Targeted delivery of ribavirin improves outcome of murine viral fulminant hepatitis via enhanced anti-viral activity

Inhibition of tick-borne encephalitis virus in cell cultures by ribavirin

Tick-borne encephalitis virus (TBEV) belonging to arboviruses is a major member of zoonotic pathogens. TBEV infection causes severe human encephalitis without specific antiviral drugs. Due to its use of antiviral drug against a wide range of viruses, we investigated antiviral effect of ribavirin against TBEV in susceptible human cell lines A549 and SH-SY5Y. Ribavirin displayed minor cytotoxicity on multiple cell lines. Ribavirin obviously impaired TBEV replication and protected the infected cells from cytopathic effect. Importantly, ribavirin markedly inhibited TBEV propagation, as evidenced by impairment of TBEV production and viral RNA replication. Treatment with ribavirin (co-treatment and post-treatment) led to a dose-dependent reduction in TBEV titers as well as the viral RNA levels. Antiviral protein myxovirus resistance A mRNA expression was significantly up-regulated and signal transducer and activator of transcription 3 was activated in TBEV-infected A549 cells upon the ribavirin treatment. Induction of inflammatory cytokine tumor necrosis factor alpha by TBEV was decreased in A549 cells with the treatment of ribavirin, whereas interleukin 1 beta release appeared to be unaffected. These results suggest that ribavirin might represent a promising safe and effective antiviral drug against TBEV.

Antiviral Drug Delivery System for Enhanced Bioactivity, Better Metabolism and Pharmacokinetic Characteristics

Antiviral drugs (AvDs) are the primary resource in the global battle against viruses, including the recent fight against corona virus disease 2019 (COVID-19). Most AvDs require multiple medications, and their use frequently leads to drug resistance, since they have poor oral bioavailability and low efficacy due to their low solubility/low permeability. Characterizing the in vivo metabolism and pharmacokinetic characteristics of AvDs may help to solve the problems associated with AvDs and enhance their efficacy. In this review of AvDs, we systematically investigated their structure-based metabolic reactions and related enzymes, their cellular pharmacology, and the effects of metabolism on AvD pharmacodynamics and pharmacokinetics. We further assessed how delivery systems achieve better metabolism and pharmacology of AvDs. This review suggests that suitable nanosystems may help to achieve better pharmacological activity and pharmacokinetic behavior of AvDs by altering drug metabolism through the utilization of advanced nanotechnology and appropriate administration routes. Notably, such AvDs as ribavirin, remdesivir, favipiravir, chloroquine, lopinavir and ritonavir have been confirmed to bind to the severe acute respiratory syndrome-like coronavirus (SARS-CoV-2) receptor and thus may represent anti-COVID-19 treatments. Elucidating the metabolic and pharmacokinetic characteristics of AvDs may help pharmacologists to identify new formulations with high bioavailability and efficacy and help physicians to better treat virus-related diseases, including COVID-19.

Harnessing molecular recognition for localized drug delivery

A grand challenge in drug delivery is providing the right dose, at the right anatomic location, for the right duration of time to maximize therapeutic efficacy while minimizing off-target toxicity and other deleterious side-effects. Two general modalities are receiving broad attention for localized drug delivery. In the first, referred to as "targeted accumulation", drugs or drug carriers are engineered to have targeting moieties that promote their accumulation at a specific tissue site from circulation. In the second, referred to as "local anchoring", drugs or drug carriers are inserted directly into the tissue site of interest where they persist for a specified duration of time. This review surveys recent advances in harnessing molecular recognition between proteins, peptides, nucleic acids, lipids, and carbohydrates to mediate targeted accumulation and local anchoring of drugs and drug carriers.

