A Multiple siRNA-Based Anti-HIV/SHIV Microbicide Shows Protection in Both In Vitro and In Vivo Models

SiRNAs as antiviral drugs - Current status, therapeutic potential and challenges

Traditionally, antiviral drugs target viral enzymes and or structural proteins, identified through large drug screens or rational drug design. The screening, chemical optimisation, small animal toxicity studies and clinical trials mean time to market is long for a new compound, and in the event of a novel virus or pandemic, weeks, and months matter. Small interfering RNAs (siRNAs) as a gene silencing platform is an alluring alternative. SiRNAs are now approved for use in the clinic to treat a range of diseases, are cost effective, scalable, and can be easily programmed to target any viral target in a matter of days. Despite the large number of preclinical studies that clearly show siRNAs are highly effective antivirals this has not translated into clinical success with no products on the market. This review provides a comprehensive overview of both the clinical and preclinical work in this area and outlines the challenges the field faces going forward that need to be addressed in order to see siRNA antivirals become a clinical reality.

Cutting edge strategies for screening of novel anti-HIV drug candidates against HIV infection: A concise overview of cell based assays

The advent of Highly Active Antiretroviral Therapy has majorly contributed towards reducing the morbidity and mortality associated with HIV infected people, thus improving the quality of their life. Still, the eradication of HIV infection has not been achieved due to some important limitations such as non-adherence to therapy, cellular toxicity, restricted bioavailability of antiretroviral drugs and emergence of drug resistant viruses. Moreover, persistence of latent HIV-reservoirs even under antiviral-drug pressure is the major obstacle in HIV cure. Currently used antiretrovirals can suppress the viral replication in activated CD4⁺ cells, however, it has been observed that the available antiretroviral therapy appears inadequate to reduce latent reservoirs established in resting memory CD4⁺ T cells. Therefore, for eradication or reduction of latent reservoirs many immunotherapeutic and pharmacologic approaches including latency reversing agents are being studied constantly. Additionally, promising therapeutic strategies including discovery of novel drugs and drug targets are continuously being explored. Therefore, preclinical testing has become an important step of drug development process, continuously demanding innovative, but less time consuming evaluation strategies. Present review attempts to gather and line-up the information on existing cell-based methodologies applied for assessing drug candidates for their antiretroviral potential. Further, we intend to outline the advanced and reliable cell based methodologies that would expedite the process of discovery and development of antiretrovirals.

Small Interfering RNAs and their Delivery Systems: A Novel Powerful Tool for the Potential Treatment of HIV Infections

Small interfering RNAs (siRNAs) have rapidly developed into biomedical research as a novel tool for the potential treatment of various human diseases. They are based on altered gene expression. In spite of the availability of highly active antiretroviral therapy (HAART), there is a specific interest in developing siRNAs as a therapeutic agent for human immunodeficiency virus (HIV) due to several problems including toxicity and drug resistance along with long term treatment. The successful use of siRNAs for therapeutic goals needs safe and effective delivery to specific cells and tissues. Indeed, the efficiency of gene silencing depends on the potency of the carrier used for siRNA delivery. The combination of siRNA and nano-carriers is a potent method to prevent the limitations of siRNA formulation. Three steps were involved in non-viral siRNA carriers such as the complex formation of siRNA with a cationic carrier, conjugation of siRNA with small molecules, and encapsulation of siRNA within nanoparticles. In this mini-review, the designed siRNAs and their carriers are described against HIV-1 infections both in vitro and in vivo.

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.

Production and Characterization of Anti-CCR5 siRNA-Loaded Polycaprolactone Nanoparticles for Topical Pre-exposure Prophylaxis

Topical posttranscriptional silencing of host factors involved in HIV-1 sexual transmission, such as CCR5, presents the potential to prevent new cases of infection. However, issues concerning proper engineering of safe and effective delivery systems for anti-CCR5 siRNA may impair the ability to yield suitable silencing at the mucosal level. Here we describe the production protocol of anti-CCR5 siRNA-loaded polycaprolactone-based nanoparticles (≈100 nm). Furthermore, we present data regarding the physicochemical and in vitro biological characterization of obtained nanosystems, which support their potential as microbicide candidates for topical pre-exposure prophylaxis of HIV-1 infection.

