Differential inhibition of intra- and inter-molecular protease cleavages by antiviral compounds.

IMPORTANCE: Most protease-targeted antiviral development evaluates the ability of small molecules to inhibit the cleavage of artificial substrates. However, before they can cleave any other substrates, viral proteases need to cleave themselves out of the viral polyprotein in which they have been translated. This can occur either intra- or inter-molecularly. Whether this process occurs intra- or inter-molecularly has implications for the potential for precursors to accumulate and for the effectiveness of antiviral drugs. We argue that evaluating candidate antivirals for their ability to block these cleavages is vital to drug development because the buildup of uncleaved precursors can be inhibitory to the virus and potentially suppress the selection of drug-resistant variants.

Rational design of highly potent broad-spectrum enterovirus inhibitors targeting the nonstructural protein 2C.

There is a great need for antiviral drugs to treat enterovirus (EV) and rhinovirus (RV) infections, which can be severe and occasionally life-threatening. The conserved nonstructural protein 2C, which is an AAA+ ATPase, is a promising target for drug development. Here, we present a structure-activity relationship study of a previously identified compound that targets the 2C protein of EV-A71 and several EV-B species members, but not poliovirus (PV) (EV-C species). This compound is structurally related to the Food and Drug Administration (FDA)-approved drug fluoxetine-which also targets 2C-but has favorable chemical properties. We identified several compounds with increased antiviral potency and broadened activity. Four compounds showed broad-spectrum EV and RV activity and inhibited contemporary strains of emerging EVs of public health concern, including EV-A71, coxsackievirus (CV)-A24v, and EV-D68. Importantly, unlike (S)-fluoxetine, these compounds are no longer neuroactive. By raising resistant EV-A71, CV-B3, and EV-D68 variants against one of these inhibitors, we identified novel 2C resistance mutations. Reverse engineering of these mutations revealed a conserved mechanism of resistance development. Resistant viruses first acquired a mutation in, or adjacent to, the α2 helix of 2C. This mutation disrupted compound binding and provided drug resistance, but this was at the cost of viral fitness. Additional mutations at distantly localized 2C residues were then acquired to increase resistance and/or to compensate for the loss of fitness. Using computational methods to identify solvent accessible tunnels near the α2 helix in the EV-A71 and PV 2C crystal structures, a conserved binding pocket of the inhibitors is proposed.

Inhibitory antibodies identify unique sites of therapeutic vulnerability in rhinovirus and other enteroviruses.

The existence of multiple serotypes renders vaccine development challenging for most viruses in the Enterovirus genus. An alternative and potentially more viable strategy for control of these viruses is to develop broad-spectrum antivirals by targeting highly conserved proteins that are indispensable for the virus life cycle, such as the 3C protease. Previously, two single-chain antibody fragments, YDF and GGVV, were reported to effectively inhibit human rhinovirus 14 proliferation. Here, we found that both single-chain antibody fragments target sites on the 3C protease that are distinct from its known drug site (peptidase active site) and possess different mechanisms of inhibition. YDF does not block the active site but instead noncompetitively inhibits 3C peptidase activity through an allosteric effect that is rarely seen for antibody protease inhibitors. Meanwhile, GGVV antagonizes the less-explored regulatory function of 3C in genome replication. The interaction between 3C and the viral genome 5' noncoding region has been reported to be important for enterovirus genome replication. Here, the interface between human rhinovirus 14 3C and its 5' noncoding region was probed by hydrogen-deuterium exchange coupled mass spectrometry and found to partially overlap with the interface between GGVV and 3C. Consistently, prebinding of GGVV completely abolishes interaction between human rhinovirus 14 3C and its 5' noncoding region. The epitopes of YDF and GGVV, therefore, represent two additional sites of therapeutic vulnerability in rhinovirus. Importantly, the GGVV epitope appears to be conserved across many enteroviruses, suggesting that it is a promising target for pan-enterovirus inhibitor screening and design.