Pharmaceutical Technology Innovation Strategy Based on the Function of Blood Transport Proteins as DDS Carriers for the Treatment of Intractable Disorders and Cancer

Blood transport proteins are biogenic molecules with unique and interesting inherent characteristics that make up living organisms. As the utilization of their inherent characteristics can be a groundbreaking strategy to resolve and improve several clinical problems, attempts have been made to develop pharmaceutical and biomedical preparations based on blood transport proteins for the treatment and diagnosis of disorders. Among various blood transport proteins, we focus on the immense potential of hemoglobin and albumin to serve as carriers of biomedical gases (oxygen and carbon monoxide) and anticancer agents (low-molecular compounds and antisense oligodeoxynucleotides), respectively, for the development of innovative drug delivery systems (DDS) to treat intractable disorders and solid cancers. In this review, I introduce the pharmaceutical technology, strategies, and application of DDS carriers that have been designed on the basis of the structure and function of hemoglobin and albumin. In addition, the prospect of using hemoglobin and albumin as materials for DDS carriers is discussed.

Synthesis and antiviral activity of novel spirocyclic nucleosides

A diverse range of spirocyclic nucleosides have been prepared from a common precursor and tested for their antiviral activity.

Advanced Prodrug Strategies in Nucleoside and Non-Nucleoside Antiviral Agents: A Review of the Recent Five Years

Background: Poor pharmacokinetic profiles and resistance are the main two drawbacks from which currently used antiviral agents suffer, thus make them excellent targets for research, especially in the presence of viral pandemics such as HIV and hepatitis C. Methods: The strategies employed in the studies covered in this review were sorted by the type of drug synthesized into ester prodrugs, targeted delivery prodrugs, macromolecular prodrugs, other nucleoside conjugates, and non-nucleoside drugs. Results: Utilizing the ester prodrug approach a novel isopropyl ester prodrug was found to be potent HIV integrase inhibitor. Further, employing the targeted delivery prodrug zanamivir and valine ester prodrug was made and shown a sole delivery of zanamivir. Additionally, VivaGel, a dendrimer macromolecular prodrug, was found to be very efficient and is now undergoing clinical trials. Conclusions: Of all the strategies employed (ester, targeted delivery, macromolecular, protides and nucleoside analogues, and non-nucleoside analogues prodrugs), the most promising are nucleoside analogues and macromolecular prodrugs. The macromolecular prodrug VivaGel works by two mechanisms: envelope mediated and receptor mediated disruption. Nucleotide analogues have witnessed productive era in the recent past few years. The era of non-interferon based treatment of hepatitis (through direct inhibitors of NS5A) has dawned.

Equilibrative nucleoside transporter 1 expression in primary human hepatocytes is highly variable and determines uptake of ribavirin

Aims Ribavirin is a nucleoside analogue and remains a necessary component of both interferon-based and directly acting anti-viral regimens for the treatment of hepatitis C virus infection. The achievable concentration of ribavirin within hepatocytes is likely to be an important determinant of therapeutic outcome. In vitro expression levels of equilibrative nucleoside transporter 1 (ENT1) has been shown to be a predictor of treatment response in patients receiving nucleoside-based chemotherapeutic agents. We therefore investigated whether a similar relationship existed between ENT1 expression and ribavirin uptake in freshly isolated primary hepatocytes. Methods Primary hepatocytes were cultured on collagen-coated plates and exposed to ribavirin. Parallel samples were taken for high-performance liquid chromatography to assess ribavirin uptake and for quantitative polymerase chain reaction to evaluate ENT1 expression. Similar assays were performed on the human hepatoma cell line (Huh7). ENT1 gene sequence was analysed by cloning of polymerase chain reaction amplified complementary DNA followed by direct sequencing. Results There was a strong direct correlation between expression of ENT1 in primary hepatocytes and ribavirin uptake at 24 hr. Huh7 cells expressed ENT1 at similar levels to the majority of primary hepatocytes, but did not take up ribavirin. Sequencing revealed that ENT1 in Huh7 cells is wild type. Conclusions In this study, we clearly demonstrate that ribavirin uptake in primary human hepatocytes is variable and correlates with ENT1 expression. This variation in ENT1 expression may account for differences in response rate in patients receiving ribavirin-based anti-hepatitis C virus therapy.