Recent advances in siRNA delivery mediated by lipid-based nanoparticles

Small interfering RNA (siRNA) has been expected to be a unique pharmaceutic for the treatment of broad-spectrum intractable diseases. However, its unfavorable properties such as easy degradation in the blood and negative-charge density are still a formidable barrier for clinical use. For disruption of this barrier, siRNA delivery technology has been significantly advanced in the past two decades. The approval of Patisiran (ONPATTRO™) for the treatment of transthyretin-mediated amyloidosis, the first approved siRNA drug, is a most important milestone. Since lipid-based nanoparticles (LNPs) are used in Patisiran, LNP-based siRNA delivery is now of significant interest for the development of the next siRNA formulation. In this review, we describe the design of LNPs for the improvement of siRNA properties, bioavailability, and pharmacokinetics. Recently, a number of siRNA-encapsulated LNPs were reported for the treatment of intractable diseases such as cancer, viral infection, inflammatory neurological disorder, and genetic diseases. We believe that these contributions address and will promote the development of an effective LNP-based siRNA delivery system and siRNA formulation.

Data Mining Approach for Extraction of Useful Information About Biologically Active Compounds from Publications

A lot of high quality data on the biological activity of chemical compounds are required throughout the whole drug discovery process: from development of computational models of the structure-activity relationship to experimental testing of lead compounds and their validation in clinics. Currently, a large amount of such data is available from databases, scientific publications, and patents. Biological data are characterized by incompleteness, uncertainty, and low reproducibility. Despite the existence of free and commercially available databases of biological activities of compounds, they usually lack unambiguous information about peculiarities of biological assays. On the other hand, scientific papers are the primary source of new data disclosed to the scientific community for the first time. In this study, we have developed and validated a data-mining approach for extraction of text fragments containing description of bioassays. We have used this approach to evaluate compounds and their biological activity reported in scientific publications. We have found that categorization of papers into relevant and irrelevant may be performed based on the machine-learning analysis of the abstracts. Text fragments extracted from the full texts of publications allow their further partitioning into several classes according to the peculiarities of bioassays. We demonstrate the applicability of our approach to the comparison of the endpoint values of biological activity and cytotoxicity of reference compounds.

Pharmaceutical Vehicles for Vaginal and Rectal Administration of Anti-HIV Microbicide Nanosystems

Prevention strategies play a key role in the fight against HIV/AIDS. Vaginal and rectal microbicides hold great promise in tackling sexual transmission of HIV-1, but effective and safe products are yet to be approved and made available to those in need. While most efforts have been placed in finding and testing suitable active drug candidates to be used in microbicide development, the last decade also saw considerable advances in the design of adequate carrier systems and formulations that could lead to products presenting enhanced performance in protecting from infection. One strategy demonstrating great potential encompasses the use of nanosystems, either with intrinsic antiviral activity or acting as carriers for promising microbicide drug candidates. Polymeric nanoparticles, in particular, have been shown to be able to enhance mucosal distribution and retention of promising antiretroviral compounds. One important aspect in the development of nanotechnology-based microbicides relates to the design of pharmaceutical vehicles that allow not only convenient vaginal and/or rectal administration, but also preserve or even enhance the performance of nanosystems. In this manuscript, we revise relevant work concerning the selection of vaginal/rectal dosage forms and vehicle formulation development for the administration of microbicide nanosystems. We also pinpoint major gaps in the field and provide pertinent hints for future work.