A novel druggable interprotomer pocket in the capsid of rhino- and enteroviruses.

Rhino- and enteroviruses are important human pathogens, against which no antivirals are available. The best-studied inhibitors are "capsid binders" that fit in a hydrophobic pocket of the viral capsid. Employing a new class of entero-/rhinovirus inhibitors and by means of cryo-electron microscopy (EM), followed by resistance selection and reverse genetics, we discovered a hitherto unknown druggable pocket that is formed by viral proteins VP1 and VP3 and that is conserved across entero-/rhinovirus species. We propose that these inhibitors stabilize a key region of the virion, thereby preventing the conformational expansion needed for viral RNA release. A medicinal chemistry effort resulted in the identification of analogues targeting this pocket with broad-spectrum activity against Coxsackieviruses B (CVBs) and compounds with activity against enteroviruses (EV) of groups C and D, and even rhinoviruses (RV). Our findings provide novel insights in the biology of the entry of entero-/rhinoviruses and open new avenues for the design of broad-spectrum antivirals against these pathogens.

Influence of the Structural Features of Carrageenans from Red Algae of the Far Eastern Seas on Their Antiviral Properties.

The structural diversity and unique physicochemical properties of sulphated polysaccharides of red algae carrageenans (CRGs), to a great extent, determine the wide range of their antiviral properties. This work aimed to compare the antiviral activities of different structural types of CRGs: against herpes simplex virus type 1 (HSV-1) and enterovirus (ECHO-1). We found that CRGs significantly increased the resistance of Vero cells to virus infection (preventive effect), directly affected virus particles (virucidal effect), inhibited the attachment and penetration of virus to cells, and were more effective against HSV-1. CRG1 showed the highest virucidal effect on HSV-1 particles with a selective index (SI) of 100. CRG2 exhibited the highest antiviral activity by inhibiting HSV-1 and ECHO-1 plaque formation, with a SI of 110 and 59, respectively, when it was added before virus infection. CRG2 also significantly reduced the attachment of HSV-1 and ECHO-1 to cells compared to other CRGs. It was shown by molecular docking that tetrasaccharides-CRGs are able to bind with the HSV-1 surface glycoprotein, gD, to prevent virus-cell interactions. The revealed differences in the effect of CRGs on different stages of the lifecycle of the viruses are apparently related to the structural features of the investigated compounds.

Viral engagement with host receptors blocked by a novel class of tryptophan dendrimers that targets the 5-fold-axis of the enterovirus-A71 capsid.

Enterovirus A71 (EV-A71) is a non-polio neurotropic enterovirus with pandemic potential. There are no antiviral agents approved to prevent or treat EV-A71 infections. We here report on the molecular mechanism by which a novel class of tryptophan dendrimers inhibits (at low nanomolar to high picomolar concentration) EV-A71 replication in vitro. A lead compound in the series (MADAL385) prevents binding and internalization of the virus but does not, unlike classical capsid binders, stabilize the particle. By means of resistance selection, reverse genetics and cryo-EM, we map the binding region of MADAL385 to the 5-fold vertex of the viral capsid and demonstrate that a single molecule binds to each vertex. By interacting with this region, MADAL385 prevents the interaction of the virus with its cellular receptors PSGL1 and heparan sulfate, thereby blocking the attachment of EV-A71 to the host cells.

Antivirals blocking entry of enteroviruses and therapeutic potential.

Viruses from the genus Enterovirus (EV) of the Picornaviridae family are known to cause diseases such as hand foot and mouth disease (HFMD), respiratory diseases, encephalitis and myocarditis. The capsid of EV is an attractive target for the development of direct-acting small molecules that can interfere with viral entry. Some of the capsid binders have been evaluated in clinical trials but the majority have failed due to insufficient efficacy or unacceptable off-target effects. Furthermore, most of the capsid binders exhibited a low barrier to resistance. Alternatively, host-targeting inhibitors such as peptides derived from the capsid of EV that can recognize cellular receptors have been identified. However, the majority of these peptides displayed low anti-EV potency (µM range) as compared to the potency of small molecule compounds (nM range). Nonetheless, the development of anti-EV peptides is warranted as they may complement the small-molecules in a drug combination strategy to treat EVs. Lastly, structure-based approach to design antiviral peptides should be utilized to unearth potent anti-EV peptides.

