Potent small molecule inhibitors against the 3C protease of foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is one of the most devastating diseases of livestock which can cause significant economic losses, especially when introduced to FMD-free countries. FMD virus (FMDV) belongs to the family Picornaviridae and is antigenically heterogeneous with seven established serotypes. The prevailing preventive and control strategies are limited to restriction of animal movement and elimination of infected or exposed animals, which can be potentially combined with vaccination. However, FMD vaccination has limitations including delayed protection and lack of cross-protection against different serotypes. Recently, antiviral drug use for FMD outbreaks has increasingly been recognized as a potential tool to augment the existing early response strategies, but limited research has been reported on potential antiviral compounds for FMDV. FMDV 3C protease (3Cpro) cleaves the viral-encoded polyprotein into mature and functional proteins during viral replication. The essential role of viral 3Cpro in viral replication and the high conservation of 3Cpro among different FMDV serotypes make it an excellent target for antiviral drug development. We have previously reported multiple series of inhibitors against picornavirus 3Cpro or 3C-like proteases (3CLpros) encoded by coronaviruses or caliciviruses. In this study, we conducted structure-activity relationship studies for our in-house focused compound library containing 3Cpro or 3CLpro inhibitors against FMDV 3Cpro using enzyme and cell-based assays. Herein, we report the discovery of aldehyde and α-ketoamide inhibitors of FMDV 3Cpro with high potency. These data inform future preclinical studies that are related to the advancement of these compounds further along the drug development pathway.IMPORTANCEFood-and-mouth disease (FMD) virus (FMDV) causes devastating disease in cloven-hoofed animals with a significant economic impact. Emergency response to FMD outbreaks to limit FMD spread is critical, and the use of antivirals may overcome the limitations of existing control measures by providing immediate protection for susceptible animals. FMDV encodes 3C protease (3Cpro), which is essential for virus replication and an attractive target for antiviral drug discovery. Here, we report a structure-activity relationship study on multiple series of protease inhibitors and identified potent inhibitors of FMDV 3Cpro. Our results suggest that these compounds have the potential for further development as FMD antivirals.

Clinical features of adverse events associated with Xiyanping-Ribavirin combination: A systematic review

ETHNOPHARMACOLOGICAL RELEVANCE

In China, Xiyanping (XYP) has been widely used in combination with Ribavirin (RB) for the treatment of infectious diseases. It has been found that this combination may change the severity of XYP-associated adverse events (AEs).

AIM

To provide a comprehensive review about the clinal features of AEs of XYP-RB combination from randomized controlled trials, cohort studies, case-control studies, case reports, case series, and data from the National Adverse Drug Reaction Monitoring Information System (NADRMIS).

MATERIALS AND METHODS

Seven electronic databases were searched in March 2021. Articles on AEs associated with XYP published from January 2004 to December 2020 in the NADRMIS were included. Data on the incidence of AEs, distribution of AEs, occurrence time of AEs, type and possible signal of AEs, primary diseases, allergic history, family history of allergies, dosage, and combination interval were extracted.

RESULTS

We included 228 cases of AEs with XYP-RB combination (63 cases from randomized controlled trials, 1 from a cohort study, and 164 from the NADRMIS). The most common primary disease was hand-foot-and-mouth disease. The main age distribution was 0-6 years (118 cases, 72%) and 8 cases (6.8%) experienced serious AEs. The combination group showed a significant reduction than the RB group in the incidence of AEs in those with hand-foot-and-mouth disease (risk ratio = 0.54, 95% confidence interval = 0.38-0.78, P = 0.0008) and children with viral pneumonia (risk ratio = 0.36, 95% confidence interval = 0.14-0.95, P = 0.04). Allergic history and infusion interval were not described in the randomized controlled trials. AEs were reported in 57.9% of cases in the first combination (XYP-RB were combined for the first time) (NADRMIS), 56.4% of which were skin and appendage reactions, and the risk signal of skin and appendage reactions was a maximum (Information Component = 6.21).

CONCLUSION

The major AE associated with XYP-RB combination was skin and appendage reactions. Most of the combination AEs were pseudo-allergic reactions. These findings suggest that we should increase awareness about the safety of XYP-RB combination treatment and standardize medication protocol, especially for children. Unless absolutely necessary, children should avoid combination therapy. More rigorous high-quality studies are needed to obtain more evidence.

