Recent advances in RNAi-based strategies for therapy and prevention of HIV-1/AIDS

Lymphocyte Membrane- and 12p1-Dual-Functionalized Nanoparticles for Free HIV-1 Trapping and Precise siRNA Delivery into HIV-1-Infected Cells

Despite the success of small interfering RNA (siRNA) in clinical settings and its potential value in human immunodeficiency virus (HIV) therapy, the rapid clearance and absence of precise delivery to target cells still hinder the therapeutic effect of siRNA. Herein, a new system, which can escape immune recognition, has HIV-1 neutralizing capacity, and the ability to deliver siRNA specifically into HIV-1-infected cells, is constructed by functionalizing siRNA delivery lipid nanoparticles with the lymphocyte membrane and 12p1. The constructed system is shown to escape uptake by the mononuclear phagocyte system. The constructed system exhibits strong binding ability with gp120, thus displaying distinguished neutralizing breadth and potency. The constructed system neutralizes all tested HIV-1 pseudotyped viruses with a geometric mean 80% inhibitory concentration (IC80) of 29.75 µg mL^-1 and inhibits X4-tropic HIV-1 with an IC80 of 64.20 µg mL^-1 , and R5-tropic HIV-1 with an IC80 of 16.39 µg mL^-1 . The new system also specifically delivers siRNA into the cytoplasm of HIV-1-infected cells and exhibits evident gene silencing of tat and rev. Therefore, this new system can neutralize HIV-1 and deliver siRNA selectively into HIV-1-infected cells and may be a promising therapeutic candidate for the precise therapy of HIV.

The Amsterdam petunia germplasm collection: A tool in plant science

Petunia hybrida is a plant model system used by many researchers to investigate a broad range of biological questions. One of the reasons for the success of this organism as a lab model is the existence of numerous mutants, involved in a wide range of processes, and the ever-increasing size of this collection owing to a highly active and efficient transposon system. We report here on the origin of petunia-based research and describe the collection of petunia lines housed in the University of Amsterdam, where many of the existing genotypes are maintained.

Lipidic lyotropic liquid crystals: Insights on biomedical applications

Liquid crystals (LCs) possess unique physicochemical properties, translatable into a wide range of applications. To date, lipidic lyotropic LCs (LLCs) have been extensively explored in drug delivery and imaging owing to the capability to encapsulate and release payloads with different characteristics. The current landscape of lipidic LLCs in biomedical applications is provided in this review. Initially, the main properties, types, methods of fabrication and applications of LCs are showcased. Then, a comprehensive discussion of the main biomedical applications of lipidic LLCs accordingly to the application (drug and biomacromolecule delivery, tissue engineering and molecular imaging) and route of administration is examined. Further discussion of the main limitations and perspectives of lipidic LLCs in biomedical applications are also provided. STATEMENT OF SIGNIFICANCE: Liquid crystals (LCs) are those systems between a solid and liquid state that possess unique morphological and physicochemical properties, translatable into a wide range of biomedical applications. A short description of the properties of LCs, their types and manufacturing procedures is given to serve as a background to the topic. Then, the latest and most innovative research in the field of biomedicine is examined, specifically the areas of drug and biomacromolecule delivery, tissue engineering and molecular imaging. Finally, prospects of LCs in biomedicine are discussed to show future trends and perspectives that might be utilized. This article is an ampliation, improvement and actualization of our previous short forum article "Bringing lipidic lyotropic liquid crystal technology into biomedicine" published in TIPS.

Multiplexed shRNA-miRs as a candidate for anti HIV-1 therapy: strategies, challenges, and future potential