Potential Use of Biological Proteins for Liver Failure Therapy

Biological proteins have unlimited potential for use as pharmaceutical products due to their various biological activities, which include non-toxicity, biocompatibility, and biodegradability. Recent scientific advances allow for the development of novel innovative protein-based products that draw on the quality of their innate biological activities. Some of them hold promising potential for novel therapeutic agents/devices for addressing hepatic diseases such as hepatitis, fibrosis, and hepatocarcinomas. This review attempts to provide an overview of the development of protein-based products that take advantage of their biological activity for medication, and discusses possibilities for the therapeutic potential of protein-based products produced through different approaches to specifically target the liver (or hepatic cells: hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells, and Kupffer cells) in the treatment of hepatic diseases.

Highly active macromolecular prodrugs inhibit expression of the hepatitis C virus genome in the host cells

Efficacious, potent, and at the same time nontoxic macromolecular prodrugs of ribavirin are designed taking advantage over prodrug activation by the intracellular milieu. Activity of these prodrugs is illustrated in the cells hosting hepatitis C virus replication and also in the cells implicated in the inflammatory response to the viral infection.

Development of biodegradable nanoparticles for liver-specific ribavirin delivery

Ribavirin is an antiviral drug used for the treatment of chronic hepatitis C. However, ribavirin induces severe side effects such as hemolytic anemia. In this study, we prepared biodegradable nanoparticles as ribavirin carriers to modulate the pharmacokinetics of the drug. The nanoparticles encapsulating ribavirin monophosphate (RMP) were prepared from the blend of poly(d,l-lactic acid) homopolymer and arabinogalactan (AG)-poly(l-lysine) conjugate by using the solvent diffusion method in the presence of iron (III). RMP was efficiently and stably embedded in the nanoparticles and gradually released for 37 days in phosphate-buffered saline at 37°C. The coating of AG on the nanoparticles surfaces was verified by measuring the zeta potentials and performing an aggregation test of the nanoparticles using galactose-binding lectin. Moreover, the nanoparticles were efficiently internalized in cultured HepG2 cells. Ribavirin was drastically accumulated to the liver of mice after intravenous administration of the RMP-loaded nanoparticles, after which the ribavirin content gradually decreased for at least 7 days. Our results indicated successful development of nanoparticles with dual functions, targeting to the liver and sustained release of ribavirin, and suggested that the present strategy could help to advance the clinical application of ribavirin as a therapeutic agent for chronic hepatitis C.

Macromolecular (pro)drugs with concurrent direct activity against the hepatitis C virus and inflammation

Macromolecular prodrugs (MPs) are a powerful tool to alleviate side-effects and improve the efficacy of the broad-spectrum antiviral agent ribavirin. In this work, we sought an understanding of what makes an optimal formulation within the macromolecular parameter space--nature of the polymer carrier, average molar mass, drug loading, or a good combination thereof. A panel of MPs based on biocompatible synthetic vinylic and (meth)acrylic polymers was tested in an anti-inflammatory assay with relevance to alleviating inflammation in the liver during hepatitis C infection. Pristine polymer carriers proved to have a pronounced anti-inflammatory activity, a notion which may prove significant in developing MPs for antiviral and anticancer treatments. With conjugated ribavirin, MPs revealed enhanced activity but also higher toxicity. Therapeutic windows and therapeutic indices were determined and discussed to reveal the most potent formulation and those with optimized safety. Polymers were also tested as inhibitors of replication of the hepatitis C viral RNA using a subgenomic viral replicon system. For the first time, negatively charged polymers are revealed to have an intracellular activity against hepatitis C virus replication. Concerted activity of the polymer and ribavirin afforded MPs which significantly increased the therapeutic index of ribavirin-based treatment. Taken together, the systematic investigation of the macromolecular space identified lead candidates with high efficacy and concurrent direct activity against the hepatitis C virus and inflammation.