Preclinical Safety Evaluation of HIV-1 gp120 Responsive Microbicide Delivery System in C57BL/6 Female Mice

Many novel vaginal/rectal microbicide formulations failed clinically due to safety concerns, indicating the need for the early investigation of lead microbicide formulations. In this study, the preclinical safety of an HIV-1 gp120 and mannose responsive microbicide delivery system (MRP) is evaluated in C57BL/6 mice. MRP was engineered through the layer-by-layer coating of calcium carbonate (CaCO₃) with Canavalia ensiformis lectin (Con A) and glycogen. MRP mean particle diameter and zeta potential were 857.8 ± 93.1 nm and 2.37 ± 4.12 mV, respectively. Tenofovir (TFV) encapsulation and loading efficiencies in MRP were 70.1% and 16.3% w/w, respectively. When exposed to HIV-1 rgp120 (25 μg/mL), MRP released a significant amount of TFV (∼5-fold higher) in vaginal and seminal fluid mixture compared to the control (pre-exposure) level (∼59 μg/mL) in vaginal fluid alone. Unlike the positive control treated groups (e.g., nonoxynol-9), no significant histological damages and CD45+ cells infiltration were observed in the vaginal and major reproductive organ epithelial layers. This was probably due to MRP biocompatibility and its isosmolality (304.33 ± 0.58 mOsm/kg). Furthermore, compared to negative controls, there was no statistically significant increase in pro-inflammatory cytokines such as IL1α, Ilβ, IL7, IP10, and TNFα. Collectively, these data suggest that MRP is a relatively safe nanotemplate for HIV-1 gp120 stimuli responsive vaginal microbicide delivery system.

Current State of Microbicide Development

Efforts in developing an effective vaccine for human immunodeficiency virus (HIV) has been challenging as HIV strains are highly variable and exhibit extraordinary mutability. Despite condom usage and pre-exposure prophylaxis as excellent prevention strategies, lack of accessibility in some developing countries and low adherence due to sociocultural factors continue to act as barriers in reducing the HIV epidemic. Microbicides are topical therapies developed to prevent HIV and other sexually transmitted infections during intercourse. Microbicides applied vaginally or rectally are intended to prevent HIV infection at the site of transmission by either inhibiting its entry into immune cells or prevent viral replication. This review will summarize some of the current state-of-the-art microbicide formulations that are in preclinical and clinical stages of development and discuss some of the challenges associated with microbicide development.

Nanobiotechnology medical applications: Overcoming challenges through innovation

Biomedical Nanotechnology (BNT) has rapidly become a revolutionary force that is driving innovation in the medical field. BNT is a subclass of nanotechnology (NT), and often operates in cohort with other subclasses, such as mechanical or electrical NT for the development of diagnostic assays, therapeutic implants, nano-scale imaging systems, and medical machinery. BNT is generating solutions to many conventional challenges through the development of enhanced therapeutic delivery systems, diagnostic techniques, and theranostic therapies. Therapeutically, BNT has generated many novel nanocarriers (NCs) that each express specifically designed physiochemical properties that optimize their desired pharmacokinetic profile. NCs are also being integrated into nanoscale platforms that further enhance their delivery by controlling and prolonging their release profile. Nano-platforms are also proving to be highly efficient in tissue regeneration when combined with the appropriate growth factors. Regarding diagnostics, NCs are being designed to perform targeted delivery of luminescent tags and contrast agents that enhance the NC -aided imaging capabilities and resulting diagnostic accuracy of the presence of diseased cells. This technology has also been advancing the ability for surgeons to practice true precision surgical techniques. Incorporating therapeutic and diagnostic NC-components within a single NC can facilitate both functions, referred to as theranostics, which facilitates real-time in vivo tracking and observation of drug release events via enhanced imaging. Additionally, stimuli-responsive theranostic NCs are quickly developing as vectors for tumor ablation therapies by providing a model that facilitates the location of cancer cells for the application of an external stimulus. Overall, BNT is an interdisciplinary approach towards health care, and has the potential to significantly improve the quality of life for humanity by significantly decreasing the treatment burden for patients, and by providing non-invasive therapeutics that confer enhanced therapeutic efficiency and safety

Interfering RNA with multi-targets for efficient gene suppression in HCC cells

RNA interference (RNAi) technology has been widely used in therapeutics development, especially multiple targeted RNAi strategy, which is a better method for multiple gene suppression. In the study, interfering RNAs (iRNAs) were designed for carrying two or three different siRNA sequences in different secondary structure formats (loop or cloverleaf). By using these types of iRNAs, co-inhibition of survivin and B-cell lymphoma-2 (Bcl-2) was investigated in hepatocellular carcinoma (HCC) cells, and we obtained promising gene silencing effects without showing undesirable interferon response. Furthermore, suppression effects on proliferation, invasion, and induced apoptosis in HCC cells were validated. The results suggest that long iRNAs with secondary structure may be a preferred strategy for multigenic disease therapy, especially for cancer and viral gene therapy and their iRNA drug development.