Efficacy and application of a novel topical anaesthetic wound formulation for treating cattle with Foot-and-Mouth disease: A field trial in Cameroon

Recently, a wound dressing formulation, (Tri-Solfen®, Medical Ethics Pty Ltd, Australia; TS) registered for use in ruminant husbandry in Australia, was registered for Foot-and-Mouth Disease (FMD) therapy in large ruminants in Laos, following clinical observations of improved welfare and healing following treatment of FMD lesions. In November 2019, an FMD outbreak in Cameroon provided an opportunity for a field trial, comparing clinical responses and recoveries to treatments on a sample of cattle (n = 36) comprising three equal groups of animals (n = 12), comparing responses to three treatments: (i) the application to lesions of TS, (ii) the administration of parenteral oxytetraycline commonly used for FMD in Cameroon; and (iii) an untreated control group (C). Appetite scores, lesion healing scores, and changes in dimensions of lesions, were recorded over a 15-day study period. Cattle treated with TS achieved both superior appetite and lesion healing scores with more rapid reduction in dimensions of lesions than other groups. Farmer observations indicated the TS treatment group had a more rapid return to eating with cessation of excessive salivation, and more rapid return of mobility (walking) with absence of overt lameness. The findings indicate that although mortality is usually low in FMD outbreaks, the disease is a debilitating and painful disorder with negative animal welfare impacts that should be addressed. All farmers expressed their desire that the product be made available for use in their region and modelling indicates that TS therapy imposes no additional financial burden on farmers, with the treatment likely to be provided at a similar or reduced cost to current treatment choices. As use of antibiotics for treatment of a viral disease potentially increases pressures for development of antimicrobial resistance and residues in the food chain, TS as an alternative non-antimicrobial therapy should be promoted for wider use in FMD outbreaks.

A Novel Plasmid DNA-Based Foot and Mouth Disease Virus Minigenome for Intracytoplasmic mRNA Production

Picornaviruses are non-enveloped, single-stranded RNA viruses that cause highly contagious diseases, such as polio and hand, foot-and-mouth disease (HFMD) in human, and foot-and-mouth disease (FMD) in animals. Reverse genetics and minigenome of picornaviruses mainly depend on in vitro transcription and RNA transfection; however, this approach is inefficient due to the rapid degradation of RNA template. Although DNA-based reverse genetics systems driven by mammalian RNA polymerase I and/or II promoters display the advantage of rescuing the engineered FMDV, the enzymatic functions are restricted in the nuclear compartment. To overcome these limitations, we successfully established a novel DNA-based vector, namely pKLS3, an FMDV minigenome containing the minimum cis-acting elements of FMDV essential for intracytoplasmic transcription and translation of a foreign gene. A combination of pKLS3 minigenome and the helper plasmids yielded the efficient production of uncapped-green florescent protein (GFP) mRNA visualized in the transfected cells. We have demonstrated the application of the pKLS3 for cell-based antiviral drug screening. Not only is the DNA-based FMDV minigenome system useful for the FMDV research and development but it could be implemented for generating other picornavirus minigenomes. Additionally, the prospective applications of this viral minigenome system as a vector for DNA and mRNA vaccines are also discussed.

Beneficial effects of antioxidants in improving health conditions of sheep infected with foot-and-mouth disease

The effect of multinutrient antioxidant treatment on sheep naturally infected with FMD virus was investigated in terms of general health conditions, serum proteins profile, and antioxidant/oxidant parameters. Twenty diseased sheep were divided into 4 equal groups (n = 5) and underwent certain therapeutic protocols for 8 weeks as follows: GI, infected not treated group; GII, infected and treated with the ideal and usual line of treatment against FMD virus infection; GIII, infected animals supplemented orally zinc methionine at a dose of 5 g/head/day and vitamin E with selenium-enriched yeast at the same dose level; GIV, infected animals received both the ideal treatment and antioxidants. The animals under experiment were clinically evaluated. Blood samples were obtained for the comet assay and biochemical examination at zero time and at the 8th week after treatment. Results revealed that DNA damage reduced in both GIII and GIV groups which received antioxidants. In the GI group, the activity of SOD and GPx and the level of total antioxidant capacity (TAC) markedly decreased. However, in both GIII and GIV groups treated with multinutrient antioxidants, GPx and TAC values significantly increased after treatment in comparison with the values of the same groups before treatment. After treatment with multinutrient antioxidants, α1-, β-, and γ-globulins levels markedly increased in GII and GIII groups while α2-globulin level decreased. The improvement in healing of clinical signs and general health conditions was clear in the GIV group. Finally, FMD infection in sheep was found to be associated with oxidative stress. The use of antioxidants as therapeutic approaches recovers and improves general health conditions and performance of affected animals.

In Vitro and in Vivo Antiviral Activity of Mizoribine Against Foot-And-Mouth Disease Virus

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hoofed animals, which has significant economic consequences in affected countries. As the currently available vaccines against FMD provide no protection until 4–7 days post-vaccination, the only alternative method to control the spread of FMD virus (FMDV) during outbreaks is the application of antiviral agents. Hence, it is important to identify effective antiviral agents against FMDV infection. In this study, we found that mizoribine has potent antiviral activity against FMDV replication in IBRS-2 cells. A time-of-drug-addition assay demonstrated that mizoribine functions at the early stage of replication. Moreover, mizoribine also showed antiviral effect on FMDV in vivo. In summary, these results revealed that mizoribine could be a potential antiviral drug against FMDV.

