Viral surface glycoproteins, gp120 and gp41, as potential drug targets against HIV-1: brief overview one quarter of a century past the approval of zidovudine, the first anti-retroviral drug

Immunological and molecular assessment of HIV-1 mutations for antiretroviral drug resistance in Saudi Arabia

Human Immunodeficiency Virus (HIV) is a significant threat to public health. HIV genotyping and antiretroviral resistance testing may have contributed to improved non-treated management. Immune markers might assist HIV-1 diagnosis and drug-resistant variant identification. HIV-1 immunogenicity and molecular characteristics of antiretroviral drug resistance are evaluated in 56 treatment-naive HIV patients. DNA sequencing and retroviral resistance testing identified HIV-1 genotypes. 55.4% of patients were susceptible to protease inhibitors (PI), nucleoside reverse transcriptase inhibitors (NRTI), and non-nucleoside reverse transcriptase inhibitors (NNRTI) antiretroviral drugs, whereas 44.6% had drug-resistance mutations against at least one antiretroviral drug. 3.6% of cases had PI-resistant mutations, while 30.4% had NRTI-resistant mutations, and 30.4% had NNRTI-resistant mutations. In patients who are susceptible to PI, the mean value of human plasma sCD80 is 2.11 ± 0.65 ng/mL; in patients with mutations, it is 3.93 ± 2.91 ng/mL. Individuals who are susceptible to PI have plasma sCD27 levels of 78.7 ± 63.2 U/mL, whereas individuals who are mutant have levels of 56.5 ± 32.1 U/mL. IP-10's mean value was 363 ± 109.2 pg/mL for the susceptible patients and 429 ± 20.7 pg/mL for the mutated patients. In susceptible patients, the plasma sCD4 level is 0.163 ± 0.229 ng/mL; in mutant patients, it is 0.084 ± 0.012 ng/mL. The data showed a relative relation between immunological parameters such as sCD80, sCD27, sCD4, and IP-10 and mutation for drug resistance.

A quantum mechanical investigation of nanocone oxide as a drug carrier for zidovudine: AIDS drug

Traditionally, nanocones as a drug delivery material allow controlled drug delivery close to the target area while reducing the toxicity and generic accumulation associated with traditional intravenous injection methods. In the current study, density functional theory (DFT) is employed to investigate the therapeutic potential of carbon nanocone oxide (ONC) as a carrier with zidovudine drug for the treatment of human immunodeficiency virus (HIV). The electronic ground state and excited state were studied to evaluate the drug carrier potential of ONC and Zidovudine-ONC complex. The Frontier Molecular Orbitals (FMOs) and Molecular Electrostatic Potential (MEPs) revealed that the ONC carrier acts as a donor and zidovudine as an acceptor. The FMOs confirmed the interaction between drug and carrier stabilization energy by calculating chemical hardness, material softness, electronegativity, Ionization energy and electron affinity. The natural bond analysis (NBO), non-covalent interaction (NCI) and electron localization function (ELF) revealed the charge transfer between zidovudine and ONC. The density of state (DOS) and Charge Deposition analysis (CDA) provided the charge transfer. To study the excited state of zidovudine, transition density matrix (TDM), UV(Ultra-visible), IR (infrared), Raman, and NMR (Nuclear Magnetic Resonance) spectra of ONC and zidovudine-ONC complex have been plotted. The spectra showed a significant red shift in the zidovudine-ONC complex. Photoinduced electron studies (PET) showed fluorescence quenching because of the interaction between the drug and the carrier and provided a graphical explanation of the distinct excited state. All the results show that the ONC carrier has therapeutic potential as a zidovudine carrier for the treatment of Human Immunodeficiency Virus (HIV).

Natural products as potential lead compounds to develop new antiviral drugs over the past decade

Virus infection has been one of the main causes of human death since the ancient times. Even though more and more antiviral drugs have been approved in clinic, long-term use can easily lead to the emergence of drug resistance and side effects. Fortunately, there are many kinds of metabolites which were produced by plants, marine organisms and microorganisms in nature with rich structural skeletons, and they are natural treasure house for people to find antiviral active substances. Aiming at many types of viruses that had caused serious harm to human health in recent years, this review summarizes the natural products with antiviral activity that had been reported for the first time in the past ten years, we also sort out the source, chemical structure and safety indicators in order to provide potential lead compounds for the research and development of new antiviral drugs.

