Intracerebral delivery of small interfering RNAs (siRNAs) using adenoviral vector protects mice against lethal peripheral rabies challenge

Nebulised delivery of RNA formulations to the lungs: From aerosol to cytosol

In the past decade RNA-based therapies such as small interfering RNA (siRNA) and messenger RNA (mRNA) have emerged as new and ground-breaking therapeutic agents for the treatment and prevention of many conditions from viral infection to cancer. Most clinically approved RNA therapies are parenterally administered which impacts patient compliance and adds to healthcare costs. Pulmonary administration via inhalation is a non-invasive means to deliver RNA and offers an attractive alternative to injection. Nebulisation is a particularly appealing method due to the capacity to deliver large RNA doses during tidal breathing. In this review, we discuss the unique physiological barriers presented by the lung to efficient nebulised RNA delivery and approaches adopted to circumvent this problem. Additionally, the different types of nebulisers are evaluated from the perspective of their suitability for RNA delivery. Furthermore, we discuss recent preclinical studies involving nebulisation of RNA and analysis in in vitro and in vivo settings. Several studies have also demonstrated the importance of an effective delivery vector in RNA nebulisation therefore we assess the variety of lipid, polymeric and hybrid-based delivery systems utilised to date. We also consider the outlook for nebulised RNA medicinal products and the hurdles which must be overcome for successful clinical translation. In summary, nebulised RNA delivery has demonstrated promising potential for the treatment of several lung-related conditions such as asthma, COPD and cystic fibrosis, to which the mode of delivery is of crucial importance for clinical success.

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.

Treat the "Untreatable" by a Photothermal Agent: Triggering Heat and Immunological Responses for Rabies Virus Inactivation

Rabies is a fatal neurological zoonotic disease caused by the rabies virus (RABV), and the approved post-exposure prophylaxis (PEP) procedure remains unavailable in areas with inadequate medical systems. Although strategies have been proposed for PEP and postinfection treatment (PIT), because of the complexity of the treatment procedures and the limited curative outcome, developing an effective treatment strategy remains a holy grail in rabies research. Herein, a facile approach is proposed involving photothermal therapy (PTT) and photothermally triggered immunological effects to realize effective PEP and PIT simultaneously. The designed photothermal agent (N+ TT-mCB nanoparticles) featured positively charged functional groups and high photo-to-heat efficiency, which are favorable for virus targeting and inactivation. The level of the virus at the site of infection in mice is significantly decreased upon treatment with orthotopic PTT, and the transfer of the virus to the brain is significantly inhibited. Furthermore, the survival ratio of the mice three days postinfection is increased by intracranial injection of N+ TT-mCB and laser irradiation. Overall, this work provides a platform for the effective treatment of RABV and opens a new avenue for future antiviral studies.

Nanoparticle Delivery Platforms for RNAi Therapeutics Targeting COVID-19 Disease in the Respiratory Tract

Since December 2019, a pandemic of COVID-19 disease, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly spread across the globe. At present, the Food and Drug Administration (FDA) has issued emergency approval for the use of some antiviral drugs. However, these drugs still have limitations in the specific treatment of COVID-19, and as such, new treatment strategies urgently need to be developed. RNA-interference-based gene therapy provides a tractable target for antiviral treatment. Ensuring cell-specific targeted delivery is important to the success of gene therapy. The use of nanoparticles (NPs) as carriers for the delivery of small interfering RNA (siRNAs) to specific tissues or organs of the human body could play a crucial role in the specific therapy of severe respiratory infections, such as COVID-19. In this review, we describe a variety of novel nanocarriers, such as lipid NPs, star polymer NPs, and glycogen NPs, and summarize the pre-clinical/clinical progress of these nanoparticle platforms in siRNA delivery. We also discuss the application of various NP-capsulated siRNA as therapeutics for SARS-CoV-2 infection, the challenges with targeting these therapeutics to local delivery in the lung, and various inhalation devices used for therapeutic administration. We also discuss currently available animal models that are used for preclinical assessment of RNA-interference-based gene therapy. Advances in this field have the potential for antiviral treatments of COVID-19 disease and could be adapted to treat a range of respiratory diseases.