Macromolecular prodrugs of ribavirin: concerted efforts of the carrier and the drug

Polymers in tune. Automated parallel polymer synthesis is developed to obtain libraries of macromolecular prodrugs of ribavirin, a broad-spectrum antiviral agent. As many as 10 identified lead polymer conjugates exhibit therapeutic efficacy matching that of the pristine drug and at the same time suppressed the origin of the main side effect of ribavirin.

Narrow therapeutic window of ribavirin as an inhibitor of nitric oxide synthesis is broadened by macromolecular prodrugs

Ribavirin (RBV), a broad-spectrum antiviral agent, is a standard medication against hepatitis C virus (HCV). However, despite the decades of clinical success, the mechanism of action of this drug against HCV remains a subject of debate. Furthermore, the appeal of this therapeutic agent is considerably lessened by unfavorable pharmacokinetics. This interdisciplinary study contributes to the understanding of intracellular effects exerted by RBV and presents a successful design of macromolecular prodrugs of RBV to achieve a safer treatment. Specifically, we demonstrate that RBV exhibits a pronounced anti-inflammatory activity in cultured macrophages as is evidenced by a 2-fold decrease in the levels of produced nitric oxide achieved using a clinically relevant concentration of this drug. However, this effect was characterized by a rather narrow therapeutic window with experimental values of EC50 and IC50 being 7 and 19 μM, respectively. Macromolecular prodrugs were obtained using an acrylate derivative of RBV, RAFT polymerization technique, and N-vinyl pyrrolidone as a partner monomer. The synthesized polymers were characterized with uniform molecular weights, relatively narrow polydispersities, and gradually increasing content of RBV. The resulting polymer therapeutics were effective in delivering their payload to the cultured macrophages and afforded a significantly wider therapeutic window, as much as >1000 μM (18-fold in relative values). Taken together, this work contributes significantly to the development of safer methods for delivery of RBV, as well as understanding the mechanism of action and origins of the side effects of this broad-spectrum antiviral agent.

Macromolecular prodrugs for controlled delivery of ribavirin

Ribavirin (RBV)-containing polymers are synthesized based on poly(N-vinylpyrrolidone) and poly(acrylic acid), two polymers with extensive characterization in biomedicine. The copolymers are shown to exhibit a minor to negligible degree of association with erythrocytes, thus effectively eliminating the origin of the main side effects of RBV. The therapeutic benefit of macromolecular RBV prodrugs is illustrated by matched efficacy in suppressing production of nitric oxide by stimulated cultured macrophages as compared to pristine RBV with no associated cytotoxicity, which is in stark contrast to an RBV-based treatment which results in a significant decrease in cell viability. These results contribute to the development of antiviral polymer therapeutics and delivery of RBV in particular.

Macromolecular prodrugs of ribavirin combat side effects and toxicity with no loss of activity of the drug

Chemi-enzymatic synthesis of ribavirin acrylate and subsequent RAFT co-polymerization with acrylic acid afforded a formulation of a broad spectrum antiviral drug which avoids accumulation in erythrocytes, the origin of the main side effect of ribavirin. In cultured macrophages the macromolecular prodrugs exhibited decreased toxicity while maintaining the anti-inflammatory action of ribavirin.

Contribution of ribavirin transporter gene polymorphism to treatment response in peginterferon plus ribavirin therapy for HCV genotype 1b patients

BACKGROUND

Standard-dose ribavirin is crucial for the standard-of-care treatment of chronic hepatitis C virus (HCV) infection. Equilibrative nucleoside transporter 1 (ENT1), encoded by SLC29A1 gene, is the main transporter that imports ribavirin into human hepatocytes.

AIMS

To determine whether single nucleotide polymorphisms (SNPs) at the SLC29A1 gene could influence the probability of treatment response compared with other baseline and host genetic factors.

METHODS

A total of 526 East Asian patients monoinfected with HCV genotype 1b who had received pegylated interferon alpha plus ribavirin therapy were enrolled in this study. They were assigned randomly to the derivation and confirmatory groups. SNPs related to the IL28B, ITPA and SLC29A1 genes were genotyped using real-time detection polymerase chain reaction. Factors associated with sustained virological response (SVR) were analysed using multiple logistic regression analysis.

