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Potential benefits of sequential inhibitor-mutagen treatments of RNA virus infections.

ABSTRACT: Lethal mutagenesis is an antiviral strategy consisting of virus extinction associated with enhanced mutagenesis. The use of non-mutagenic antiviral inhibitors has faced the problem of selection of inhibitor-resistant virus mutants. Quasispecies dynamics predicts, and clinical results have confirmed, that combination therapy has an advantage over monotherapy to delay or prevent selection of inhibitor-escape mutants. Using ribavirin-mediated mutagenesis of foot-and-mouth disease virus (FMDV), here we show that, contrary to expectations, sequential administration of the antiviral inhibitor guanidine (GU) first, followed by ribavirin, is more effective than combination therapy with the two drugs, or than either drug used individually. Coelectroporation experiments suggest that limited inhibition of replication of interfering mutants by GU may contribute to the benefits of the sequential treatment. In lethal mutagenesis, a sequential inhibitor-mutagen treatment can be more effective than the corresponding combination treatment to drive a virus towards extinction. Such an advantage is also supported by a theoretical model for the evolution of a viral population under the action of increased mutagenesis in the presence of an inhibitor of viral replication. The model suggests that benefits of the sequential treatment are due to the involvement of a mutagenic agent, and to competition for susceptible cells exerted by the mutant spectrum. The results may impact lethal mutagenesis-based protocols, as well as current antiviral therapies involving ribavirin.

SUBMITTER: Perales C

PROVIDER: S-EPMC2771356 | biostudies-other | 2009 Nov

REPOSITORIES: biostudies-other

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Lycorine, a non-nucleoside RNA dependent RNA polymerase inhibitor, as potential treatment for emerging coronavirus infections.

Project description:BackgroundHighly effective novel treatments need to be developed to suppress emerging coronavirus (CoV) infections such as COVID-19. The RNA dependent RNA polymerase (RdRp) among the viral proteins is known as an effective antiviral target. Lycorine is a phenanthridine Amaryllidaceae alkaloid isolated from the bulbs of Lycoris radiata (L'Hér.) Herb. and has various pharmacological bioactivities including antiviral function.PurposeWe investigated the direct-inhibiting action of lycorine on CoV's RdRp, as potential treatment for emerging CoV infections.MethodsWe examined the inhibitory effect of lycorine on MERS-CoV, SARS-CoV, and SARS-CoV-2 infections, and then quantitatively measured the inhibitory effect of lycorine on MERS-CoV RdRp activity using a cell-based reporter assay. Finally, we performed the docking simulation with lycorine and SARS-CoV-2 RdRp.ResultsLycorine efficiently inhibited these CoVs with IC50 values of 2.123 ± 0.053, 1.021 ± 0.025, and 0.878 ± 0.022 μM, respectively, comparable with anti-CoV effects of remdesivir. Lycorine directly inhibited MERS-CoV RdRp activity with an IC50 of 1.406 ± 0.260 μM, compared with remdesivir's IC50 value of 6.335 ± 0.731 μM. In addition, docking simulation showed that lycorine interacts with SARS-CoV-2 RdRp at the Asp623, Asn691, and Ser759 residues through hydrogen bonding, at which the binding affinities of lycorine (-6.2 kcal/mol) were higher than those of remdesivir (-4.7 kcal/mol).ConclusionsLycorine is a potent non-nucleoside direct-acting antiviral against emerging coronavirus infections and acts by inhibiting viral RdRp activity; therefore, lycorine may be a candidate against the current COVID-19 pandemic.

| S-EPMC7738280 | biostudies-literature

Sequential Chikungunya and Zika Virus Infections in a Traveler from Honduras.

Project description:Zika virus (ZIKV) and chikungunya virus (CHIKV) are currently circulating in overlapping areas in the American continents and may both be transmitted by Aedes spp. mosquitoes. The first documented case, to the authors' knowledge, of sequential CHIKV and ZIKV infections diagnosed in a nonendemic area in a returning traveler is reported. The implications for heightened clinical surveillance for these infections and specific patient recommendations are emphasized.

| S-EPMC5094234 | biostudies-literature

Sequential seasonal H1N1 influenza virus infections protect ferrets against novel 2009 H1N1 influenza virus.