Recent advancements in molecular marker-assisted selection and applications in plant breeding programmes

Background

DNA markers improved the productivity and accuracy of classical plant breeding by means of marker-assisted selection (MAS). The enormous number of quantitative trait loci (QTLs) mapping read for different plant species have given a plenitude of molecular marker-gene associations.

Main body of the abstract

In this review, we have discussed the positive aspects of molecular marker-assisted selection and its precise applications in plant breeding programmes. Molecular marker-assisted selection has considerably shortened the time for new crop varieties to be brought to the market. To explore the information about DNA markers, many reviews have been published in the last few decades; all these reviews were intended by plant breeders to obtain information on molecular genetics. In this review, we intended to be a synopsis of recent developments of DNA markers and their application in plant breeding programmes and devoted to early breeders with little or no knowledge about the DNA markers. The progress made in molecular plant breeding, plant genetics, genomics selection, and editing of genome contributed to the comprehensive understanding of DNA markers and provides several proofs on the genetic diversity available in crop plants and greatly complemented plant breeding devices.

Short conclusion

MAS has revolutionized the process of plant breeding with acceleration and accuracy, which is continuously empowering plant breeders around the world.

Trying to treat the untreatable: experimental approaches to clear rabies virus infection from the CNS

Rabies virus causes an invariably fatal encephalitis following the onset of clinical disease. Despite the availability of safe and effective vaccines, the clinical stages of rabies encephalitis remain untreatable, with few survivors being documented. A principal obstacle to the treatment of rabies is the neurotropic nature of the virus, with the blood-brain barrier size exclusion limit rendering the delivery of antiviral drugs and molecules to the central nervous system inherently problematic. This review focuses on efforts to try and overcome barriers to molecule delivery to treat clinical rabies and overviews current progress in the development of experimental live rabies virus vaccines that may have future applications in the treatment of clinical rabies, including the attenuation of rabies virus vectors through either the duplication or mutation of existing genes or the incorporation of non-viral elements within the genome. Rabies post-infection treatment (PIT) remains the holy grail of rabies research.

Synthesis and in vitro activities evaluation of arctigenin derivatives against spring viraemia of carp virus

Spring viraemia of carp virus (SVCV) is a viral fish pathogen causing high mortality in several carp species and other cultivated fish. However, robust anti-SVCV drugs currently are extremely scarce. For the purpose of seeking out anti-SVCV drugs, here a total of 35 arctigenin derivatives were designed, synthesized and evaluated for their anti-viral activities. By comparing the inhibitory concentration at half-maximal activity (IC₅₀) of the 15 screened candidate drugs (max inhibitory response surpassing 90%) in epithelioma papulosum cyprini (EPC) cells infected with SVCV, 2Q and 6 A were chosen for additional validation studies, with an IC₅₀ of 0.077 μg/mL and 0.095 μg/mL, respectively. Further experiments revealed that 2Q and 6 A could significantly decrease SVCV-induced apoptosis and have a protective effect on cell morphology at 48 and 72 h post-infection. Moreover, the reactive oxygen species (ROS) induced upon SVCV infection could be obviously inhibited by 2Q and 6 A, while SVCV-infected cells were clearly observed. On account of these findings, 2Q and 6 A could have a promising application for the treatment of infection of SVCV and provide a considerable reference for novel antivirals in aquaculture.

Rabies - epidemiology, pathogenesis, public health concerns and advances in diagnosis and control: a comprehensive review

