Use Of Antivirals Research Articles

Oral antiviral treatments for COVID-19: opportunities and challenges

The use of antiviral COVID-19 medications can successfully inhibit SARS-CoV-2 replication and prevent disease progression to a more severe form. However, the timing of antiviral treatment plays a crucial role in this regard. Oral antiviral drugs provide an opportunity to manage SARS-CoV-2 infection without a need for hospital admission, easing the general burden that COVID-19 can have on the healthcare system. This review paper (i) presents the potential pharmaceutical antiviral targets, including various host-based targets and viral-based targets, (ii) characterizes the first-generation anti-SARS-CoV-2 oral drugs (nirmatrelvir/ritonavir and molnupiravir), (iii) summarizes the clinical progress of other oral antivirals for use in COVID-19, (iv) discusses ethical issues in such clinical trials and (v) presents challenges associated with the use of oral antivirals in clinical practice. Oral COVID-19 antivirals represent a part of the strategy to adapt to long-term co-existence with SARS-CoV-2 in a manner that prevents healthcare from being overwhelmed. It is pivotal to ensure equal and fair global access to the currently available oral antivirals and those authorized in the future.

A placental specific miRNA miR-517a-3p exerts anti-human cytomegalovirus activity

Human cytomegalovirus congenital infection is the leading non-genetic cause of fetal malformation in developed countries. There are currently no safe antivirals for use during pregnancy. Placental trophoblast cells specifically secrete exosomes containing miRNA from the chromosome 19 miRNA cluster (C19MC) which confer viral resistance to recipient cells. We show the highly expressed C19MC miRNA miR-517a-3p inhibits HCMV replication and viral protein expression in both fibroblast and trophoblast cell cultures (71.6% and 50.4% inhibition of HCMV DNA at 7 days post infection respectively; p < 0.05). This naturally occurring molecule has potential for opening-up antiviral therapeutic strategies for pregnancy.

An in vitro diagnostic certified point of care single nucleotide test for IL28B polymorphisms.

Numerous genetic polymorphisms have been identified as associated with disease or treatment outcome, but the routine implementation of genotyping into actionable medical care remains limited. Point-of-care (PoC) technologies enable rapid and real-time treatment decisions, with great potential for extending molecular diagnostic approaches to settings with limited medical infrastructure (e.g., CLIA certified diagnostic laboratories). With respect to resource-limited settings, there is a need for simple devices to implement biomarker guided treatment strategies. One relevant example is chronic hepatitis C infection, for which several treatment options are now approved. Single nucleotide polymorphisms (SNPs) in the IL-28B / IFNL3 locus have been well described to predict both spontaneous clearance and response to interferon based therapies. We utilized the Genedrive® platform to develop an assay for the SNP rs12979860 variants (CC, CT and TT). The assay utilizes a hybrid thermal engine, permitting rapid heating and cooling, enabling an amplification based assay with genetic variants reported using endpoint differential melting cure analysis in less than 60 minutes. We validated this assay using non-invasive buccal swab sampling in a prospective study of 246 chronic HCV patients, achieving 100% sensitivity and 100% specificity (95% exact CI: 98.8–100%)) in 50 minutes as compared to conventional lab based PCR testing. Our results provide proof of concept that precision medicine is feasible in resource-limited settings, offering the first CE-IVD (in vitro diagnostics) validated PoC SNP test. We propose that IL-28B genotyping may be useful for directing patients towards lower cost therapies, and rationing use of costly direct antivirals for use in those individuals showing genetic risk.

Antiviral screening identifies adenosine analogs targeting the endogenous dsRNA Leishmania RNA virus 1 (LRV1) pathogenicity factor

The endogenous double-stranded RNA (dsRNA) virus Leishmaniavirus (LRV1) has been implicated as a pathogenicity factor for leishmaniasis in rodent models and human disease, and associated with drug-treatment failures in Leishmania braziliensis and Leishmania guyanensis infections. Thus, methods targeting LRV1 could have therapeutic benefit. Here we screened a panel of antivirals for parasite and LRV1 inhibition, focusing on nucleoside analogs to capitalize on the highly active salvage pathways of Leishmania, which are purine auxotrophs. Applying a capsid flow cytometry assay, we identified two 2'-C-methyladenosine analogs showing selective inhibition of LRV1. Treatment resulted in loss of LRV1 with first-order kinetics, as expected for random virus segregation, and elimination within six cell doublings, consistent with a measured LRV1 copy number of about 15. Viral loss was specific to antiviral nucleoside treatment and not induced by growth inhibitors, in contrast to fungal dsRNA viruses. Comparisons of drug-treated LRV1+ and LRV1- lines recapitulated LRV1-dependent pathology and parasite replication in mouse infections, and cytokine secretion in macrophage infections. Agents targeting Totiviridae have not been described previously, nor are there many examples of inhibitors acting against dsRNA viruses more generally. The compounds identified here provide a key proof-of-principle in support of further studies identifying efficacious antivirals for use in in vivo studies of LRV1-mediated virulence.