Project description:Individuals <60 years of age had the lowest incidence of infection, with ~25% of these people having preexisting, cross-reactive antibodies to novel 2009 H1N1 influenza. Many people >60 years old also had preexisting antibodies to novel H1N1. These observations are puzzling because the seasonal H1N1 viruses circulating during the last 60 years were not antigenically similar to novel H1N1. We therefore hypothesized that a sequence of exposures to antigenically different seasonal H1N1 viruses can elicit an antibody response that protects against novel 2009 H1N1. Ferrets were preinfected with seasonal H1N1 viruses and assessed for cross-reactive antibodies to novel H1N1. Serum from infected ferrets was assayed for cross-reactivity to both seasonal and novel 2009 H1N1 strains. These results were compared to those of ferrets that were sequentially infected with H1N1 viruses isolated prior to 1957 or more-recently isolated viruses. Following seroconversion, ferrets were challenged with novel H1N1 influenza virus and assessed for viral titers in the nasal wash, morbidity, and mortality. There was no hemagglutination inhibition (HAI) cross-reactivity in ferrets infected with any single seasonal H1N1 influenza viruses, with limited protection to challenge. However, sequential H1N1 influenza infections reduced the incidence of disease and elicited cross-reactive antibodies to novel H1N1 isolates. The amount and duration of virus shedding and the frequency of transmission following novel H1N1 challenge were reduced. Exposure to multiple seasonal H1N1 influenza viruses, and not to any single H1N1 influenza virus, elicits a breadth of antibodies that neutralize novel H1N1 even though the host was never exposed to the novel H1N1 influenza viruses.

| S-EPMC3554183 | biostudies-literature

Evolutionary potential of an RNA virus.

Project description:RNA viruses are remarkably adaptable to changing environments. This is medically important because it enables pathogenic viruses to escape the immune response and chemotherapy and is of considerable theoretical interest since it allows the investigation of evolutionary processes within convenient time scales. A number of earlier studies have addressed the dynamics of adapting RNA virus populations. However, it has been difficult to monitor the trajectory of molecular changes in RNA genomes in response to selective pressures. To address the problem, we developed a novel in vitro evolution system based on a recombinant double-stranded RNA bacteriophage, phi 6, containing a beta-lactamase (bla) gene marker. Carrier-state bacterial cells are resistant to ampicillin, and after several passages, they become resistant to high concentrations of another beta-lactam antibiotic, cefotaxime, due to mutations in the virus-borne bla gene. We monitored the changes in bla cDNAs induced by cefotaxime selection and observed an initial explosion in sequence variants with multiple mutations throughout the gene. After four passages, a stable, homogeneous population of bla sequences containing three specific nonsynonymous mutations was established. Of these, two mutations (E104K and G238S) have been previously reported for beta-lactamases from cefotaxime-resistant bacterial isolates. These results extend our understanding of the molecular mechanisms of viral adaptation and also demonstrate the possibility of using an RNA virus as a vehicle for directed evolution of heterologous proteins.

| S-EPMC369421 | biostudies-other

The cost-effectiveness, health benefits, and financial costs of new antiviral treatments for hepatitis C virus.

Project description:BackgroundNew hepatitis C virus (HCV) treatments deliver higher cure rates with fewer contraindications, increasing demand for treatment and healthcare costs. The cost-effectiveness of new treatments is unknown.MethodsWe conducted a microsimulation of guideline testing followed by alternative treatment regimens for HCV among the US population aged 20 and older to estimate cases identified, treated, sustained viral response, deaths, medical costs, quality-adjusted life-years (QALYs), and the incremental cost-effectiveness ratio (ICER) of different treatment options expressed as discounted lifetime costs and benefits from the healthcare perspective.ResultsCompared to treatment with pegylated interferon and ribavirin (PR), and a protease inhibitor for HCV genotype (G) 1 and PR alone for G2/3, treatment with PR and Sofosbuvir (PRS) for G1/4 and treatment with Sofosbuvir and ribavirin (SR) for G2/3 increased QALYs by 555 226, reduced deaths by 80 682, and increased costs by $26.2 billion at an ICER of $47 304 per QALY gained. As compared to PRS/SR, treating with an all oral regimen of Sofosbuvir and Simeprevir (SS) for G1/4 and SR for G2/3, increased QALYs by 1 110 451 and reduced deaths by an additional 164 540 at an incremental cost of $80.1 billion and an ICER of $72 169. In sensitivity analysis, where treatment with SS effectiveness was set to the list price of Viekira Pak and then Harvoni, treatment cost $24 921 and $25 405 per QALY gained as compared to PRS/SR.ConclusionsNew treatments are cost-effectiveness per person treated, but pent-up demand for treatment may create challenges for financing.