Rabies is a zoonotic, fatal and progressive neurological infection caused by rabies virus of the genus Lyssavirus and family Rhabdoviridae. It affects all warm-blooded animals and the disease is prevalent throughout the world and endemic in many countries except in Islands like Australia and Antarctica. Over 60,000 peoples die every year due to rabies, while approximately 15 million people receive rabies post-exposure prophylaxis (PEP) annually. Bite of rabid animals and saliva of infected host are mainly responsible for transmission and wildlife like raccoons, skunks, bats and foxes are main reservoirs for rabies. The incubation period is highly variable from 2 weeks to 6 years (avg. 2-3 months). Though severe neurologic signs and fatal outcome, neuropathological lesions are relatively mild. Rabies virus exploits various mechanisms to evade the host immune responses. Being a major zoonosis, precise and rapid diagnosis is important for early treatment and effective prevention and control measures. Traditional rapid Seller's staining and histopathological methods are still in use for diagnosis of rabies. Direct immunofluoroscent test (dFAT) is gold standard test and most commonly recommended for diagnosis of rabies in fresh brain tissues of dogs by both OIE and WHO. Mouse inoculation test (MIT) and polymerase chain reaction (PCR) are superior and used for routine diagnosis. Vaccination with live attenuated or inactivated viruses, DNA and recombinant vaccines can be done in endemic areas. This review describes in detail about epidemiology, transmission, pathogenesis, advances in diagnosis, vaccination and therapeutic approaches along with appropriate prevention and control strategies.

Use of rapid fluorescent focus inhibition test (RFFIT) for in vitro evaluation of anti-rabies activity

Even in the twenty-first century, rabies remains one of the most dreaded diseases in many parts of the world. An effective chemotherapeutic still remains elusive. The present study was aimed at in vitro evaluation of crude extracts of Allamanda cathartica and Cynodon dactylon for their potential anti-rabies activity based on the principle of immunofluorescence. The extracts were tested for cytotoxicity and screened for the presence of phytochemicals. While A. cathartica extracts were found to be non-toxic, the CC₅₀ of C. dactylon (water and methanol) cold extracts were found to be 8.17 and 9.20 mg/mL respectively on BHK-21 cell line. Rapid Fluorescent Focus Inhibition Test (RFFIT) was used to evaluate anti-rabies activities of these plants against the rabies challenge virus standard strain. We observed 50% inhibition of 10 TCID₅₀ CVS at 5 mg/mL (IC₅₀) whereas florescence (no inhibition) was observed with A. cathartica extracts. The present study highlights the use of modified RFFIT as a method of choice for testing anti-rabies activity over assays based on evaluation of cytopathic effect.

Short interfering RNAs targeting a vampire-bat related rabies virus phosphoprotein mRNA

The aim of this study was to assess the in vitro and in vivo effects of short-interfering RNAs (siRNAs) against rabies virus phosphoprotein (P) mRNA in a post-infection treatment for rabies as an extension of a previous report (Braz J Microbiol. 2013 Nov 15;44(3):879-82). To this end, rabies virus strain RABV-4005 (related to the Desmodus rotundus vampire bat) were used to inoculate BHK-21 cells and mice, and the transfection with each of the siRNAs was made with Lipofectamine-2000™. In vitro results showed that siRNA 360 was able to inhibit the replication of strain RABV-4005 with a 1log decrease in virus titter and 5.16-fold reduction in P mRNA, 24h post-inoculation when compared to non-treated cells. In vivo, siRNA 360 was able to induce partial protection, but with no significant difference when compared to non-treated mice. These results indicate that, despite the need for improvement for in vivo applications, P mRNA might be a target for an RNAi-based treatment for rabies.

Rabies Control and Treatment: From Prophylaxis to Strategies with Curative Potential

Rabies is an acute, fatal, neurological disease that affects almost all kinds of mammals. Vaccination (using an inactivated rabies vaccine), combined with administration of rabies immune globulin, is the only approved, effective method for post-exposure prophylaxis against rabies in humans. In the search for novel rabies control and treatment strategies, live-attenuated viruses have recently emerged as a practical and promising approach for immunizing and controlling rabies. Unlike the conventional, inactivated rabies vaccine, live-attenuated viruses are genetically modified viruses that are able to replicate in an inoculated recipient without causing adverse effects, while still eliciting robust and effective immune responses against rabies virus infection. A number of viruses with an intrinsic capacity that could be used as putative candidates for live-attenuated rabies vaccine have been intensively evaluated for therapeutic purposes. Additional novel strategies, such as a monoclonal antibody-based approach, nucleic acid-based vaccines, or small interfering RNAs (siRNAs) interfering with virus replication, could further add to the arena of strategies to combat rabies. In this review, we highlight current advances in rabies therapy and discuss the role that they might have in the future of rabies treatment. Given the pronounced and complex impact of rabies on a patient, a combination of these novel modalities has the potential to achieve maximal anti-rabies efficacy, or may even have promising curative effects in the future. However, several hurdles regarding clinical safety considerations and public awareness should be overcome before these approaches can ultimately become clinically relevant therapies.