Peptide Triazole Thiol Irreversibly Inactivates Metastable HIV-1 Env by Accessing Conformational Triggers Intrinsic to Virus-Cell Entry

KR13, a peptide triazole thiol previously established to inhibit HIV-1 infection and cause virus lysis, was evaluated by flow cytometry against JRFL Env-presenting cells to characterize induced Env and membrane transformations leading to irreversible inactivation. Transiently transfected HEK293T cells were preloaded with calcein dye, treated with KR13 or its thiol-blocked analogue KR13b, fixed, and stained for gp120 (35O22), MPER (10E8), 6-helix-bundle (NC-1), immunodominant loop (50-69), and fusion peptide (VRC34.01). KR13 induced dose-dependent transformations of Env and membrane characterized by transient poration, MPER exposure, and 6-helix-bundle formation (analogous to native fusion events), but also reduced immunodominant loop and fusion peptide exposure. Using a fusion peptide mutant (V504E), we found that KR13 transformation does not require functional fusion peptide for poration. In contrast, simultaneous treatment with fusion inhibitor T20 alongside KR13 prevented membrane poration and MPER exposure, showing that these events require 6-helix-bundle formation. Based on these results, we formulated a model for PTT-induced Env transformation portraying how, in the absence of CD4/co-receptor signaling, PTT may provide alternate means of perturbing the metastable Env-membrane complex, and inducing fusion-like transformation. In turn, the results show that such transformations are intrinsic to Env and can be diverted for irreversible inactivation of the protein complex.

Computational Modulation of the V3 Region of Glycoprotein gp125 of HIV-2

HIV-2 infection is frequently neglected in HIV/AIDS campaigns. However, a special emphasis must be given to HIV-2 as an untreated infection that also leads to AIDS and death, and for which the efficacy of most available drugs is limited against HIV-2. HIV envelope glycoproteins mediate binding to the receptor CD4 and co-receptors at the surface of the target cell, enabling fusion with the cell membrane and viral entry. Here, we developed and optimized a computer-assisted drug design approach of an important HIV-2 glycoprotein that allows us to explore and gain further insights at the molecular level into protein structures and interactions crucial for the inhibition of HIV-2 cell entry. The 3D structure of a key HIV-2ROD gp125 region was generated by a homology modeling campaign. To disclose the importance of the main structural features and compare them with experimental results, 3D-models of six mutants were also generated. These mutations revealed the selective impact on the behavior of the protein. Furthermore, molecular dynamics simulations were performed to optimize the models, and the dynamic behavior was tackled to account for structure flexibility and interactions network formation. Structurally, the mutations studied lead to a loss of aromatic features, which is very important for the establishment of π-π interactions and could induce a structural preference by a specific coreceptor. These new insights into the structure-function relationship of HIV-2 gp125 V3 and surrounding regions will help in the design of better models and the design of new small molecules capable to inhibit the attachment and binding of HIV with host cells.

Genotyping and antiretroviral drug resistance of human immunodeficiency Virus-1 in Jazan, Saudi Arabia

Determination of human immunodeficiency virus-1 (HIV-1) genotypes and identification of antiretroviral drug-resistant mutations. Among treatment naïve HIV patients in Jazan, Saudi Arabia. HIV is a major public health problem. HIV genotyping and antiretroviral resistance testing is an important guide for better management of treatment-naive. Antiretroviral resistance testing before starting of treatment regimen leads to a better virological response. A total of 57 samples of treatment-naive patients were collected from King Fahd Central Hospital in Jazan, Saudi Arabia. Samples were tested for HIV-1 antibodies, western blot, viral load, HIV-1 genotypes through direct sequencing, and antiretroviral resistance testing. The HIV-1 Genotypes were as follow; C: 66.6%, D: 10.5%, G: 8.8%, B: 7.0%, CRF01_AE: 3.5%, A and CRF02_AG: 1.8% each. 77.2% of cases showed susceptibility to the 3 major classes of antiretroviral drugs; Protease inhibitor (PI), Nucleoside reverse transcriptase inhibitor (NRTI), and non-nucleoside reverse transcriptase inhibitors (NNRTI); while 8.8% had mutations conferring resistance to NRTI. Mutations conferring resistance to PI were detected in 7.0% of cases, and 1.8% of cases had mutations conferring resistance to both NRTI and PI. Mutations conferring resistance to NNRTI were detected in 5.3% of cases. Mutations associated with antiretroviral drugs include (V82A+I84IV), (L10F+Q58E), (L10F+V82Y), L10FV, L33LF, L89LMV, M184V, E138A, V106I, and V179VD. The prevalence of HIV-1 antiretroviral resistance mutations is 22.8% in the studied population, which may warrant antiretroviral drug resistance testing as a pretreatment to help and guide physicians for the proper HIV treatment.

