A potential long-acting bictegravir loaded nano-drug delivery system for HIV-1 infection: A proof-of-concept study

Biocompatible metal-organic frameworks as promising platforms to eradicate HIV reservoirs ex vivo in people living with HIV

The HIV attacks the immune system provoking an infection that is considered a global health challenge. Despite antiretroviral treatments being effective in reducing the plasma viral load in the blood to undetectable levels in people living with HIV (PLWH), the disease is not cured and has become chronic. This happens because of the existence of anatomical and cellular viral reservoirs, mainly located in the lymph nodes and gastrointestinal tract, which are composed of infected CD4+ T cells with a resting memory phenotype and inaccessible to antiretroviral therapy. Herein, a new therapeutic strategy based on nanotechnology is presented. Different combinations of antiretroviral drugs (bictegravir/tenofovir/emtricitabine and nevirapine/tenofovir/emtricitabine) and toll-like receptor agonists were encapsulated into metal-organic frameworks (MOFs) PCN-224 and ZIF-8. The encapsulation efficiencies of all the drugs, as well as their release rate from the carriers, were measured. In vitro studies about the cell viability, the hemocompatibility, and the platelet aggregation of the MOFs were carried out. Epifluorescence microscopy assays confirmed the ability of ZIF-8 to target a carboxyfluorescein probe inside HeLa cell lines and PBMCs. These results pave the way for the use of these structures to eliminate latent HIV reservoirs from anatomical compartments through the activation of innate immune cells, and a higher efficacy of the triplet combinations of antiretroviral drugs.

Nanomedicine for the Treatment of Viral Diseases: Smaller Solution to Bigger Problems

The continuous evolution of new viruses poses a danger to world health. Rampant outbreaks may advance to pandemic level, often straining financial and medical resources to breaking point. While vaccination remains the gold standard to prevent viral illnesses, these are mostly prophylactic and offer minimal assistance to those who have already developed viral illnesses. Moreover, the timeline to vaccine development and testing can be extensive, leading to a lapse in controlling the spread of viral infection during pandemics. Antiviral therapeutics can provide a temporary fix to tide over the time lag when vaccines are not available during the commencement of a disease outburst. At times, these medications can have negative side effects that outweigh the benefits, and they are not always effective against newly emerging virus strains. Several limitations with conventional antiviral therapies may be addressed by nanotechnology. By using nano delivery vehicles, for instance, the pharmacokinetic profile of antiviral medications can be significantly improved while decreasing systemic toxicity. The virucidal or virus-neutralizing qualities of other special nanomaterials can be exploited. This review focuses on the recent advancements in nanomedicine against RNA viruses, including nano-vaccines and nano-herbal therapeutics.

Biktarvy for the treatment of HIV infection: Progress and prospects

Bictegravir (BIC), a second-generation integrase strand-transfer inhibitor (INSTI) with high resilience to INSTI-resistance mutations, is integrated as a key component of Biktarvy® - a fixed-dose once-daily triple-drug regimen of bictegravir (BIC), emtricitabine (FTC) plus tenofovir alafenamide (TAF). Based on the accumulated evidence from HIV clinical trials and real-world studies, the clinical effectiveness of BIC + FTC + TAF has been proven non-inferior to other fixed-dose once-daily combinations such as dolutegravir + FTC + TAF and dolutegravir + abacavir + lamivudine. Biktarvy also shows limited drug-drug interactions and a high barrier to drug resistance. According to recent HIV guidelines, BIC + FTC + TAF is recommended as initial and long-term therapy for the treatment of HIV infection. For the pre-exposure prophylaxis, tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide (TAF) remains advisable, but BIC may be possibly added to TDF or TAF. In the development of a long-acting once-monthly regimen, the novel nano-formulation of BIC + FTC + TAF could be possibly developed in the future.