Subversion of the Immune Response by Rabies Virus

Rabies has affected mankind for several centuries and is one of the oldest known zoonoses. It is peculiar how little is known regarding the means by which rabies virus (RABV) evades the immune response and kills its host. This review investigates the complex interplay between RABV and the immune system, including the various means by which RABV evades, or advantageously utilizes, the host immune response in order to ensure successful replication and spread to another host. Different factors that influence immune responses—including age, sex, cerebral lateralization and temperature—are discussed, with specific reference to RABV and the effects on host morbidity and mortality. We also investigate the role of apoptosis and discuss whether it is a detrimental or beneficial mechanism of the host’s response to infection. The various RABV proteins and their roles in immune evasion are examined in depth with reference to important domains and the downstream effects of these interactions. Lastly, an overview of the means by which RABV evades important immune responses is provided. The research discussed in this review will be important in determining the roles of the immune response during RABV infections as well as to highlight important therapeutic target regions and potential strategies for rabies treatment.

Effects of lentiviral RNA interference-mediated downregulation of integrin-linked kinase on biological behaviors of human lens epithelial cells

AIM

To investigate the effects of lentivirus (LV) mediated integrin-linked kinase (ILK) RNA interference (RNAi) on biological behaviors of human lens epithelial cells (LECs).

METHODS

Human cataract LECs and immortalized human LEC line, human lens epithelial (HLE) B-3 cells were transfected by lentiviral vector expressing ILK-specific short hairpin RNA (shRNA) and then stimulated by transforming growth factor-β (TGF-β), the silencing of ILK gene and protein was identified by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot methods; biological behaviors including cell cycle and apoptosis, cell morphology, α-smooth muscle actin (SMA) stress fiber formation and cell migration were examined.

RESULTS

Remarkable decreases of ILK protein expression were detected in LECs carrying lentiviral ILK-shRNA vector; flow cytometry revealed arresting of cell cycle progression through the G1/S transition and higher apoptosis rate in ILK-RNAi-LV transfected cells. Less α-SMA stress fiber formation and migration was observed in ILK-RNAi-LV transfected LECs.

CONCLUSION

The present study demonstrated that ILK was an important regulator for LECs proliferation and migration. LV mediated ILK RNAi is an effective way to decrease ILK-regulated cell growth by arresting cell cycle progression and increasing cell apoptosis, as well as, to prevent cell migration by inhibiting TGF-β induced α-SMA stress fiber formation. Thus, LV mediated ILK RNAi might be useful to prevent posterior capsular opacification.

Evaluation of short-interfering RNAs treatment in experimental rabies due to wild-type virus

We have evaluated the efficacy of short-interfering RNAs targeting the nucleoprotein gene and also the brain immune response in treated and non-treated infected mice. Mice were inoculated with wild-type virus, classified as dog (hv2) or vampire bat (hv3) variants and both groups were treated or leaved as controls. No difference was observed in the lethality rate between treated and non-treated groups, although clinical evaluation of hv2 infected mice showed differences in the severity of clinical disease (p = 0.0006). Evaluation of brain immune response 5 days post-inoculation in treated hv2 group showed no difference among the analyzed genes, whereas after 10 days post-inoculation there was increased expression of 2′,5′-oligoadenylate synthetase 1, tumor necrosis factor alpha, interleukin 12, interferon gamma, and C-X-C motif chemokine 10 associated with higher expression of N gene in the same period (p < 0.0001). In hv2 non-treated group only higher interferon beta expression was found at day 5. The observed differences in results of the immune response genes between treated and non-treated groups is not promising as they had neither impact on mortality nor even a reduction in the expression of N gene in siRNA treated animals. This finding suggests that the use of pre-designed siRNA alone may not be useful in rabies treatment.