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

Metastable HIV-1 Surface Protein Env Sensitizes Cell Membranes to Transformation and Poration by Dual-Acting Virucidal Entry Inhibitors

Dual-acting virucidal entry inhibitors (DAVEIs) have previously been shown to cause irreversible inactivation of HIV-1 Env-presenting pseudovirus by lytic membrane transformation. This study examined whether this transformation could be generalized to include membranes of Env-presenting cells. Flow cytometry was used to analyze HEK293T cells transiently transfected with increasing amounts of DNA encoding JRFL Env, loaded with calcein dye, and treated with serial dilutions of microvirin (Q831K/M83R)-DAVEI. Comparing calcein retention against intact Env expression (via Ab 35O22) on individual cells revealed effects proportional to Env expression. "Low-Env" cells experienced transient poration and calcein leakage, while "high-Env" cells were killed. The cell-killing effect was confirmed with an independent mitochondrial activity-based cell viability assay, showing dose-dependent cytotoxicity in response to DAVEI treatment. Transfection with increasing quantities of Env DNA showed further shifts toward "High-Env" expression and cytotoxicity, further reinforcing the Env dependence of the observed effect. Controls with unlinked DAVEI components showed no effect on calcein leakage or cell viability, confirming a requirement for covalently linked DAVEI compounds to achieve Env transformation. These data demonstrate that the metastability of Env is an intrinsic property of the transmembrane protein complex and can be perturbed to cause membrane disruption in both virus and cell contexts.

Rational Design of Colchicine Derivatives as anti-HIV Agents via QSAR and Molecular Docking

BACKGROUND

Human immunodeficiency virus (HIV) is an infective agent that causes an acquired immunodeficiency syndrome (AIDS). Therefore, the rational design of inhibitors for preventing the progression of the disease is required.

OBJECTIVE

This study aims to construct quantitative structure-activity relationship (QSAR) models, molecular docking and newly rational design of colchicine and derivatives with anti-HIV activity.

METHODS

A data set of 24 colchicine and derivatives with anti-HIV activity were employed to develop the QSAR models using machine learning methods (e.g. multiple linear regression (MLR), artificial neural network (ANN) and support vector machine (SVM)), and to study a molecular docking.

RESULTS

The significant descriptors relating to the anti-HIV activity included JGI2, Mor24u, Gm and R8p+ descriptors. The predictive performance of the models gave acceptable statistical qualities as observed by correlation coefficient (Q2) and root mean square error (RMSE) of leave-one out cross-validation (LOO-CV) and external sets. Particularly, the ANN method outperformed MLR and SVM methods that displayed LOO-CV 2 Q and RMSELOO-CV of 0.7548 and 0.5735 for LOOCV set, and Ext 2 Q of 0.8553 and RMSEExt of 0.6999 for external validation. In addition, the molecular docking of virus-entry molecule (gp120 envelope glycoprotein) revealed the key interacting residues of the protein (cellular receptor, CD4) and the site-moiety preferences of colchicine derivatives as HIV entry inhibitors for binding to HIV structure. Furthermore, newly rational design of colchicine derivatives using informative QSAR and molecular docking was proposed.

CONCLUSION

These findings serve as a guideline for the rational drug design as well as potential development of novel anti-HIV agents.

Anti-HIV activity of new higher order G-quadruplex aptamers obtained from tetra-end-linked oligonucleotides

By combining the ability of short G-rich oligodeoxyribonucleotides (ODNs) containing the sequence 5'CGGA3' to form higher order G-quadruplex (G4) complexes with the tetra-end-linked (TEL) concept to produce aptamers targeting the HIV envelope glycoprotein 120 (gp120), three new TEL-ODNs (1-3) having the sequence 5'CGGAGG3' were synthesized with the aim of studying the effect of G4 dimerization on their anti-HIV activity. Furthermore, in order to investigate the effect of the groups at the 5' position, the 5' ends of 1-3 were left uncapped (1) or capped with either the lipophilic dimethoxytrityl (DMT) (2) or the hydrophilic glucosyl-4-phosphate (3) moieties. The here reported results demonstrate that only the DMT-substituted TEL-ODN 2 is effective in protecting human MT-4 cell cultures from HIV infection (76% max protection), notwithstanding all the three new aptamers proved to be capable of forming stable higher order dimeric G4s when annealed in K+-containing buffer, thus suggesting that the recognition of a hydrophobic pocket on the target glycoprotein by the aptamers represents a main structural feature for triggering their anti-HIV activity.