RESULTS

Multivariate analysis for the derivation group identified six baseline variables significantly and independently associated with SVR: age [P = 0.023, odds ratio (OR) = 0.97], gender (P = 0.0047, OR = 2.25), platelet count (P = 0.00017, OR = 1.11), viral load (P = 0.00026, OR = 0.54), IL28B SNP rs12979860 (P = 1.09 × 10(-7) , OR = 8.68) and SLC29A1 SNP rs6932345 (P = 0.030, OR = 1.85). Using the model constructed by these independent variables, positive and negative predictive values and predictive accuracy were 73.3, 70.1 and 71.9% respectively. For the confirmatory group, they were 71.4, 84.6 and 75.3% respectively. The SLC29A1 and IL28B SNPs were also significantly associated with rapid virological response.

CONCLUSIONS

The SNP at the major ribavirin transporter ENT1 gene SLC29A1 was one of significantly independent factors influencing treatment response, although the impact on the prediction was small.

Efficacy and cytotoxicity of a liver-targeted nitric oxide-releasing drug in the treatment of liver injury in mice

AIM: To evaluate the efficacy and cytotoxicity of NO-040527, a new liver-targeted nitric oxide-releasing drug, in the treatment of liver injury induced with carbon tetrachloride, acetaminophen or D-galactosamine in mice.

METHODS: Liver injury was induced in mice by intraperitoneal injection of carbon tetrachloride, acetaminophen or D-galactosamine. NO-040527 was orally administered to animals 1 h before and 12 h after the induction of liver injury. The animals were killed 24 h after drug delivery, and blood samples were taken to determine serum ALT and AST levels using an automatic biochemical analyzer. The cytotoxicity of the targeted conjugate was determined by methyl thiazol tetrazolium (MTT) assay.

RESULTS: NO-040527 could significantly inhibit carbon tetrachloride-induced elevation of ALT and AST in mice (both P < 0.01) in a dose-dependent manner. At the same dose (55 mg/kg), NO-040527 exhibited better efficacy than control drug NCX-1000 (P < 0.05) in lowering carbon tetrachloride-induced elevation of serum ALT and AST levels. Similarly, NO-040527 could also significantly inhibit acetaminophen-induced elevation of ALT and AST (both P < 0.01) though no dose-dependent effect was noted. At the same dose (55 mg/kg), NO-040527 exhibited similar efficacy to NCX-1000 in lowering acetaminophen-induced elevation of serum ALT and AST levels. NO-040527 showed no protective effects against liver injury induced with D-galactosamine. No significant differences were noted in serum ALT and AST levels between untreated mice with D-galactosamine-induced liver injury and those treated with medium- or low-dose NO-040527. However, the levels of serum ALT and AST in mice with D-galactosamine-induced liver injury treated with high-dose NO-040527 was higher than those in untreated ones. NO-040527 at a dose of 500 μmol/L began to show cytotoxicity (cell viability rate: 45.96% ± 29.46%; P = 0.058). Significant cytotoxicity was noted when the dose of NO-040527 rose to 1000 μmol/L (P < 0.005). NO-040527 at 50 and 100 μmol/L could accelerate cell growth (cell viability rate: 137.67% ± 8.47% and 152.65% ± 10.084%, respectively; both P < 0.05).

CONCLUSION: NO-040527 has good protective effects against carbon tetrachloride- or acetaminophen-induced liver injury in mice. NO-040527 is cytotoxic when used at high dose.

Role of ribavirin in HCV treatment response: now and in the future

IMPORTANCE OF THE FIELD

Ribavirin is a broad spectrum antiviral agent that is used with pegylated IFN (Peg-IFN) for HCV treatment. Ribavirin does not significantly reduce HCV viral load when used alone but increases rates of sustained virologic response (SVR) when combined with Peg-IFN. HCV genotype 1 infected patients require higher doses of ribavirin administered for a longer duration of time versus HCV genotypes 2 and 3 patients who respond effectively to Peg-IFN with lower doses of ribavirin and shorter duration of therapy. Higher serum concentrations of ribavirin are associated with higher response rates but also higher rates of hemolytic anemia which is a dose limiting side effect. Alternatives to current therapy are under clinical evaluation.