Inhibition of spring viraemia of carp virus replication in an Epithelioma papulosum cyprini cell line by RNAi

Spring viraemia of carp virus (SVCV) is an aetiological agent of a serious disease affecting carp farms in Europe and is a member of the Rhabdoviridae family of viruses. The genome of SVCV codes for five proteins: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and RNA-dependent RNA polymerase (L). RNA-mediated interference (RNAi) by small interfering RNAs (siRNAs) is a powerful tool to inhibit gene transcription and is used to study genes important for viral replication. In previous studies regarding another member of Rhabdoviridae, siRNA inhibition of the rabies virus nucleoprotein gene provided in vitro and in vivo protection against rabies. In this study, synthetic siRNA molecules were designed to target SVCV-N and SVCV-P transcripts to inhibit SVCV replication and were tested in an epithelioma papulosum cyprini (EPC) cell line. Inhibition of gene transcription was measured by real-time quantitative reverse-transcription PCR (RT-qPCR). The efficacy of using siRNA for inhibition of viral replication was analysed by RT-qPCR measurement of a reporter gene (glycoprotein) expression and by virus endpoint titration. Inhibition of nucleoprotein and phosphoprotein gene expression by siRNA reduced SVCV replication. However, use of tandem siRNAs that target phosphoprotein and nucleoprotein worked best at reducing SVCV replication.

Rabies vaccines: where do we stand, where are we heading?

Rabies being the most lethal zoonotic, vaccine-preventable viral disease with worldwide distribution of reservoir wild animals presents unique challenges for its diagnosis, management and control. Although vaccines available are highly effective, which had played the key role in controlling rabies in North America, western Europe and in a number of Asian and Latin American countries, the requirement of multiple doses along with boosters, associated cost to reduce the incidence in wild animals and prophylactic human vaccination has remained a major impediment towards achieving the same goals in poorer parts of the world such as sub-Saharan Africa and southeast Asia. Current efforts to contain rabies worldwide are directed towards the development of more safe, cheaper and efficacious vaccines along with anti-rabies antibodies for post-exposure prophylaxis. The work presented here provides an overview of the advances made towards controlling the human rabies, particularly in last 10 years, and future perspective.

Protection of mice against lethal rabies virus challenge using short interfering RNAs (siRNAs) delivered through lentiviral vector

The antiviral potential of small interfering RNAs (siRNAs) targeting rabies virus (RV) polymerase (L) and nucleoprotein (N) genes delivered through lentiviral vector was investigated. For in vitro evaluation, siRNAs expressing BHK-21 cell lines (BHK-L and BHK-N) were developed using transduction with Lenti-L and Lenti-N lentiviruses encoding siRNAs against RV-L and N genes, respectively. When these cell lines were challenged in vitro with RV Pasteur virus-11 (PV-11) strain, there was reduction in number of RV-specific foci and target gene transcripts indicating inhibitory effect on RV multiplication. For in vivo evaluation, mice were treated intracerebrally with lentiviruses and challenged with 20 LD₅₀ of RV challenge virus standard-11 (CVS-11) strain by intramuscular route in masseter muscle. Five out of eight mice treated with Lenti-N survived indicating 62.5 % protection. The control and Lenti-L-treated mice died within 7–10 days indicating lethal nature of challenge virus and no protection. These results demonstrated that siRNA targeting RV-N could not only inhibit RV multiplication, but also conferred protection in mice against lethal RV challenge. These findings have implication on therapeutic use of siRNA targeting RV-N against RV infection.