Inhibition of HIV Entry by Targeting the Envelope Transmembrane Subunit gp41

BACKGROUND

The transmembrane subunit of the HIV envelope protein, gp41 is a vulnerable target to inhibit HIV entry. There is one fusion inhibitor T20 (brand name: Fuzeon, generic name: enfuvirtide) available by prescription. However, it has several drawbacks such as a high level of development of drug resistance, a short-half life in vivo, rapid renal clearance, low oral bioavailability, and it is only used as a salvage therapy. Therefore, investigators have been studying a variety of different modalities to attempt to overcome these limitations.

METHODS

Comprehensive literature searches were performed on HIV gp41, inhibition mechanisms, and inhibitors. The latest structural information was collected, and multiple inhibition strategies targeting gp41 were reviewed.

RESULTS

Many of the recent advances in inhibitors were peptide-based. Several creative modification strategies have also been performed to improve inhibitory efficacy of peptides and to overcome the drawbacks of T20 treatment. Small compounds have also been an area of intense research. There is a wide variety in development from those identified by virtual screens targeting specific regions of the protein to natural products. Finally, broadly neutralizing antibodies have also been important area of research. The inaccessible nature of the target regions for antibodies is a challenge, however, extensive efforts to develop better neutralizing antibodies are ongoing.

CONCLUSION

The fusogenic protein, gp41 has been extensively studied as a promising target to inhibit membrane fusion between the virus and target cells. At the same time, it is a challenging target because the vulnerable conformations of the protein are exposed only transiently. However, advances in biochemical, biophysical, structural, and immunological studies are coming together to move the field closer to an understanding of gp41 structure and function that will lead to the development of novel drugs and vaccines.

Striking HIV-1 Entry by Targeting HIV-1 gp41. But, Where Should We Target?

HIV-1 gp41 facilitates the viral fusion through a conformational switch involving the association of three C-terminal helices along the conserved hydrophobic grooves of three N-terminal helices coiled-coil. The control of these structural rearrangements is thought to be central to HIV-1 entry and, therefore, different strategies of intervention are being developed. Herewith, we describe a procedure to simulate the folding of an HIV-1 gp41 simplified model. This procedure is based on the construction of plausible conformational pathways, which describe protein transition between non-fusogenic and fusogenic conformations. The calculation of the paths started with 100 molecular dynamics simulations of the non-fusogenic conformation, which were found to converge to different intermediate states. Those presenting defined criteria were selected for separate targeted molecular dynamics simulations, subjected to a force constant imposing a movement towards the gp41 fusogenic conformation. Despite significant diversity, a preferred sequence of events emerged when the simulations were analyzed in terms of the formation, breakage and evolution of the contacts. We pointed out 29 residues as the most relevant for the movement of gp41; also, 2696 possible interactions were reduced to only 48 major interactions, which reveals the efficiency of the method. The analysis of the evolution of the main interactions lead to the detection of four main behaviors for those contacts: stable, increasing, decreasing and repulsive interactions. Altogether, these results suggest a specific small cavity of the HIV-1 gp41 hydrophobic groove as the preferred target to small molecules.

StaRProtein, a web server for prediction of the stability of repeat proteins

Repeat proteins have become increasingly important due to their capability to bind to almost any proteins and the potential as alternative therapy to monoclonal antibodies. In the past decade repeat proteins have been designed to mediate specific protein-protein interactions. The tetratricopeptide and ankyrin repeat proteins are two classes of helical repeat proteins that form different binding pockets to accommodate various partners. It is important to understand the factors that define folding and stability of repeat proteins in order to prioritize the most stable designed repeat proteins to further explore their potential binding affinities. Here we developed distance-dependant statistical potentials using two classes of alpha-helical repeat proteins, tetratricopeptide and ankyrin repeat proteins respectively, and evaluated their efficiency in predicting the stability of repeat proteins. We demonstrated that the repeat-specific statistical potentials based on these two classes of repeat proteins showed paramount accuracy compared with non-specific statistical potentials in: 1) discriminate correct vs. incorrect models 2) rank the stability of designed repeat proteins. In particular, the statistical scores correlate closely with the equilibrium unfolding free energies of repeat proteins and therefore would serve as a novel tool in quickly prioritizing the designed repeat proteins with high stability. StaRProtein web server was developed for predicting the stability of repeat proteins.