Evaluation of cytotoxic and antiviral activities of aqueous leaves extracts of different plants against foot and mouth disease virus infection in farming animals

Cytotoxic and antiviral activity of aqueous leaves extracts of three plants: Azadirachta indica, Moringa oleifera and Morus alba against Foot and Mouth disease virus (FMDV) were determined using MTT assay (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide). Eight different concentrations of each plant were evaluated. Cytotoxic and antiviral activity of each extract was evaluated as cell survival percentage and results were expressed as Means ± S.D. From the tested plant extracts, Azadirachta indica & Moringa oleifera exhibited cytotoxicity at 200 & 100 μ/ml respectively. In case of antiviral assay, Moringa oleifera showed potent antiviral activity (p<0.05) while Azadirachta indica showed significant antiviral activity in the range of 12.5-50 μ/ml & 50-100 μ/ml respectively. In contrast no anti-FMDV activity in the present study was observed with Morus alba, although all the tested concentrations were found to be safe.

Antiviral activity of punicalagin toward human enterovirus 71 in vitro and in vivo

Human enterovirus 71 is one of the major causative agents of hand, foot and mouth disease in children and has caused mortalities in large-scale outbreaks in the Asia-Pacific region in recent years. No vaccine or antiviral therapy is available currently in the clinic. In this work, we investigated the antiviral effect of punicalagin on enterovirus 71 both in vitro and in vivo. The results showed that punicalagin reduced the viral cytopathic effect on rhabdomyosarcoma cells with an IC₅₀) value of 15 μg/ml. Moreover, punicalagin treatment of mice challenged with a lethal dose of enterovirus 71 resulted in a reduction of mortality and relieved clinical symptoms by inhibiting viral replication. Our work suggested that punicalagin have the potential for further development as antiviral agents against enterovirus 71.

Effect of the route of foot-and-mouth disease virus infection of piglets on the course of disease

Three different routes of Foot-and-mouth disease virus (FMDV) infection of piglets, namely intranasal (i.n.) through drops, intradermal (i.d.) into the foot, and intramuscular (i.m.) were compared regarding the onset and severity of the disease. The results showed that the i.d. injection of the virus resulted in the fastest onset of the disease. The i.m. injection led to a delayed onset, but the final effect was identical with i.d. injection. Moreover, the i.m. injection was simpler to perform and easier to evaluate. Therefore, the i.m. injection of piglets is recommended as the optimal infection route for evaluation of the FMDV vaccine potency.

Structural analysis of foot-and-mouth disease virus 3C protease: a viable target for antiviral drugs?

Foot-and-mouth disease virus causes a major global agricultural problem that is difficult to control with existing vaccines. Structural analyses of the viral 3C protease not only have provided fresh insights into the catalytic mechanism of an unusual class of chymotrypsin-like cysteine proteases, but also are generating valuable information to drive the quest for effective antiviral therapies.

2'-C-methylcytidine as a potent and selective inhibitor of the replication of foot-and-mouth disease virus

We report on the potent and selective in vitro antiviral activity of 2'-C-methylcytidine (2'-C-MetCyt) against foot-and-mouth disease virus (FMDV). FMDV belongs to the Picornaviridae and has the potential to cause devastating epidemics in livestock. The 50% and 90% effective concentrations (EC50 and EC90) for inhibition of the FMDV-induced cytopathic effect (CPE) formation were 6.4+/-3.8 and 10.8+/-5.4 microM. Comparable EC50 values for inhibition of viral RNA synthesis were observed. Treatment of FMDV-infected BHK-21 cells with 77 microM 2'-C-MetCyt resulted in a (1.6-3.2)x10(3)-fold reduction of infectious virus yield. Time-of-drug addition experiments suggest that 2'-C-MetCyt interacts with viral replication at a time point that coincides with the onset of intracellular viral RNA synthesis. In contrast to emergency vaccination, a potent and selective antiviral agent may provide almost immediate (prophylactic/therapeutic) protection against infection and thus constitute an important alternative/supplementary option to contain outbreaks such as those caused by FMDV.

Foot-and-mouth disease virus 3C protease: recent structural and functional insights into an antiviral target

The 3C protease from foot-and-mouth disease virus (FMDV 3C(pro)) is critical for viral pathogenesis, having vital roles in both the processing of the polyprotein precursor and RNA replication. Although recent structural and functional studies have revealed new insights into the mechanism and function of the enzyme, key questions remain that must be addressed before the potential of FMDV 3C(pro) as an antiviral drug target can be realised.

