Dengue structural proteins as antiviral drug targets: Current status in the drug discovery & development

Development in the Inhibition of Dengue Proteases as Drug Targets

BACKGROUND

Viral infections continue to increase morbidity and mortality severely. The flavivirus genus has fifty different species, including the dengue, Zika, and West Nile viruses that can infect 40% of individuals globally, who reside in at least a hundred different countries. Dengue, one of the oldest and most dangerous human infections, was initially documented by the Chinese Medical Encyclopedia in the Jin period. It was referred to as "water poison," connected to flying insects, i.e., Aedes aegypti and Aedes albopictus. DENV causes some medical expressions like dengue hemorrhagic fever, acute febrile illness, and dengue shock syndrome.

OBJECTIVE

According to the World Health Organization report of 2012, 2500 million people are in danger of contracting dengue fever worldwide. According to a recent study, 96 million of the 390 million dengue infections yearly show some clinical or subclinical severity. There is no antiviral drug or vaccine to treat this severe infection. It can be controlled by getting enough rest, drinking plenty of water, and using painkillers. The first dengue vaccine created by Sanofi, called Dengvaxia, was previously approved by the USFDA in 2019. All four serotypes of the DENV1-4 have shown re-infection in vaccine recipients. However, the usage of Dengvaxia has been constrained by its adverse effects.

CONCLUSION

Different classes of compounds have been reported against DENV, such as nitrogen-containing heterocycles (i.e., imidazole, pyridine, triazoles quinazolines, quinoline, and indole), oxygen-containing heterocycles (i.e., coumarins), and some are mixed heterocyclic compounds of S, N (thiazole, benzothiazine, and thiazolidinediones), and N, O (i.e., oxadiazole). There have been reports of computationally designed compounds to impede the molecular functions of specific structural and non-structural proteins as potential therapeutic targets. This review summarized the current progress in developing dengue protease inhibitors.

Updates in the Management of Dengue Shock Syndrome: A Comprehensive Review

Dengue is a very serious public health problem that can manifest a wide range of symptoms from asymptomatic to fatal conditions, such as dengue shock syndrome (DSS). It is a life-threatening mosquito-borne viral infection widely spread in tropical areas. Dengue virus transmission occurs from an infected Aedes mosquito to humans. Various factors are responsible for the occurrence of the disease, such as viral load, age of the host, immune status of the host, and genetic variability. Dengue infection occurs in three phases: febrile, critical, and recovery. The febrile phase lasts for seven days and manifests symptoms such as high-grade fever, headache, arthralgia, and backache, and in some cases, the upper respiratory tract and gastrointestinal tract are also involved. Severe dengue is characterized by endothelial dysfunction that causes vascular permeability and plasma leakage. The fundamental mechanisms of these immune pathologies are not yet known. Dengue manifests various complications such as dengue encephalopathy, encephalitis, stroke, ocular involvement, acute transverse myelitis, myalgia, and cerebellar syndrome, but the most commonly seen is liver involvement. Dengue is managed supportively because there are no proven curative treatments. The cornerstone of care during the critical period of dengue is prudent fluid resuscitation. The first fluid of preference is a crystalloid. Prophylactic transfusion of platelets is not advised. The occurrence of four antigenically different dengue virus serotypes, each able to elicit a cross-reactive and disease-enhancing antibody response against the other three serotypes, has made the creation of the dengue vaccine a difficult undertaking. The development of a dengue vaccine has faced significant challenges due to a lack of the best animal models and a variety of immunological conditions in people, particularly in endemic locations. Dengvaxia is a live attenuated vaccine, which was developed by Sanofi. It is made up of four chimeric vaccine viruses produced by Vero cells.

S-Adenosyl-l-Homocysteine Exhibits Potential Antiviral Activity Against Dengue Virus Serotype-3 (DENV-3) in Bangladesh: A Viroinformatics-Based Approach

Dengue outbreak is one of the concerning issues in Bangladesh due to the annual outbreak with the alarming number of death and infection. However, there is no effective antiviral drug available to treat dengue-infected patients. This study evaluated and screened antiviral drug candidates against dengue virus serotype 3 (DENV-3) through viroinformatics-based analyses. Since 2017, DENV-3 has been the predominant serotype in Bangladesh. We selected 3 non-structural proteins of DENV-3, named NS3, NS4A, and NS5, as antiviral targets. Protein modeling and validation were performed with VERIFY-3D, Ramachandran plotting, MolProbity, and PROCHECK. We found 4 drug-like compounds from DRUGBANK that can interact with these non-structural proteins of DENV-3. Then, the ADMET profile of these compounds was determined by admetSAR2, and molecular docking was performed with AutoDock, SWISSDOCK, PatchDock, and FireDock. Furthermore, they were subjected to molecular dynamics (MD) simulation study using the DESMOND module of MAESTRO academic version 2021-4 (force field OPLS_2005) to determine their solution's stability in a predefined body environment. Two drug-like compounds named Guanosine-5'-Triphosphate (DB04137) and S-adenosyl-l-homocysteine (DB01752) were found to have an effective binding with these 3 proteins (binding energy > 33.47 KJ/mole). We found NS5 protein was stable and equilibrated in a 100 ns simulation run along with a negligible (<3Å) root-mean-square fluctuation value. The root-mean-square deviation value of the S-adenosyl-l-homocysteine-NS5 complex was less than 3Å, indicating stable binding between them. The global binding energy of S-adenosyl-l-homocysteine with NS5 was -40.52 KJ/mole as ∆G. Moreover, these 2 compounds mentioned above are non-carcinogenic according to their ADMET (chemical absorption, distribution, metabolism, excretion, and toxicity) profile (in silico). These outcomes suggest the suitability of S-adenosyl-l-homocysteine as a potential drug candidate for dengue drug discovery research.

