Viral Vectors Applied for RNAi-Based Antiviral Therapy

Nanocarriers for cutting-edge cancer immunotherapies

Cancer immunotherapy aims to harness the body's own immune system for effective and long-lasting elimination of malignant neoplastic tissues. Owing to the advance in understanding of cancer pathology and immunology, many novel strategies for enhancing immunological responses against various cancers have been successfully developed, and some have translated into excellent clinical outcomes. As one promising strategy for the next generation of immunotherapies, activating the multi-cellular network (MCN) within the tumor microenvironment (TME) to deploy multiple mechanisms of action (MOAs) has attracted significant attention. To achieve this effectively and safely, delivering multiple or pleiotropic therapeutic cargoes to the targeted sites of cancerous tissues, cells, and intracellular organelles is critical, for which numerous nanocarriers have been developed and leveraged. In this review, we first introduce therapeutic payloads categorized according to their predicted functions in cancer immunotherapy and their physicochemical structures and forms. Then, various nanocarriers, along with their unique characteristics, properties, advantages, and limitations, are introduced with notable recent applications in cancer immunotherapy. Following discussions on targeting strategies, a summary of each nanocarrier matching with suitable therapeutic cargoes is provided with comprehensive background information for designing cancer immunotherapy regimens.

Utilizing shRNA-expressing lentivectors for viral hemorrhagic septicemia virus suppression via NV gene targeting

Background

Viral hemorrhagic septicemia virus or VHSV, is a single-stranded negative-sense RNA virus that is a member of the Rhabdoviridae family's genus Novirhabdovirus. Its major host is rainbow trout. Severe clinical symptoms and a higher mortality rate in fish populations are caused by this virus. Regretfully, there is currently no medication or vaccination available to treat it. Recently, there has been a lot of interest in developing antiviral therapies employing interfering RNA (RNAi), particularly shRNA. This study used shRNAs targeting the NV gene of VHSV to test its effectiveness in preventing VHSV proliferation in cell culture. Using the VHSV-Fil3 strain, the appropriate oligonucleotide sequence for NV gene coding was chosen for this purpose. Subsequently, shRNA molecules were designed and synthesized with the aid of shRNA design tools. The shRNAs were transfected into HEK293T cells after being cloned into the suitable vectors using the third generation of lentiviral packaging system. The CS2-2 cell line was subsequently transduced with these shRNA-expressing lentiviruses in order to challenge the VHS virus. Finally, TCID50 was employed to calculate the viral infectious titer in order to assess the effectiveness of shRNAs.

Results

According to the final calculations, all shRNAs exhibited antiviral activity. When compared to the control groups, the shRNAs 1, 2, and 3 considerably lowered VHSV output in the TCID50 test (nearly 99.99, 99.99, and 99.99%, respectively, compared to cells with VHSV inoculation and nearly 99.98, 99.98, and 99.97%, respectively, compared to cells with VHSV and scrambled vector inoculation).

Conclusion

Thus, it can be declared that RNA interference (RNAi) has the potential to be an exceptionally effective therapeutic option against viruses like VHSV.

Deciphering the multifaceted role of microRNAs in hepatocellular carcinoma: Integrating literature review and bioinformatics analysis for therapeutic insights

Hepatocellular carcinoma (HCC) poses a significant global health challenge, necessitating innovative therapeutic strategies. MicroRNAs (miRNAs) have emerged as pivotal regulators of HCC pathogenesis, influencing key processes such as self-renewal, angiogenesis, glycolysis, autophagy, and metastasis. This article integrates findings from a comprehensive literature review and bioinformatics analysis to elucidate the role of miRNAs in HCC. We discuss how dysregulation of miRNAs can drive HCC initiation, progression, and metastasis by modulating various signaling pathways and target genes. Moreover, leveraging high-throughput technology and bioinformatics tools, we identify key miRNAs involved in multiple cancer hallmarks, offering insights into potential combinatorial therapeutic strategies. Through our analysis considering p-values and signaling pathways associated with key features, we unveil miRNAs with simultaneous roles across critical cancer characteristics, providing a basis for the development of high-performance biomarkers. The microRNAs, miR-34a-5p, miR-373-3p, miR-21-5p, miR-214-5p, miR-195-5p, miR-139-5p were identified to be shared microRNAs in stemness, angiogenesis, glycolysis, autophagy, EMT, and metastasis of HCC. However, challenges such as miRNA stability and delivery hinder the translation of miRNA-based therapeutics into clinical practice. This review underscores the importance of further research to overcome existing barriers and realize the full potential of miRNA-based interventions for HCC management.