The spread of HIV is on the rise and has become a global issue, especially for underdeveloped and developing countries. This is due to the fact that HIV majorly occurs asymptomatically and is implausible for early diagnosis. Recent advances in research and science have enabled the investigation of a new potential treatment involving gene-based therapy, known as RNA interference (RNAi) that will direct gene silencing and further compensate for natural variants and viral mutants. Several types of small regulatory RNA are discussed in this present study, including microRNA (miRNA), small interfering RNA (siRNA), and short hairpin RNA (shRNA).This paper examines the mechanism of RNAi as a viable HIV therapy, using a minimum of four shRNAs to target both dispensable host components (CCR5) and viral genes (Gag, Env, Tat, Pol I, Pol II and Vif). Moreover, a multiplexed mechanism of shRNAs and miRNA is known to be effective in preventing viral escape due to mutation as the miRNA develops a general polycistronic platform for the expression of a large amount of shRNA-miRs. Several administration methods as well as the advantages of this RNAi treatment are also discussed in this study. The administration methods include (1) ex vivo delivery with the help of viral vectors, nanoparticles, and electroporation, (2) nonspecific in vivo delivery using non-viral carriers including liposomes, dendrimers and aptamers, as well as (3) targeted delivery that uses antibodies, modified nanoparticles, nucleic acid aptamers, and tissue-specific serotypes of AAV. Moreover, the advantages of this treatment are related to the effectiveness in silencing the HIV gene, which is more compatible compared to other gene therapy treatments, such as ZFN, TALEN, and CRISPR/Cas9.

Targeted Immuno-Antiretroviral to Promote Dual Protection against HIV: A Proof-of-Concept Study

The C-C motif chemokine receptor-5 (CCR5) expression on the T-cell surface is the prime barrier to HIV/AIDS eradication, as it promotes both active human immunodeficiency virus (HIV)-infection and latency; however, antiretrovirals (ARVs) suppress plasma viral loads to non-detectable levels. Keeping this in mind, we strategically designed a targeted ARVs-loaded nanoformulation that targets CCR5 expressing T-cells (e.g., CD4+ cells). Conceptually, CCR5-blocking and targeted ARV delivery would be a dual protection strategy to prevent HIV infection. For targeting CCR5+ T-cells, the nanoformulation was surface conjugated with anti-CCR5 monoclonal antibodies (CCR5 mAb) and loaded with dolutegravir+tenofovir alafenamide (D+T) ARVs to block HIV replication. The result demonstrated that the targeted-ARV nanoparticle's multimeric CCR5 binding property improved its antigen-binding affinity, prolonged receptor binding, and ARV intracellular retention. Further, nanoformulation demonstrated high binding affinity to CCR5 expressing CD4+ cells, monocytes, and other CCR5+ T-cells. Finally, the short-term pre-exposure prophylaxis study demonstrated that prolonged CCR5 blockage and ARV presence further induced a "protective immune phenotype" with a boosted T-helper (Th), temporary memory (TM), and effector (E) sub-population. The proof-of-concept study that the targeted-ARV nanoformulation dual-action mechanism could provide a multifactorial solution toward achieving HIV "functional cure."

Nanoparticle-based strategies to target HIV-infected cells

Antiretroviral drugs employed for the treatment of human immunodeficiency virus (HIV) infections have remained largely ineffective due to their poor bioavailability, numerous adverse effects, modest uptake in infected cells, undesirable drug-drug interactions, the necessity for long-term drug therapy, and lack of access to tissues and reservoirs. Nanotechnology-based interventions could serve to overcome several of these disadvantages and thereby improve the therapeutic efficacy of antiretrovirals while reducing the morbidity and mortality due to the disease. However, attempts to use nanocarriers for the delivery of anti-retroviral drugs have started gaining momentum only in the past decade. This review explores in-depth the various nanocarriers that have been employed for the treatment of HIV infections highlighting their merits and possible demerits.

CCR5 as a Coreceptor for Human Immunodeficiency Virus and Simian Immunodeficiency Viruses: A Prototypic Love-Hate Affair