In vitro antiviral activity of peptide-rich extracts from seven Nigerian plants against three non-polio enterovirus species C serotypes.

BACKGROUND: As frequent viral outbreaks continue to pose threat to public health, the unavailability of antiviral drugs and challenges associated with vaccine development underscore the need for antiviral drugs discovery in emergent moments (endemic or pandemic). Plants in response to microbial and pest attacks are able to produce defence molecules such as antimicrobial peptides as components of their innate immunity, which can be explored for viral therapeutics. METHODS: In this study, partially purified peptide-rich fraction (P-PPf) were obtained from aqueous extracts of seven plants by reverse-phase solid-phase extraction and cysteine-rich peptides detected by a modified TLC method. The peptide-enriched fractions and the aqueous (crude polar) were screened for antiviral effect against three non-polio enterovirus species C members using cytopathic effect reduction assay. RESULTS: In this study, peptide fraction obtained from Euphorbia hirta leaf showed most potent antiviral effect against Coxsackievirus A13, Coxsackievirus A20, and Enterovirus C99 (EV-C99) with IC50 < 2.0 µg/mL and selective index ≥ 81. EV-C99 was susceptible to all partially purified peptide fractions except Allamanda blanchetii leaf. CONCLUSION: These findings establish the antiviral potentials of plants antimicrobial peptides and provides evidence for the anti-infective use of E. hirta in ethnomedicine. This study provides basis for further scientific investigation geared towards the isolation, characterization and mechanistic pharmacological study of the detected cysteine-rich peptides.

Lactoferrin affects rhinovirus B-14 entry into H1-HeLa cells.

Lactoferrin is part of the innate immune system, with antiviral activity against numerous DNA and RNA viruses. Rhinoviruses, the leading cause of the common cold, are associated with exacerbation of respiratory illnesses such as asthma. Here, we explored the effect of bovine lactoferrin (BLf) on RV-B14 infectivity. Using different assays, we show that the effect of BLf is strongest during adhesion of the virus to the cell and entry. Tracking the internalisation of BLf and virus revealed a degree of colocalisation, although their interaction was only confirmed in vitro using empty viral particles, indicating a possible additional influence of BLf on other infection steps.

Bioactive prenylated C6-C3 derivatives from the stems and leaves of Illicium fargesii.

Seventeen new prenylated C6-C3 derivatives, namely, illifargeins A-M (1-13), including three pairs of enantiomers (1, 5, and 12) and one norillifargeal A (14), together with eight known analogues (15-22), were isolated from the stems and leaves of Illicium fargesii. The structures of the new compounds were elucidated using spectroscopic data (UV, IR, 1D and 2D NMR, and HRESIMS). Their absolute configurations were determined by using experimental and calculated ECD data analysis, as well as a modified Mosher's method. Compounds 1a, 1b, 2, 3, 5a, 7, 10, 11, 15, 16, 19, and 20 showed potential activity against Coxsackie virus B3, with IC50 values ranging from 6.23 to 33.33 µM. Compounds 9 and 15 exhibited potential activity against influenza virus A, with IC50 values of 11.11 and 19.24 µM, respectively. Compounds 2, 3, and 18 exhibited potential anti-oxidant activity, with IC50 values ranging from 1.43 to 6.71 µM.

Synthesis of 1,2,3-triazolyl nucleoside analogues and their antiviral activity.