Nanotechnologies for early diagnosis, in situ disease monitoring, and prevention

Nanotechnology is an enabling technology with great potential for applications in stem cell research and regenerative medicine. Fluorescent nanodiamond (FND), an inherently biocompatible and nontoxic nanoparticle, is well suited for such applications. We had developed a prospective isolation method using CD157, CD45, and CD54 to obtain lung stem cells. Labeling of CD45⁻CD54⁺CD157⁺ cells with FNDs did not eliminate their abilities for self-renewal and differentiation. The FND labeling in combination with cell sorting, fluorescence lifetime imaging microscopy, and immunostaining identified transplanted stem cells allowed tracking of their engraftment and regenerative capabilities with single-cell resolution. Time-gated fluorescence (TGF) imaging in mouse tissue sections indicated that they reside preferentially at the bronchoalveolar junctions of lungs, especially in naphthalene-injured mice. Our results presented in Subchapter 1.1 demonstrate not only the remarkable homing capacity and regenerative potential of the isolated stem cells, but also the ability of finding rare lung stem cells in vivo using FNDs.

The topical use of antiretroviral-based microbicides, namely of a dapivirine ring, has been recently shown to partially prevent transmission of HIV through the vaginal route. Among different formulation approaches, nanotechnology tools and principles have been used for the development of tentative vaginal and rectal microbicide products. Subchapter 1.2 provides an overview of antiretroviral drug nanocarriers as novel microbicide candidates and discusses recent and relevant research on the topic. Furthermore, advances in developing vaginal delivery platforms for the administration of promising antiretroviral drug nanocarriers are reviewed. Although mostly dedicated to the discussion of nanosystems for vaginal use, the development of rectal nanomicrobicides is also addressed.

Infectious diseases are currently responsible for over 8 million deaths per year. Efficient treatments require accurate recognition of pathogens at low concentrations, which in the case of blood infection (septicemia) can go as low as 1 mL^–1. Detecting and quantifying bacteria at such low concentrations is challenging and typically demands cultures of large samples of blood (∼1 mL) extending over 24–72 h. This delay seriously compromises the health of patients and is largely responsible for the death toll of bacterial infections. Recent advances in nanoscience, spectroscopy, plasmonics, and microfluidics allow for the development of optical devices capable of monitoring minute amounts of analytes in liquid samples. In Subchapter 1.3 we critically discuss these recent developments that will, in the future, enable the multiplex identification and quantification of microorganisms directly on their biological matrix with unprecedented speed, low cost, and sensitivity.

Radiolabeled nanoparticles (NPs) are finding an increasing interest in a broad range of biomedical applications. They may be used to detect and characterize diseases, to deliver relevant therapeutics, and to study the pharmacokinetic/pharmacodynamic parameters of nanomaterials. The use of radiotracer techniques in the research of novel NPs offers many advantages, but there are still some limitations. The binding of radionuclides to NPs has to be irreversible to prevent their escape to other tissues or organs. Due to the short half-lives of radionuclides, the manufacturing process is time limited and difficult, and there is also a risk of contamination. Subchapter 1.4 presents the main selection criteria for radionuclides and applicable radiolabeling procedures used for the radiolabeling of various NPs. Also, an overview of different types of NPs that have so far been labeled with radionuclides is presented.