Trends in nano-platforms for the treatment of viral infectious diseases

Viral diseases have always been a major health issue, from the currently eradicated poliovirus to the still unresolved human immunodeficiency virus, and have since become a recent global threat brought about by the COVID-19 pandemic. Pathogenic viruses easily spread through various means such as contaminated food and water intake, exchange of bodily fluids, or even inhalation of airborne particles mainly due to their miniscule size. Furthermore, viral coats contain virulent proteins which trigger assimilation into target cells on contact through either direct penetration or induction of endocytosis. In some viruses their outer envelope contains masking ligands that create a means of escape from detection of immune cells. To deal with the nanometer size range and biomolecular-based invasion mechanism, nanoparticles are highly suitable for the treatment. The review highlights the progress in nanoparticle technology, particularly viral therapeutics, including therapeutic strategies and existing clinical applications.

Long-acting HIV Pre-exposure Prophylaxis (PrEP) approaches: Recent advances, emerging technologies and development challenges

Introduction:

Poor or inconsistent adherence to daily oral pre-exposure prophylaxis (PrEP) has emerged as a key barrier to effective HIV prevention. The advent of potent long-acting (LA) antiretrovirals (ARVs) in conjunction with advances in controlled release technologies has enabled LA ARV drug delivery systems (DDS) capable of providing extended dosing intervals and overcome the challenge of suboptimal drug adherence with daily oral dosing.

Areas covered:

This review discusses the current state of the LA PrEP field, recent advances, and emerging technologies, including ARV prodrug modifications and new DDS. Technological challenges, knowledge gaps, preclinical testing considerations, and future directions important in the context of clinical translation and implementation of LA HIV PrEP are discussed.

Expert opinion:

The HIV prevention field is evolving faster than ever and the bar for developing next-generation LA HIV prevention options continues to rise. The requirements for viable LA PrEP products to be implemented in resource-limited settings are challenging, necessitating proactive consideration and product modifications during the design and testing of promising new candidates. If successfully translated, next-generation LA PrEP that are safe, affordable, highly effective, and accepted by both end-users and key stakeholders will offer significant potential to curb the HIV pandemic.

Meta-Analysis of Drug Delivery Approaches for Treating Intracellular Infections

This meta-analysis aims to evaluate the trend, methodological quality and completeness of studies on intracellular delivery of antimicrobial agents. PubMed, Embase, and reference lists of related reviews were searched to identify original articles that evaluated carrier-mediated intracellular delivery and pharmacodynamics (PD) of antimicrobial therapeutics against intracellular pathogens in vitro and/or in vivo. A total of 99 studies were included in the analysis. The most commonly targeted intracellular pathogens were bacteria (62.6%), followed by viruses (16.2%) and parasites (15.2%). Twenty-one out of 99 (21.2%) studies performed neither microscopic imaging nor flow cytometric analysis to verify that the carrier particles are present in the infected cells. Only 31.3% of studies provided comparative inhibitory concentrations against a free drug control. Approximately 8% of studies, albeit claimed for intracellular delivery of antimicrobial therapeutics, did not provide any experimental data such as microscopic imaging, flow cytometry, and in vitro PD. Future research on intracellular delivery of antimicrobial agents needs to improve the methodological quality and completeness of supporting data in order to facilitate clinical translation of intracellular delivery platforms for antimicrobial therapeutics.

Light sheet based volume flow cytometry (VFC) for rapid volume reconstruction and parameter estimation on the go