CCR5, a chemokine receptor central for orchestrating lymphocyte/cell migration to the sites of inflammation and to the immunosurveillance, is involved in the pathogenesis of a wide spectrum of health conditions, including inflammatory diseases, viral infections, cancers and autoimmune diseases. CCR5 is also the primary coreceptor for the human immunodeficiency viruses (HIVs), supporting its entry into CD4+ T lymphocytes upon transmission and in the early stages of infection in humans. A natural loss-of-function mutation CCR5-Δ32, preventing the mutated protein expression on the cell surface, renders homozygous carriers of the null allele resistant to HIV-1 infection. This phenomenon was leveraged in the development of therapies and cure strategies for AIDS. Meanwhile, over 40 African nonhuman primate species are long-term hosts of simian immunodeficiency virus (SIV), an ancestral family of viruses that give rise to the pandemic CCR5 (R5)-tropic HIV-1. Many natural hosts typically do not progress to immunodeficiency upon the SIV infection. They have developed various strategies to minimize the SIV-related pathogenesis and disease progression, including an array of mechanisms employing modulation of the CCR5 receptor activity: (i) deletion mutations abrogating the CCR5 surface expression and conferring resistance to infection in null homozygotes; (ii) downregulation of CCR5 expression on CD4+ T cells, particularly memory cells and cells at the mucosal sites, preventing SIV from infecting and killing cells important for the maintenance of immune homeostasis, (iii) delayed onset of CCR5 expression on the CD4+ T cells during ontogenetic development that protects the offspring from vertical transmission of the virus. These host adaptations, aimed at lowering the availability of target CCR5+ CD4+ T cells through CCR5 downregulation, were countered by SIV, which evolved to alter the entry coreceptor usage toward infecting different CD4+ T-cell subpopulations that support viral replication yet without disruption of host immune homeostasis. These natural strategies against SIV/HIV-1 infection, involving control of CCR5 function, inspired therapeutic approaches against HIV-1 disease, employing CCR5 coreceptor blocking as well as gene editing and silencing of CCR5. Given the pleiotropic role of CCR5 in health beyond immune disease, the precision as well as costs and benefits of such interventions needs to be carefully considered.

Specific properties of shRNA-mediated CCR5 downregulation that enhance the inhibition of HIV-1 infection in combination with shRNA targeting HIV-1 rev

Treatment with RNAi against HIV-1 transcripts efficiently inhibits viral replication but induces selection of escape mutants; therefore, the CCR5 coreceptor was suggested as an additional target. Blocking viral and host transcripts improved the antiviral effect. We have used short hairpin RNA (shRNA) targeting the human CCR5 (shCCR5) or the HIV-1 rev (shRev) transcripts to demonstrate distinctive properties of anti-CCR5 shRNA: shCCR5 induced more sustained protection than shRev; partial reduction in CCR5 expression substantially decreased HIV-1 infection, and shCCR5 performed better than shRev in the mixed shRNA-treated and untreated cultures. These observations indicate that CCR5 inhibitors should be conveniently included in HIV-1 gene silencing treatment schedules when only a certain cell fraction is protected to further reduce endogenous virus in a properly ART-treated HIV-1 infected individual.

Nanomedicine based approaches for combating viral infections

Millions of people die each year from viral infections across the globe. There is an urgent need to overcome the existing gap and pitfalls of the current antiviral therapy which include increased dose and dosing frequency, bioavailability challenges, non-specificity, incidences of resistance and so on. These stumbling blocks could be effectively managed by the advent of nanomedicine. Current review emphasizes over an enhanced understanding of how different lipid, polymer and elemental based nanoformulations could be potentially and precisely used to bridle the said drawbacks in antiviral therapy. The dawn of nanotechnology meeting vaccine delivery, role of RNAi therapeutics in antiviral treatment regimen, various regulatory concerns towards clinical translation of nanomedicine along with current trends and implications including unexplored research avenues for advancing the current drug delivery have been discussed in detail.

The Use of CRISPR/Cas9 as a Tool to Study Human Infectious Viruses

Clustered regularly interspaced short palindromic repeats (CRISPR) systems are a set of versatile gene-editing toolkit that perform diverse revolutionary functions in various fields of application such as agricultural practices, food industry, biotechnology, biomedicine, and clinical research. Specially, as a novel antiviral method of choice, CRISPR/Cas9 system has been extensively and effectively exploited to fight against human infectious viruses. Infectious diseases including human immunodeficiency virus (HIV), hepatitis B virus (HBV), human papillomavirus (HPV), and other viruses are still global threats with persistent potential to probably cause pandemics. To facilitate virus removals, the CRISPR/Cas9 system has already been customized to confer new antiviral capabilities into host animals either by modifying host genome or by directly targeting viral inherent factors in the form of DNA. Although several limitations and difficulties still need to be conquered, this technology holds great promises in the treatment of human viral infectious diseases. In this review, we will first present a brief biological feature of CRISPR/Cas9 systems, which includes a description of CRISPR/Cas9 structure and composition; thereafter, we will focus on the investigations and applications that employ CRISPR/Cas9 system to combat several human infectious viruses and discuss challenges and future perspectives of using this new platform in the preclinical and clinical settings as an antiviral strategy.