Discovery of small molecular inhibitors targeting HIV-1 gp120-CD4 interaction drived from BMS-378806

The HIV-1 entry into host cells is a complex, multi-factors involved, and multi-step process. Especially, the attachment of HIV-1 envelope glycoprotein gp120 to the host cell receptor CD4 is the first key step during entry process, representing a promising antiviral therapeutic target. Among the HIV-1 attachment inhibitors blocking the interaction between gp120 and CD4 cells, BMS-378806 and NBD-556 are two representative small molecular chemical entities. Particularly, BMS-378806 and its derivatives are newly identified class of orally bioavailable HIV-1 inhibitors that interfere gp120-CD4 interaction. In this review, we focused on describing the structure-activity relationships (SARs), structural modifications, in vitro or even in vivo pharmacodynamics and pharmacokinetics of BMS-378806 and its analogues as HIV-1 gp120 attachment inhibitors. In addition, the brief SARs, structural modifications of NBD-556 and its derivatives targeting the "Phe-43 cavity" as CD4 mimics were also described.

Expression, purification and crystallization of CTB-MPR, a candidate mucosal vaccine component against HIV-1

CTB-MPR is a fusion protein between the B subunit of cholera toxin (CTB) and the membrane-proximal region of gp41 (MPR), the transmembrane envelope protein of Human immunodeficiency virus 1 (HIV-1), and has previously been shown to induce the production of anti-HIV-1 antibodies with antiviral functions. To further improve the design of this candidate vaccine, X-ray crystallography experiments were performed to obtain structural information about this fusion protein. Several variants of CTB-MPR were designed, constructed and recombinantly expressed in Escherichia coli. The first variant contained a flexible GPGP linker between CTB and MPR, and yielded crystals that diffracted to a resolution of 2.3 Å, but only the CTB region was detected in the electron-density map. A second variant, in which the CTB was directly attached to MPR, was shown to destabilize pentamer formation. A third construct containing a polyalanine linker between CTB and MPR proved to stabilize the pentameric form of the protein during purification. The purification procedure was shown to produce a homogeneously pure and monodisperse sample for crystallization. Initial crystallization experiments led to pseudo-crystals which were ordered in only two dimensions and were disordered in the third dimension. Nanocrystals obtained using the same precipitant showed promising X-ray diffraction to 5 Å resolution in femtosecond nanocrystallography experiments at the Linac Coherent Light Source at the SLAC National Accelerator Laboratory. The results demonstrate the utility of femtosecond X-ray crystallography to enable structural analysis based on nano/microcrystals of a protein for which no macroscopic crystals ordered in three dimensions have been observed before.

Recent patents and emerging therapeutics for HIV infections: a focus on protease inhibitors

The inclusion of protease inhibitors (PIs) in highly active antiretroviral therapy has significantly improved clinical outcomes in HIV-1-infected patients. To date, PIs are considered to be the most important therapeutic agents for the treatment of HIV infections. Despite high anti-HIV-1 potency, poor oral bioavailability of PIs has been a major concern. For achieving therapeutic concentrations, large doses of PIs are administered, which results in unacceptable systemic toxicities. Such severe and long-term toxicities necessitate the development of safer and potentially promising PIs. Recently, considerable attention has been paid to the development of newer compounds capable of inhibiting wild-type and resistant HIV-1 protease. Some of these PIs have displayed potent HIV-1 protease inhibitory activity. In this review, we have made an attempt to provide an overview on clinically approved and newly developing PIs, and related recent patents in the development of novel PIs.

Synthesis and evaluation of phosphorus containing, specific CDK9/CycT1 inhibitors

Although there is a significant effort in the design of a selective CDK9/CycT1 inhibitor, no compound has been proven to be a specific inhibitor of this kinase so far. The aim of this research was to develop novel and selective phosphorus containing CDK9/CycT1 inhibitors. Molecules bearing phosphonamidate, phosphonate, and phosphinate moieties were synthesized. Prepared compounds were evaluated in an enzymatic CDK9/CycT1 assay. The most potent molecules were tested in cell-based toxicity and HIV proliferation assays. Selectivity of shortlisted compounds against CDKs and other kinases was tested. The best compound was shown to be a highly specific, ATP-competitive inhibitor of CDK9/CycT1 with antiviral activity.

Structure-based design, synthesis and validation of CD4-mimetic small molecule inhibitors of HIV-1 entry: conversion of a viral entry agonist to an antagonist

This Account provides an overview of a multidisciplinary consortium focused on structure-based strategies to devise small molecule antagonists of HIV-1 entry into human T-cells, which if successful would hold considerable promise for the development of prophylactic modalities to prevent HIV transmission and thereby alter the course of the AIDS pandemic.

Entry of the human immunodeficiency virus (HIV) into target T-cells entails an interaction between CD4 on the host T-cell and gp120, a component of the trimeric envelope glycoprotein spike on the virion surface. The resultant interaction initiates a series of conformational changes within the envelope spike that permits binding to a chemokine receptor, formation of the gp41 fusion complex, and cell entry. A hydrophobic cavity at the CD4–gp120 interface, defined by X-ray crystallography, provided an initial site for small molecule antagonist design. This site however has evolved to facilitate viral entry. As such, the binding of prospective small molecule inhibitors within this gp120 cavity can inadvertently trigger an allosteric entry signal.