Hypoxia-Inducible Factor 1-Alpha (HIF-1α) and Cancer: Mechanisms of Tumor Hypoxia and Therapeutic Targeting

Hypoxia-inducible factor 1-alpha (HIF-1α) is necessary for cells to adapt to low oxygen levels often present in the tumor microenvironment. HIF-1α triggers a transcriptional program that promotes invasion, angiogenesis, metabolic reprogramming, and cell survival when it is active in hypoxic environments. These processes together lead to the growth and spread of tumors. This review article examines the molecular mechanisms by which HIF-1α contributes to tumor progression, including its regulation by oxygen-dependent and independent pathways, interactions with oncogenic signaling networks, and impact on the tumor microenvironment. Additionally, we explore current therapeutic strategies targeting HIF-1α, such as small molecule inhibitors, RNA interference, and immunotherapy approaches. Understanding the multifaceted roles of HIF-1α in cancer biology not only elucidates the complexities of tumor hypoxia but also opens avenues for developing novel and more effective cancer therapies.

Evaluation of the effect of RNA secondary structure on Cas13d-mediated target RNA cleavage

The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas13d system was adapted as a powerful tool for targeting viral RNA sequences, making it a promising approach for antiviral strategies. Understanding the influence of template RNA structure on Cas13d binding and cleavage efficiency is crucial for optimizing its therapeutic potential. In this study, we investigated the effect of local RNA secondary structure on Cas13d activity. To do so, we varied the stability of a hairpin structure containing the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) target sequence, allowing us to determine the threshold RNA stability at which Cas13d activity is affected. Our results demonstrate that Cas13d possesses the ability to effectively bind and cleave highly stable RNA structures. Notably, we only observed a decrease in Cas13d activity in the case of exceptionally stable RNA hairpins with completely base-paired stems, which are rarely encountered in natural RNA molecules. A comparison of Cas13d and RNA interference (RNAi)-mediated cleavage of the same RNA targets demonstrated that RNAi is more sensitive for local target RNA structures than Cas13d. These results underscore the suitability of the CRISPR-Cas13d system for targeting viruses with highly structured RNA genomes.

Resistance of the CRISPR-Cas13a Gene-Editing System to Potato Spindle Tuber Viroid Infection in Tomato and Nicotiana benthamiana

Gene-editing technology, specifically the CRISPR-Cas13a system, has shown promise in breeding plants resistant to RNA viruses. This system targets RNA and, theoretically, can also combat RNA-based viroids. To test this, the CRISPR-Cas13a system was introduced into tomato plants via transient expression and into Nicotiana benthamiana through transgenic methods, using CRISPR RNAs (crRNAs) targeting the conserved regions of both sense and antisense genomes of potato spindle tuber viroid (PSTVd). In tomato plants, the expression of CRISPR-Cas13a and crRNAs substantially reduced PSTVd accumulation and alleviated disease symptoms. In transgenic N. benthamiana plants, the PSTVd levels were lower as compared to wild-type plants. Several effective crRNAs targeting the PSTVd genomic RNA were also identified. These results demonstrate that the CRISPR-Cas13a system can effectively target and combat viroid RNAs, despite their compact structures.

Inorganic nanocarriers for siRNA delivery for cancer treatments

RNA interference is one of the emerging methodologies utilized in the treatment of a wide variety of diseases including cancer. This method specifically uses therapeutic RNAs (TpRNAs) like small interfering RNAs (siRNAs) to regulate/silence the cancer-linked genes, thereby minimizing the distinct activities of the cancer cells while aiding in their apoptosis. But, many complications arise during the transport/delivery of these TpRNAs that include poor systemic circulation, instability/degradation inside the body environment, no targeting capacity and also low cellular internalization. These difficulties can be overcome by using nanocarriers to deliver the TpRNAs inside the cancer cells. The following are the various categories of nanocarriers-viral vectors (e.g. lentivirus and adenovirus) and non-viral nanocarriers (self-assembling nanocarriers and inorganic nanocarriers). Viral vectors suffer from disadvantages like high immunogenicity compared to the non-viral nanocarriers. Among non-viral nanocarriers, inorganic nanocarriers gained significant attention as their inherent properties (like magnetic properties) can aid in the effective cellular delivery of the TpRNAs. Most of the prior reports have discussed about the delivery of TpRNAs through self-assembling nanocarriers; however very few have reviewed about their delivery using the inorganic nanoparticles. Therefore, in this review, we have mainly focussed on the delivery of TpRNAs-i.e. siRNA, especially programmed death ligand-1 (PD-L1), survivin, B-cell lymphoma-2 (Bcl-2), vascular endothelial growth factor and other siRNAs using the inorganic nanoparticles-mainly magnetic, metal and silica nanoparticles. Moreover, we have also discussed about the combined delivery of these TpRNAs along with chemotherapeutic drugs (mainly doxorubicin) andin vitroandin vivotherapeutic effectiveness.