John AL, Rathore APS. Dengue: Update on Clinically Relevant Therapeutic Strategies and Vaccines

Dengue viruses (DENV) continue to circulate worldwide, resulting in a significant burden on human health. There are four antigenically distinct serotypes of DENV, an infection of which could result in a potentially life-threatening disease. Current treatment options are limited and rely on supportive care. Although one dengue vaccine is approved for dengue-immune individuals and has modest efficacy, there is still a need for therapeutics and vaccines that can reduce dengue morbidities and lower the infection burden. There have been recent advances in the development of promising drugs for the treatment of dengue. These include direct antivirals that can reduce virus replication as well as host-targeted drugs for reducing inflammation and/or vascular pathologies. There are also new vaccine candidates that are being evaluated for their safety and efficacy in preventing dengue disease. This review highlights nuances in the current standard-of-care treatment of dengue. We also discuss emerging treatment options, therapeutic drugs, and vaccines that are currently being pursued at various stages of preclinical and clinical development.

Inhibitory Potential of Chromene Derivatives on Structural and Non-Structural Proteins of Dengue Virus

Dengue fever is a mosquito-borne viral disease that has become a serious health issue across the globe. It is caused by a virus of the Flaviviridae family, and it comprises five different serotypes (DENV-1 to DENV-5). As there is no specific medicine or effective vaccine for controlling dengue fever, there is an urgent need to develop potential inhibitors against it. Traditionally, various natural products have been used to manage dengue fever and its co-morbid conditions. A detailed analysis of these plants revealed the presence of various chromene derivatives as the major phytochemicals. Inspired by these observations, authors have critically analyzed the anti-dengue virus potential of various 4H chromene derivatives. Further, in silico, in vitro, and in vivo reports of these scaffolds against the dengue virus are detailed in the present manuscript. These analogues exerted their activity by interfering with various stages of viral entry, assembly, and replications. Moreover, these analogues mainly target envelope protein, NS2B-NS3 protease, and NS5 RNA-dependent RNA polymerase, etc. Overall, chromene-containing analogues exerted a potent activity against the dengue virus and the present review will be helpful for the further exploration of these scaffolds for the development of novel antiviral drug candidates.

Seeking heterocyclic scaffolds as antivirals against dengue virus

Dengue is one of the most typical viral infection categorized in the Neglected Tropical Diseases (NTDs). It is transmitted via the female Aedes aegypti mosquito to humans and majorly puts risk to the lives of more than half of the world. Recent advancements in medicinal chemistry have led to the design and development of numerous potential heterocyclic scaffolds as antiviral drug candidates for the inhibition of the dengue virus (DENV). Thus, in this review, we have discussed the significance of inhibitory and antiviral activities of nitrogen, oxygen, and mixed (nitrogen-sulfur and nitrogen-oxygen) heterocyclic scaffolds that are published in the last seven years (2016–2022). Furthermore, we have also discussed the probable mechanisms of action and the diverse structure-activity relationships (SARs) of the heterocyclic scaffolds. In addition, this review has elaborately outlined the mechanism of viral infection and the life cycle of DENV in the host cells. The wide set of heterocycles and their SARs will aid in the development of pharmaceuticals that will allow the researchers to synthesize the promising anti-dengue drug candidate in the future.

Hit-to-Lead Short Peptides against Dengue Type 2 Envelope Protein: Computational and Experimental Investigations

Data from the World Health Organisation show that the global incidence of dengue infection has risen drastically, with an estimated 400 million cases of dengue infection occurring annually. Despite this worrying trend, there is still no therapeutic treatment available. Herein, we investigated short peptide fragments with a varying total number of amino acid residues (peptide fragments) from previously reported dengue virus type 2 (DENV2) peptide-based inhibitors, DN58wt (GDSYIIIGVEPGQLKENWFKKGSSIGQMF), DN58opt (TWWCFYFCRRHHPFWFFYRHN), DS36wt (LITVNPIVTEKDSPVNIEAE), and DS36opt (RHWEQFYFRRRERKFWLFFW), aided by in silico approaches: peptide–protein molecular docking and 100 ns of molecular dynamics (MD) simulation via molecular mechanics using Poisson–Boltzmann surface area (MMPBSA) and molecular mechanics generalised Born surface area (MMGBSA) methods. A library of 11,699 peptide fragments was generated, subjected to in silico calculation, and the candidates with the excellent binding affinity and shown to be stable in the DI-DIII binding pocket of DENV2 envelope (E) protein were determined. Selected peptides were synthesised using conventional Fmoc solid-phase peptide chemistry, purified by RP-HPLC, and characterised using LCMS. In vitro studies followed, to test for the peptides’ toxicity and efficacy in inhibiting the DENV2 growth cycle. Our studies identified the electrostatic interaction (from free energy calculation) to be the driving stabilising force for the E protein–peptide interactions. Five key E protein residues were also identified that had the most interactions with the peptides: (polar) LYS36, ASN37, and ARG350, and (nonpolar) LEU351 and VAL354; these residues might play crucial roles in the effective binding interactions. One of the peptide fragments, DN58opt_8-13 (PFWFFYRH), showed the best inhibitory activity, at about 63% DENV2 plague reduction, compared with no treatment. This correlates well with the in silico studies in which the peptide possessed the lowest binding energy (−9.0 kcal/mol) and was maintained steadily within the binding pocket of DENV2 E protein during the MD simulations. This study demonstrates the use of computational studies to expand research on lead optimisation of antiviral peptides, thus explaining the inhibitory potential of the designed peptides.