Effective inhibition of HIV-1 production by short hairpin RNAs and small interfering RNAs targeting a highly conserved site in HIV-1 Gag RNA is optimized by evaluating alternative length formats

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 discovery and development of RNA-based therapies for treatment of HIV-1 infection

INTRODUCTION

Long-term control of HIV-1 infection can potentially be achieved using autologous stem cell transplants with gene-modified cells. Non-coding RNAs represent a diverse class of therapeutic agents including ribozymes, RNA aptamers and decoys, small interfering RNAs, short hairpin RNAs, and U1 interference RNAs that can be designed to inhibit HIV-1 replication. They have been engineered for delivery as drugs to complement current HIV-1 therapies and as gene therapies for a potential HIV-1 functional cure.

AREAS COVERED

This review surveys the past three decades of development of these RNA technologies with a focus on their efficacy and safety for treating HIV-1 infections. We describe the mechanisms of each RNA-based agent, targets they have been developed against, efforts to enhance their stability and efficacy, and we evaluate their performance in past and ongoing preclinical and clinical trials.

EXPERT OPINION

RNA-based technologies are among the top candidates for gene therapies where they can be stably expressed for long-term suppression of HIV-1. Advances in both gene and drug delivery strategies and improvements to non-coding RNA stability and antiviral properties will cooperatively drive forward progress in improving drug therapy and engineering HIV-1 resistant cells.

Cloning and Detection of Aptamer-Ribozyme Conjugations

RNA aptamers can be used to target proteins or nucleic acids for therapeutic purposes and are candidates for RNA-mediated gene therapy. Like other small therapeutic RNAs, they can be expressed in cells from DNA templates that include a cellular promoter upstream of the RNA coding sequence. Secondary structures flanking aptamers can be used to enhance the activity or stability of these molecules. Notably, flanking self-cleaving ribozymes to remove extraneous nucleotides included during transcription as well as flanking hairpins to improve RNA stability have been used to increase the effect of therapeutic aptamers. Here we describe the cloning procedure of aptamers containing different flanking secondary structures and methods to compare their expression levels by a northern blot protocol optimized for the detection of small RNA molecules.

Efficacy, accumulation, and transcriptional profile of anti-HIV shRNAs expressed from human U6, 7SK, and H1 promoters

The expression of short hairpin RNAs (shRNAs) in cells has many potential therapeutic applications, including as a functional cure for HIV. The RNA polymerase III promoters H1, 7SK, and U6 have all been used to express shRNAs. However, there have been no direct and simultaneous comparisons of shRNA potency, expression level, and transcriptional profile between the promoters. We show that the 7SK and U6 promoters result in higher shRNA levels and potency compared to the H1 promoter but that in transduced T lymphocytes, higher expression levels can also lead to growth defects. We present evidence that Dicer cleavage of shRNAs is measured from the first base pair in the shRNA stem, rather than from the 5' end as previously shown for structurally related microRNAs. As a result, guide-strand identity was unaffected by variations in 5' transcription start sites among the different promoters, making expression levels the main determinant of shRNA potency. While all promoters generated shRNAs with variable start sites, the U6 promoter was the most accurate in using its intended +1 position. Our results have implications for the development of therapeutic small RNAs for gene therapy and for our understanding of how shRNAs are processed in cells.

A U1i RNA that Enhances HIV-1 RNA Splicing with an Elongated Recognition Domain Is an Optimal Candidate for Combination HIV-1 Gene Therapy

U1 interference (U1i) RNAs can be designed to correct splicing defects and target pathogenic RNA, such as HIV-1 RNA. In this study, we show that U1i RNAs that enhance HIV-1 RNA splicing are more effective at inhibiting HIV-1 production compared to top U1i RNAs that inhibit polyadenylation of HIV-1 RNA. A U1i RNA was also identified targeting a site upstream of the first splice acceptor site in the Gag coding region that was effective at inhibiting HIV-1 production. U1-T6, which enhanced HIV-1 RNA splicing, was superior to an antiviral short hairpin RNA (shRNA) currently in clinical trials. To increase specificity, the recognition domain of U1-T6 was elongated by 3–6 nt. The elongated molecules inhibited HIV-1 production from different HIV-1 strains, including one with a mismatch in the target site. These results suggest that lengthening the recognition domain can enhance the specificity of U1i RNAs for their intended target sites while at the same time allowing them to tolerate single mismatch mutations. Overall, our results demonstrate that U1-T6 with an elongated recognition domain inhibits HIV-1 production and has both the efficacy and specificity to be a promising candidate for HIV-1 gene therapy.

Small RNAs to treat human immunodeficiency virus type 1 infection by gene therapy

Current drug therapies for human immunodeficiency virus type 1 (HIV) infection are effective in preventing progression to acquired immune deficiency syndrome but do not eliminate the infection and are associated with unwanted side effects. A potential alternative is to modify the genome of patient cells via gene therapy to confer HIV resistance to these cells. Small RNAs are the largest and most diverse group of anti-HIV genes that have been developed for engineering HIV resistant cells. In this review, we summarize progress on the three major classes of anti-HIV RNAs including short hairpin RNAs that use the RNA interference pathway, RNA decoys and aptamers that bind specifically to a protein or RNA as well as ribozymes that mediate cleavage of specific targets. We also review methods used for the delivery of these genes into the genome of patient cells and provide some perspectives on the future of small RNAs in HIV therapy.