| S-EPMC5759765 | biostudies-literature

Patients' willingness to accept the risks and benefits of new treatments for chronic hepatitis C virus infection.

Project description:BackgroundSome patients with chronic hepatitis C virus (HCV) infection forego treatment due to concerns about treatment efficacy, treatment duration, and side effects.ObjectiveThe purpose of this study was to quantify patient preferences among possible outcomes associated with new, direct-acting antiviral agents (DAAs) for the treatment of HCV infection and determine which treatment features are most important to patients in making treatment decisions.MethodsAdult participants with a self-reported physician diagnosis of HCV infection in five countries completed a web-enabled, choice-format conjoint analysis survey. The survey presented participants with 20 treatment-choice questions. Each treatment-choice question included a pair of hypothetical treatment profiles with varying levels of six attributes: treatment duration; chance of getting rid of the virus completely (i.e. likelihood of a sustained virologic response [SVR]); weeks on an additional, third medicine (i.e. a DAA); risk of a severe rash; risk of severe anemia; and number of times a day the third medicine is taken. Treatment-choice questions were based on a pre-determined experimental design with known statistical properties. Random-parameters logit was used to estimate preference weights for all attribute levels and the mean relative importance of each attribute.Results284 participants completed the survey. Likelihood of an SVR was the most important outcome to participants, followed by severe anemia risk, severe rash risk, therapy type (a combination of total weeks of treatment and weeks on the third medicine), and dosing of the third medicine. Controlling for other factors, preferences were similar across all therapy types examined.ConclusionPatients with HCV infection indicate a willingness to accept an increased risk of side effects for sufficient improvement in the likelihood of treatment response.

| S-EPMC3714139 | biostudies-literature

Patterns of RNA Editing in Newcastle Disease Virus Infections.

Project description:The expression of accessory non-structural proteins V and W in Newcastle disease virus (NDV) infections depends on RNA editing. These proteins are derived from frameshifts of the sequence coding for the P protein via co-transcriptional insertion of one or two guanines in the mRNA. However, a larger number of guanines can be inserted with lower frequencies. We analysed data from deep RNA sequencing of samples from in vitro and in vivo NDV infections to uncover the patterns of mRNA editing in NDV. The distribution of insertions is well described by a simple Markov model of polymerase stuttering, providing strong quantitative confirmation of the molecular process hypothesised by Kolakofsky and collaborators three decades ago. Our results suggest that the probability that the NDV polymerase would stutter is about 0.45 initially, and 0.3 for further subsequent insertions. The latter probability is approximately independent of the number of previous insertions, the host cell, and viral strain. However, in LaSota infections, we also observe deviations from the predicted V/W ratio of about 3:1 according to this model, which could be attributed to deviations from this stuttering model or to further mechanisms downregulating the abundance of W protein.

| S-EPMC7693698 | biostudies-literature

Nucleosides for the treatment of respiratory RNA virus infections.