Dexamethasone inhibits virus production and the secretory IgA response in oesophageal-pharyngeal fluid in cattle persistently infected with foot-and-mouth disease virus

Cattle persistently infected with foot-and-mouth disease virus were treated with dexamethasone to suppress the immune system in an attempt to influence the level of virus recovery from oesophageal pharyngeal (probang) samples. Twelve carrier cattle were assigned to one of three groups: control; 0.1 mg/kg dexamethasone; and 0.5 mg/kg dexamethasone. Groups 2 and 3 were injected intramuscularly three times weekly for 3 weeks with dexamethasone between days 33 and 56 post-infection with foot-and-mouth disease virus (FMDV). Cattle in both groups developed a leucocytosis, neutrophilia and lymphopenia. The secretory IgA response to FMDV infection was inhibited following, but not during, dexamethasone treatment between days 70 and 98 post-infection (P < 0.05). FMDV recovery from probang samples was reduced between days 40 and 64 post-infection (P < 0.05) during treatment with either 0.1 or 0.5 mg/kg dexamethasone. Following cessation of dosing with dexamethasone virus recovery returned to control levels. These observations suggest dexamethasone inhibits shedding of FMDV in a reversible manner which may be related to its immunosuppressive, anti-inflammatory or physiological actions.

Protection of guinea pigs against local and systemic foot-and-mouth disease after administration of synthetic lipid amine (Avridine) liposomes

Injection of the synthetic lipid amine, Avridine, in the form of liposomes, protected guinea pigs against the development of lesions from foot-and-mouth disease virus (FMDV) inoculated intradermally into the rear footpads. The animals were protected against the development of vesicles at the inoculation site as well as the systemic spread of virus. Maximal protection was obtained after intracardial injection of 5-10 mg doses of liposomal Avridine. Lower doses yielded decreased protection. Subcutaneous or intraperitoneal routes of liposomal Avridine injection were ineffective. Protection was maximal 0-24 h after injection of liposomes. Ethanol and emulsion formulations of Avridine could induce protection when injected intracardially but had toxic side effects. Guinea pigs protected against the first FMDV inoculation by liposomal and ethanol formulations of Avridine continued to be protected against lesions after a second inoculation 15-45 days later. FMDV protective antibody titers of these animals ranged from a low of less than 1:10 to greater than 1:1000.

[Antiviral activity of modified RNAses]

Antiviral activity of pancreatic RNase and RNase from Act.rimosus modified by various dextran derivatives was studied with respect to aphthosa and Ayzeku disease viruses. Antiviral activity of pancreatic RNase modified by dextran m-aminobenzylhydroxymethyl ether was lower than biological activity of RNase from Act.rimosus modified by the same dextran. Antiviral activity of pancreatic enzyme modified by dialdehyde dextran also changed insignificantly. Modification by dextran hydroxyethylsulfonylanisole ether, dextran m-aminobenzylhydroxymethyl ether in the presence of pyridine or dextran sulfate resulted in a more pronounced increase in antiviral activity of pancreatic enzyme. Therefore, biological activity of the modified nucleases depended on the nature of the enzyme and dextran modifying it.

[Comparative study of the antiviral activity of pancreatic and microbial RNAse]

The efficacy of pancreatic RNase with microbial enzymes (RN-ases) of Act. rimosus and Bacillus intermedius) was studied comparatively in vitro in a transplantable cell culture of the swine embryokidney with respect to the aphthosa virus (AV) and the virus of the Aujeszky disease (VAD). The VAD proved to be most sensitive to RNases. RNase of Bac. intermedius showed the highest antiviral efficacy. The enzymes were active in vivo, when the albino mice and newborn rabbits were infected with the AV, the RNase of Bac. intermedius being also most active in this case.

[Effect of migillin on protein synthesis in intact and virally infected TKCE and FL cells]

The effect of migillin was studied with respect to protein synthesis in the cells of TKCE (transplantable line of cells of the kidneys of cow embryos) and FL--intact and infected with viruses of aphtous fever A22, strain 550 and poliomyelitis of type III, strain Saukett respectively. Simultaneously the effect of migillin on sensitivity of the cells to the above viruses was tested. The synthesis of protein was determined by incorporation of C14-glycine into the acid insoluble fraction of the cells. It was found that protein synthesis significantly increased under the effect of migillin in both the intact cells and the cells infected with the viruses. The viruses of aphtous fever and poliomyelitis inhibited the synthesis of proteins. The antibiotic increased the activity of dehydrogenases and respiration of HEp-2 cells. Migillin markedly suppressed reproduction of the poliomyelitis virus, the effect on the virus of aphtous fever was lower in the cell culture. In guinea pigs the antiviral effect of the antibiotic resulted in prolongation of the incubation period and retardation of the aphtous fever process generalization. The results of the experiments showed that migillin stimulated the activity of dehydrogenases, respiration, protein synthesis in the cell cultures and possessed antiviral activity in vitro and in vivo.