Optical imaging is paramount for disease diagnosis and to access its progression over time. The proposed optical flow imaging (VFC/iLIFE) is a powerful technique that adds new capabilities (3D volume visualization, organelle-level resolution, and multi-organelle screening) to the existing system. Unlike state-of-the-art point-illumination-based biomedical imaging techniques, the sheet-based VFC technique is capable of single-shot sectional visualization, high throughput interrogation, real-time parameter estimation, and instant volume reconstruction with organelle-level resolution of live specimens. The specimen flow system was realized on a multichannel (Y-type) microfluidic chip that enables visualization of organelle distribution in several cells in-parallel at a relatively high flow-rate (2000 nl/min). The calibration of VFC system requires the study of point emitters (fluorescent beads) at physiologically relevant flow-rates (500-2000 nl/min) for determining flow-induced optical aberration in the system point spread function (PSF). Subsequently, the recorded raw images and volumes were computationally deconvolved with flow-variant PSF to reconstruct the cell volume. High throughput investigation of the mitochondrial network in HeLa cancer cell was carried out at sub-cellular resolution in real-time and critical parameters (mitochondria count and size distribution, morphology, entropy, and cell strain statistics) were determined on-the-go. These parameters determine the physiological state of cells, and the changes over-time, revealing the metastatic progression of diseases. Overall, the developed VFC system enables real-time monitoring of sub-cellular organelle organization at a high-throughput with high-content capacity.

Use of long-acting injectable antiretroviral agents for human immunodeficiency Virus: A review

The development of potent antiretroviral drugs has significantly reduced morbidity and mortality associated with human immunodeficiency virus infection, however, the effectiveness of these medications depends upon consistent daily oral intake. Non-adherence can lead to the emergence of resistance, treatment failure and disease progression. This has necessitated the development of long-acting antiretroviral formulations administrable via an infrequent dosing regimen. Long-acting injectable forms of cabotegravir and rilpivirine have reached various stages in clinical trials both for the treatment and prevention of HIV. Other long-acting agents are at various stages of development. This review evaluates the current research on the development of long-acting injectable antiretroviral agents for the treatment and prevention of HIV.

Long-Acting Cabotegravir for HIV/AIDS Prophylaxis

The retrovirus HIV-1 is the etiological agent of the decades-long AIDS pandemic. Although vaccination is the most common preexposure route to prevent acquisition of viral disease, scalable efficacious vaccination strategies have yet to be developed for HIV-1. By contrast, small molecule inhibitors of the HIV-1 enzymes reverse transcriptase, integrase, and protease have been developed that effectively block virus replication. Three different drug compounds are commonly prescribed for people living with HIV as once-daily oral tablets. Once-daily pills composed of two different reverse transcriptase inhibitors are moreover approved as preexposure prophylaxis (PrEP) treatment for virus naïve individuals who may partake in behaviors associated with increased risk of HIV-1 acquisition such as unprotected sex or injection drug use. Long-acting (LA) injectable HIV-1 enzyme inhibitors are at the same time being developed to sidestep adherence noncompliance issues that can arise from self-administered once-daily oral dosing regimens. Cabotegravir (CAB)-LA, which inhibits integrase strand transfer activity, has in recent clinical trials been shown to prevent HIV-1 acquisition more effectively than once-daily oral dosed reverse transcriptase inhibitors. In this Perspective, we examine bench to bedside aspects of CAB-LA treatment and development, starting from the biochemical basis of HIV-1 integration and pharmacological inhibition of integrase catalysis. We also review the results of recent clinical trials that evaluated CAB-LA, as well as the promises and challenges that surround its use for HIV/AIDS PrEP.

Recent Advances on Nanomaterials to COVID-19 Management: A Systematic Review on Antiviral/Virucidal Agents and Mechanisms of SARS-CoV-2 Inhibition/Inactivation

The current pandemic of coronavirus disease 2019 (COVID-19) is recognized as a public health emergency of worldwide concern. Nanomaterials can be effectively used to detect, capture/inactivate or inhibit coronavirus cell entry/replication in the human host cell, preventing infection. Their potential for nanovaccines, immunoengineering, diagnosis, repurposing medication, and disinfectant surfaces targeting the novel coronavirus (SARS-CoV-2) is highlighted. In this systematic review the aim is to present an unbiased view of which and how nanomaterials can reduce the spread of COVID-19. Herein, the focus is on SARS-CoV-2, analyzing 46 articles retrieved before December 31, 2020. The interface between nanomaterials is described, and the main mechanisms to inhibit SARS-CoV-2 pathogenesis and viral inactivation are also discussed. Nanocarbons, biopolymeric, copper, and silver nanoparticles are potential antiviral and virucidal agents toward self-cleaning and reusable filter media and surfaces (e.g., facial masks), drug administration, vaccines, and immunodiagnostic assays. Trends in toxicology research and safety tests can help fill the main gaps in the literature and overcome health surveillance's challenges. Phytochemicals delivery by nanocarriers also stand out as candidates to target and bio-friendly therapy. Nanocellulose might fill in the gaps. Future research using nanomaterials targeting novel therapies/prophylaxis measures to COVID-19 and future outbreaks is discussed.