Based on the fact that a search for influenza antivirals among nucleoside analogues has drawn very little attention of chemists, the present study reports the synthesis of a series of 1,2,3-triazolyl nucleoside analogues in which a pyrimidine fragment is attached to the ribofuranosyl-1,2,3-triazol-4-yl moiety by a polymethylene linker of variable length. Target compounds were prepared by the Cu alkyne-azide cycloaddition (CuAAC) reaction. Derivatives of uracil, 6-methyluracil, 3,6-dimethyluracil, thymine and quinazolin-2,4-dione with ω-alkyne substituent at the N1 (or N5) atom and azido 2,3,5-tri-O-acetyl-D-ß-ribofuranoside were used as components of the CuAAC reaction. All compounds synthesized were evaluated for antiviral activity against influenza virus A/PR/8/34/(H1N1) and coxsackievirus B3. The best values of IC50 (inhibiting concentration) and SI (selectivity index) were demonstrated by the lead compound 4i in which the 1,2,3-triazolylribofuranosyl fragment is attached to the N1 atom of the quinazoline-2,4-dione moiety via a butylene linker (IC50 = 30 µM, SI = 24) and compound 8n in which the 1,2,3-triazolylribofuranosyl fragment is attached directly to the N5 atom of the 6-methyluracil moiety (IC50 = 15 µM, SI = 5). According to theoretical calculations, the antiviral activity of the 1,2,3-triazolyl nucleoside analogues 4i and 8n against H1N1 (A/PR/8/34) influenza virus can be explained by their influence on the functioning of the polymerase acidic protein (PA) of RNA-dependent RNA polymerase (RdRP).

Antifungal Triazole Posaconazole Targets an Early Stage of the Parechovirus A3 Life Cycle.

Viruses in species Parechovirus A (Picornaviridae) are associated with a wide variety of clinical manifestations. Parechovirus A3 (PeV-A3) is known to cause sepsis-like illness, meningitis, and encephalitis in infants and young children. To date, no specific therapies are available to treat PeV-A3-infected children. We had previously identified two FDA-cleared antifungal drugs, itraconazole (ITC) and posaconazole (POS), with potent and specific antiviral activity against PeV-A3. Time-of-addition and synchronized infection assays revealed that POS targets an early stage of the PeV-A3 life cycle. POS exerts an antiviral effect, evidenced by a reduction in viral titer following the addition of POS to Vero-P cells before infection, coaddition of POS and PeV-A3 to Vero-P cells, incubation of POS and PeV-A3 prior to Vero-P infection, and at attachment. POS exerts less of an effect on virus entry. A PeV-A3 enzyme-linked immunosorbent assay inhibition experiment, using an anti-PeV-A3 monoclonal antibody, suggested that POS binds directly to the PeV-A3 capsid. POS-resistant PeV-A3 strains developed by serial passage in the presence of POS acquired substitutions in multiple regions of the genome, including the capsid. Reverse genetics confirmed substitutions in capsid proteins VP0, VP3, and VP1 and nonstructural proteins 2A and 3A. Single mutants VP0_K66R, VP0_A124T, VP3_N88S, VP1_Y224C, 2A_S78L, and 3A_T1I were 4-, 9-, 12-, 34-, 51-, and 119-fold more resistant to POS, respectively, than the susceptible prototype strain. Our studies demonstrate that POS may be a valuable tool in developing an antiviral therapy for PeV-A3.

Novel Ionophores Active against La Crosse Virus Identified through Rapid Antiviral Screening.