CRISPR therapy towards an HIV cure

Tools based on RNA interference (RNAi) and the recently developed clustered regularly short palindromic repeats (CRISPR) system enable the selective modification of gene expression, which also makes them attractive therapeutic reagents for combating HIV infection and other infectious diseases. Several parallels can be drawn between the RNAi and CRISPR-Cas9 platforms. An ideal RNAi or CRISPR-Cas9 therapeutic strategy for treating infectious or genetic diseases should exhibit potency, high specificity and safety. However, therapeutic applications of RNAi and CRISPR-Cas9 have been challenged by several major limitations, some of which can be overcome by optimal design of the therapy or the design of improved reagents. In this review, we will discuss some advantages and limitations of anti-HIV strategies based on RNAi and CRISPR-Cas9 with a focus on the efficiency, specificity, off-target effects and delivery methods.

siRNAs and viruses: The good, the bad and the way forward

There are no available antivirals for many viruses or strains, while current antivirals are limited by toxicity and drug resistance. Therefore, alternative strategies, such as RNA interference (RNAi) are required. RNAi suppresses gene expression of any mRNA, making it an attractive candidate for antiviral therapeutics. Studies have evaluated siRNAs in a range of viruses, with some showing promising results. However, issues with stability and delivery of siRNAs remain. These may be minimized by modifying the siRNA structure, using an efficient delivery vector and targeting multiple regions of a virus's genome in a single dose. Finding these solutions could accelerate the progress of RNAi-based antivirals. This review highlights selected examples of antiviral siRNAs, limitations of RNAi and strategies to overcome these limitations.

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.

Induction of E. coli-derived endonuclease MazF suppresses HIV-1 production and causes apoptosis in latently infected cells

The current antiretroviral therapy cannot cure the patients infected with human immunodeficiency virus type 1 (HIV-1) due to the existence of latently infected cells capable of virus production from harboring proviral DNA. MazF is an ACA nucleotide sequence-specific endoribonuclease derived from Escherichia coli. The conditional expression of MazF by binding of HIV-1 Tat to the promoter region of a MazF-expression vector has previously been shown to selectively inhibit HIV-1 replication in acutely infected cells. The expression of MazF significantly suppressed tumor necrosis factor (TNF)-α-induced HIV-1 production and viral RNA expression in the HIV-1 latently infected cell line OM-10.1 transduced with the MazF-expression vector (OM-10.1/MFR). Moreover, the viability of OM-10.1/MFR cells decreased with increasing concentrations of TNF-α, whereas such decrease was not observed for HL-60 cells transduced with the MazF-expression vector (HL-60/MFR), the uninfected parental cell line of OM-10.1. TNF-α increased the expression of cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase in OM-10.1/MFR cells, indicating that the cell death was caused by the induction of apoptosis. TNF-α-induced expression of MazF mRNA was detected in OM-10.1/MFR but not HL-60/MFR cells, suggesting that TNF-α-induced apoptosis of latently infected cells was due to the expression of MazF. Thus, the anti-HIV-1 gene therapy using the MazF-expression vector may have potential for the cure of HIV-1 infection in combination with suitable latency reversing agents through reducing the size of latently infected cells without viral reactivation.

Reduce and Control: A Combinatorial Strategy for Achieving Sustained HIV Remissions in the Absence of Antiretroviral Therapy

Human immunodeficiency virus (HIV-1) indefinitely persists, despite effective antiretroviral therapy (ART), within a small pool of latently infected cells. These cells often display markers of immunologic memory and harbor both replication-competent and -incompetent proviruses at approximately a 1:100 ratio. Although complete HIV eradication is a highly desirable goal, this likely represents a bridge too far for our current and foreseeable technologies. A more tractable goal involves engineering a sustained viral remission in the absence of ART––a “functional cure.” In this setting, HIV remains detectable during remission, but the size of the reservoir is small and the residual virus is effectively controlled by an engineered immune response or other intervention. Biological precedence for such an approach is found in the post-treatment controllers (PTCs), a rare group of HIV-infected individuals who, following ART withdrawal, do not experience viral rebound. PTCs are characterized by a small reservoir, greatly reduced inflammation, and the presence of a poorly understood immune response that limits viral rebound. Our goal is to devise a safe and effective means for replicating durable post-treatment control on a global scale. This requires devising methods to reduce the size of the reservoir and to control replication of this residual virus. In the following sections, we will review many of the approaches and tools that likely will be important for implementing such a “reduce and control” strategy and for achieving a PTC-like sustained HIV remission in the absence of ART.