Nanotechnology advances in pathogen- and host-targeted antiviral delivery: multipronged therapeutic intervention for pandemic control

The COVID-19 pandemic's high mortality rate and severe socioeconomic impact serve as a reminder of the urgent need for effective countermeasures against viral pandemic threats. In particular, effective antiviral therapeutics capable of stopping infections in its tracks is critical to reducing infection fatality rate and healthcare burden. With the field of drug delivery witnessing tremendous advancement in the last two decades owing to a panoply of nanotechnology advances, the present review summarizes and expounds on the research and development of therapeutic nanoformulations against various infectious viral pathogens, including HIV, influenza, and coronaviruses. Specifically, nanotechnology advances towards improving pathogen- and host-targeted antiviral drug delivery are reviewed, and the prospect of achieving effective viral eradication, broad-spectrum antiviral effect, and resisting viral mutations are discussed. As several COVID-19 antiviral clinical trials are met with lackluster treatment efficacy, nanocarrier strategies aimed at improving drug pharmacokinetics, biodistributions, and synergism are expected to not only contribute to the current disease treatment efforts but also expand the antiviral arsenal against other emerging viral diseases.

A Concept Evaluation Study of a New Combination Bictegravir plus Tenofovir Alafenamide Nanoformulation with Prolonged Sustained-Drug-Release Potency for HIV-1 Preexposure Prophylaxis

The antiretroviral treatment (ART) approach is the best-prescribed approach to date for preexposure prophylaxis (PrEP) for high-risk individuals. However, the daily combination antiretroviral (cARV) regimen has become cumbersome for healthy individuals, leading to nonadherence. Recent surveys showed high acceptance of parenteral sustained-release ART enhancing PrEP adherence. Our approach is to design a parenteral nanoparticle (NP)-based cARV sustained-release (cARV-SR) system as long-acting HIV PrEP. Here, we report a new combination of two potent ARVs (tenofovir alafenamide fumarate [TAF] and bictegravir [BIC]) loaded as a nanoformulation intended as a cARV-SR for PrEP. The BIC+TAF NPs were fabricated by using a standardized in-house methodology. In vitro intracellular kinetics, cytotoxicity, and HIV-1 protection studies demonstrated that BIC+TAF encapsulation prolonged drug retention, reduced drug-associated cytotoxicity, and enhanced HIV protection. In human peripheral blood mononuclear cells, nanoformulated BIC+TAF demonstrated significant (P < 0.05) improvement in the drug's selectivity index by 472 times compared to the BIC+TAF in solution. In vivo pharmacokinetic study of BIC, TAF, and respective drug metabolites in female BALB/c mice after single subcutaneous doses of BIC+TAF NPs demonstrated plasma drug concentrations of BIC and tenofovir above the intracellular 50% inhibitory concentration during the entire 30-day study period and prolonged persistence of both active drugs in the HIV target organs, including the vagina, colon, spleen, and lymph nodes. This report demonstrates that the encapsulation of BIC+TAF in a nanoformulation improved its therapeutic selectivity and the in vivo pharmacokinetics of free drugs. Based on these preliminary studies, we hypothesize that cARV-SR has potential as an innovative once-monthly delivery treatment for PrEP.