Bunyaviruses are significant human pathogens, causing diseases ranging from hemorrhagic fevers to encephalitis. Among these viruses, La Crosse virus (LACV), a member of the California serogroup, circulates in the eastern and midwestern United States. While LACV infection is often asymptomatic, dozens of cases of encephalitis are reported yearly. Unfortunately, no antivirals have been approved to treat LACV infection. Here, we developed a method to rapidly test potential antivirals against LACV infection. From this screen, we identified several potential antiviral molecules, including known antivirals. Additionally, we identified many novel antivirals that exhibited antiviral activity without affecting cellular viability. Valinomycin, a potassium ionophore, was among our top targets. We found that valinomycin exhibited potent anti-LACV activity in multiple cell types in a dose-dependent manner. Valinomycin did not affect particle stability or infectivity, suggesting that it may preclude virus replication by altering cellular potassium ions, a known determinant of LACV entry. We extended these results to other ionophores and found that the antiviral activity of valinomycin extended to other viral families, including bunyaviruses (Rift Valley fever virus, Keystone virus), enteroviruses (coxsackievirus, rhinovirus), flavirivuses (Zika virus), and coronaviruses (human coronavirus 229E [HCoV-229E] and Middle East respiratory syndrome CoV [MERS-CoV]). In all viral infections, we observed significant reductions in virus titer in valinomycin-treated cells. In sum, we demonstrate the importance of potassium ions to virus infection, suggesting a potential therapeutic target to disrupt virus replication.

Related Enteric Viruses Have Different Requirements for Host Microbiota in Mice.

Accumulating evidence suggests that intestinal bacteria promote enteric virus infection in mice. For example, previous work demonstrated that antibiotic treatment of mice prior to oral infection with poliovirus reduced viral replication and pathogenesis. Here, we examined the effect of antibiotic treatment on infection with coxsackievirus B3 (CVB3), a picornavirus closely related to poliovirus. We treated mice with a mixture of five antibiotics to deplete host microbiota and examined CVB3 replication and pathogenesis following oral inoculation. We found that, as seen with poliovirus, CVB3 shedding and pathogenesis were reduced in antibiotic-treated mice. While treatment with just two antibiotics, vancomycin and ampicillin, was sufficient to reduce CVB3 replication and pathogenesis, this treatment had no effect on poliovirus. The quantity and composition of bacterial communities were altered by treatment with the five-antibiotic cocktail and by treatment with vancomycin and ampicillin. To determine whether more-subtle changes in bacterial populations impact viral replication, we examined viral infection in mice treated with milder antibiotic regimens. Mice treated with one-tenth the standard concentration of the normal antibiotic cocktail supported replication of poliovirus but not CVB3. Importantly, a single dose of one antibiotic, streptomycin, was sufficient to reduce CVB3 shedding and pathogenesis while having no effect on poliovirus shedding and pathogenesis. Overall, replication and pathogenesis of CVB3 are more sensitive to antibiotic treatment than poliovirus, indicating that closely related viruses may differ with respect to their reliance on microbiota.IMPORTANCE Recent data indicate that intestinal bacteria promote intestinal infection of several enteric viruses. Here, we show that coxsackievirus, an enteric virus in the picornavirus family, also relies on microbiota for intestinal replication and pathogenesis. Relatively minor depletion of the microbiota was sufficient to decrease coxsackievirus infection, while poliovirus infection was unaffected. Surprisingly, a single dose of one antibiotic was sufficient to reduce coxsackievirus infection. Therefore, these data indicate that closely related viruses may differ with respect to their reliance on microbiota.

Cellular N-myristoyltransferases play a crucial picornavirus genus-specific role in viral assembly, virion maturation, and infectivity.

In nearly all picornaviruses the precursor of the smallest capsid protein VP4 undergoes co-translational N-terminal myristoylation by host cell N-myristoyltransferases (NMTs). Curtailing this modification by mutation of the myristoylation signal in poliovirus has been shown to result in severe assembly defects and very little, if any, progeny virus production. Avoiding possible pleiotropic effects of such mutations, we here used pharmacological abrogation of myristoylation with the NMT inhibitor DDD85646, a pyrazole sulfonamide originally developed against trypanosomal NMT. Infection of HeLa cells with coxsackievirus B3 in the presence of this drug decreased VP0 acylation at least 100-fold, resulting in a defect both early and late in virus morphogenesis, which diminishes the yield of viral progeny by about 90%. Virus particles still produced consisted mainly of provirions containing RNA and uncleaved VP0 and, to a substantially lesser extent, of mature virions with cleaved VP0. This indicates an important role of myristoylation in the viral maturation cleavage. By electron microscopy, these RNA-filled particles were indistinguishable from virus produced under control conditions. Nevertheless, their specific infectivity decreased by about five hundred fold. Since host cell-attachment was not markedly impaired, their defect must lie in the inability to transfer their genomic RNA into the cytosol, likely at the level of endosomal pore formation. Strikingly, neither parechoviruses nor kobuviruses are affected by DDD85646, which appears to correlate with their native capsid containing only unprocessed VP0. Individual knockout of the genes encoding the two human NMT isozymes in haploid HAP1 cells further demonstrated the pivotal role for HsNMT1, with little contribution by HsNMT2, in the virus replication cycle. Our results also indicate that inhibition of NMT can possibly be exploited for controlling the infection by a wide spectrum of picornaviruses.