Antiviral Combination Approach as a Perspective to Combat Enterovirus Infections.

Human enteroviruses distributed worldwide are causative agents of a broad spectrum of diseases with extremely high morbidity, including a series of severe illnesses of the central nervous system, heart, endocrine pancreas, skeleton muscles, etc., as well as the common cold contributing to the development of chronic respiratory diseases, including the chronic obstructive pulmonary disease. The above mentioned diseases along with the significantly high morbidity and mortality in children, as well as in the high-risk populations (immunodeficiencies, neonates) definitely formulate the chemotherapy as the main tool for the control of enterovirus infections. At present, clinically effective antivirals for use in the treatment of enteroviral infection do not exist, in spite of the large amount of work carried out in this field. The main reason for this is the development of drug resistance. We studied the process of development of resistance to the strongest inhibitors of enteroviruses, WIN compounds (VP1 protein hydrophobic pocket blockers), especially in the models in vivo, Coxsackievirus B (CV-B) infections in mice. We introduced the tracing of a panel of phenotypic markers (MIC50 value, plaque shape and size, stability at 50℃, pathogenicity in mice) for characterization of the drug-mutants (resistant and dependent) as a very important stage in the study of enterovirus inhibitors. Moreover, as a result of VP1 RNA sequence analysis performed on the model of disoxaril mutants of CVB1, we determined the molecular basis of the drug-resistance. The monotherapy courses were the only approach used till now. For the first time in the research for anti-enterovirus antivirals our team introduced the testing of combination effect of the selective inhibitors of enterovirus replication with different mode of action. This study resulted in the selection of a number of very effective in vitro double combinations with synergistic effect and a broad spectrum of sensitive enteroviruses. The most prospective attainment in our examinations in this field was the development of a novel scheme for the combined application of anti-enteroviral substances in coxsackievirus B1 neuroinfection in newborn mice. It consisted of a consecutive, alternating and non simultaneous administration of the substances in the combination. The triple combination - disoxaril- guanidine. HCl-oxoglaucine (DGO) showed a high effectiveness expressed in the marked reduction of the mortality rate in infected mice as compared both to the placebo group, and to the partner compounds used alone every day, and to the same combination applied simultaneously every day. The studies of the drug sensitivity of viral brain isolates from mice treated with DGO combination showed not only preserved, but even increased sensitivity to the drugs included in the combination. Obviously, the consecutive alternating administration of anti-enteroviral substances hinders the occurrence of drug-resistance in the course of the experimental enteroviral infections in mice.

Effect of consecutive alternating administration (CAA) of a triple anti-enteroviral combination on Coxsackievirus B1 neuroinfection in mice

Currently, clinically effective antivirals for use in the treatment of enteroviral (EV) infections do not exist. The main reason is the development of drug resistance, the principle obstacle in the development of EV infection chemotherapy, based til now on monotherapy. The most important achievement of our previous studies was the development of a novel scheme for in vivo application of a triple combination of EV inhibitors with different modes of action against Coxsackievirus B (CVB) infections in mice. It consists of consecutive alternating administration (CAA) of the substances in the combination. Here, we tested the effect of the triple combination pleconaril, guanidine-HCl, and oxoglaucine (PGO) via CAA in newborn mice infected with a neurotropic strain of CVB1 (20 LD50 per mouse). This combination manifested a considerable protective effect with pleconaril doses of 25–200mg/kg: it decreased mortality rate (protection index, PI, between 31.3% and 67.7%) and increased mean survival time (MST) by 4–6days. Pleconaril monotherapy demonstrated activity similar to that of PGO via CAA, as measured by PI values, but MST values were slightly lower. However, it also greatly suppressed growth of infected suckling mice, especially at 200mg/kg. This toxic effect was avoided with CAA of PGO at pleconaril doses of 25–100mg/kg. Pleconaril monotherapy administered every 3days was ineffective. The PGO with CAA treatment course decreased infectious virus content, whereas pleconaril monotherapy did not. Analysis of drug-sensitivity in brain samples from CVB1 infected mice, based on IC50 (50% inhibitory concentration) values from cell culture experiments, showed that the CAA course counteracted the development of drug resistance to pleconaril and oxoglaucine in the triple PGO combination and increased drug sensitivity. In contrast, pleconaril and oxoglaucine monotherapies resulted in drug resistance. This data clearly proves the effectiveness of the proposed novel approach—the CAA treatment course—for combined application of EV replication inhibitors.

Potential applications for antiviral therapy and prophylaxis in bovine medicine.

