetic biology applications. Here, we present the genome of a new Streptomyces phage, ϕJoe, and investigate the conditions for integration and excision of the ϕJoe genome. ϕJoe belongs to the largest Streptomyces phage cluster (R4-like) and encodes a serine integrase. The attB site from Streptomyces venezuelae was used efficiently by an integrating plasmid, pCMF92, constructed using the ϕJoe int-attP locus. The attB site for ϕJoe integrase was occupied in several Streptomyces genomes, including that of S. coelicolor, by a mobile element that varies in gene content and size between host species. Serine integrases require a phage-encoded recombination directionality factor (RDF) to activate the excision reaction. The ϕJoe RDF was identified, and its function was confirmed in vivo Both the integrase and RDF were active in in vitro recombination assays. The ϕJoe site-specific recombination system is likely to be an important addition to the synthetic biology and genome engineering toolbox.IMPORTANCEStreptomyces spp. are prolific producers of secondary metabolites, including many clinically useful antibiotics. Bacteriophage-derived integrases are important tools for genetic engineering, as they enable integration of heterologous DNA into the Streptomyces chromosome with ease and high efficiency. Recently, researchers have been applying phage integrases for a variety of applications in synthetic biology, including rapid assembly of novel combinations of genes, biosensors, and biocomputing. An important requirement for optimal experimental design and predictability when using integrases, however, is the need for multiple enzymes with different specificities for their integration sites. In order to provide a broad platform of integrases, we identified and validated the integrase from a newly isolated Streptomyces phage, ϕJoe. ϕJoe integrase is active in vitro and in vivo The specific recognition site for integration is present in a wide range of different actinobacteria, including Streptomyces venezuelae, an emerging model bacterium in Streptomyces research.
TL;DR: Kuwanon‐L, a natural product active as an HIV‐1 integrase (IN) inhibitor, might exert its overall antiviral activity through binding to multiple viral targets, and can be considered an attractive lead for the development of new classes of antiviral agents able to overcome the problem of resistance.
Abstract: In recent years many advances have been made in the fight against HIV-1 infection. However, the lack of a vaccine, together with the increasing resistance to the highly active anti-retroviral therapy (HAART), make HIV-1 infection still a serious global emergency. Thus, new compounds with original modes of action are continuously required, and natural products have ever been a very interesting class of pharmacologically active molecules. Some of them have been used since ancient times against viral infections. Here we present a work in which we suggest that kuwanon-L, a natural product active as an HIV-1 integrase (IN) inhibitor, might exert its overall antiviral activity through binding to multiple viral targets. Specific enzymatic tests, together with a time-of-addition (TOA) experiment, support our hypothesis of binding both to IN and to reverse transcriptase (RT). Overall, this compound can be considered an attractive lead for the development of new classes of antiviral agents able to overcome the problem of resistance, due to its ability to exert its action by binding simultaneously to multiple viral targets.
TL;DR: These compounds, by impairing the integration of HIV-1 viral DNA into the host DNA, lead to an accumulation of unintegrated circular viral DNA forms that could be at the origin of the INSTI resistance.
Abstract: Integrase strand-transfer inhibitors (INSTIs) such as raltegravir, elvitegravir or dolutegravir, are efficient antiretroviral agents used in HIV treatment in order to inhibit retroviral integration. By contrast to raltegravir treatments leading to well-identified mutation resistance pathways at the integrase level, recent clinical studies report several cases of patients failing dolutegravir treatment without clearly identified resistance mutation in the integrase gene raising the mechanism behind the resistance. These compounds, by impairing the integration of HIV-1 viral DNA into the host DNA, lead to an accumulation of unintegrated circular viral DNA forms. This viral DNA could be at the origin of the INSTI resistance by two different ways. The first one, sustained by a recent report, involves 2-LTR circles integration and the second one involves expression of accumulated unintegrated viral DNA leading to a basal production of viral particles maintaining the viral information.
TL;DR: It is reported that the integrase inhibitor dolutegravir and the CCR5 inhibitor maraviroc reduced inflammation of human adult endothelial cells to different extents while raltegravIR was neutral.
Abstract: BACKGROUND Ageing HIV-infected patients present an increased incidence of cardiovascular diseases, endothelial dysfunction being an early alteration. Some protease inhibitors (PIs) have been shown to increase the risk of cardiovascular disease. We evaluated here the effects of CCR5 or integrase inhibitors as compared to PIs on endothelial functions in vitro. METHODS Human coronary artery endothelial cells (HCAEC) from adult and old non-HIV-infected donors were treated for 15 days with the CCR5 inhibitor maraviroc, the integrase inhibitors dolutegravir or raltegravir or the ritonavir-boosted PIs, darunavir (DRV/r) or atazanavir (ATV/r), all at Cmax concentrations. We evaluated endothelial function, secretion of adhesion molecules and cytokines, inflammation, oxidative stress and senescence. RESULTS In endothelial cells from adult donors, we confirmed that ATV/r and DRV/r adversely affected all assessed endothelial functions and enhanced senescence, these effects being mild for DRV/r. Raltegravir had no effect and maraviroc a mild anti-inflammatory effect. Dolutegravir decreased inflammation, by inhibiting the NFκB pathway, and senescence, by repressing the p21 pathway. Moreover, HCAEC from an old donor presented, constitutively, a high level of senescence. Raltegravir mildly affected inflammation and senescence while maraviroc and dolutegravir decreased oxidative stress, inflammation and senescence and improved endothelial dysfunction. CONCLUSIONS We report here that the integrase inhibitor dolutegravir and the CCR5 inhibitor maraviroc reduced inflammation of human adult endothelial cells to different extents while raltegravir was neutral. Dolutegravir also reduced senescence, while PI/r increased inflammation and senescence. It is important to address the clinical relevance of these results.