Identification of an antiviral compound isolated from Pistacia lentiscus.

This study screened mastic gum (Pistacia lentiscus L.) for antiviral activity against herpes simplex virus type 2 (HSV-2), coxsackievirus type B3, and adenovirus type 5. The organs of this plant (leaves, stem, and seed) were macerated sequentially using solvents of increasing polarity (hexane, dichloromethane, ethyl acetate, and methanol). Only the methanol extract of stem exhibited significant activity against HSV-2. This extract showed anti-HSV-2 activity with a selectivity index of 51 (50% cytotoxic concentration = 186 µg/mL; 50% inhibitory concentration = 3.63 µg/mL), and demonstrated direct inhibition against this virus with a virucidal selectivity index of 620 (50% virucidal concentration = 0.30 µg/mL). A bio-guided assay involving thin-layer chromatography led to the isolation of two active compounds, which have been identified as dammaradienone and dammaradienol using high-performance liquid chromatography-diode array detection coupled with electrospray ionization mass spectrometry. P. lentiscus has been widely studied for other biological activities. However, to our knowledge, this is the first report of P. lentiscus L. exhibiting antiviral activity.

Development of broad-spectrum enterovirus antivirals based on quinoline scaffold.

Non-polio enteroviruses such as enterovirus A71 (EV-A71), EV-D68, and coxsackievirus B3 (CVB3) are significant human pathogens with disease manifestations ranging from mild flu-like symptoms to more severe encephalitis, myocarditis, acute flaccid paralysis/myelitis, and even death. There is currently no effective antivirals to prevent or treat non-polio enterovirus infection. In this study, we report our progress in developing potent and broad-spectrum antivirals against these non-polio enteroviruses. Starting from our previously developed lead compounds that had potent antiviral activity against EV-D68, we synthesized 43 analogs and profiled their broad-spectrum antiviral activity against additional EV-D68, EV-A71, and CVB3 viruses. Promising candidates were also selected for mouse microsomal stability test to prioritize lead compounds for future in vivo mouse model studies. Collectively, this multi-parameter optimization process revealed a promising lead compound 6aw that showed single-digit to submicromolar EC50 values against two EV-D68 strains (US/KY and US/MO), two EV-A71 strains (Tainan and US/AK), and one CVB3 strain, with a high selectivity index. Encouragingly, 6aw was stable in mouse microsomes with a half-life of 114.7 min. Overall, 6aw represents one of the most potent broad-spectrum antiviral against non-polio enteroviruses, rendering it a promising lead candidate for non-polio enteroviruses with translational potential.

High Amplification of the Antiviral Activity of Curcumin through Transformation into Carbon Quantum Dots.