Structural characterization of the CD4–gp120 interface, which provided the foundation for small molecule structure-based inhibitor design, will be presented first. An integrated approach combining biochemical, virological, structural, computational, and synthetic studies, along with a detailed analysis of ligand binding energetics, revealed that modestly active small molecule inhibitors of HIV entry can also promote viral entry into cells lacking the CD4 receptor protein; these competitive inhibitors were termed small molecule CD4 mimetics. Related congeners were subsequently identified with both improved binding affinity and more potent viral entry inhibition. Further assessment of the affinity-enhanced small molecule CD4 mimetics demonstrated that premature initiation of conformational change within the viral envelope spike, prior to cell encounter, can lead to irreversible deactivation of viral entry machinery. Related congeners, which bind the same gp120 site, possess different propensities to elicit the allosteric response that underlies the undesired enhancement of CD4-independent viral entry.

Subsequently, key hotspots in the CD4–gp120 interface were categorized using mutagenesis and isothermal titration calorimetry according to the capacity to increase binding affinity without triggering the allosteric signal. This analysis, combined with cocrystal structures of small molecule viral entry agonists with gp120, led to the development of fully functional antagonists of HIV-1 entry. Additional structure-based design exploiting two hotspots followed by synthesis has now yielded low micromolar inhibitors of viral entry.

Enhanced central nervous system transduction with lentiviral vectors pseudotyped with RVG/HIV-1gp41 chimeric envelope glycoproteins

To investigate the potential benefits which may arise from pseudotyping the HIV-1 lentiviral vector with its homologous gp41 envelope glycoprotein (GP) cytoplasmic tail (CT), we created chimeric RVG/HIV-1gp41 GPs composed of the extracellular and transmembrane sequences of RVG and either the full-length gp41 CT or C terminus gp41 truncations sequentially removing existing conserved motifs. Lentiviruses (LVs) pseudotyped with the chimeric GPs were evaluated in terms of particle release (physical titer), biological titers, infectivity, and in vivo central nervous system (CNS) transduction. We report here that LVs carrying shorter CTs expressed higher levels of envelope GP and showed a higher average infectivity than those bearing full-length GPs. Interestingly, complete removal of GP CT led to vectors with the highest transduction efficiency. Removal of all C-terminal gp41 CT conserved motifs, leaving just 17 amino acids (aa), appeared to preserve infectivity and resulted in a significantly increased physical titer. Furthermore, incorporation of these 17 aa in the RVG CT notably enhanced the physical titer. In vivo stereotaxic delivery of LV vectors exhibiting the best in vitro titers into rodent striatum facilitated efficient transduction of the CNS at the site of injection. A particular observation was the improved retrograde transduction of neurons in connected distal sites that resulted from the chimeric envelope R5 which included the "Kennedy" sequence (Ken) and lentivirus lytic peptide 2 (LLP2) conserved motifs in the CT, and although it did not exhibit a comparable high titer upon pseudotyping, it led to a significant increase in distal retrograde transduction of neurons.

IMPORTANCE

In this study, we have produced novel chimeric envelopes bearing the extracellular domain of rabies fused to the cytoplasmic tail (CT) of gp41 and pseudotyped lentiviral vectors with them. Here we report novel effects on the transduction efficiency and physical titer of these vectors, depending on CT length and context. We also managed to achieve increased neuronal transduction in vivo in the rodent CNS, thus demonstrating that the efficiency of these vectors can be enhanced following merely CT manipulation. We believe that this paper is a novel contribution to the field and opens the way for further attempts to surface engineer lentiviral vectors and make them more amenable for applications in human disease.