Polymers in the Delivery of siRNA for the Treatment of Virus Infections

Viral diseases remain a major cause of death worldwide. Despite advances in vaccine and antiviral drug technology, each year over three million people die from a range of viral infections. Predominant viruses include human immunodeficiency virus, hepatitis viruses, and gastrointestinal and respiratory viruses. Now more than ever, robust, easily mobilised and cost-effective antiviral strategies are needed to combat both known and emerging disease threats. RNA interference and small interfering (si)RNAs were initially hailed as a “magic bullet”, due to their ability to inhibit the synthesis of any protein via the degradation of its complementary messenger RNA sequence. Of particular interest was the potential for attenuating viral mRNAs contributing to the pathogenesis of disease that were not able to be targeted by vaccines or antiviral drugs. However, it was soon discovered that delivery of active siRNA molecules to the infection site in vivo was considerably more difficult than anticipated, due to a number of physiological barriers in the body. This spurred a new wave of investigation into nucleic acid delivery vehicles which could facilitate safe, targeted and effective administration of the siRNA as therapy. Amongst these, cationic polymer delivery vehicles have emerged as a promising candidate as they are low-cost and easy to produce at an industrial scale, and bind to the siRNA by non-specific electrostatic interactions. These nanoparticles (NPs) can be functionally designed to target the infection site, improve uptake in infected cells, release the siRNA inside the endosome and facilitate delivery into the cell cytoplasm. They may also have the added benefit of acting as adjuvants. This chapter provides a background around problems associated with the translation of siRNA as antiviral treatments, reviews the progress made in nucleic acid therapeutics and discusses current methods and progress in overcoming these challenges. It also addresses the importance of combining physicochemical characterisation of the NPs with in vitro and in vivo data.

Nanomedicine in the development of anti-HIV microbicides

Prevention plays an invaluable role in the fight against HIV/AIDS. The use of microbicides is considered an interesting potential approach for topical pre-exposure prophylaxis of HIV sexual transmission. The prospects of having an effective product available are expected to be fulfilled in the near future as driven by recent and forthcoming results of clinical trials. Different dosage forms and delivery strategies have been proposed and tested for multiple microbicide drug candidates presently at different stages of the development pipeline. One particularly interesting approach comprises the application of nanomedicine principles to the development of novel anti-HIV microbicides, but its implications to efficacy and safety are not yet fully understood. Nanotechnology-based systems, either presenting inherent anti-HIV activity or acting as drug nanocarriers, may significantly influence features such as drug solubility, stability of active payloads, drug release, interactions between active moieties and virus/cells, intracellular drug delivery, drug targeting, safety, antiviral activity, mucoadhesive behavior, drug distribution and tissue penetration, and pharmacokinetics. The present manuscript provides a comprehensive and holistic overview of these topics as relevant to the development of vaginal and rectal microbicides. In particular, recent advances pertaining inherently active microbicide nanosystems and microbicide drug nanocarriers are discussed.

Chitosan nanoparticles in drug therapy of infectious and inflammatory diseases

INTRODUCTION

Chitosan, a polymer from the chitin family has diverse pharmaceutical and bio-medical utility because of its easy widespread availability, non-toxicity, biocompatibility, biodegradability, rich functionalities and high drug-loading capacity. Recent pharmaceutical research has examined the use of chitosan-based systems for drug delivery applications in various diseases. The availability of functional groups permits the conjugation of specific ligands and thus helps to target loaded drugs to the site of infection/inflammation. Slow biodegradation of chitosan permits controlled and sustained release of loaded moieties; reduces the dosing frequency and is useful for improving patient compliance in infectious drug therapy. The muco-adhesion offered by chitosan makes it an attractive candidate for anti-inflammatory drug delivery, where rapid clearance of the active moiety due to the increased tissue permeability is the major problem. The pH-dependent swelling and drug release properties of chitosan present a means of passive targeting of active drug moieties to inflammatory sites.

AREAS COVERED

Development of chitosan-based nanoparticulate systems for drug delivery applications is reviewed. The current state of chitosan-based nanosystems; with particular emphasis on drug therapy in inflammatory and infectious diseases is also covered.

EXPERT OPINION

The authors believe that chitosan-based nanosystems, due to the special and specific advantages, will have a promising role in the management of infectious and inflammatory diseases.