Small interfering RNA (siRNA)-based therapeutic applications against viruses: principles, potential, and challenges

RNA has emerged as a revolutionary and important tool in the battle against emerging infectious diseases, with roles extending beyond its applications in vaccines, in which it is used in the response to the COVID-19 pandemic. Since their development in the 1990s, RNA interference (RNAi) therapeutics have demonstrated potential in reducing the expression of disease-associated genes. Nucleic acid-based therapeutics, including RNAi therapies, that degrade viral genomes and rapidly adapt to viral mutations, have emerged as alternative treatments. RNAi is a robust technique frequently employed to selectively suppress gene expression in a sequence-specific manner. The swift adaptability of nucleic acid-based therapeutics such as RNAi therapies endows them with a significant advantage over other antiviral medications. For example, small interfering RNAs (siRNAs) are produced on the basis of sequence complementarity to target and degrade viral RNA, a novel approach to combat viral infections. The precision of siRNAs in targeting and degrading viral RNA has led to the development of siRNA-based treatments for diverse diseases. However, despite the promising therapeutic benefits of siRNAs, several problems, including impaired long-term protein expression, siRNA instability, off-target effects, immunological responses, and drug resistance, have been considerable obstacles to the use of siRNA-based antiviral therapies. This review provides an encompassing summary of the siRNA-based therapeutic approaches against viruses while also addressing the obstacles that need to be overcome for their effective application. Furthermore, we present potential solutions to mitigate major challenges.

RNA Vaccines: Yeast as a Novel Antigen Vehicle

In the last decades, technological advances for RNA manipulation enabled and expanded its application in vaccine development. This approach comprises synthetic single-stranded mRNA molecules that direct the translation of the antigen responsible for activating the desired immune response. The success of RNA vaccines depends on the delivery vehicle. Among the systems, yeasts emerge as a new approach, already employed to deliver protein antigens, with efficacy demonstrated through preclinical and clinical trials. β-glucans and mannans in their walls are responsible for the adjuvant property of this system. Yeast β-glucan capsules, microparticles, and nanoparticles can modulate immune responses and have a high capacity to carry nucleic acids, with bioavailability upon oral immunization and targeting to receptors present in antigen-presenting cells (APCs). In addition, yeasts are suitable vehicles for the protection and specific delivery of therapeutic vaccines based on RNAi. Compared to protein antigens, the use of yeast for DNA or RNA vaccine delivery is less established and has fewer studies, most of them in the preclinical phase. Here, we present an overview of the attributes of yeast or its derivatives for the delivery of RNA-based vaccines, discussing the current challenges and prospects of this promising strategy.

Noncoding RNA therapeutics for substance use disorder

Although noncoding RNAs (ncRNAs) have been shown to regulate maladaptive neuroadaptations that drive compulsive drug use, ncRNA-targeting therapeutics for substance use disorder (SUD) have yet to be clinically tested. Recent advances in RNA-based drugs have improved many therapeutic issues related to immune response, specificity, and delivery, leading to multiple successful clinical trials for other diseases. As the need for safe and effective treatments for SUD continues to grow, novel nucleic acid-based therapeutics represent an appealing approach to target ncRNA mechanisms in SUD. Here, we review ncRNA processes implicated in SUD, discuss recent therapeutic approaches for targeting ncRNAs, and highlight potential opportunities and challenges of ncRNA-targeting therapeutics for SUD.