Non-natural peptide triazole antagonists of HIV-1 envelope gp120

We investigated the derivation of non-natural peptide triazole dual receptor site antagonists of HIV-1 Env gp120 to establish a pathway for developing peptidomimetic antiviral agents. Previously we found that the peptide triazole HNG-156 [R-I-N-N-I-X-W-S-E-A-M-M-CONH(2), in which X=ferrocenyltriazole-Pro (FtP)] has nanomolar binding affinity to gp120, inhibits gp120 binding to CD4 and the co-receptor surrogate mAb 17b, and has potent antiviral activity in cell infection assays. Furthermore, truncated variants of HNG-156, typified by UM-24 (Cit-N-N-I-X-W-S-CONH(2)) and containing the critical central stereospecific (L)X-(L)W cluster, retain the functional characteristics of the parent peptide triazole. In the current work, we examined the possibility of replacing natural with unnatural residue components in UM-24 to the greatest extent possible. The analogue with the critical "hot spot" residue Trp 6 replaced with L-3-benzothienylalanine (Bta) (KR-41), as well as a completely non-natural analogue containing D-amino acid substitutions outside the central cluster (KR-42, (D)Cit-(D)N-(D)N-(D)I-X-Bta-(D)S-CONH(2)), retained the dual receptor site antagonism/antiviral activity signature. The results define differential functional roles of subdomains within the peptide triazole and provide a structural basis for the design of metabolically stable peptidomimetic inhibitors of HIV-1 Env gp120.

Premature and accelerated aging: HIV or HAART?

Highly active antiretroviral therapy (HAART) has significantly increased life expectancy of the human immunodeficiency virus (HIV)-positive population. Nevertheless, the average lifespan of HIV-patients remains shorter compared to uninfected individuals. Immunosenescence, a current explanation for this difference invokes heavily on viral stimulus despite HAART efficiency in viral suppression. We propose here that the premature and accelerated aging of HIV-patients can also be caused by adverse effects of antiretroviral drugs, specifically those that affect the mitochondria. The nucleoside reverse transcriptase inhibitor (NRTI) antiretroviral drug class for instance, is known to cause depletion of mitochondrial DNA via inhibition of the mitochondrial specific DNA polymerase-γ. Besides NRTIs, other antiretroviral drug classes such as protease inhibitors also cause severe mitochondrial damage by increasing oxidative stress and diminishing mitochondrial function. We also discuss important areas for future research and argue in favor of the use of Caenorhabditis elegans as a novel model system for studying these effects.

Role of human immunodeficiency virus type 1 envelope structure in the induction of broadly neutralizing antibodies

Very soon after the discovery of neutralizing antibodies (NAbs) toward human immunodeficiency virus type 1 (HIV-1) infection, it became apparent that characterization of these NAbs would be an important step in finding a cure for or a vaccine to eradicate HIV-1. Since the initial description of broadly cross-clade NAbs naturally produced in HIV-1 patients, numerous studies have described new viral targets for these antibodies. More recently, studies concerning new groups of patients able to control their viremia, such as long-term nonprogressors (LTNPs) or elite controllers, have described the generation of numerous envelope-targeted NAbs. Recent studies have marked a new stage in research on NAbs with the description of antibodies obtained from a worldwide screening of HIV-positive patients. These studies have permitted the discovery of NAb families with great potential for both neutralization and neutralization breadth, such as PG, PGT, CH, and highly active agonistic anti-CD4 binding site antibodies (HAADs), of which VRC01 and its variants are members. These antibodies are able to neutralize more than 80% of circulating strains without any autoreactivity and can be rapidly integrated into clinical trials in order to test their protective potential. In this review, we will focus on new insights into HIV-1 envelope structure and their implications for the generation of potent NAbs.

Behavioral effects of chronic methamphetamine treatment in HIV-1 gp120 transgenic mice

Methamphetamine (METH) dependence is frequently comorbid with HIV infection. Both factors are independently characterized by inhibitory deficits, which may manifest as increased motor activity, inappropriate perseverative behavior, and elevated exploratory responses to novel stimuli, but the effect of combined METH exposure and HIV is not well understood. In this study, we administered a chronic escalation/binge regimen of METH or vehicle treatment to wildtype (WT) or transgenic (tg) mice expressing the HIV-1 gp120 envelope protein and quantified disinhibition during the 7 days following drug withdrawal. We hypothesized that gp120tg mice administered chronic METH would exhibit more pronounced inhibitory deficits compared to vehicle-treated WT or gp120tg animals. Our results showed that METH treatment alone increased novel object interaction while female METH-treated gp120tg mice exhibited the highest level of exploration (holepoking) compared to other female mice. Transgenic mice exhibited fewer rears relative to WT, slightly less locomotion, and also demonstrated a trend toward more perseverative motor patterns. In summary, both METH treatment and gp120 expression may modify inhibition, but such effects are selective and dependent upon variations in age and sex that could impact dopamine and frontostriatal function. These findings illustrate the need to improve our knowledge about the combined effects of HIV and substance use and facilitate improved treatment methods for comorbid disease and drug dependence.