Antiviral therapy for human rabies

Human rabies is virtually always fatal despite numerous attempts at aggressive therapy. Most survivors received one or more doses of rabies vaccine prior to the onset of the disease. The Milwaukee Protocol has proved to be ineffective for rabies and should no longer be used. New approaches are needed and an improved understanding of basic mechanisms responsible for the clinical disease in rabies may prove to be useful for the development of novel therapeutic approaches. Antiviral therapy is thought to be an important component of combination therapy for the management of human rabies, and immunotherapy and neuroprotective therapy should also be strongly considered. There are many important issues for consideration regarding drug delivery to the central nervous system in rabies, which are in part related to the presence of the blood-brain barrier and also the blood-spinal cord barrier. Ribavirin and interferon-α have proved to be disappointing agents for the therapy of rabies. There is insufficient evidence to support the continued use of ketamine or amantadine for the therapy of rabies. Minocycline or corticosteroids should not be used because of concerns about aggravating the disease. A variety of new antiviral agents are under development and evaluation, including favipiravir, RNA interference (for example, small interfering [si]RNAs) and novel targeted approaches, including interference with viral capsid assembly and viral egress.

Aptamers targeting rabies virus-infected cells inhibit street rabies virus in vivo

Rabies is a viral infection of the CNS that is almost always fatal once symptoms occur. No effective treatment of the disease is available and novel antiviral strategies are urgently required. Street rabies viruses are field isolates known to be highly neurotropic. Aptamers are single-stranded oligonucleotides that bind their targets with high affinity and specificity and thus have potential for use in diagnostic and therapeutic applications. In this study, we demonstrate that the aptamers FO24 and FO21, which target RABV-infected cells, can significantly protect mice from a lethal dose of the street rabies virus FJ strain in vivo. Groups receiving preexposure prophylaxis had higher survival rates than the groups receiving postexposure prophylaxis. When mice were inoculated with aptamers (4 nmol) for 24h by intracranial or intramuscular injection prior to intramuscular inoculation with the FJ strain, approximately 60% of the mice survived. These results indicate that the FO21 and FO24 aptamers may be used to develop preventative antiviral therapy against rabies disease.

Novel approaches and challenges to treatment of central nervous system viral infections

Existing and emerging viral central nervous system (CNS) infections are major sources of human morbidity and mortality. Treatments of proven efficacy are currently limited predominantly to herpesviruses and human immunodeficiency virus (HIV). Development of new therapies has been hampered by the lack of appropriate animal model systems for some important viruses and by the difficulty in conducting human clinical trials for diseases that may be rare, or in the case of arboviral infections, often have variable seasonal and geographic incidence. Nonetheless, many novel approaches to antiviral therapy are available, including candidate thiazolide and pyrazinecarboxamide derivatives with potential broad‐spectrum antiviral efficacy. New herpesvirus drugs include viral helicase‐primase and terminase inhibitors. The use of antisense oligonucleotides and other strategies to interfere with viral RNA translation has shown efficacy in experimental models of CNS viral disease. Identifying specific molecular targets within viral replication cycles has led to many existing antiviral agents and will undoubtedly continue to be the basis of future drug design. A promising new area of research involves therapies based on enhanced understanding of host antiviral immune responses. Toll‐like receptor agonists and drugs that inhibit specific cytokines as well as interferon preparations have all shown potential therapeutic efficacy. Passive transfer of virus‐specific cytotoxic T lymphocytes has been used in humans and may provide an effective therapy for some herpesvirus infections and potentially for progressive multifocal leukoencephalopathy. Humanized monoclonal antibodies directed against specific viral proteins have been developed and in several cases evaluated in humans in settings including West Nile virus and HIV infection and in pre‐exposure prophylaxis for rabies. Ann Neurol 2013;74:412–422

Evaluation of single and dual siRNAs targeting rabies virus glycoprotein and nucleoprotein genes for inhibition of virus multiplication in vitro