Development and application of ribonucleic acid therapy strategies against COVID-19

The Coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome 2 coronavirus (SARS-CoV-2), remaining a global health crisis since its outbreak until now. Advanced biotechnology and research findings have revealed many suitable viral and host targets for a wide range of therapeutic strategies. The emerging ribonucleic acid therapy can modulate gene expression by post-transcriptional gene silencing (PTGS) based on Watson-Crick base pairing. RNA therapies, including antisense oligonucleotides (ASO), ribozymes, RNA interference (RNAi), aptamers, etc., were used to treat SARS-CoV whose genome is similar to SARV-CoV-2, and the past experience also applies for the treatment of COVID-19. Several studies against SARS-CoV-2 based on RNA therapeutic strategy have been reported, and a dozen of relevant preclinical or clinical trials are in process globally. RNA therapy has been a very active and important part of COVID-19 treatment. In this review, we focus on the progress of ribonucleic acid therapeutic strategies development and application, discuss corresponding problems and challenges, and suggest new strategies and solutions.

Design of siRNA molecules for silencing of membrane glycoprotein, nucleocapsid phosphoprotein, and surface glycoprotein genes of SARS-CoV2

The global COVID-19 pandemic caused by SARS-CoV2 infected millions of people and resulted in more than 4 million deaths worldwide. Apart from vaccines and drugs, RNA silencing is a novel approach for treating COVID-19. In the present study, siRNAs were designed for the conserved regions targeting three structural genes, M, N, and S, from forty whole-genome sequences of SARS-CoV2 using four different software, RNAxs, siDirect, i-Score Designer, and OligoWalk. Only siRNAs which were predicted in common by all the four servers were considered for further shortlisting. A multistep filtering approach has been adopted in the present study for the final selection of siRNAs by the usage of different online tools, viz., siRNA scales, MaxExpect, DuplexFold, and SMEpred. All these web-based tools consider several important parameters for designing functional siRNAs, e.g., target-site accessibility, duplex stability, position-specific nucleotide preference, inhibitory score, thermodynamic parameters, GC content, and efficacy in cleaving the target. In addition, a few parameters like GC content and dG value of the entire siRNA were also considered for shortlisting of the siRNAs. Antisense strands were subjected to check for any off-target similarities using BLAST. Molecular docking was carried out to study the interactions of guide strands with AGO2 protein. A total of six functional siRNAs (two for each gene) have been finally selected for targeting M, N, and S genes of SARS-CoV2. The siRNAs have not shown any off-target effects, interacted with the domain(s) of AGO2 protein, and were efficacious in cleaving the target mRNA. However, the siRNAs designed in the present study need to be tested in vitro and in vivo in the future.

Novel Therapies of Hepatitis B and D

Hepatitis B virus (HBV) infection is a global public health issue and is a major cause of cirrhosis and hepatocellular carcinoma (HCC). Hepatitis D virus (HDV) requires the hepatitis B surface antigen (HBsAg) to replicate. The eradication of HBV, therefore, can also cure HDV. The current therapies for chronic hepatitis B and D are suboptimal and cannot definitely cure the viruses. In order to achieve functional or complete cure of these infections, novel therapeutic agents that target the various sites of the viral replicative cycle are necessary. Furthermore, novel immunomodulatory agents are also essential to achieve viral clearance. Many of these new promising compounds such as entry inhibitors, covalently closed circular DNA (cccDNA) inhibitors, small interfering RNAs (siRNAs), capsid assembly modulators and nucleic acid polymers are in various stages of clinical developments. In this review article, we provided a comprehensive overview of the structure and lifecycle of HBV, the limitations of the current therapies and a summary of the novel therapeutic agents for both HDV and HBV infection.

From bench side to clinic: Potential and challenges of RNA vaccines and therapeutics in infectious diseases

The functional and structural versatility of Ribonucleic acids (RNAs) makes them ideal candidates for overcoming the limitations imposed by small molecule-based drugs. Hence, RNA-based biopharmaceuticals such as messenger RNA (mRNA) vaccines, antisense oligonucleotides (ASOs), small interfering RNAs (siRNAs), microRNA mimics, anti-miRNA oligonucleotides (AMOs), aptamers, riboswitches, and CRISPR-Cas9 are emerging as vital tools for the treatment and prophylaxis of many infectious diseases. Some of the major challenges to overcome in the area of RNA-based therapeutics have been the instability of single-stranded RNAs, delivery to the diseased cell, and immunogenicity. However, recent advancements in the delivery systems of in vitro transcribed mRNA and chemical modifications for protection against nucleases and reducing the toxicity of RNA have facilitated the entry of several exogenous RNAs into clinical trials. In this review, we provide an overview of RNA-based vaccines and therapeutics, their production, delivery, current advancements, and future translational potential in treating infectious diseases.