It is demonstrated that carbon quantum dots derived from curcumin (Cur-CQDs) through one-step dry heating are effective antiviral agents against enterovirus 71 (EV71). The surface properties of Cur-CQDs, as well as their antiviral activity, are highly dependent on the heating temperature during synthesis. The one-step heating of curcumin at 180 °C preserves many of the moieties of polymeric curcumin on the surfaces of the as-synthesized Cur-CQDs, resulting in superior antiviral characteristics. It is proposed that curcumin undergoes a series of structural changes through dehydration, polymerization, and carbonization to form core-shell CQDs whose surfaces remain a pyrolytic curcumin-like polymer, boosting the antiviral activity. The results reveal that curcumin possesses insignificant inhibitory activity against EV71 infection in RD cells [half-maximal effective concentration (EC50 ) >200 µg mL-1 ] but exhibits high cytotoxicity toward RD cells (half-maximal cytotoxic concentration (CC50 ) <13 µg mL-1 ). The EC50 (0.2 µg mL-1 ) and CC50 (452.2 µg mL-1 ) of Cur-CQDs are >1000-fold lower and >34-fold higher, respectively, than those of curcumin, demonstrating their far superior antiviral capabilities and high biocompatibility. In vivo, intraperitoneal administration of Cur-CQDs significantly decreases mortality and provides protection against virus-induced hind-limb paralysis in new-born mice challenged with a lethal dose of EV71.

Effects of Acetylshikonin on the Infection and Replication of Coxsackievirus A16 in Vitro and in Vivo.

Coxsackievirus A16 (CVA16) is one of the most prevalent enteroviral pathogens associated with hand, foot, and mouth disease. In the present study, we have investigated (1) whether the bioactive compound acetylshikonin (AS) inhibits CVA16 infection in vitro and in vivo and (2) the potential antiviral mechanism(s). The results suggest that AS is nontoxic at concentrations of up to 5 µmol/L and could directly inactivate virus particles at relatively low concentrations (0.08 µmol/L), thereby rendering CVA16 incapable of cellular entry. Correspondingly, the expression of viral RNA in vitro was also reduced 100-fold ( P < 0.05) when compared to infected, untreated controls. Results from a CVA16-infected neonatal mouse model indicate that, in comparison to the virus-infected, untreated group, body weights of the mice in the virus-infected, compound-treated group increased more steadily with less severe clinical symptoms. In addition, viral loads in internal organs significantly decreased in treated animals, concomitantly with both reduced pathology and diminished expression of the proinflammatory cytokines IFN-γ and IL-6. In conclusion, AS exerted an inhibitory effect on CVA16 infection in vitro and in vivo. Our study provides a basis for further investigations of AS-type compounds to develop therapeutics to mitigate CVA-associated disease in children.

The inactivation of the non-enveloped enterovirus 71 (EV71) by a novel disinfectant gel formulation for topical use.

BACKGROUND: Hand-foot-mouth disease may cause severe central nervous system complications and even death, that is induced mainly by enterovirus 71 (EV71), which is a non-enveloped virus. Inactivation of the EV71 on hands could effectively inhibit the transmission. However, the inactivations of the EV71 by conventional disinfectants including the alcohols are poor, due to the high stability of the EV71. A novel pyridyl imidazolidinone compound (TJAB1099) was designed to specifically inhibit EV71 replication in vitro. It may potentially be developed as formulations applied on hands for EV71 transmission control. METHODS: The stress stability of TJAB1099 was first evaluated after storing in high temperature (60 °C, RH 10%), high humidity (25 °C, RH90%), and the high-intensity photolysis (4500 Lx ± 500 Lx) for 15 days, respectively. A wash-free antimicrobial gel containing the TJAB1099 was developed using the copolymer carrier. The antiviral activity, the acute oral toxicity, and the local irritation of the antimicrobial gel were evaluated accordingly. RESULTS: The results indicated that the TJAB1099 was stable during the storage in high temperature and humidity. However, a significant change (p < .0001) was detected when TJAB1099 stored in the high-intensity photolysis. The antimicrobial gel containing 1 µM TJAB1099 could inhibit EV71 significantly higher than the ethanol (75%) (p < .0001) and commercialized disinfectant products (p < .0001). The results of acute oral toxicity and the local irritation suggest that the TJAB1099 containing antimicrobial gel was not causing skin irritations and acute oral toxicity symptoms. CONCLUSIONS: The results suggest that the antimicrobial gel containing TJAB1099 was safe and could effectively inhibit EV71 transmission in vitro.