Recent Advances in Oligonucleotide-Based Therapy for Transthyretin Amyloidosis: Clinical Impact and Future Prospects

Transthyretin (TTR) amyloidosis, also known as transthyretin-related familial amyloidotic polyneuropathy (ATTR-FAP), is a fatal hereditary systemic amyloidosis caused by mutant forms of TTR. Although conventional treatments for ATTR-FAP, such as liver transplantation (LT) and TTR tetramer stabilizer, reportedly halt the progression of clinical manifestation, these therapies have several limitations. Oligonucleotide-based therapy, e.g. small interfering RNA (siRNA)- and antisense oligonucleotides (ASOs)-based therapy, hold enormous potential for the treatment of intractable diseases such as ATTR-FAP, by specifically regulating the gene responsible for the disease. Clinical evidence strongly suggests that LT inhibits mutant TTR production, thus improving the manifestation of ATTR-FAP. Therefore, an oligonucleotide-based therapy for ATTR-FAP, which reduces the production of TTR by the liver, has recently been developed in preclinical and clinical studies. This review focuses on recent advances in oligonucleotide-based therapy and future prospects of next-generation oligonucleotide-based drugs for therapeutic use against ATTR-FAP.

Gene Therapy Approaches to Functional Cure and Protection of Hematopoietic Potential in HIV Infection

Although current antiretroviral drug therapy can suppress the replication of human immunodeficiency virus (HIV), a lifelong prescription is necessary to avoid viral rebound. The problem of persistent and ineradicable viral reservoirs in HIV-infected people continues to be a global threat. In addition, some HIV-infected patients do not experience sufficient T-cell immune restoration despite being aviremic during treatment. This is likely due to altered hematopoietic potential. To achieve the global eradication of HIV disease, a cure is needed. To this end, tremendous efforts have been made in the field of anti-HIV gene therapy. This review will discuss the concepts of HIV cure and relative viral attenuation and provide an overview of various gene therapy approaches aimed at a complete or functional HIV cure and protection of hematopoietic functions.

Turning Up Your Nose for a Flaviviral Encephalitis Cure

siRNA approaches have demonstrated promise in treating viral infections in animal models, but poor delivery limits clinical application. In this issue of Cell Host & Microbe, Beloor et al. (2018) report that nose-to-brain delivery of viral-targeted siRNA cures mice from West Nile virus encephalitis, with potential implications for human infection.

An Emerging Role for Circular RNAs in Osteoarthritis

Circular RNAs (circRNAs) are currently classed as non-coding RNAs that, unlike the better known canonical linear RNAs, form a covalently closed continuous loop without 5' or 3' polarities. With the development of high throughput sequencing technology, a large number of circRNAs have been discovered in many species. More importantly, growing evidence suggests that circRNAs are abundant, evolutionally conserved, and relatively stable in cells and tissues. Strikingly, recent studies have discovered that circRNAs can serve as microRNA sponges, interact with RNA-binding protein, and regulate gene transcription, as well as protein translation. Osteoarthritis (OA) is the most common chronic degenerative joint disease. CircRNAs are differentially expressed in OA cartilage. Moreover, some circRNAs are involved in multiple pathological processes during OA, mainly extracellular matrix degradation, inflammation, and apoptosis. In this review, we briefly delineate the biogenesis, characteristics, and biofunctions of circRNAs, and then, focus on the role of circRNAs in the occurrence and progression OA.

Lipid-Based Liquid Crystalline Nanoparticles Facilitate Cytosolic Delivery of siRNA via Structural Transformation

RNA interference (RNAi) technology has shown great promise for the treatment of cancer and other genetic disorders. Despite the efforts to increase the target tissue distribution, the safe and effective delivery of siRNA to the diseased cells with sufficient cytosolic transport is another critical factor for successful RNAi clinical application. Here, the constructed lipid-based liquid crystalline nanoparticles, called nano-Transformers, can transform thestructure in the intracellular acidic environment and perform high-efficient siRNA delivery for cancer treatment. The developed nano-Transformers have satisfactory siRNA loading efficiency and low cytotoxicity. Different from the traditional cationic nanocarriers, the endosomal membrane fusion induced by the conformational transition of lipids contributes to the easy dissociation of siRNA from nanocarriers and direct release of free siRNA into cytoplasm. We show that transfection with cyclin-dependent kinase 1 (CDK1)-siRNA-loaded nano-Transformers causes up to 95% reduction of relevant mRNA in vitro and greatly inhibits the tumor growth without causing any immunogenic response in vivo. This work highlights that the lipid-based nano-Transformers may become the next generation of siRNA delivery system with higher efficacy and improved safety profiles.