Project description:Influenza virus, respiratory syncytial virus, human metapneumovirus, parainfluenza virus, coronaviruses, and rhinoviruses are among the most common viruses causing mild seasonal colds. These RNA viruses can also cause lower respiratory tract infections leading to bronchiolitis and pneumonia. Young children, the elderly, and patients with compromised cardiac, pulmonary, or immune systems are at greatest risk for serious disease associated with these RNA virus respiratory infections. In addition, swine and avian influenza viruses, together with severe acute respiratory syndrome-associated and Middle Eastern respiratory syndrome coronaviruses, represent significant pandemic threats to the general population. In this review, we describe the current medical need resulting from respiratory infections caused by RNA viruses, which justifies drug discovery efforts to identify new therapeutic agents. The RNA polymerase of respiratory viruses represents an attractive target for nucleoside and nucleotide analogs acting as inhibitors of RNA chain synthesis. Here, we present the molecular, biochemical, and structural fundamentals of the polymerase of the four major families of RNA respiratory viruses: Orthomyxoviridae, Pneumoviridae/Paramyxoviridae, Coronaviridae, and Picornaviridae. We summarize past and current efforts to develop nucleoside and nucleotide analogs as antiviral agents against respiratory virus infections. This includes molecules with very broad antiviral spectrum such as ribavirin and T-705 (favipiravir), and others targeting more specifically one or a few virus families. Recent advances in our understanding of the structure(s) and function(s) of respiratory virus polymerases will likely support the discovery and development of novel nucleoside analogs.

| S-EPMC5890544 | biostudies-literature

Sequential packaging of RNA genomic segments during the assembly of Bluetongue virus.

Project description:Bluetongue virus (BTV), a member of the Orbivirus genus within the Reoviridae family, has a genome of 10 double-stranded RNA segments, with three distinct size classes. Although the packaging of the viral genome is evidently highly specific such that every virus particle contains a set of 10 RNA segments, the order and mechanism of packaging are not understood. In this study we have combined the use of a cell-free in vitro assembly system with a novel RNA-RNA interaction assay to investigate the mechanism of single-stranded (ss) RNAs packaging during nascent capsid assembly. Exclusion of single or multiple ssRNA segments in the packaging reaction or their addition in different order significantly altered the outcome and suggested a particular role for the smallest segment, S10. Our data suggests that genome packaging probably initiates with the smallest segment which triggers RNA-RNA interaction with other smaller segments forming a complex network. Subsequently, the medium to larger size ssRNAs are recruited until the complete genome is packaging into the capsid. The untranslated regions of the smallest RNA segment, S10, is critical for the instigation of this process. We suggest that the selective packaging observed in BTV may also apply to other members of the Reoviridae family.

| S-EPMC4267631 | biostudies-literature

Novel nonnucleoside inhibitor of hepatitis C virus RNA-dependent RNA polymerase.

Project description:A novel nonnucleoside inhibitor of hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp), [(1R)-5-cyano-8-methyl-1-propyl-1,3,4,9-tetrahydropyano[3,4-b]indol-1-yl] acetic acid (HCV-371), was discovered through high-throughput screening followed by chemical optimization. HCV-371 displayed broad inhibitory activities against the NS5B RdRp enzyme, with 50% inhibitory concentrations ranging from 0.3 to 1.8 microM for 90% of the isolates derived from HCV genotypes 1a, 1b, and 3a. HCV-371 showed no inhibitory activity against a panel of human polymerases, including mitochondrial DNA polymerase gamma, and other unrelated viral polymerases, demonstrating its specificity for the HCV polymerase. A single administration of HCV-371 to cells containing the HCV subgenomic replicon for 3 days resulted in a dose-dependent reduction of the steady-state levels of viral RNA and protein. Multiple treatments with HCV-371 for 16 days led to a >3-log10 reduction in the HCV RNA level. In comparison, multiple treatments with a similar inhibitory dose of alpha interferon resulted in a 2-log10 reduction of the viral RNA level. In addition, treatment of cells with a combination of HCV-371 and pegylated alpha interferon resulted in an additive antiviral activity. Within the effective antiviral concentrations of HCV-371, there was no effect on cell viability and metabolism. The intracellular antiviral specificity of HCV-371 was demonstrated by its lack of activity in cells infected with several DNA or RNA viruses. Fluorescence binding studies show that HCV-371 binds the NS5B with an apparent dissociation constant of 150 nM, leading to high selectivity and lack of cytotoxicity in the antiviral assays.

| S-EPMC529219 | biostudies-literature

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