Nanotechnology-Assisted RNA Delivery: From Nucleic Acid Therapeutics to COVID-19 Vaccines

In recent years, the main quest of science has been the pioneering of the groundbreaking biomedical strategies needed for achieving a personalized medicine. Ribonucleic acids (RNAs) are outstanding bioactive macromolecules identified as pivotal actors in regulating a wide range of biochemical pathways. The ability to intimately control the cell fate and tissue activities makes RNA-based drugs the most fascinating family of bioactive agents. However, achieving a widespread application of RNA therapeutics in humans is still a challenging feat, due to both the instability of naked RNA and the presence of biological barriers aimed at hindering the entrance of RNA into cells. Recently, material scientists' enormous efforts have led to the development of various classes of nanostructured carriers customized to overcome these limitations. This work systematically reviews the current advances in developing the next generation of drugs based on nanotechnology-assisted RNA delivery. The features of the most used RNA molecules are presented, together with the development strategies and properties of nanostructured vehicles. Also provided is an in-depth overview of various therapeutic applications of the presented systems, including coronavirus disease vaccines and the newest trends in the field. Lastly, emerging challenges and future perspectives for nanotechnology-mediated RNA therapies are discussed.

Aptamer-based diagnostic and therapeutic approaches in animals: Current potential and challenges

Fast and precise diagnosis of infectious and non-infectious animal diseases and their targeted treatments are of utmost importance for their clinical management. The existing biochemical, serological and molecular methods of disease diagnosis need improvement in their specificity, sensitivity and cost and, are generally not amenable for being used as points-of-care (POC) device. Further, with dramatic changes in environment and farm management practices, one should also arm ourselves and prepare for emerging and re-emerging animal diseases such as cancer, prion diseases, COVID-19, influenza etc. Aptamer - oligonucleotide or short peptides that can specifically bind to target molecules - have increasingly become popular in developing biosensors for sensitive detection of analytes, pathogens (bacteria, virus, fungus, prions), drug residues, toxins and, cancerous cells. They have also been proven successful in the cellular delivery of drugs and targeted therapy of infectious diseases and physiological disorders. However, the in vivo application of aptamer-mediated biosensing and therapy in animals has been limited. This paper reviews the existing reports on the application of aptamer-based biosensors and targeted therapy in animals. It also dissects the various modifications to aptamers that were found to be successful in in vivo application of the aptamers in diagnostics and therapeutics. Finally, it also highlights major challenges and future directions in the application of aptamers in the field of veterinary medicine.

Adenovirus type 5 vectors encoding short hairpin RNAs targeting dengue virus 5' non-translated region and capsid gene suppress pre-established dengue infection in cultured epithelial and myeloid cells

Dengue, a mosquito-borne viral disease, caused by any of four serotypes of dengue viruses (DENV-1, -2, -3 and -4), is estimated to affect >1 million of the world's population daily. We showed earlier that a recombinant human adenovirus type 5 (HuAd5) vector, encoding a short hairpin RNA (shRNA), targeting a conserved sequence in the DENV genome, could effectively suppress pre-established DENV-2 infection in Vero cells. In this study, we identified an additional conserved shRNA target in the DENV genome, developed a HuAd5 vector to target this site, and evaluated if HuAd5-delivered shRNAs suppress pre-established infection by the remaining three DENV serotypes, not only in Vero cells, but also in macrophages, the in vivo sites of DENV replication in infected individuals. We also assessed the effect of anti-HuAd5 antibodies on shRNA delivery. We show that recombinant HuAd5 vectors, encoding shRNAs targeting conserved DENV genomic sequences, in the 5' non-translated region and capsid gene, can suppress ongoing replication of all four prototypic DENV serotypes in Vero cells and in a HuAd5-refractory human macrophage cell line expressing a DENV attachment factor. DENV suppression was assessed on the basis of inhibition of viral antigen secretion, viral RNA replication and progeny virus generation. Interestingly, HuAd5 vector-mediated DENV suppression in the macrophage cell line was dependent on the presence of anti-HuAd5 antibody. This suggests that HuAd5 vector complexed to its antibody enters these cells through the Fc receptor pathway. This may have implications for specific targeting of HuAd5 vector-mediated antiviral RNA interference therapy to macrophages.