Nanotechnology for virus treatment

The continued emergence of novel viruses poses a significant threat to global health. Uncontrolled outbreaks can result in pandemics that have the potential to overburden our healthcare and economic systems. While vaccination is a conventional modality that can be employed to promote herd immunity, antiviral vaccines can only be applied prophylactically and do little to help patients who have already contracted viral infections. During the early stages of a disease outbreak when vaccines are unavailable, therapeutic antiviral drugs can be used as a stopgap solution. However, these treatments do not always work against emerging viral strains and can be accompanied by adverse effects that sometimes outweigh the benefits. Nanotechnology has the potential to overcome many of the challenges facing current antiviral therapies. For example, nanodelivery vehicles can be employed to drastically improve the pharmacokinetic profile of antiviral drugs while reducing their systemic toxicity. Other unique nanomaterials can be leveraged for their virucidal or virus-neutralizing properties. In this review, we discuss recent developments in antiviral nanotherapeutics and provide a perspective on the application of nanotechnology to the SARS-CoV-2 outbreak and future virus pandemics.

Bictegravir Plus Tenofovir Alafenamide Nanoformulation as a Long-Acting Pre-Exposure Prophylaxis Regimen: Application of Modeling to Design Non-Human Primate Pharmacokinetic Experiments

Bictegravir (BIC) and tenofovir alafenamide fumarate (TAF), two potent anti-HIV drugs, had been nanoformulated (nBIC-TAF) to achieve once-a-month PrEP coverage. In-vivo mouse experiments for nBIC-TAF exhibited favorable subcutaneous (SC) pharmacokinetics. To probe the clinical suitability of the nBIC-TAF, as the next step, we intend to study nBIC-TAF in non-human primates (NHP), as the best preclinical model to foster clinical trials. Before entering an expensive NHP study, however, we seek to improve our a priori understanding about nBIC-TAF in higher species, having just mouse data. The mechanism-based pharmacokinetic modeling (MBPK) has been used as an appropriate method for pharmacokinetic modeling and interspecies scaling for nanoformulations. Via the use of MBPK, in this work, we created a model for nBIC-TAF able to predict plasma concentration-time curves in NHP. BIKTARVY is a daily oral combination of BIC, TAF, and emtricitabine (Gilead Science, CA), approved for HIV therapy. Using BIKTARVY equivalent dosages (from their NHP studies), we predicted that, following just one SC dose of nBIC-TAF in NHP, both BIC and tenofovir will have detectable and above in vitro efficacy levels for 28 days. Furthermore, the MBPK was able to provide a mechanistic explanation regarding the long-acting mechanism characterizing nBIC-TAF: nanoparticles stores in the SC space from which drugs slowly dissociate. Dissociated drugs in the SC space then buffer the plasma pool over time, yielding an extended-release effect in the plasma. Overall, we predicted for nBIC-TAF a promising long-acting pharmacokinetic in NHP, potentially usable as monthly PrEP. These results will help investigators to gain confidence for facing regulatory submissions at early stages.

pH-sensitive chitosan nanoparticles loaded with dolutegravir as milk and food admixture for paediatric anti-HIV therapy

The present study aims to develop Chitosan-based polymeric nanoparticles of anti-HIV drug Dolutegravir, to aid appropriate dose adjustment and ease of oral administration as milk and food admixture for children. The isolated Chitosan from the crab shell species Portunus Sanguinolentus has been characterized for their physicochemical properties. Nanoparticles were developed with varying ratio of drug: Chitosan and assessed for particle size (140-548 nm), zeta potential (+26.1 mV) with a maximum of 75 % drug content. Nanoparticles exhibited improved stability and drug release in the 0.1 N HCl medium compared to pure drug. The MTT assay and the Syncytia inhibition assay in C8166 (T-lymphatic cell line) infected with HIV_IIIB viral strain, which showed better therapeutic efficiency and lesser cytotoxicity compared to the pure drug. In consonance with the data obtained, the use of chitosan from a novel source for drug delivery carrier has opened exceptional prospects for delivering drugs efficiently to paediatrics.