Small interfering RNAs (siRNAs) targeting rabies virus (RV) glycoprotein (G) and nucleoprotein (N) genes were evaluated as antiviral agents against rabies virus in vitro in BHK-21 cells. To select effective siRNAs targeting RV-G, a plasmid-based transient co-transfection approach was used. In this, siRNAs were expressed as short hairpin RNAs (shRNAs), and their ability to inhibit RV-G gene expression was evaluated in cells transfected with a plasmid expressing RV-G. The nine different siRNAs designed to target RV-G exhibited varying degrees of knockdown of RV-G gene expression. One siRNA (si-G7) with considerable effect in knockdown of RV-G expression also demonstrated significant inhibition of RV multiplication in BHK-21 cells after in vitro challenge with the RV Pasteur virus-11 (PV-11) strain. A decrease in the number of fluorescent foci in siRNA-treated cells and a reduction (86.8 %) in the release of RV into infected cell culture supernatant indicated the anti-rabies potential of siRNA. Similarly, treatment with one siRNA targeting RV-N resulted in a decrease in the number of fluorescent foci and a reduction (85.9 %) in the release of RV. As a dual gene silencing approach where siRNAs targeting RV-G and RV-N genes were expressed from single construct, the anti-rabies-virus effect was observed as an 87.4 % reduction in the release of RV. These results demonstrate that siRNAs targeting RV-G and N, both in single and dual form, have potential as antiviral agent against rabies.

Adeno-associated viruses serotype 2-mediated RNA interference efficiently inhibits rabies virus replication in vitro and in vivo

To investigate the potential of adeno-associated viruses serotype 2 (AAV2)-mediated RNA interference (RNAi) as an antiviral agent against rabies, recombinant AAV2 vectors expressing siRNA targeting the nucleoprotein (N) gene of rabies virus (RABV) (rAAV-N796) were constructed and evaluated. When NA cells pretreated with rAAV-N796 were challenged with RABV, there was a 37.8 ± 3.4% to 55.1 ± 5.3% reduction in RABV virus titer. When cells pre-challenged with RABV were treated with rAAV-N796, there was a 4.4 ± 1.4 to 28.8 ± 3.2% reduction in RABV virus titer. Relative quantification of RABV transcripts using real-time PCR and Western blot revealed that the knockdown of RABV-N gene transcripts was based on the rAAV-N796 inoculation titer. When any NA cells were treated with rAAV-N796 before or after challenged with RABV, significant reduction in virus titer was observed in both administrations. Mice treated intracerebrally with rAAV-N796 exhibited 50 ± 5.3 and 62.5 ± 4.7% protection when challenged intracerebrally or intramuscally, respectively, with lethal RABV. When mice treated intramuscularly with rAAV-N796 were challenged intramuscularly with lethal RABV, they exhibited 37.5 ± 3.7% protection. When mice were intracerebrally and intramuscularly with rAAV-N796 24 hr after exposure to RABV infection, they exhibited 25 ± 4.1% protection The N gene mRNA levels in the brains of challenged mice with three different administrations were reduced (55, 68, 32 and 25%, respectively). These results indicated that AAV2 vector-mediated siRNA delivery in vitro in NA cells inhibited RABV multiplication, inhibited RABV multiplication in vivo in the mice brain and imparted partial protection against lethal rabies. So, it may have a potential to be used as an alternative antiviral approach against rabies.

Small interfering RNAs targeting the rabies virus nucleoprotein gene

Rabies virus (RABV) infection continues to be a global threat to human and animal health, yet no curative therapy has been developed. RNA interference (RNAi) therapy, which silences expression of specific target genes, represents a promising approach for treating viral infections in mammalian hosts. We designed six small interfering (si)RNAs (N473, N580, N783, N796, N799 and N1227) that target the conserved region of the RABV challenge virus standard (CVS)-11 strain nucleoprotein (N) gene. Using a plasmid-based transient expression model, we demonstrated that N796, N580 and N799 were capable of significantly inhibiting viral replication in vitro and in vivo. These three siRNAs effectively suppressed RABV expression in infected baby hamster kidney-21 (BHK-21) cells, as evidenced by direct immunofluorescence assay, viral titer measurements, real-time PCR, and Western blotting. In addition, liposome-mediated siRNA expression plasmid delivery to RABV-infected mice significantly increased survival, compared to a non-liposome-mediated delivery method. Collectively, our results showed that the three siRNAs, N796, N580 and N799, targeting the N gene could potently inhibit RABV CVS-11 reproduction. These siRNAs have the potential to be developed into new and effective prophylactic anti-RABV drugs.