Plasmids Expressing shRNAs Specific to the Nucleocapsid Gene Inhibit the Replication of Porcine Deltacoronavirus In Vivo

Simple Summary

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogen distributed globally, which causes substantial economic losses in the swine industry. The characterization of the receptor promiscuity may pose a risk of cross-species transmission. However, the options for pharmaceutical interventions are limited. In this study, the vectors expressing shRNAs targeting the nucleocapsid gene were generated to assess the inhibition effect of PDCoV reproduction. Our preliminary results demonstrate that a dual shRNA expression system is an effective strategy in combating PDCoV infection without cytotoxicity, which would facilitate the ongoing development of RNAi-based therapeutic drugs against viral diseases.

Abstract

Porcine deltacoronavirus (PDCoV) is a novel enteric coronavirus and is becoming one of the major causative agents of diarrhea in pig herds in recent years. To date, there are no commercial vaccines or antiviral pharmaceutical agents available to control PDCoV infection. Therefore, developing a reliable strategy against PDCoV is urgently needed. In this study, to observe the antiviral activity of RNA interference (RNAi), four short hairpin RNAs (shRNAs) specific to the nucleocapsid (N) gene of PDCoV were designed and tested in vitro. Of these, a double-shRNA-expression vector, designated as pSil-double-shRNA-N1, was the most effectively expressed, and the inhibition of PDCoV replication was then further evaluated in neonatal piglets. Our preliminary results reveal that plasmid-based double-shRNA-expression targeting the N gene of PDCoV can significantly protect LLC-PK1 cells and piglets from pathological lesions induced by PDCoV. Our study could benefit the investigation of the specific functions of viral genes related to PDCoV infection and offer a possible methodology of RNAi-based therapeutics for PDCoV infection.

Cell Penetrating Peptides Used in Delivery of Therapeutic Oligonucleotides Targeting Hepatitis B Virus

Peptide Nucleic Acid (PNAs) and small noncoding RNAs including small interfering RNAs (siRNAs) represent a new class of oligonucleotides considered as an alternative therapeutic strategy in the chronic hepatitis B treatment. Indeed, chronic hepatitis B virus (HBV) infection remains a major public health problem worldwide, despite the availability of an effective prophylactic vaccine. Current therapeutic approaches approved for chronic HBV treatment are pegylated-interferon alpha (IFN)-α and nucleos(t)ide analogues (NAs). Both therapies do not completely eradicate viral infection and promote severe side effects. In this context, the development of new effective treatments is imperative. This review focuses on antiviral activity of both PNAs and siRNAs targeting hepatitis B virus. Thus, we briefly present our results on the ability of PNAs to decrease hepadnaviral replication in duck hepatitis B virus (DHBV) model. Interestingly, other oligonucleotides as siRNAs could significantly inhibit HBV antigen expression in transient replicative cell culture. Because the application of these oligonucleotides as new antiviral drugs has been hampered by their poor intracellular bioavailability, we also discuss the benefits of their coupling to different molecules such as the cell penetrating peptides (CPPs), which were used as vehicles to deliver therapeutic agents into the cells.

Are Viral Vectors Any Good for RNAi Antiviral Therapy?

RNA interference (RNAi) represents a novel approach for alternative antiviral therapy. However, issues related to RNA delivery and stability have presented serious obstacles for obtaining good therapeutic efficacy. Viral vectors are capable of efficient delivery of RNAi as short interfering RNA (siRNA), short hairpin RNA (shRNA) and micro-RNA (miRNA). Efficacy in gene silencing for therapeutic applications against viral diseases has been demonstrated in various animal models. Rotavirus (RV) miR-7 can inhibit rotavirus replication by targeting the RV nonstructural protein 5. Viral gene silencing by targeting the RNAi pathway showed efficient suppression of hepatitis B virus replication by adeno-associated virus (AAV)-based delivery of RNAi hepatitis B virus (HBV) cassettes. Hepatitis C virus replication has been targeted by short hairpin RNA molecules expressed from lentivirus vectors. Potentially, RNAi-based approaches could be suitable for antiviral drugs against COVID-19.