Anti-HIV activity of semisynthetic derivatives of andrographolide and computational study of HIV-1 gp120 protein binding

Andrographolide, a diterpene lactone of the Andrographis paniculata, displays anti-HIV activity in vitro. A series of andrographolide derivatives have been synthesized and evaluated for their anti-HIV activity in a cell-free virus infectivity assay using TZM-bl cells. As compared to andrographolide, 3-nitrobenzylidene derivative 6 showed higher in vitro anti-HIV activity, whereas 2',6'-dichloro-nicotinoyl ester derivative 9 showed higher Therapeutic Index. The andrographolide and its derivatives, 6 and 9, inhibited gp120-mediated cell fusion of HL2/3 cells (expressing gp120 on its surface) with TZM-bl cells (expressing CD4 and co-receptors CCR5 & CXCR4). Further, computational studies revealed that these molecules bind to the important residues of V3 loop of gp120. These results suggest that andrographolide derivatives may be promising candidates for prevention of HIV infection.

Age- and ethanol concentration-dependent effects of acute binge drinking in the HIV-1 transgenic rat

BACKGROUND

Binge drinking is common in young people. Alcoholic beverages vary significantly in their ethanol (EtOH) concentration (alcohol by volume). We previously showed EtOH concentration-dependent activation of the hypothalamic supraoptic nucleus. In the HIV-infected population, incidence of alcohol abuse is close to 50%. We found age-dependent expression of HIV-1 viral proteins in the HIV-1 transgenic (HIV-1Tg) rat. Thus, we hypothesized that there are age- and EtOH concentration-dependent effects of binge drinking in HIV-1-positive individuals.

METHODS

Blood ethanol concentration was measured in adult F344 rats after gavage (i.g.) administration of water, 20% EtOH, or 52% EtOH. We also compared expression of the HIV-1 viral protein Tat in the brain, spleen, and liver of adult and adolescent HIV-1Tg rats following binge i.g. administration of water, 20% EtOH, or 52% EtOH for 3 days (4.8 g/kg/d) using absolute quantitative real-time reverse transcription-polymerase chain reaction. In a parallel study, we assessed age-dependent motor function in the HIV-1Tg rats 1 day after exposure to 20% EtOH using the open-field test.

RESULTS

Blood ethanol concentration was significantly higher in the 52% EtOH-treated F344 rats compared to the 20% EtOH animals at 90 minutes posttreatment. In the adult HIV-1Tg rats, HIV-1 Tat expression (copies per microgram of total RNA) was significantly increased in the brain, liver, and spleen of the 52% EtOH group, but not in the 20% EtOH group. However, in the adolescent animals, HIV-1 Tat expression in the 52% EtOH group was increased in the brain and liver, but not in the spleen. A significant reduction in locomotor activity occurred in 20% EtOH-treated adult HIV-1Tg rats compared to the water control, although no difference was observed in the adolescent HIV-1Tg animals.

CONCLUSIONS

Our data indicate that binge alcohol drinking can have age- and EtOH concentration-dependent effects in the presence of HIV-1 infection.

Structure-based design, synthesis, and characterization of dual hotspot small-molecule HIV-1 entry inhibitors

Cellular infection by HIV-1 is initiated with a binding event between the viral envelope glycoprotein gp120 and the cellular receptor protein CD4. The CD4-gp120 interface is dominated by two hotspots: a hydrophobic gp120 cavity capped by Phe43(CD4) and an electrostatic interaction between residues Arg59(CD4) and Asp368(gp120). The CD4 mimetic small-molecule NBD-556 (1) binds within the gp120 cavity; however, 1 and related congeners demonstrate limited viral neutralization breadth. Herein, we report the design, synthesis, characterization, and X-ray structures of gp120 in complex with small molecules that simultaneously engage both binding hotspots. The compounds specifically inhibit viral infection of 42 tier 2 clades B and C viruses and are shown to be antagonists of entry into CD4-negative cells. Dual hotspot design thus provides both a means to enhance neutralization potency of HIV-1 entry inhibitors and a novel structural paradigm for inhibiting the CD4-gp120 protein-protein interaction.

Role of glycans and glycoproteins in disease development by Mycobacterium tuberculosis

Glycoproteins play a critical role in host-pathogen interactions, antigenicity, and virulence determination, and are therefore, considered as potential drug targets. The cell wall of Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), dominantly contains sugars and lipids. Despite the efforts taken by the World Health Organization to reduce the incidence rate, the prevalence of TB is increasing in certain regions. This is mainly attributed to the emergence of multidrug-resistant bacteria. Factors that contribute to Mtb virulence and antigenicity remain elusive. However, several studies have shown that sugars and lipids are mainly responsible for Mtb pathogenesis and resistance to numerous drugs. This review gives insight into the role of glycoproteins in mycobacterium pathogenesis, disease development, and its implications in drug development.