Optimization of Polycistronic Anti-CCR5 Artificial microRNA Leads to Improved Accuracy of Its Lentiviral Vector Transfer and More Potent Inhibition of HIV-1 in CD4⁺ T-Cells

C-C chemokine receptor type 5 (CCR5) is utilized by human immunodeficiency virus (HIV) as a co-receptor for cell entry. Suppression of the CCR5 gene by artificial microRNAs (amiRNAs) could confer cell resistance. In previous work, we created a lentivector that encoded the polycistron of two identical amiRNAs that could effectively suppress CCR5. However, tandem repeats in lentiviral vectors led to deletions of the repeated sequences during reverse transcription of the vector RNA. To solve this problem, we have created a new amiRNA against CCR5, mic1002, which has a different microRNA scaffold and targets a different sequence. Replacing one of the two identical tandem amiRNAs in the polycistron with the mic1002 amiRNA increased the accuracy of its lentiviral vector transfer while retaining its ability to effectively suppress CCR5. A lentiviral vector containing two heterogenic amiRNAs significantly inhibited HIV replication in a vector-transduced human CD4⁺ lymphocyte culture.

The Expanding Therapeutic Perspective of CCR5 Blockade

CCR5 and its interaction with chemokine ligands have been crucial for understanding and tackling HIV-1 entry into target cells. However, over time, CCR5 has witnessed an impressive transition from being considered rather unimportant in physiology and pathology to becoming central in a growing number of pathophysiological conditions. It now turns out that the massive efforts devoted to combat HIV-1 entry by interfering with CCR5, and the subsequent production of chemokine ligand variants, small chemical compounds, and other molecular entities and strategies, may set the therapeutic standards for a wealth of different pathologies. Expressed on various cell types, CCR5 plays a vital role in the inflammatory response by directing cells to sites of inflammation. Aside HIV-1, CCR5 has been implicated in other infectious diseases and non-infectious diseases such as cancer, atherosclerosis, and inflammatory bowel disease. Individuals carrying the CCR5Δ32 mutation live a normal life and are warranted a natural barrier to HIV-1 infection. Therefore, CCR5 antagonism and gene-edited knockout of the receptor gained growing interest for the therapeutic role that CCR5 blockade may play in the attenuation of the severity or progression of numerous diseases.

RNA Interference Therapies for an HIV-1 Functional Cure

HIV-1 drug therapies can prevent disease progression but cannot eliminate HIV-1 viruses from an infected individual. While there is hope that elimination of HIV-1 can be achieved, several approaches to reach a functional cure (control of HIV-1 replication in the absence of drug therapy) are also under investigation. One of these approaches is the transplant of HIV-1 resistant cells expressing anti-HIV-1 RNAs, proteins or peptides. Small RNAs that use RNA interference pathways to target HIV-1 replication have emerged as competitive candidates for cell transplant therapy and have been included in all gene combinations that have so far entered clinical trials. Here, we review RNA interference pathways in mammalian cells and the design of therapeutic small RNAs that use these pathways to target pathogenic RNA sequences. Studies that have been performed to identify anti-HIV-1 RNA interference therapeutics are also reviewed and perspectives on their use in combination gene therapy to functionally cure HIV-1 infection are provided.