Cat and Mouse: HIV Transcription in Latency, Immune Evasion and Cure/Remission Strategies

There is broad scientific and societal consensus that finding a cure for HIV infection must be pursued. The major barrier to achieving a cure for HIV/AIDS is the capacity of the HIV virus to avoid both immune surveillance and current antiretroviral therapy (ART) by rapidly establishing latently infected cell populations, termed latent reservoirs. Here, we provide an overview of the rapidly evolving field of HIV cure/remission research, highlighting recent progress and ongoing challenges in the understanding of HIV reservoirs, the role of HIV transcription in latency and immune evasion. We review the major approaches towards a cure that are currently being explored and further argue that small molecules that inhibit HIV transcription, and therefore uncouple HIV gene expression from signals sent by the host immune response, might be a particularly promising approach to attain a cure or remission. We emphasize that a better understanding of the game of "cat and mouse" between the host immune system and the HIV virus is a crucial knowledge gap to be filled in both cure and vaccine research.

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.

Cell and gene therapy strategies to eradicate HIV reservoirs

PURPOSE OF REVIEW

Highly active antiretroviral treatment has dramatically improved the prognosis for people living with HIV by preventing AIDS-related morbidity and mortality through profound suppression of viral replication. However, a long-lived viral reservoir persists in latently infected cells that harbor replication-competent HIV genomes. If therapy is discontinued, latently infected memory cells inevitably reactivate and produce infectious virus, resulting in viral rebound. The reservoir is the biggest obstacle to a cure of HIV.

RECENT FINDINGS

This review summarizes significant advances of the past year in the development of cellular and gene therapies for HIV cure. In particular, we highlight work done on suppression or disruption of HIV coreceptors, vectored delivery of antibodies and antibody-like molecules, T-cell therapies and HIV genome disruption.

SUMMARY

Several recent advancements in cellular and gene therapies have emerged at the forefront of HIV cure research, potentially having broad implications for the future of HIV treatment.

'Dual' peptidyl-oligonucleotide conjugates: Role of conformational flexibility in catalytic cleavage of RNA

Traditional therapeutic interventions against abnormal gene expression in disease states at the level of expressed proteins are becoming increasingly difficult due to poor selectivity, off-target effects and associated toxicity. Upstream catalytic targeting of specific RNA sequences offers an alternative platform for drug discovery to achieve more potent and selective treatment through antisense interference with disease-relevant RNAs. We report a novel class of catalytic biomaterials, comprising amphipathic RNA-cleaving peptides placed between two RNA recognition motifs, here demonstrated to target the TΨC loop and 3'- acceptor stem of tRNA^Phe. These unique peptidyl-oligonucleotide 'dual' conjugates (DCs) were created by phosphoramidate or thiol-maleimide conjugation chemistry of a TΨC-targeting oligonucleotide to the N-terminus of the amphipathic peptide sequence, followed by amide coupling of a 3'-acceptor stem-targeting oligonucleotide to the free C-terminal carboxylic acid functionality of the same peptide. Hybridization of the DCs bearing two spatially-separated recognition motifs with the target tRNA^Phe placed the peptide adjacent to a single-stranded RNA region and promoted cleavage within the 'action radius' of the catalytic peptide. Up to 100% cleavage of the target tRNA^Phe was achieved by the best candidate (i.e. DC6) within 4 h, when conformational flexibility was introduced into the linker regions between the peptide and oligonucleotide components. This study provides the strong position for future development of highly selective RNA-targeting agents that can potentially be used for disease-selective treatment at the level of messenger, micro, and genomic viral RNA.

Evaluation of the Efficacy And Toxicity of RNAs Targeting HIV-1 Production for Use in Gene or Drug Therapy

Small RNA therapies targeting post-integration steps in the HIV-1 replication cycle are among the top candidates for gene therapy and have the potential to be used as drug therapies for HIV-1 infection. Post-integration inhibitors include ribozymes, short hairpin (sh) RNAs, small interfering (si) RNAs, U1 interference (U1i) RNAs and RNA aptamers. Many of these have been identified using transient co-transfection assays with an HIV-1 expression plasmid and some have advanced to clinical trials. In addition to measures of efficacy, small RNAs have been evaluated for their potential to affect the expression of human RNAs, alter cell growth and/or differentiation, and elicit innate immune responses. In the protocols described here, a set of transient transfection assays designed to evaluate the efficacy and toxicity of RNA molecules targeting post-integration steps in the HIV-1 replication cycle are described. We have used these assays to identify new ribozymes and optimize the format of shRNAs and siRNAs targeting HIV-1 RNA. The methods provide a quick set of assays that are useful for screening new anti-HIV-1 RNAs and could be adapted to screen other post-integration inhibitors of HIV-1 replication.

Efficient inhibition of human immunodeficiency virus replication using novel modified microRNA-30a targeting 3'-untranslated region transcripts

RNA interference (RNAi)-based gene therapy is currently considered to be a combinatorial anti-human immunodeficiency virus-1 (HIV-1) therapy. Although artificial polycistronic microRNAs (miRs) can reduce HIV-1 escape mutant variants, this approach may increase the risk of side effects. The present study aimed to optimize the efficiency of anti-HIV RNAi gene therapy in order to reduce the cell toxicity induced by multi-short hairpin RNA expression. An artificial miR-30a-3'-untranslated region (miR-3-UTR) obtained from a single RNA polymerase II was used to simultaneously target all viral transcripts. The results of the present study demonstrated that HIV-1 replication was significantly inhibited in the cells with the miR-3-UTR construct, suggesting that miR-3'-UTR may serve as a promising tool for RNAi-based gene therapy in the treatment of HIV-1.