Viral disease is one of the major causes of financial loss and animal suffering in today's cattle industry. Increases in global commerce and average herd size, urbanization, vertical integration within the industry and alterations in global climate patterns have allowed the spread of pathogenic viruses, or the introduction of new viral species, into regions previously free of such pathogens, creating the potential for widespread morbidity and mortality in naïve cattle populations. Despite this, no antiviral products are currently commercially licensed for use in bovine medicine, although significant progress has been made in the development of antivirals for use against bovine viral diarrhea virus (BVDV), foot and mouth disease virus (FMDV) and bovine herpesvirus (BHV). BVDV is extensively studied as a model virus for human antiviral studies. Consequently, many compounds with efficacy have been identified and a few have been successfully used to prevent infection in vivo although commercial development is still lacking. FMDV is also the subject of extensive antiviral testing due to the importance of outbreak containment for maintenance of export markets. Thirdly, BHV presents an attractive target for antiviral development due to its worldwide presence. Antiviral studies for other bovine viral pathogens are largely limited to preliminary studies. This review summarizes the current state of knowledge of antiviral compounds against several key bovine pathogens and the potential for commercial antiviral applications in the prevention and control of several selected bovine diseases.

Minimum Costs for Producing Hepatitis C Direct-Acting Antivirals for Use in Large-Scale Treatment Access Programs in Developing Countries

Several combinations of 2 or 3 direct-acting antivirals (DAAs) can cure hepatitis C virus (HCV) in the majority of treatment-naive patients. DAAs for HCV infection have similar mechanisms of action and chemical structures to antiretrovirals for human immunodeficiency virus (HIV) infection. Generic antiretrovirals are currently manufactured at very low prices, to treat 10 million people with HIV/AIDS in developing countries. Four HCV DAAs, currently either in phase 3 development or recent approval (daclatasvir, sofosbuvir, simeprevir, faldaprevir), and ribavirin were classified by chemical structure, molecular weight, total daily dose, and complexity of synthesis. The likely range of manufacturing costs per gram of DAA were then projected as formulated product cost, based upon treating a minimum of 1 million patients annually (to arrive at volume demand) combined with an analysis of the complexity of synthesis and a 40% margin for formulation. Projections were then compared with actual costs of antiretrovirals with similar structures. Minimum manufacturing costs of antiretrovirals were US$0.2-$2.1 per gram. The complexity of chemical synthesis for HCV DAAs was ranked from lowest to highest: ribavirin, daclatasvir, sofosbuvir, faldaprevir, and simeprevir. Predicted manufacturing costs (US dollars) for 12-week courses of HCV DAAs were $21-$63 for ribavirin, $10-$30 for daclatasvir, $68-$136 for sofosbuvir, $100-$210 for faldaprevir, and $130-$270 for simeprevir. Within the next 15 years, large-scale manufacture of 2 or 3 drug combinations of HCV DAAs is feasible, with minimum target prices of $100-$250 per 12-week treatment course. These low prices could make widespread access to HCV treatment in low- and middle-income countries a realistic goal.

Preparing for the Next Influenza Pandemic

There are 3 requirements for an influenza virus to cause a pandemic. It must be antigenically novel, cause severe disease, and transmit easily from human to human. Highly pathogenic avian influenza viruses of the H5N1 subtype currently circulating in bird populations in Asia, Africa, and Europe have met 2 of these criteria, and there is significant concern that these viruses will be the cause of the next pandemic. International efforts to prepare for a possible pandemic are underway. Priorities for pandemic planning include surveillance of influenza viruses in wild bird populations and at the avian-human interface, research into factors affecting the pathogenicity of these strains, stockpiling effective antivirals for use as a stopgap until an appropriate vaccine can be developed and distributed, and gaining an improved understanding of the utility of nonpharmaceutical interventions to slow or prevent the spread of these viruses within humans. Although considerable progress has been made in recent years towards readying the world for such an event, there is more work to be done. Physicians and hospitals can begin by educating themselves on the problem and developing a pandemic plan for their own practice or organization.

Replication of West Nile virus in equine peripheral blood mononuclear cells

A cell model of primary monocytes and other mononuclear cells isolated from equine blood was used to study the kinetics of West Nile virus (WNV) replication in a natural host. West Nile virus has emerged on the North American continent as a significant cause of morbidity and mortality in a wide range of avian and mammalian species. While other flaviviruses are known to infect monocytes and lymphocytes, the ability of WNV to productively replicate in specific immune cells of peripheral blood has not been assessed. In this study, enriched populations of monocytes and lymphocytes as well as purified monocytes, CD4+, CD8+ and B lymphocytes were obtained from equine blood. Productive WNV replication was demonstrated by viral growth curves, quantitative RT-PCR for WNV RNA, and indirect immunofluorescence detection of a non-structural WNV protein. Enriched and purified monocytes consistently supported productive viral replication in blood from nine of nine horses tested while a minor subset of CD4+ lymphocytes supported productive replication in cells from three of the nine horses tested. Peak viral titers of 3.2–6.6 log 10 PFU/ml were reached at 6 days post-inoculation (p.i.) and titers were maintained through 10–15 days p.i. Activation of monocytes with bacterial lipopolysaccharide, which resulted in activation of nuclear transcription factor κB (NF-κB) plus elevation of nitric oxide and type I interferon levels, reduced or eliminated WNV replication. These results suggest that immune cells of the peripheral blood may serve as target cells for initial replication of WNV and may play a role in subsequent viral dissemination. Furthermore, primary equine immune cell cultures represent a potentially useful model of a natural WNV host when testing compounds such as antivirals for use in WNV treatment.