Nanosystems Applied to HIV Infection: Prevention and Treatments

Sexually-transmitted infections (STIs) are a global health concern worldwide as they cause acute diseases, infertility, and significant mortality. Among the bacterial, viral, and parasitic pathogens that can be sexually transmitted, human immunodeficiency virus (HIV) has caused one of the most important pandemic diseases, which is acquired immune deficiency syndrome (AIDS). 32.7 million people have died from AIDS-related illnesses since the start of the epidemic. Moreover, in 2019, 38 million people were living with HIV worldwide. The need to deal with this viral infection becomes more obvious, because it represents not only a problem for public health, but also a substantial economic problem. In this context, it is necessary to focus efforts on developing methods for prevention, detection and treatment of HIV infections that significantly reduce the number of newly infected people and provide a better quality of life for patients. For several decades, biomedical research has been developed allowing quick solutions through the contribution of effective tools. One of them is the use of polymers as vehicles, drug carrier agents, or as macromolecular prodrugs. Moreover, nanosystems (NSs) play an especially important role in the diagnosis, prevention, and therapy against HIV infection. The purpose of this work is to review recent research into diverse NSs as potential candidates for prevention and treatment of HIV infection. Firstly, this review highlights the advantages of using nanosized structures for these medical applications. Furthermore, we provide an overview of different types of NSs used for preventing or combating HIV infection. Then, we briefly evaluate the most recent developments associated with prevention and treatment alternatives. Additionally, the implications of using different NSs are also addressed.

Recent advances in long-acting nanoformulations for delivery of antiretroviral drugs

In spite of introduction of combination antiretroviral therapy (cART) against human immunodeficiency virus (HIV) infection; inaccessibility and poor adherence to oral cART costs 10 in 100,000 death worldwide. Failure in adherence leads to viral rebound, emergence of drug resistance and anticipated HIV infection in high risk individuals. Various Long-acting antiretroviral (LA ARV) nanoformulations including nano-prodrug, solid drug nanoparticles (SDN), nanocrystals, aspherical nanoparticles, polymeric and lipidic nanoparticles have shown plasma/tissue drug concentration in the therapeutic range for several weeks during pre-clinical evaluation. LA ARV nanoformulations therefore have replaced cART as better alternative for the treatment of HIV infection. Cabenuva™ is recently approved by Health Canada containing LA cabotegravir+LA rilpivirine nanocrystals (ViiV healthcare) for once monthly administration by intramuscular route. The LA nanoformulation due to its nanosize insist on better stability, delivery to lymphatic, slow release into systemic circulation via lymphatic-circulatory system conjoint and secondary drug depot within infiltered immune cells at site of administration and systemic circulation in contrast to conventional drugs. However, the pharmacokinetic, biodistribution and efficacy of LA nanoformulations hinge onto physicochemical properties of the drugs and route of administration. Therefore, current review emphasizes on these contradistinctive factors that affects the reproducibility, safety, efficacy and toxicity of LA anti-HIV nanoformulations. Moreover, it expatiates on application of profuse nanoformulations for long-acting effect with promising preclinical discoveries and two clinical leads. To add on, utilization of physiology-based and mechanism-based pharmacokinetic modelling and in vivo animal models which could lead to enhanced safety and efficacy of LA ARV nanoformulations in humans have been included.

Pharmacokinetics of HIV therapies in pregnant patients: an update

INTRODUCTION

Mother-to-child transmission (MTCT) of HIV is thought to account for over 90% of new pediatric infections, and is associated with poor maternal and fetal outcomes. As such ensuring further reduction in MTCT is a priority in HIV treatment and prevention programs.

AREAS COVERED

This review aims to provide a comprehensive update on the pharmacokinetics of recently approved antiretroviral drugs and novel drug formulations and delivery systems. Alongside recent recommendations for dose adjustments, and an overview of the implications of co-infections on the pharmacokinetics of antiretrovirals relevant to pregnant HIV positive patients. Additionally, potential opportunities to progress pharmacokinetic research of new treatments in this population are highlighted.