AREAS COVERED IN THIS REVIEW

Systematic literature review of ribavirin use in HCV patients from 1995 to 2009 was conducted.

WHAT THE READER WILL GAIN

To review the efficacy and safety of ribavirin in current HCV treatment and in new therapies in Phase III clinical trials.

TAKE HOME MESSAGE

Ribavirin is a drug which is essential to produce higher SVR rates both with Peg-IFN and HCV protease inhibitors currently in Phase III clinical trials. Thus, ribavirin is and will remain an important drug to achieving higher SVR rates in HCV infected persons.

Characterization of ribavirin uptake systems in human hepatocytes

BACKGROUND & AIMS

The purpose of this study was to identify the major ribavirin uptake transporter(s) in human hepatocytes and to determine if these previously unidentified transporters are involved in hepatic ribavirin uptake. Furthermore, we aimed to address what causes the difference in uptake levels among human hepatocytes.

METHODS

Profiles of ribavirin uptake and nucleoside transporter mRNA expression in Caucasian hepatocytes (HH268, HH283 and HH291) were characterized by transport assay and reverse transcription-polymerase chain reaction (RT-PCR). The 5'-side of the SLC29A1 gene structure was characterized by determination of transcription start sites and by RT-PCR.

RESULTS

Equilibrative nucleoside transporter 1 (ENT1)-mediated uptake was exclusively involved in ribavirin uptake in HH268 and HH283 and was responsible for the largest ribavirin uptake fraction in HH291. The level of ENT1-mediated uptake in HH291 was higher than that in HH268 and HH283. Characterization of the SLC29A1 gene structure revealed the existence of several ENT1 mRNA isoforms in the human liver, and the levels of four ENT1 mRNA isoforms in HH291 were higher than those in HH268 or HH283. No ENT2-mediated uptake was observed in any hepatocyte lines. Na(+)-dependent uptake was detected only in HH291; however, mRNA levels of concentrative nucleoside transporters (CNTs) were at trace levels in all hepatocyte lines.

CONCLUSIONS

ENT1, but not ENT2 or CNTs, is a major ribavirin uptake transporter in human hepatocytes. The different ENT1-mediated ribavirin uptake levels in different hepatocyte lines are associated with different expression levels of specific isoforms of ENT1 mRNAs. Furthermore, an unidentified Na(+)-dependent ribavirin transport system might exist in human hepatocytes.

Telbivudine preserves T-helper 1 cytokine production and downregulates programmed death ligand 1 in a mouse model of viral hepatitis

Telbivudine is an orally bioavailable L-nucleoside with potent and specific anti-hepatitis B virus activity. The higher rate of hepatitis B e antigen (HBeAg) seroconversion during telbivudine treatment than other potent anti-HBV agents suggests a potential immunomodulatory effect. We sought to determine the effects of telbivudine on the immune system, particularly on cytokine production and T-cell response, using an animal model with mouse hepatitis virus strain 3 (MHV-3)-induced hepatitis. The effects of telbivudine on virus replication and cytokine production were investigated in vitro using MHV-3-infected macrophages, and the effects on T-cell response were investigated in vivo in an MHV-3-induced viral hepatitis model. Telbivudine had no effect on MHV-3 replication in macrophages. However, the production of tumour necrosis factor-alpha and interleukin-12 was increased significantly in MHV-3-induced macrophages treated with telbivudine. In vivo survival was enhanced in telbivudine-treated mice, with marked normalization in clinical conditions and histological lesions. Serum levels of interferon-gamma were elevated significantly after telbivudine treatment in MHV-3-infected C3H mice. In contrast, serum interleukin-4 levels were decreased significantly. Furthermore, telbivudine treatment enhanced the ability of T cells to undergo proliferation and secrete cytokines but did not affect cytotoxicity of infected hepatocytes. Of note, we found that telbivudine treatment suppressed programmed death ligand 1 expression on T cells. The results demonstrate the immunomodulatory properties of telbivudine, independent of its antiviral activity, in a mouse model of MHV-3-induced hepatitis.