CCR5-edited gene therapies for HIV cure: Closing the door to viral entry

Human immunodeficiency virus (HIV) was first reported and characterized more than three decades ago. Once thought of as a death sentence, HIV infection has become a chronically manageable disease. However, it is estimated that a staggering 0.8% of the world's population is infected with HIV, with more than 1 million deaths reported in 2015 alone. Despite the development of effective anti-retroviral drugs, a permanent cure has only been documented in one patient to date. In 2007, an HIV-positive patient received a bone marrow transplant to treat his leukemia from an individual who was homozygous for a mutation in the CCR5 gene. This mutation, known as CCR5Δ32, prevents HIV replication by inhibiting the early stage of viral entry into cells, resulting in resistance to infection from the majority of HIV isolates. More than 10 years after his last dose of anti-retroviral therapy, the transplant recipient remains free of replication-competent virus. Multiple groups are now attempting to replicate this success through the use of other CCR5-negative donor cell sources. Additionally, developments in the use of lentiviral vectors and targeted nucleases have opened the doors of precision medicine and enabled new treatment methodologies to combat HIV infection through targeted ablation or down-regulation of CCR5 expression. Here, we review historical cases of CCR5-edited cell-based therapies, current clinical trials and future benefits and challenges associated with this technology.

RNA Interference-Induced Innate Immunity, Off-Target Effect, or Immune Adjuvant?

RNA interference (RNAi) is a natural cellular mechanism that inhibits gene expression in a sequence-specific manner. In the last decade, RNAi has become a cornerstone in basic biological systems research and drug development efforts. The RNAi-based manipulation of mammalian cells facilitates target identification and validation; assists in identifying human disease etiologies; and expedites the development of treatments for infectious diseases, cancer, and other conditions. Several RNAi-based approaches are currently undergoing assessment in phase I and II clinical trials. However, RNAi-associated immune stimulation might act as a hurdle to safe and effective RNAi, particularly in clinical applications. The induction of innate immunity may originate from small interfering RNA (siRNA) sequence-dependent delivery vehicles and even the RNAi process itself. However, in the case of antagonistic cancers and viral infection, immune activation is beneficial; thus, immunostimulatory small interfering RNAs were designed to create bifunctional small molecules with RNAi and immunostimulatory activities. This review summarizes the research studies of RNAi-associated immune stimulation and the approaches for manipulating immunostimulatory activities.

Vaccine nanoparticles for protection against HIV infection

The development of a successful vaccine against HIV is a major global challenge. Antiretroviral therapy is the standard treatment against HIV-1 infection. However, only 46% of the eligible people received the therapy in 2015. Furthermore, suboptimal adherence poses additional obstacles. Therefore, there is an urgent need for an HIV-1 vaccine. The most promising clinical trial to date is Phase III RV144, which for the first time demonstrated the feasibility of vaccine-mediated immune protection against HIV-1. Nevertheless, its 31% efficacy and limited durability underscore major hurdles. Here, we discuss recent progress in HIV-1 vaccine development with a special emphasis on nanovaccines, which are at the forefront of efforts to develop a successful HIV-1 vaccine.

Achieving HIV-1 Control through RNA-Directed Gene Regulation

HIV-1 infection has been transformed by combined anti-retroviral therapy (ART), changing a universally fatal infection into a controllable infection. However, major obstacles for an HIV-1 cure exist. The HIV latent reservoir, which exists in resting CD4+ T cells, is not impacted by ART, and can reactivate when ART is interrupted or ceased. Additionally, multi-drug resistance can arise. One alternate approach to conventional HIV-1 drug treatment that is being explored involves gene therapies utilizing RNA-directed gene regulation. Commonly known as RNA interference (RNAi), short interfering RNA (siRNA) induce gene silencing in conserved biological pathways, which require a high degree of sequence specificity. This review will provide an overview of the silencing pathways, the current RNAi technologies being developed for HIV-1 gene therapy, current clinical trials, and the challenges faced in progressing these treatments into clinical trials.

Gene Therapy: A Paradigm Shift in Dentistry

Gene therapy holds a promising future for bridging the gap between the disciplines of medicine and clinical dentistry. The dynamic treatment approaches of gene therapy have been advancing by leaps and bounds. They are transforming the conventional approaches into more precise and preventive ones that may limit the need of using drugs and surgery. The oral cavity is one of the most accessible areas for the clinical applications of gene therapy for various oral tissues. The idea of genetic engineering has become more exciting due to its advantages over other treatment modalities. For instance, the body is neither subjected to an invasive surgery nor deep wounds, nor is it susceptible to systemic effects of drugs. The aim of this article is to review the gene therapy applications in the field of dentistry. In addition, therapeutic benefits in terms of treatment of diseases, minimal invasion and maximum outcomes have been discussed.