EXPERT OPINION

In order to improve our understanding of how to provide safe and effective treatment to HIV positive pregnant women, further work is required to enable their inclusion in early stages of clinical trials. Incentives must be created for this research, in the form of additional investment by key stakeholders and regulatory agencies. Furthermore, as the incidence of MTCT is reduced globally there is a need to conduct long-term pharmacovigilance studies in uninfected children exposed to HIV and antiretrovirals in utero, in order to determine the safest and most effective antiretroviral therapies.

The Design of Poly(lactide-co-glycolide) Nanocarriers for Medical Applications

Polymeric biomaterials have found widespread applications in nanomedicine, and poly(lactide-co-glycolide), (PLGA) in particular has been successfully implemented in numerous drug delivery formulations due to its synthetic malleability and biocompatibility. However, the need for preconception in these formulations is increasing, and this can be achieved by selection and elimination of design variables in order for these systems to be tailored for their specific applications. The starting materials and preparation methods have been shown to influence various parameters of PLGA-based nanocarriers and their implementation in drug delivery systems, while the implementation of computational simulations as a component of formulation studies can provide valuable information on their characteristics. This review provides a critical summary of the synthesis and applications of PLGA-based systems in bio-medicine and outlines experimental and computational design considerations of these systems.

Multifaceted HIV integrase functionalities and therapeutic strategies for their inhibition

Antiretroviral inhibitors that are used to manage HIV infection/AIDS predominantly target three enzymes required for virus replication: reverse transcriptase, protease, and integrase. Although integrase inhibitors were the last among this group to be approved for treating people living with HIV, they have since risen to the forefront of treatment options. Integrase strand transfer inhibitors (INSTIs) are now recommended components of frontline and drug-switch antiretroviral therapy formulations. Integrase catalyzes two successive magnesium-dependent polynucleotidyl transferase reactions, 3' processing and strand transfer, and INSTIs tightly bind the divalent metal ions and viral DNA end after 3' processing, displacing from the integrase active site the DNA 3'-hydroxyl group that is required for strand transfer activity. Although second-generation INSTIs present higher barriers to the development of viral drug resistance than first-generation compounds, the mechanisms underlying these superior barrier profiles are incompletely understood. A separate class of HIV-1 integrase inhibitors, the allosteric integrase inhibitors (ALLINIs), engage integrase distal from the enzyme active site, namely at the binding site for the cellular cofactor lens epithelium-derived growth factor (LEDGF)/p75 that helps to guide integration into host genes. ALLINIs inhibit HIV-1 replication by inducing integrase hypermultimerization, which precludes integrase binding to genomic RNA and perturbs the morphogenesis of new viral particles. Although not yet approved for human use, ALLINIs provide important probes that can be used to investigate the link between HIV-1 integrase and viral particle morphogenesis. Herein, I review the mechanisms of retroviral integration as well as the promises and challenges of using integrase inhibitors for HIV/AIDS management.

Human Vault Nanoparticle Targeted Delivery of Antiretroviral Drugs to Inhibit Human Immunodeficiency Virus Type 1 Infection

"Vaults" are ubiquitously expressed endogenous ribonucleoprotein nanoparticles with potential utility for targeted drug delivery. Here, we show that recombinant human vault nanoparticles are readily engulfed by certain key human peripheral blood mononuclear cells (PBMC), predominately dendritic cells, monocytes/macrophages, and activated T cells. As these cell types are the primary targets for human immunodeficiency virus type 1 (HIV-1) infection, we examined the utility of recombinant human vaults for targeted delivery of antiretroviral drugs. We chemically modified three different antiretroviral drugs, zidovudine, tenofovir, and elvitegravir, for direct conjugation to vaults. Tested in infection assays, drug-conjugated vaults inhibited HIV-1 infection of PBMC with equivalent activity to free drugs, indicating vault delivery and drug release in the cytoplasm of HIV-1-susceptible cells. The ability to deliver functional drugs via vault nanoparticle conjugates suggests their potential utility for targeted drug delivery against HIV-1.