Ribavirin mode of action in chronic hepatitis C: from clinical use back to molecular mechanisms

Ribavirin is an old broad-spectrum antiviral that is highly effective when used in combination with interferon-alpha and also as part of triple therapies containing new inhibitors of the hepatitis C virus (HCV) non-structural (NS)3/4 protease or HCV NS5B polymerase for the treatment of patients with chronic hepatitis C. However, the molecular mechanisms by which ribavirin enhances early and sustained virological response rates during interferon-based antiviral HCV therapy are still unknown. Several mechanisms including (i) immunomodulatory properties, (ii) inhibition of the inosine monophosphate dehydrogenase, (iii) direct inhibition of the HCV-encoded NS5B RNA polymerase, (iv) induction of lethal mutagenesis and (v) modulation of interferon-stimulated gene expression are currently proposed. Here, we discuss recent advances from in vitro data and their importance for the situation in patients with chronic hepatitis C. Furthermore, theoretical aspects from mathematical modelling of ribavirin action in chronic hepatitis C are reviewed.

Human uridine-cytidine kinase phosphorylation of ribavirin: a convenient method for activation of ribavirin for conjugation to proteins

Ribavirin is a synthetic nucleoside analog that is used for the treatment of hepatitis C virus (HCV) infection. Its primary toxicity is hemolytic anemia, which sometimes necessitates dose reduction or discontinuation of therapy. Selective delivery of ribavirin into liver cells would be desirable to enhance its antiviral activity and avoid systemic side effects. One approach to liver-specific targeting is conjugation of the ribavirin with asialoglycoprotein that is taken up specifically by liver cells. Human uridine-cytidine kinase-1 (UCK-1) was used for ribavirin phosphorylation to its monophosphate form. 1-Ethyl-3-diisopropylaminocarbodiimide (EDC) was used as a coupling agent. The best results were obtained using direct conjugation protocol with a molar ratio of 6.5 ribavirin monophosphate (RMP) molecules per one asialoorosomucoid (AsOR) molecule. Our findings show that ribavirin is a potential substrate of UCK-1, and RMP formed could be chemically coupled to AsOR to form a conjugate for liver specific targeting.

Antiviral effects of antisense morpholino oligomers in murine coronavirus infection models

The recent emergence of novel pathogenic human and animal coronaviruses has highlighted the need for antiviral therapies that are effective against a spectrum of these viruses. We have used several strains of murine hepatitis virus (MHV) in cell culture and in vivo in mouse models to investigate the antiviral characteristics of peptide-conjugated antisense phosphorodiamidate morpholino oligomers (P-PMOs). Ten P-PMOs directed against various target sites in the viral genome were tested in cell culture, and one of these (5TERM), which was complementary to the 5' terminus of the genomic RNA, was effective against six strains of MHV. Further studies were carried out with various arginine-rich peptides conjugated to the 5TERM PMO sequence in order to evaluate efficacy and toxicity and thereby select candidates for in vivo testing. In uninfected mice, prolonged P-PMO treatment did not result in weight loss or detectable histopathologic changes. 5TERM P-PMO treatment reduced viral titers in target organs and protected mice against virus-induced tissue damage. Prophylactic 5TERM P-PMO treatment decreased the amount of weight loss associated with infection under most experimental conditions. Treatment also prolonged survival in two lethal challenge models. In some cases of high-dose viral inoculation followed by delayed treatment, 5TERM P-PMO treatment was not protective and increased morbidity in the treated group, suggesting that P-PMO may cause toxic effects in diseased mice that were not apparent in the uninfected animals. However, the strong antiviral effect observed suggests that with further development, P-PMO may provide an effective therapeutic approach against a broad range of coronavirus infections.