TL;DR: A wide repertoire of resistance mutations in the integrase gene occur in HIV-2-infected patients failing on raltegravir, including emerging variants Q148K and Q148R and a novel change G118R.
Abstract: Background: A broader extent of amino acid substitutions in the integrase of HIV-2 compared with HIV-1 might enable greater cross-resistance between raltegravir and dolutegravir in HIV-2 infection. Few studies have examined the virological response to dolutegravir in HIV-2 patients that failed raltegravir. Methods: All patients recorded in the HIV-2 Spanish cohort were examined. The integrase coding region was sequenced in viraemic patients. Changes associated with resistance to raltegravir and dolutegravir in HIV-1 were recorded. Results: From 319 HIV-2-infected patients recorded in the HIV-2 Spanish cohort, 53 integrase sequences from 30 individuals were obtained (20 raltegravir naive and 10 raltegravir experienced). Only one secondary mutation (E138A) was found in one of the 20 raltegravir-naive HIV-2 patients. For raltegravir-experienced individuals, the resistance mutation profile in 9 of 10 viraemic patients was as follows: N155H+A153G/S (four); Y143G+A153S (two); Q148R+G140A/S (two); and Y143C+Q91R (one). Of note, all patients with Y143G and N155H developed a rare non-polymorphic mutation at codon 153. Rescue therapy with dolutegravir was given to 5 of these 10 patients. After > 6months on dolutegravir therapy, three patients with baseline N155H experienced viral rebound. In two of them N155H was replaced by Q148K/R and in another by G118R. Conclusions: A wide repertoire of resistance mutations in the integrase gene occur in HIV-2-infected patients failing on raltegravir. Although dolutegravir may allow successful rescue in most HIV-2 raltegravir failures, we report and characterize three cases of dolutegravir resistance in HIV-2 patients, emerging variants Q148K and Q148R and a novel change G118R.
TL;DR: Naturally occurring compounds discovered from two Myanmar medicinal plants are summarized and Viral protein R (Vpr) is one of the promising drug targets among the HIV accessory proteins, and the search for inhibitors continues in anti-HIV drug discovery.
Abstract: Human immunodeficiency virus type-1 (HIV-1) is a lentiviral family member that encodes the retroviral Gag, Pol, and Env proteins, along with six additional accessory proteins, Tat, Rev, Vpu, Vif, Nef, and Vpr. The currently approved anti-HIV drugs target the Pol and Env encoded proteins. However, these drugs are only effective in reducing viral replication. Furthermore, the drugs' toxicities and the emergence of drug-resistant strains have become serious worldwide problems. Resistance eventually arises to all of the approved anti-HIV drugs, including the newly approved drugs that target HIV integrase (IN). Drug resistance likely emerges because of spontaneous mutations that occur during viral replication. Therefore, new drugs that effectively block other viral components must be developed to reduce the rate of resistance and suppress viral replication with little or no long-term toxicity. The accessory proteins may expand treatment options. Viral protein R (Vpr) is one of the promising drug targets among the HIV accessory proteins. However, the search for inhibitors continues in anti-HIV drug discovery. In this review, we summarize the naturally occurring compounds discovered from two Myanmar medicinal plants as well as their structure-activity relationships. A total of 49 secondary metabolites were isolated from Kaempferia pulchra rhizomes and Picrasama javanica bark, and the types of compounds were identified as isopimarane diterpenoids and picrasane quassinoids, respectively. Among the isolates, 7 diterpenoids and 15 quassinoids were found to be Vpr inhibitors lacking detectable toxicity, and their potencies varied according to their respective functionalities.
TL;DR: It is shown here that serine integrases can be fused to their cognate RDFs to create single proteins that catalyse efficient attL × attR recombination in vivo and in vitro, whereas attP × attB recombination efficiency is reduced.
Abstract: Bacteriophage serine integrases are extensively used in biotechnology and synthetic biology for assembly and rearrangement of DNA sequences. Serine integrases promote recombination between two different DNA sites, attP and attB, to form recombinant attL and attR sites. The 'reverse' reaction requires another phage-encoded protein called the recombination directionality factor (RDF) in addition to integrase; RDF activates attL × attR recombination and inhibits attP × attB recombination. We show here that serine integrases can be fused to their cognate RDFs to create single proteins that catalyse efficient attL × attR recombination in vivo and in vitro, whereas attP × attB recombination efficiency is reduced. We provide evidence that activation of attL × attR recombination involves intra-subunit contacts between the integrase and RDF moieties of the fusion protein. Minor changes in the length and sequence of the integrase-RDF linker peptide did not affect fusion protein recombination activity. The efficiency and single-protein convenience of integrase-RDF fusion proteins make them potentially very advantageous for biotechnology/synthetic biology applications. Here, we demonstrate efficient gene cassette replacement in a synthetic metabolic pathway gene array as a proof of principle.